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1.  Determining Risk for Severe Leptospirosis by Molecular Analysis of Environmental Surface Waters for Pathogenic Leptospira 
PLoS Medicine  2006;3(8):e308.
Although previous data indicate that the overall incidence of human leptospirosis in the Peruvian Amazon is similar in urban and rural sites, severe leptospirosis has been observed only in the urban context. As a potential explanation for this epidemiological observation, we tested the hypothesis that concentrations of more virulent Leptospira would be higher in urban than in rural environmental surface waters.
Methods and Findings
A quantitative real-time PCR assay was used to compare levels of Leptospira in urban and rural environmental surface waters in sites in the Peruvian Amazon region of Iquitos. Molecular taxonomic analysis of a 1,200-bp segment of the leptospiral 16S ribosomal RNA gene was used to identify Leptospira to the species level. Pathogenic Leptospira species were found only in urban slum water sources (Fisher's exact test; p = 0.013). The concentration of pathogen-related Leptospira was higher in urban than rural water sources (~103 leptospires/ml versus 0.5 × 102 leptospires/ml; F = 8.406, p < 0.05). Identical 16S rRNA gene sequences from Leptospira interrogans serovar Icterohaemorrhagiae were found in urban slum market area gutter water and in human isolates, suggesting a specific mode of transmission from rats to humans. In a prospective, population-based study of patients presenting with acute febrile illness, isolation of L. interrogans-related leptospires from humans was significantly associated with urban acquisition (75% of urban isolates); human isolates of other leptospiral species were associated with rural acquisition (78% of rural isolates) (chi-square analysis; p < 0.01). This distribution of human leptospiral isolates mirrored the distribution of leptospiral 16S ribosomal gene sequences in urban and rural water sources.
Our findings data support the hypothesis that urban severe leptospirosis in the Peruvian Amazon is associated with higher concentrations of more pathogenic leptospires at sites of exposure and transmission. This combined quantitative and molecular taxonomical risk assessment of environmental surface waters is globally applicable for assessing risk for leptospiral infection and severe disease in leptospirosis-endemic regions.
Vinetz and colleagues used a quantitative real time PCR assay combined with molecular taxonomic analysis to quantify Leptospira in environmental surface waters in the Peruvian Amazon region of Iquitos.
Editors' Summary
Humans catch many diseases from animals—so-called zoonotic infections. Often, these occur in limited regions of the world. However, one—leptospirosis—occurs in temperate and tropical climates, and in urban and rural settings, making it the most widespread zoonotic disease. Leptospirosis is caused by Leptospira, a large group of closely related spiral-shaped bacteria that live in both domestic animals (for example, cattle) and wild animals (particularly rats). Millions of humans become infected each year with leptospires through close contact with water, food, or soil contaminated with the urine of infected animals—swimming or wading in contaminated water is particularly hazardous. Some infected people have no symptoms; others develop a flu-like disease that clears up within a few days. However, in 5%–10% of infected people, the disease progresses to a second, sometimes fatal phase. This is usually characterized by jaundice, kidney problems, and an enlarged spleen (it's then called Weil disease) but can also involve the lungs (pulmonary leptospirosis). Leptospirosis can be successfully treated with antibiotics if treatment is started soon after infection.
Why Was This Study Done?
In a recent study in the Peruvian Amazon, half of the people visiting urban hospitals and rural health posts with acute fever had antibodies in their blood to Leptospira, suggesting that they had acute leptospirosis. However, only patients living in urban areas developed pulmonary leptospirosis. In this study, the researchers tested the hypothesis that this pattern arose because more virulent types of Leptospira were present at higher levels in urban environmental surface water than in rural water sources.
What Did the Researchers Do and Find?
Between June 2003 and March 2004, the researchers isolated strains of Leptospira from patients with acute fever who visited a hospital in the town of Iquitos or clinics in nearby villages. Early in 2004, they also collected a large number of different water samples from an urban slum in Iquitos and from a nearby rural community. They measured the concentrations of Leptospira in these samples by using a molecular technique called real-time PCR (polymerase chain reaction) to detect and quantify a type of RNA found only in disease-causing Leptospira. They also identified which specific Leptospira were present in the water samples and the patient samples by sequencing this RNA. The researchers found that leptospires were present in both urban and rural water samples (particularly in samples from gutters and puddles in the urban slum's market area) but that their concentration in the positive water samples from the urban sites was 20 times that in the positive samples from the rural sites. Furthermore, the distribution of different Leptospira types isolated from the patients mirrored that of the bacteria in the local environment. So, one particular type of Leptospira interrogans known as icterohaemorrhagiae—the leptospire most commonly associated with severe leptospirosis in the patients—was found more often in the urban water samples than in the rural ones. Finally, the researchers discovered a new group of Leptospira in the rural environment. This group may contain one or several new species of Leptospira but whether any of them causes human disease is unknown.
What Do These Findings Mean?
These results support the researchers' hypothesis that pulmonary leptospirosis in urban areas of the Peruvian Amazon is associated with high environmental levels of specific disease-causing leptospires. The researchers were able to discover this link only by using molecular techniques—this sort of study is impossible with traditional bacteriological techniques because Leptospira are hard to grow in the laboratory and cannot be isolated efficiently from environmental water sources. Different types can't be identified using a microscope. The researchers' findings need to be validated in other settings, but they suggest that environmental interventions such as reducing sources of standing water and clearing away garbage in urban areas might reduce the number of cases of severe leptospirosis. The distribution of different Leptospira types also suggests that whereas rats may be the main disease reservoir in towns, cattle, pigs, and bats may be more important in rural settings in Peru and presumably elsewhere. Overall, this new information, together with the availability of molecular methods for rapid clinical diagnosis and environmental risk assessment, should aid attempts to control leptospirosis around the world.
Additional Information.
Please access these Web sites via the online version of this summary at
US Centers for Disease Control and Prevention, information for patients and professionals on leptospirosis
The Leptospirosis Information Center, information and advice on human leptospirosis for the public and medical professionals
MedlinePlus encyclopedia entry on leptospirosis
NHS Direct Online, patient information on leptospirosis from the UK National Health Service online encyclopedia
Wikipedia pages on leptospirosis (note: Wikipedia is a free online encyclopedia that anyone can edit)
PMCID: PMC1551915  PMID: 16933963
2.  Serovar Diversity of Pathogenic Leptospira Circulating in the French West Indies 
Leptospirosis is one of the most important neglected tropical bacterial diseases in Latin America and the Caribbean. However, very little is known about the circulating etiological agents of leptospirosis in this region. In this study, we describe the serological and molecular features of leptospires isolated from 104 leptospirosis patients in Guadeloupe (n = 85) and Martinique (n = 19) and six rats captured in Guadeloupe, between 2004 and 2012.
Methods and Findings
Strains were studied by serogrouping, PFGE, MLVA, and sequencing 16SrRNA and secY. DNA extracts from blood samples collected from 36 patients in Martinique were also used for molecular typing of leptospires via PCR. Phylogenetic analyses revealed thirteen different genotypes clustered into five main clades that corresponded to the species: L. interrogans, L. kirschneri, L. borgpetersenii, L. noguchi, and L. santarosai. We also identified L. kmetyi in at least two patients with acute leptospirosis. This is the first time, to our knowledge, that this species has been identified in humans. The most prevalent genotypes were associated with L. interrogans serovars Icterohaemorrhagiae and Copenhageni, L. kirschneri serovar Bogvere, and L. borgpetersenii serovar Arborea. We were unable to identify nine strains at the serovar level and comparison of genotyping results to the MLST database revealed new secY alleles.
The overall serovar distribution in the French West Indies was unique compared to the neighboring islands. Typing of leptospiral isolates also suggested the existence of previously undescribed serovars.
Author Summary
Leptospirosis is an emerging zoonotic disease caused by infection with pathogenic strains of Leptospira. Isolation of Leptospira strains is rare, making it difficult to assess their distribution worldwide. In this study, we characterized cultures of Leptospira obtained from more than one hundred leptospirosis patients from the French West Indies by serology and various molecular typing methods to identify the strains circulating in this endemic region. Typing of leptospiral isolates showed that causative agents of leptospirosis in the French West Indies are mainly from the serogroups Icterohaemorrhagiae and Ballum, but we also identified new genotypes. We also found that the distribution of the predominant pathogenic leptospiral serovars differed between the Caribbean islands. A better understanding of the epidemiology of leptospirosis will improve our knowledge in the distribution of this emerging neglected tropical disease worldwide. The identification of the circulating etiological agents of leptospirosis in the French West Indies will also help establish appropriate control and prevention measures in this area where the disease is endemic.
PMCID: PMC3597474  PMID: 23516654
3.  Epidemiology of Leptospira Transmitted by Rodents in Southeast Asia 
Leptospirosis is the most common bacterial zoonoses and has been identified as an important emerging global public health problem in Southeast Asia. Rodents are important reservoirs for human leptospirosis, but epidemiological data is lacking.
Methodology/Principal Findings
We sampled rodents living in different habitats from seven localities distributed across Southeast Asia (Thailand, Lao PDR and Cambodia), between 2009 to 2010. Human isolates were also obtained from localities close to where rodents were sampled. The prevalence of Leptospira infection was assessed by real-time PCR using DNA extracted from rodent kidneys, targeting the lipL32 gene. Sequencing rrs and secY genes, and Multi Locus Variable-number Tandem Repeat (VNTR) analyses were performed on DNA extracted from rat kidneys for Leptospira isolates molecular typing. Four species were detected in rodents, L. borgpetersenii (56% of positive samples), L. interrogans (36%), L. kirschneri (3%) and L. weilli (2%), which were identical to human isolates. Mean prevalence in rodents was approximately 7%, and largely varied across localities and habitats, but not between rodent species. The two most abundant Leptospira species displayed different habitat requirements: L. interrogans was linked to humid habitats (rice fields and forests) while L. borgpetersenii was abundant in both humid and dry habitats (non-floodable lands).
L. interrogans and L. borgpetersenii species are widely distributed amongst rodent populations, and strain typing confirmed rodents as reservoirs for human leptospirosis. Differences in habitat requirements for L. interrogans and L. borgpetersenii supported differential transmission modes. In Southeast Asia, human infection risk is not only restricted to activities taking place in wetlands and rice fields as is commonly accepted, but should also include tasks such as forestry work, as well as the hunting and preparation of rodents for consumption, which deserve more attention in future epidemiological studies.
Author Summary
Leptospirosis is the most prevalent bacterial zoonosis worldwide. Rodents are believed to be the main reservoirs of Leptospira, yet little epidemiological research has been conducted on rodents from Southeast Asia. Previous studies suggest that activities which place humans in microenvironments shared by rodents increase the probability of contracting leptospirosis. We therefore investigated the circulation of leptospiral species and strains in rodent communities and human populations in seven localities scattered throughout Southeast Asia; in Thailand, Lao PDR and Cambodia. Molecular typing assays were used to characterize leptospiral species and strains in both rodents and humans, which demonstrated common strains between humans and rodents. Additionally, we observed that the two most abundant leptospiral species; L. borgpetersenii and L. interrogans, have different habitat requirements, which supposes different modes of transmission. Lastly, in Southeast Asia, the risk of leptospiral transmission to humans is not solely limited to wetlands and rice paddy fields, but is also linked to forested areas, and activities such as the hunting and/or preparation of rodents for consumption.
PMCID: PMC4046967  PMID: 24901706
4.  Isolation and Characterization of New Leptospira Genotypes from Patients in Mayotte (Indian Ocean) 
Leptospirosis has been implicated as a severe and fatal form of disease in Mayotte, a French-administrated territory located in the Comoros archipelago (southwestern Indian Ocean). To date, Leptospira isolates have never been isolated in this endemic region.
Methods and Findings
Leptospires were isolated from blood samples from 22 patients with febrile illness during a 17-month period after a PCR-based screening test was positive. Strains were typed using hyper-immune antisera raised against the major Leptospira serogroups: 20 of 22 clinical isolates were assigned to serogroup Mini; the other two strains belonged to serogroups Grippotyphosa and Pyrogenes, respectively. These isolates were further characterized using partial sequencing of 16S rRNA and ligB gene, Multi Locus VNTR Analysis (MLVA), and pulsed field gel electrophoresis (PFGE). Of the 22 isolates, 14 were L. borgpetersenii strains, 7 L. kirschneri strains, and 1, belonging to serogoup Pyrogenes, was L. interrogans. Results of the genotyping methods were consistent. MLVA defined five genotypes, whereas PFGE allowed the recognition of additional subgroups within the genotypes. PFGE fingerprint patterns of clinical strains did not match any of the patterns in the reference strains belonging to the same serogroup, suggesting that the strains were novel serovars.
Preliminary PCR screening of blood specimen allowed a high isolation frequency of leptospires among patients with febrile illness. Typing of leptospiral isolates showed that causative agents of leptospirosis in Mayotte have unique molecular features.
Author Summary
Leptospirosis has been recognized as an increasing public health problem affecting poor people from developing countries and tropical regions. However, the epidemiology of leptospirosis remains poorly understood in remote parts of the world. In this study of patients from the island of Mayotte, we isolated 22 strains from the blood of patients during the acute phase of illness. The pathogenic Leptospira strains were characterized by serology and various molecular typing methods. Based on serological data, serogroup Mini appears to be the dominant cause of leptospirosis in Mayotte. Further molecular characterization of these isolates allowed the identification of 10 pathogenic Leptospira genotypes that could correspond to previously unknown serovars. Further progress in our understanding of the epidemiology of Leptospira circulating genotypes in highly endemic regions should contribute to the development of novel strategies for the diagnosis and prevention of this neglected emerging disease.
PMCID: PMC2889827  PMID: 20582311
5.  Sensitive Real-Time PCR Detection of Pathogenic Leptospira spp. and a Comparison of Nucleic Acid Amplification Methods for the Diagnosis of Leptospirosis 
PLoS ONE  2014;9(11):e112356.
Bacteria of the genus Leptospira, the causative agents of leptospirosis, are categorized into pathogenic and non-pathogenic species. However, the benefit of using a clinical diagnostic that is specific for pathogenic species remains unclear. In this study, we present the development of a real-time PCR (rtPCR) for the detection of pathogenic Leptospira (the pathogenic rtPCR), and we perform a comparison of the pathogenic rtPCR with a published assay that detects all Leptospira species [the undifferentiated febrile illness (UFI) assay] and a reference 16S Leptospira rtPCR, which was originally designed to detect pathogenic species.
Methodology/Principal Findings
For the pathogenic rtPCR, a new hydrolysis probe was designed for use with primers from the UFI assay, which targets the 16S gene. The pathogenic rtPCR detected Leptospira DNA in 37/37 cultured isolates from 5 pathogenic and one intermediate species. Two strains of the non-pathogenic L. biflexa produced no signal. Clinical samples from 65 patients with suspected leptospirosis were then tested using the pathogenic rtPCR and a reference Leptospira 16S rtPCR. All 65 samples had tested positive for Leptospira using the UFI assay; 62 (95.4%) samples tested positive using the pathogenic rtPCR (p = 0.24). Only 24 (36.9%) samples tested positive in the reference 16S rtPCR (p<0.0001 for comparison with the pathogenic rtPCR and UFI assays). Amplicon sequencing confirmed the detection of pathogenic Leptospira species in 49/50 cases, including 3 cases that were only detected using the UFI assay.
The pathogenic rtPCR displayed similar sensitivity to the UFI assay when testing clinical specimens with no difference in specificity. Both assays proved significantly more sensitive than a real-time molecular test used for comparison. Future studies are needed to investigate the clinical and epidemiologic significance of more sensitive Leptospira detection using these tests.
PMCID: PMC4224423  PMID: 25379890
6.  A Dominant Clone of Leptospira interrogans Associated with an Outbreak of Human Leptospirosis in Thailand 
A sustained outbreak of leptospirosis occurred in northeast Thailand between 1999 and 2003, the basis for which was unknown.
Methods and Findings
A prospective study was conducted between 2000 and 2005 to identify patients with leptospirosis presenting to Udon Thani Hospital in northeast Thailand, and to isolate the causative organisms from blood. A multilocus sequence typing scheme was developed to genotype these pathogenic Leptospira. Additional typing was performed for Leptospira isolated from human cases in other Thai provinces over the same period, and from rodents captured in the northeast during 2004. Sequence types (STs) were compared with those of Leptospira drawn from a reference collection. Twelve STs were identified among 101 isolates from patients in Udon Thani. One of these (ST34) accounted for 77 (76%) of isolates. ST34 was Leptospira interrogans, serovar Autumnalis. 86% of human Leptospira isolates from Udon Thani corresponded to ST34 in 2000/2001, but this figure fell to 56% by 2005 as the outbreak waned (p = 0.01). ST34 represented 17/24 (71%) of human isolates from other Thai provinces, and 7/8 (88%) rodent isolates. By contrast, 59 STs were found among 76 reference strains, indicating a much more diverse population genetic structure; ST34 was not identified in this collection.
Development of an MLST scheme for Leptospira interrogans revealed that a single ecologically successful pathogenic clone of L. interrogans predominated in the rodent population, and was associated with a sustained outbreak of human leptospirosis in Thailand.
Author Summary
A sustained outbreak of human leptospirosis occurred in northeast Thailand between 1999 and 2003, the basis for which was unknown. Leptospirosis is a potentially serious infection cause by bacteria known as Leptospira; infection usually occurs following environmental exposure to pathogenic Leptospira shed in the urine of an infected animal. The purpose of this study was to obtain bacterial isolates from humans with leptospirosis around the time of the Thai outbreak for genotyping, and to relate these to the maintenance host animal. To achieve this, a bacterial typing scheme (multilocus sequence typing, MLST) was developed for L. interrogans, the major cause of human disease. This approach has the advantage over existing typing schemes in that the data generated are amenable to detailed evolutionary analysis, and are readily comparable via the internet. Our results demonstrated the emergence of a dominant clone of L. interrogans serovar Autumnalis; this was the major cause of human disease during the outbreak, and was found in a maintenance host which was defined as the bandicoot rat.
PMCID: PMC2041815  PMID: 17989782
7.  Human Leptospirosis Caused by a New, Antigenically Unique Leptospira Associated with a Rattus Species Reservoir in the Peruvian Amazon 
As part of a prospective study of leptospirosis and biodiversity of Leptospira in the Peruvian Amazon, a new Leptospira species was isolated from humans with acute febrile illness. Field trapping identified this leptospire in peridomestic rats (Rattus norvegicus, six isolates; R. rattus, two isolates) obtained in urban, peri-urban, and rural areas of the Iquitos region. Novelty of this species was proven by serological typing, 16S ribosomal RNA gene sequencing, pulsed-field gel electrophoresis, and DNA-DNA hybridization analysis. We have named this species “Leptospira licerasiae” serovar Varillal, and have determined that it is phylogenetically related to, but genetically distinct from, other intermediate Leptospira such as L. fainei and L. inadai. The type strain is serovar Varillal strain VAR 010T, which has been deposited into internationally accessible culture collections. By microscopic agglutination test, “Leptospira licerasiae” serovar Varillal was antigenically distinct from all known serogroups of Leptospira except for low level cross-reaction with rabbit anti–L. fainei serovar Hurstbridge at a titer of 1∶100. LipL32, although not detectable by PCR, was detectable in “Leptospira licerasiae” serovar Varillal by both Southern blot hybridization and Western immunoblot, although on immunoblot, the predicted protein was significantly smaller (27 kDa) than that of L. interrogans and L. kirschneri (32 kDa). Isolation was rare from humans (2/45 Leptospira isolates from 881 febrile patients sampled), but high titers of MAT antibodies against “Leptospira licerasiae” serovar Varillal were common (30%) among patients fulfilling serological criteria for acute leptospirosis in the Iquitos region, and uncommon (7%) elsewhere in Peru. This new leptospiral species reflects Amazonian biodiversity and has evolved to become an important cause of leptospirosis in the Peruvian Amazon.
Author Summary
Leptospirosis has emerged as a globally important infectious disease. Its impact on public health is often difficult to determine, sometimes because of low clinical suspicion, or, as is more common, difficulty in laboratory diagnosis. Gold-standard serology-based diagnosis has a number of important limitations, including the need to use live leptospires that have a sufficient diversity of antigens to be able to detect specific anti-leptospiral antibodies; such antigens vary greatly from region to region. In this paper, we report the discovery of a new species of Leptospira in the highly biodiverse region of the Peruvian Amazon, and demonstrate that the animal source of infection for humans is the domestic rat. Detailed biological characterization of this new species shows that it is antigenically unique and represents a new serogroup and serovar, proposed as Leptospira licerasiae serogroup Iquitos serovar Varillal. Incorporation of this new isolate into serological testing of patients presenting with acute febrile illness in Iquitos, Peru, showed a far higher incidence of leptospirosis than previously suspected, showing the important of using region-specific Leptospira in diagnosis. The field-to-laboratory approach presented here has general application to the discovery of other emerging pathogens and their impact on human health.
PMCID: PMC2271056  PMID: 18382606
8.  Accuracy of Loop-Mediated Isothermal Amplification for Diagnosis of Human Leptospirosis in Thailand 
There is a lack of diagnostic tests for leptospirosis in technology-restricted settings. We developed loop-mediated isothermal amplification (LAMP) specific for the 16S ribosomal RNA gene (rrs) of pathogenic and intermediate group Leptospira species. The lower limit of detection was 10 genomic equivalents/reaction, and analytical specificity was high; we observed positive reactions for pathogenic/intermediate groups and negative reactions for non-pathogenic Leptospira species and other bacterial species. We evaluated this assay in Thailand by using a case–control study of 133 patients with laboratory-proven leptospirosis and 133 patients with other febrile illnesses. Using admission blood, we found that the rrs LAMP showed positive results in 58 of 133 cases (diagnostic sensitivity = 43.6, 95% confidence interval [CI] = 35.0–52.5) and in 22 of 133 controls (diagnostic specificity = 83.5, 95% CI = 76.0–89.3). Sensitivity was high for 39 patients who were culture positive for Leptospira spp. (84.6, 95% CI = 69.5–94.1). The rrs LAMP can provide an admission diagnosis in approximately half of patients with leptospirosis, but its clinical utility is reduced by a lower specificity.
PMCID: PMC3062458  PMID: 21460019
9.  Identification of Cell-Binding Adhesins of Leptospira interrogans 
Leptospirosis is a globally distributed bacterial infectious disease caused by pathogenic members of the genus Leptospira. Infection can lead to illness ranging from mild and non-specific to severe, with jaundice, kidney and liver dysfunction, and widespread endothelial damage. The adhesion of pathogenic Leptospira species (spp.), the causative agent of leptospirosis, to host tissue components is necessary for infection and pathogenesis. While it is well-established that extracellular matrix (ECM) components play a role in the interaction of the pathogen with host molecules, we have shown that pathogenic Leptospira interrogans binds to host cells more efficiently than to ECM components. Using in vitro phage display to select for phage clones that bind to EA.hy926 endothelial cells, we identified the putative lipoproteins LIC10508 and LIC13411, and the conserved hypothetical proteins LIC12341 and LIC11574, as candidate L. interrogans sv. Copenhageni st. Fiocruz L1–130 adhesins. Recombinant LIC11574, but not its L. biflexa homologue LBF1629, exhibited dose-dependent binding to both endothelial and epithelial cells. In addition, LIC11574 and LIC13411 bind to VE-cadherin, an endothelial cell receptor for L. interrogans. Extraction of bacteria with the non-ionic detergent Triton X-114 resulted in partitioning of the candidate adhesins to the detergent fraction, a likely indication that these proteins are outer membrane localized. All candidate adhesins were recognized by sera obtained from leptospirosis patients but not by sera from healthy individuals as assessed by western blot. This work has identified bacterial adhesins that are potentially involved in L. interrogans infection of the mammalian host, and through cadherin binding, may contribute to dissemination and vascular damage. Our findings may be of value in leptospirosis control and prevention, with the bacterial adhesins potentially serving as targets for development of diagnostics, therapeutics, and vaccines.
Author Summary
Leptospirosis, caused by pathogenic species of the genus Leptospira, is an infectious disease that has emerged as a globally important health problem. Infection can either lead to mild illness or can progress to a severe disease form manifested by jaundice, kidney and liver dysfunction, and widespread blood vessel damage. It is thought that the ability of the bacteria to recognize and bind to human and animal cells is important for Leptospira spp. to cause the disease. Using phage display, we were able to identify bacterial proteins that mediate the binding of the bacteria to host cells. One of the identified proteins, LIC11574, attaches to different types of host cells, and to VE-cadherin, a cell surface protein previously identified as receptor for disease-causing L. interrogans. All bacterial proteins identified were recognized by sera obtained from leptospirosis patients but not by sera from healthy individuals. Our findings may be of value in leptospirosis control and prevention, with these bacterial surface proteins as new targets for serodiagnosis and vaccine development.
PMCID: PMC4183468  PMID: 25275630
10.  Application of Multilocus Variable-Number Tandem-Repeat Analysis for Molecular Typing of the Agent of Leptospirosis 
Journal of Clinical Microbiology  2006;44(11):3954-3962.
Leptospirosis is a worldwide-distributed zoonosis, endemic in tropical areas. Epidemiologic investigations of leptospirosis still rely on tedious serological identification tests. Recently, molecular typing systems based on variable-number tandem-repeat (VNTR) analysis have been described and have been used to identify Leptospira interrogans strains. Although L. interrogans is the most common Leptospira species encountered in human infections around the world, other pathogenic species, such as Leptospira kirschneri and Leptospira borgpetersenii, are also frequently associated with human leptospirosis. In this study, we aimed to extend multilocus VNTR analysis (MLVA) identification of strains to species other than L. interrogans. We designed primers for VNTR loci found in L. interrogans, L. kirschneri, and L. borgpetersenii. The discriminatory power of the redefined primers was evaluated on collection strains and then on clinical strains. We also carried out a retrospective study on 156 strains isolated from patients and animals from New Caledonia, an area of high endemicity in the South Pacific. Our results show that this simple PCR-based MLVA typing technique is a powerful methodology for the epidemiology of leptospirosis.
PMCID: PMC1698352  PMID: 17088367
11.  Development and Validation of a Real-Time PCR for Detection of Pathogenic Leptospira Species in Clinical Materials 
PLoS ONE  2009;4(9):e7093.
Available serological diagnostics do not allow the confirmation of clinically suspected leptospirosis at the early acute phase of illness. Several conventional and real-time PCRs for the early diagnosis of leptospirosis have been described but these have been incompletely evaluated. We developed a SYBR Green-based real-time PCR targeting secY and validated it according to international guidelines. To determine the analytical specificity, DNA from 56 Leptospira strains belonging to pathogenic, non-pathogenic and intermediate Leptospira spp. as well as 46 other micro-organisms was included in this study. All the pathogenic Leptospira gave a positive reaction. We found no cross-reaction with saprophytic Leptospira and other micro-organisms, implying a high analytical specificity. The analytical sensitivity of the PCR was one copy per reaction from cultured homologous strain M 20 and 1.2 and 1.5 copy for heterologous strains 1342 K and Sarmin, respectively. In spiked serum & blood and kidney tissue the sensitivity was 10 and 20 copies for M 20, 15 and 30 copies for 1342 K and 30 and 50 copies for Sarmin. To determine the diagnostic sensitivity (DSe) and specificity (DSp), clinical blood samples from 26 laboratory-confirmed and 107 negative patients suspected of leptospirosis were enrolled as a prospective consecutive cohort. Based on culture as the gold standard, we found a DSe and DSp of 100% and 93%, respectively. All eight PCR positive samples that had a negative culture seroconverted later on, implying a higher actual DSp. When using culture and serology as the gold standard, the DSe was lower (89%) while the DSp was higher (100%). DSe was 100% in samples collected within the first – for treatment important - 4 days after onset of the illness. Reproducibility and repeatability of the assay, determined by blind testing kidney samples from 20 confirmed positive and 20 negative rodents both appeared 100%. In conclusion we have described for the first time the development of a robust SYBR Green real-time PCR for the detection of pathogenic Leptospira combined with a detailed assessment of its clinical accuracy, thus providing a method for the early diagnosis of leptospirosis with a well-defined satisfactory performance.
PMCID: PMC2740861  PMID: 19763264
12.  Rapid Isolation and Susceptibility Testing of Leptospira spp. Using a New Solid Medium, LVW Agar 
Pathogenic Leptospira spp., the causative agents of leptospirosis, are slow-growing Gram-negative spirochetes. Isolation of Leptospira from clinical samples and testing of antimicrobial susceptibility are difficult and time-consuming. Here, we describe the development of a new solid medium that facilitates more-rapid growth of Leptospira spp. and the use of this medium to evaluate the Etest's performance in determining antimicrobial MICs to drugs in common use for leptospirosis. The medium was developed by evaluating the effects of numerous factors on the growth rate of Leptospira interrogans strain NR-20157. These included the type of base agar, the concentration of rabbit serum (RS), and the concentration and duration of CO2 incubation during the initial period of culture. The highest growth rate of NR-20157 was achieved using a Noble agar base supplemented with 10% RS (named LVW agar), with an initial incubation at 30°C in 5% CO2 for 2 days prior to continuous culture in air at 30°C. These conditions were used to develop the Etest for three species, L. interrogans (NR-20161), L. kirschnerii (NR-20327), and L. borgpetersenii (NR-20151). The MICs were read on day 7 for all samples. The Etest was then performed on 109 isolates of pathogenic Leptospira spp. The MIC90 values for penicillin G, doxycycline, cefotaxime, ceftriaxone, and chloramphenicol were 0.64 units/ml and 0.19, 0.047, 0.5, and 2 μg/ml, respectively. The use of LVW agar, which enables rapid growth, isolation of single colonies, and simple antimicrobial susceptibility testing for Leptospira spp., provides an opportunity for new areas of fundamental and applied research.
PMCID: PMC3535913  PMID: 23114772
13.  Post-translational Modification of LipL32 during Leptospira interrogans Infection 
Leptospirosis, a re-emerging disease of global importance caused by pathogenic Leptospira spp., is considered the world's most widespread zoonotic disease. Rats serve as asymptomatic carriers of pathogenic Leptospira and are critical for disease spread. In such reservoir hosts, leptospires colonize the kidney, are shed in the urine, persist in fresh water and gain access to a new mammalian host through breaches in the skin.
Methodology/Principal Findings
Previous studies have provided evidence for post-translational modification (PTM) of leptospiral proteins. In the current study, we used proteomic analyses to determine the presence of PTMs on the highly abundant leptospiral protein, LipL32, from rat urine-isolated L. interrogans serovar Copenhageni compared to in vitro-grown organisms. We observed either acetylation or tri-methylation of lysine residues within multiple LipL32 peptides, including peptides corresponding to regions of LipL32 previously identified as epitopes. Intriguingly, the PTMs were unique to the LipL32 peptides originating from in vivo relative to in vitro grown leptospires. The identity of each modified lysine residue was confirmed by fragmentation pattern analysis of the peptide mass spectra. A synthetic peptide containing an identified tri-methylated lysine, which corresponds to a previously identified LipL32 epitope, demonstrated significantly reduced immunoreactivity with serum collected from leptospirosis patients compared to the peptide version lacking the tri-methylation. Further, a subset of the identified PTMs are in close proximity to the established calcium-binding and putative collagen-binding sites that have been identified within LipL32.
The exclusive detection of PTMs on lysine residues within LipL32 from in vivo-isolated L. interrogans implies that infection-generated modification of leptospiral proteins may have a biologically relevant function during the course of infection. Although definitive determination of the role of these PTMs must await further investigations, the reduced immune recognition of a modified LipL32 epitope suggests the intriguing possibility that LipL32 modification represents a novel mechanism of immune evasion within Leptospira.
Author Summary
Leptospirosis, caused by pathogenic Leptospira spp., constitutes an increasing global public health threat. Humans are accidental hosts, and acquire the disease primarily from contact with water sources that have been contaminated with urine from infected animals. Rats are asymptomatic carriers of infection and are critical for disease transmission to humans, particularly in urban slum environments. In this study, investigation of Leptospira directly isolated from the urine of infected rats showed acetylation or tri-methylation of the highly abundant leptospiral lipoprotein, LipL32. In comparison, Leptospira grown in culture did not result in any LipL32 lysine modifications. A synthetic peptide derived from LipL32 that incorporated a tri-methylated lysine modification exhibited less reactivity with serum from leptospirosis patients compared to an unmodified version of the peptide, suggesting LipL32 modifications may alter protein recognition by the immune response. This study reports, for the first time, modification of a Leptospira protein during infection, and suggests these modifications may have a functional consequence that contributes to bacterial persistence during infection.
PMCID: PMC4214626  PMID: 25356675
14.  A Single Multilocus Sequence Typing (MLST) Scheme for Seven Pathogenic Leptospira Species 
The available Leptospira multilocus sequence typing (MLST) scheme supported by a MLST website is limited to L. interrogans and L. kirschneri. Our aim was to broaden the utility of this scheme to incorporate a total of seven pathogenic species.
Methodology and Findings
We modified the existing scheme by replacing one of the seven MLST loci (fadD was changed to caiB), as the former gene did not appear to be present in some pathogenic species. Comparison of the original and modified schemes using data for L. interrogans and L. kirschneri demonstrated that the discriminatory power of the two schemes was not significantly different. The modified scheme was used to further characterize 325 isolates (L. alexanderi [n = 5], L. borgpetersenii [n = 34], L. interrogans [n = 222], L. kirschneri [n = 29], L. noguchii [n = 9], L. santarosai [n = 10], and L. weilii [n = 16]). Phylogenetic analysis using concatenated sequences of the 7 loci demonstrated that each species corresponded to a discrete clade, and that no strains were misclassified at the species level. Comparison between genotype and serovar was possible for 254 isolates. Of the 31 sequence types (STs) represented by at least two isolates, 18 STs included isolates assigned to two or three different serovars. Conversely, 14 serovars were identified that contained between 2 to 10 different STs. New observations were made on the global phylogeography of Leptospira spp., and the utility of MLST in making associations between human disease and specific maintenance hosts was demonstrated.
The new MLST scheme, supported by an updated MLST website, allows the characterization and species assignment of isolates of the seven major pathogenic species associated with leptospirosis.
Author Summary
Leptospirosis is a common zoonotic disease worldwide. Genotyping of the causative organisms provides important insights into disease transmission and informs preventive strategies and vaccine development. Multilocus sequence typing (MLST) is the most widespread genotyping methodology for bacterial pathogens, but the Leptospira scheme supported by a public MLST database is currently only applicable to L. interrogans and L. kirschneri. The purpose of this study was to extend the scheme to a total of seven pathogenic Leptospira species. This was achieved through the development of a modified scheme in which one of the seven MLST loci was replaced, together with newly designed primers for the remaining 6 loci. Comparison of the original and modified scheme demonstrated that they were very similar, hence sequence type (ST) assignments were largely carried over to the modified scheme. Phylogenetic trees reconstructed from concatenated sequences of the seven loci of the modified scheme demonstrated perfect classification of isolates into seven pathogenic species, which resided in clearly distinct phylogenetic clusters. Congruence was low between STs and serovars. The MLST scheme was used to gain new insights into the population genetic structure of Leptospira species associated with clinical disease and maintenance hosts in Asia.
PMCID: PMC3554523  PMID: 23359622
15.  Leptospira spp. in Rodents and Shrews in Germany 
Leptospirosis is an acute, febrile disease occurring in humans and animals worldwide. Leptospira spp. are usually transmitted through direct or indirect contact with the urine of infected reservoir animals. Among wildlife species, rodents act as the most important reservoir for both human and animal infection. To gain a better understanding of the occurrence and distribution of pathogenic leptospires in rodent and shrew populations in Germany, kidney specimens of 2973 animals from 11 of the 16 federal states were examined by PCR. Rodent species captured included five murine species (family Muridae), six vole species (family Cricetidae) and six shrew species (family Soricidae). The most abundantly trapped animals were representatives of the rodent species Apodemus flavicollis, Clethrionomys glareolus and Microtus agrestis. Leptospiral DNA was amplified in 10% of all animals originating from eight of the 11 federal states. The highest carrier rate was found in Microtus spp. (13%), followed by Apodemus spp. (11%) and Clethrionomys spp. (6%). The most common Leptospira genomospecies determined by duplex PCR was L. kirschneri, followed by L. interrogans and L. borgpetersenii; all identified by single locus sequence typing (SLST). Representatives of the shrew species were also carriers of Leptospira spp. In 20% of Crocidura spp. and 6% of the Sorex spp. leptospiral DNA was detected. Here, only the pathogenic genomospecies L. kirschneri was identified.
PMCID: PMC4143818  PMID: 25062275
Leptospira spp.; leptospirosis; rodents; shrews; Germany
16.  Pathogenomic Inference of Virulence-Associated Genes in Leptospira interrogans 
Leptospirosis is a globally important, neglected zoonotic infection caused by spirochetes of the genus Leptospira. Since genetic transformation remains technically limited for pathogenic Leptospira, a systems biology pathogenomic approach was used to infer leptospiral virulence genes by whole genome comparison of culture-attenuated Leptospira interrogans serovar Lai with its virulent, isogenic parent. Among the 11 pathogen-specific protein-coding genes in which non-synonymous mutations were found, a putative soluble adenylate cyclase with host cell cAMP-elevating activity, and two members of a previously unstudied ∼15 member paralogous gene family of unknown function were identified. This gene family was also uniquely found in the alpha-proteobacteria Bartonella bacilliformis and Bartonella australis that are geographically restricted to the Andes and Australia, respectively. How the pathogenic Leptospira and these two Bartonella species came to share this expanded gene family remains an evolutionary mystery. In vivo expression analyses demonstrated up-regulation of 10/11 Leptospira genes identified in the attenuation screen, and profound in vivo, tissue-specific up-regulation by members of the paralogous gene family, suggesting a direct role in virulence and host-pathogen interactions. The pathogenomic experimental design here is generalizable as a functional systems biology approach to studying bacterial pathogenesis and virulence and should encourage similar experimental studies of other pathogens.
Author Summary
Leptospirosis is one of the most common diseases transmitted by animals worldwide. It is important because it causes an often lethal febrile illnesses in tropical and subtropical areas associated with poor sanitation and agriculture. Leptospirosis may be epidemic, associated with natural disasters and flooding, or endemic in tropical regions. It is unknown how Leptospira cause disease and why different strains cause different severity of illness. In this study we attenuated (weakened) a highly virulent strain of L. interrogans by culturing it in vitro over several months. Comparison of the whole genome sequence before and after the attenuation process revealed a small set of genes that were mutated, and therefore associated with virulence. We discovered a putative soluble adenylate cyclase with host cell cAMP elevating activity, with implications for immune evasion and a new gene family that is upregulated in vivo during acute hamster infection. Interestingly, both Bartonella bacilliformis and Bartonella australis also have this unique gene family we describe in pathogenic Leptospira. This information aids in our understanding of Leptospira evolution and pathogenesis.
PMCID: PMC3789758  PMID: 24098822
17.  Rapid identification of pathogenic Leptospira species (Leptospira interrogans, L. borgpetersenii, and L. kirschneri) with species-specific DNA probes produced by arbitrarily primed PCR. 
Journal of Clinical Microbiology  1997;35(1):248-253.
Arbitrarily primed PCR (AP-PCR) assays can be used to discriminate between species of Leptospira. Comparative analysis of the fingerprints obtained from representative sets of serovar reference strains of Leptospira interrogans sensu stricto, L. borgpetersenii, and L. kirschneri and the reference strains of the other Leptospira spp. revealed species-specific DNA fragments. These species-specific sequences were reamplified in order to produce digoxigenin-11-dUTP-labeled genomic DNA probes that could be used to identify Leptospira species. Three probes (specific for L. interrogans sensu stricto, L. borgpetersenii, and L. kirschneri) were selected and tested with 72 representative serovar reference strains, all of which had previously been studied by DNA-DNA hybridization. The two techniques were in general agreement, and hybridization with AP-PCR-derived probes was shown to be a useful approach for rapid species determination of leptospires, without the prior need for DNA sequence information. These nonradioactive probes can be used to identify Leptospira species in nonspecialized laboratories, and this should contribute to a better knowledge of the molecular epidemiology of leptospirosis.
PMCID: PMC229548  PMID: 8968917
18.  Isolation and Molecular Characterization of Leptospira interrogans and Leptospira borgpetersenii Isolates from the Urban Rat Populations of Kuala Lumpur, Malaysia 
Rats are considered the principal maintenance hosts of Leptospira. The objectives of this study were isolation and identification of Leptospira serovars circulating among urban rat populations in Kuala Lumpur. Three hundred urban rats (73% Rattus rattus and 27% R. norvegicus) from three different sites were trapped. Twenty cultures were positive for Leptospira using dark-field microscopy. R. rattus was the dominant carrier (70%). Polymerase chain reaction (PCR) confirmed that all isolates were pathogenic Leptospira species. Two Leptospira serogroups, Javanica and Bataviae, were identified using microscopic agglutination test (MAT). Pulsed-field gel electrophoresis (PFGE) identified two serovars in the urban rat populations: L. borgpetersenii serovar Javanica (85%) and L. interrogans serovar Bataviae (15%). We conclude that these two serovars are the major serovars circulating among the urban rat populations in Kuala Lumpur. Despite the low infection rate reported, the high pathogenicity of these serovars raises concern of public health risks caused by rodent transmission of leptospirosis.
PMCID: PMC3617856  PMID: 23358635
19.  Characterization of leptospira isolates from animals and humans: phylogenetic analysis identifies the prevalence of intermediate species in India 
SpringerPlus  2013;2:362.
In this study, 191 culture isolates were recovered from suspected samples of animals and humans in Ellinghausen McCullough Johnson and Harris (EMJH) medium and assessed for its morphological features by dark field microscopy. Extracted DNA from individual culture was subjected to different PCR assays for identification and characterization of leptospira. Out of 99 positive leptospira cultures, 52 pathogenic leptospira isolates were characterized at species level by using partial RNA polymerase β-subunit (rpoB) gene sequences. Phylogenetic analysis of the nucleotide sequences revealed that 30, 8, and 14 isolates belong to L. borgpetersenii / L. interrogans, L. kirschneri, and Leptospira intermediate species, respectively. Based on analysis of 99 leptospira isolates, the prevalent Leptospira species were L. borgpetersenii or L. interrogans (30.30%), L. kirschneri (8%) and Leptospira intermediate species (14.14%) in animals and humans. To the best of authors knowledge, this is the first study to use rpoB gene nucleotide sequence based phylogenetic analysis to identify/detect Leptospira intermediate species (L. wolffii) in animals and humans in India. Hence, the prevalence of this species will surely emphasize the importance of consideration of Leptospira intermediate species and formulate a way for further studies especially in understanding the newly emerging Leptospira in animals and humans and to combat the problem associated with the disease conditions.
PMCID: PMC3736078  PMID: 23961424
Leptospira; Animals; Human; Characterization; Prevalence; Intermediate species
20.  Diagnostic Accuracy of Real-Time PCR Assays Targeting 16S rRNA and lipl32 Genes for Human Leptospirosis in Thailand: A Case-Control Study 
PLoS ONE  2011;6(1):e16236.
Rapid PCR-based tests for the diagnosis of leptospirosis can provide information that contributes towards early patient management, but these have not been adopted in Thailand. Here, we compare the diagnostic sensitivity and specificity of two real-time PCR assays targeting rrs or lipL32 for the diagnosis of leptospirosis in northeast Thailand.
Methods/Principal Findings
A case-control study of 266 patients (133 cases of leptospirosis and 133 controls) was constructed to evaluate the diagnostic sensitivity and specificity (DSe & DSp) of both PCR assays. The median duration of illness prior to admission of cases was 4 days (IQR 2–5 days; range 1–12 days). DSe and DSp were determined using positive culture and/or microscopic agglutination test (MAT) as the gold standard. The DSe was higher for the rrs assay than the lipL32 assay (56%, (95% CI 47–64%) versus 43%, (95% CI 34–52%), p<0.001). No cases were positive for the lipL32 assay alone. There was borderline evidence to suggest that the DSp of the rrs assay was lower than the lipL32 assay (90% (95% CI 83–94%) versus 93%, (95%CI 88–97%), p = 0.06). Nine controls gave positive reactions for both assays and 5 controls gave a positive reaction for the rrs assay alone. The DSe of the rrs and lipL32 assays were high in the subgroup of 39 patients who were culture positive for Leptospira spp. (95% and 87%, respectively, p = 0.25).
Early detection of Leptospira using PCR is possible for more than half of patients presenting with leptospirosis and could contribute to individual patient care.
PMCID: PMC3026019  PMID: 21283633
21.  The OmpL37 Surface-Exposed Protein Is Expressed by Pathogenic Leptospira during Infection and Binds Skin and Vascular Elastin 
Pathogenic Leptospira spp. shed in the urine of reservoir hosts into freshwater can be transmitted to a susceptible host through skin abrasions or mucous membranes causing leptospirosis. The infection process involves the ability of leptospires to adhere to cell surface and extracellular matrix components, a crucial step for dissemination and colonization of host tissues. Therefore, the elucidation of novel mediators of host-pathogen interaction is important in the discovery of virulence factors involved in the pathogenesis of leptospirosis. In this study, we assess the functional roles of transmembrane outer membrane proteins OmpL36 (LIC13166), OmpL37 (LIC12263), and OmpL47 (LIC13050), which we recently identified on the leptospiral surface. We determine the capacity of these proteins to bind to host tissue components by enzyme-linked immunosorbent assay. OmpL37 binds elastin preferentially, exhibiting dose-dependent, saturating binding to human skin (Kd, 104±19 nM) and aortic elastin (Kd, 152±27 nM). It also binds fibrinogen (Kd, 244±15 nM), fibrinogen fragment D (Kd, 132±30 nM), plasma fibronectin (Kd, 359±68 nM), and murine laminin (Kd, 410±81 nM). The binding to human skin elastin by both recombinant OmpL37 and live Leptospira interrogans is specifically enhanced by rabbit antiserum for OmpL37, suggesting the involvement of OmpL37 in leptospiral binding to elastin and also the possibility that host-generated antibodies may promote rather than inhibit the adherence of leptospires to elastin-rich tissues. Further, we demonstrate that OmpL37 is recognized by acute and convalescent leptospirosis patient sera and also by Leptospira-infected hamster sera. Finally, OmpL37 protein is detected in pathogenic Leptospira serovars and not in saprophytic Leptospira. Thus, OmpL37 is a novel elastin-binding protein of pathogenic Leptospira that may be promoting attachment of Leptospira to host tissues.
Author Summary
Leptospirosis is a potentially fatal disease in humans and livestock caused by Leptospira bacteria. Effective antibiotic treatment depends on timely, accurate diagnosis. However, current diagnostic and vaccine options are limited by their specificity for the lipid-sugar coat of leptospires, which varies among 200 serum-reactive groups. We aim to understand how leptospires infect a host, and in turn, to develop broadly effective diagnostic and immunization products. We recently described OmpL37, a new protein on the surface of leptospires. Here, we show it is made by pathogenic strains, suggesting it can be a target for detecting and protecting against a wide range of Leptospira. Moreover, leptospirosis patients and hamsters infected with leptospires make antibodies against OmpL37. Purified OmpL37 binds host proteins, including human elastin, fibrinogen, fibronectin, and mouse laminin. Although other leptospiral proteins bind multiple host proteins, OmpL37 has novel preferential affinity for skin and aorta elastin, suggesting a role in a common route of transmission through abraded skin and exposed blood vessels. Indeed, OmpL37 binding and leptospiral attachment to elastin are both enhanced by OmpL37 antiserum, further implicating a possible role for OmpL37 during infection. Thus, OmpL37 may mediate host attachment and has potential clinical application with a broad range of Leptospira.
PMCID: PMC2935396  PMID: 20844573
22.  Conservation of the S10-spc-α Locus within Otherwise Highly Plastic Genomes Provides Phylogenetic Insight into the Genus Leptospira 
PLoS ONE  2008;3(7):e2752.
S10-spc-α is a 17.5 kb cluster of 32 genes encoding ribosomal proteins. This locus has an unusual composition and organization in Leptospira interrogans. We demonstrate the highly conserved nature of this region among diverse Leptospira and show its utility as a phylogenetically informative region. Comparative analyses were performed by PCR using primer sets covering the whole locus. Correctly sized fragments were obtained by PCR from all L. interrogans strains tested for each primer set indicating that this locus is well conserved in this species. Few differences were detected in amplification profiles between different pathogenic species, indicating that the S10-spc-α locus is conserved among pathogenic Leptospira. In contrast, PCR analysis of this locus using DNA from saprophytic Leptospira species and species with an intermediate pathogenic capacity generated varied results. Sequence alignment of the S10-spc-α locus from two pathogenic species, L. interrogans and L. borgpetersenii, with the corresponding locus from the saprophyte L. biflexa serovar Patoc showed that genetic organization of this locus is well conserved within Leptospira. Multilocus sequence typing (MLST) of four conserved regions resulted in the construction of well-defined phylogenetic trees that help resolve questions about the interrelationships of pathogenic Leptospira. Based on the results of secY sequence analysis, we found that reliable species identification of pathogenic Leptospira is possible by comparative analysis of a 245 bp region commonly used as a target for diagnostic PCR for leptospirosis. Comparative analysis of Leptospira strains revealed that strain H6 previously classified as L. inadai actually belongs to the pathogenic species L. interrogans and that L. meyeri strain ICF phylogenetically co-localized with the pathogenic clusters. These findings demonstrate that the S10-spc-α locus is highly conserved throughout the genus and may be more useful in comparing evolution of the genus than loci studied previously.
PMCID: PMC2481283  PMID: 18648538
23.  Fool's Gold: Why Imperfect Reference Tests Are Undermining the Evaluation of Novel Diagnostics: A Reevaluation of 5 Diagnostic Tests for Leptospirosis 
We hypothesized that the gold standard for diagnosing leptospirosis is imperfect. We used Bayesian latent class models and random-effects meta-analysis to test this hypothesis and to determine the true accuracy of a range of alternative tests for leptospirosis diagnosis.
Background. We observed that some patients with clinical leptospirosis supported by positive results of rapid tests were negative for leptospirosis on the basis of our diagnostic gold standard, which involves isolation of Leptospira species from blood culture and/or a positive result of a microscopic agglutination test (MAT). We hypothesized that our reference standard was imperfect and used statistical modeling to investigate this hypothesis.
Methods. Data for 1652 patients with suspected leptospirosis recruited during three observational studies and one randomized control trial that described the application of culture, MAT, immunofluorescence assay (IFA), lateral flow (LF) and/or PCR targeting the 16S rRNA gene were reevaluated using Bayesian latent class models and random-effects meta-analysis.
Results. The estimated sensitivities of culture alone, MAT alone, and culture plus MAT (for which the result was considered positive if one or both tests had a positive result) were 10.5% (95% credible interval [CrI], 2.7%–27.5%), 49.8% (95% CrI, 37.6%–60.8%), and 55.5% (95% CrI, 42.9%–67.7%), respectively. These low sensitivities were present across all 4 studies. The estimated specificity of MAT alone (and of culture plus MAT) was 98.8% (95% CrI, 92.8%–100.0%). The estimated sensitivities and specificities of PCR (52.7% [95% CrI, 45.2%–60.6%] and 97.2% [95% CrI, 92.0%–99.8%], respectively), lateral flow test (85.6% [95% CrI, 77.5%–93.2%] and 96.2% [95% CrI, 87.7%–99.8%], respectively), and immunofluorescence assay (45.5% [95% CrI, 33.3%–60.9%] and 96.8% [95% CrI, 92.8%–99.8%], respectively) were considerably different from estimates in which culture plus MAT was considered a perfect gold standard test.
Conclusions. Our findings show that culture plus MAT is an imperfect gold standard against which to compare alterative tests for the diagnosis of leptospirosis. Rapid point-of-care tests for this infection would bring an important improvement in patient care, but their future evaluation will require careful consideration of the reference test(s) used and the inclusion of appropriate statistical models.
PMCID: PMC3393707  PMID: 22523263
24.  Diagnosis of Human Leptospirosis by Monoclonal Antibody-Based Antigen Detection in Urine 
Journal of Clinical Microbiology  2002;40(2):480-489.
Hybridomas secreting specific monoclonal antibodies (MAb) to all members of the genus Leptospira (clone LF9) and those that are specific only to the pathogenic species (clones LD5 and LE1) were produced. MAb LF9, which was immunoglobulin G1 (IgG1), reacted to a 38-kDa component of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated whole-cell lysates of all Leptospira spp., while MAb LD5 and MAb LE1, which were IgG1 and IgG2a, respectively, reacted to the 35- to 36-kDa components of all serogroups of the pathogenic species of Leptospira. The MAb LD5 was used in a dot blot-enzyme-linked immunosorbent assay (dot-ELISA) for detecting Leptospira antigen in urine samples serially collected from two groups of patients diagnosed with leptospirosis, i.e., 36 clinically diagnosed patients and 25 Leptospira culture confirmed patients. Their serum samples were tested serologically by IgM Dipstick assay, indirect immunofluorescence assay (IFA), and/or microscopic agglutination test (MAT). Urine samples of 26 patients diagnosed with other illnesses and 120 healthy individuals served as controls. For the first group of patients, who had been ill for an average of 3.4 days before hospitalization, the IgM Dipstick test, IFA, and MAT were positive for 69.4, 70.0, and 85.7% of patients, while the Leptospira antigenuria tested by the MAb-based dot-ELISA was positive for 75.0, 88.9, 97.2, 97.2, and 100% of patients on days 1, 2, 3, 7, and 14 of hospitalization, respectively. All but 1 of 11 patients whose serum samples collected on the first day of hospitalization were IgM seronegative, were positive by urine antigen test on day 1. This is strong evidence that detection of antigen in urine can provide diagnostic information that could be useful in directing early therapeutic intervention. The MAT was positive in 10 of 12 patients (83.3%) of the 25 culture-positive Leptospira patients who had been ill for an average of 5.04 days before hospitalization, and the Leptospira antigen was found in 64.0, 84.0, 96.0, 100, 100, 100, and 100% of the patients' urine samples collected on days 1, 2, 3, 4, 5, 6, and 7 of hospitalization, respectively. Leptospira antigenuria was found in 3 of the 26 patients diagnosed with other illnesses and 1 of the 120 healthy controls. The reasons for this positivity are discussed. The detection of antigen in urine by the monoclonal antibody-based dot-ELISA has high potential for rapid, sensitive, and specific diagnosis of leptospirosis at a low cost.
PMCID: PMC153370  PMID: 11825960
25.  Direct Detection and Differentiation of Pathogenic Leptospira Species Using a Multi-Gene Targeted Real Time PCR Approach 
PLoS ONE  2014;9(11):e112312.
Leptospirosis is a growing public and veterinary health concern caused by pathogenic species of Leptospira. Rapid and reliable laboratory tests for the direct detection of leptospiral infections in animals are in high demand not only to improve diagnosis but also for understanding the epidemiology of the disease. In this work we describe a novel and simple TaqMan-based multi-gene targeted real-time PCR approach able to detect and differentiate Leptospira interrogans, L. kirschneri, L. borgpeteresenii and L. noguchii, which constitute the veterinary most relevant pathogenic species of Leptospira. The method uses sets of species-specific probes, and respective flanking primers, designed from ompL1 and secY gene sequences. To monitor the presence of inhibitors, a duplex amplification assay targeting both the mammal β-actin and the leptospiral lipL32 genes was implemented. The analytical sensitivity of all primer and probe sets was estimated to be <10 genome equivalents (GE) in the reaction mixture. Application of the amplification reactions on genomic DNA from a variety of pathogenic and non-pathogenic Leptospira strains and other non-related bacteria revealed a 100% analytical specificity. Additionally, pathogenic leptospires were successfully detected in five out of 29 tissue samples from animals (Mus spp., Rattus spp., Dolichotis patagonum and Sus domesticus). Two samples were infected with L. borgpetersenii, two with L. interrogans and one with L. kirschneri. The possibility to detect and identify these pathogenic agents to the species level in domestic and wildlife animals reinforces the diagnostic information and will enhance our understanding of the epidemiology of leptopirosis.
PMCID: PMC4232388  PMID: 25398140

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