Leptospirosis has been reported in rural areas of Brazil. However, there is limited information about the exposure risk or the risk of Leptospira infection for rural-based populations. A cross-sectional study was carried out in order to determine the prevalence and risk factors for prior Leptospira infection in a rural subsistence farming region of the state of Rio Grande do Norte, an area in which outbreaks of leptospirosis have occurred. Among 290 individuals enrolled, 44 (15.2%) had anti-Leptospira IgM antibodies as determined by IgM ELISA. Infection tended to occur with activities related to the rice fields (P = 0.08). Our findings indicate that Leptospira infection occurs even in years of low rainfall, and may have an important impact among poor rural-based subsistence farmers in Brazil. Additional studies are needed to characterize the mode of transmission in this region.
Leptospirosis; Disease outbreaks; Surveillance; Prevalence; Rural population; Brazil
To identify prediction factors for the development of leptospirosis-associated pulmonary hemorrhage syndrome (LPHS).
The study comprised of 203 patients, aged ≥14 years, admitted with complications of the severe form of leptospirosis at the Emílio Ribas Institute of Infectology (Sao Paulo, Brazil) between 1998 to 2004. Laboratory and demographic data were obtained and the severity of illness score and involvement of the lungs and others organs were determined. Logistic regression was performed to identify independent predictors of LPHS. A validation cohort of 97 subjects with severe form of leptospirosis admitted at the same hospital between 2004-2006 was used to independently evaluate the predictive value of the model.
The overall mortality rate was 7.9%. Multivariate logistic regression revealed that five factors were independently associated with the development of LPHS: serum potassium (mmol/L) (OR=2.6; 95%CI=1.1-5.9); serum creatinine (μmol/L) (OR=1.2; 95%CI=1.1-1.4); respiratory rate (breaths/min) (OR=1.1; 95%CI=1.1-1.2); presenting shock (OR=69.9; 95%CI=20.1-236.4), and Glasgow Coma Scale Score (GCS)<15 (OR=7.7; 95%CI = 1.3-23.0). We used these findings to calculate the risk of LPHS by the use of a spreadsheet. In the validation cohort, the equation classified correctly 92% of patients (Kappa statistic = 0.80).
We developed and validated a multivariate model for predicting LPHS. This tool should prove useful in identifying LPHS patients, allowing earlier management and thereby reducing mortality.
Leptospirosis; Leptospirosis-associated pulmonary hemorrhage syndrome; ROC curve; Predictive model; Brazil
Leptospirosis disproportionately affects residents of urban slums. To understand the knowledge, attitudes, and practices regarding leptospirosis, we conducted a cross-sectional study among residents of an urban slum community in Salvador, Brazil. Of the 257 residents who were interviewed, 225 (90%) were aware of leptospirosis and more than two-thirds of respondents correctly identified the modes of disease transmission and ways to reduce exposure. However, study participants who performed risk activities such as cleaning open sewers had limited access to protective clothing such as boots (33%) or gloves (35%). Almost all respondents performed at least one activity to prevent household rat infestation, which often included use of an illegal poison. Our findings support the need for interventions targeted at the individual and household levels to reduce risk of leptospirosis until large-scale structural interventions are available to residents of urban slum communities.
Naturally acquired acute leptospirosis in monkeys is uncommon. This study reports an outbreak of severe leptospirosis among 52 capuchin (Cebus) monkeys that had been rescued from homes and housed in a wildlife rehabilitation center in Colombia in 2007. Case confirmation consisted of Leptospira isolation followed by a polymerase chain reaction targeting the LipL32 gene. The attack and mortality rates were 71% and 27%, respectively. Sixteen cases were confirmed. Necropsy revealed diffuse jaundice and pulmonary hemorrhage. Multi-locus sequence typing identified the agent to be Leptospira interrogans sequence type 17, indicating rats as the source of infection. An environmental survey confirmed rodent infestation as the cause of the outbreak. The extent of Leptospira transmission between humans and monkeys is unknown. Improper husbandry of non-human primates could create new reservoirs and transmission routes for Leptospira threatening conservation efforts and public health.
Leptospirosis; Cebus; Capuchin monkey; Outbreak; Rat
The expansion of urban slums is a key challenge for public and social policy in the 21st century. The heterogeneous and dynamic nature of slum communities limits the use of rigid slum definitions. A systematic and flexible approach to characterize, delineate and model urban slum structure at an operational resolution is essential to plan, deploy, and monitor interventions at the local and national level.
We modeled the multi-dimensional structure of urban slums in the city of Salvador, a city of 3 million inhabitants in Brazil, by integrating census-derived socioeconomic variables and remotely-sensed land cover variables. We assessed the correlation between the two sets of variables using canonical correlation analysis, identified land cover proxies for the socioeconomic variables, and produced an integrated map of deprivation in Salvador at 30 m × 30 m resolution.
The canonical analysis identified three significant ordination axes that described the structure of Salvador census tracts according to land cover and socioeconomic features. The first canonical axis captured a gradient from crowded, low-income communities with corrugated roof housing to higher-income communities. The second canonical axis discriminated among socioeconomic variables characterizing the most marginalized census tracts, those without access to sanitation or piped water. The third canonical axis accounted for the least amount of variation, but discriminated between high-income areas with white-painted or tiled roofs from lower-income areas.
Our approach captures the socioeconomic and land cover heterogeneity within and between slum settlements and identifies the most marginalized communities in a large, complex urban setting. These findings indicate that changes in the canonical scores for slum areas can be used to track their evolution and to monitor the impact of development programs such as slum upgrading.
Brucellosis is a re-emerging zoonosis with new cases reported each year in many Latin American countries, but it is mostly under-recognized. This study presents a serological investigation of infection with Brucella abortus and Brucella canis in a poor urban community in the city of Salvador, Brazil.
Human sera (n = 180) were randomly selected from 3,171 samples taken from healthy individuals during 2003-2004 and tested with C-ELISA for B. abortus and I-ELISA for B. canis.
Thirteen percent (24/180) of the individuals were positive for B. abortus and 4.6 % (8/174) were positive for B. canis. Among the variables studied only age (older than 45 years) appeared to be a risk factor for the detection of Brucella antibodies.
These results indicate the presence of Brucella infection in this settlement and highlight the need to understand the epidemiology of infection under these circumstances to establish the necessary measures for surveillance and control.
serology; Brucella abortus; Brucella canis; zoonosis; urban slum
The role of the immune response in influencing leptospirosis clinical outcomes is not yet well understood. We hypothesized that acute-phase serum cytokine responses may play a role in disease progression, risk for death, and severe pulmonary hemorrhage syndrome (SPHS).
We performed a case-control study design to compare cytokine profiles in patients with mild and severe forms of leptospirosis. Among patients hospitalized with severe disease, we compared those with fatal and nonfatal outcomes. During active outpatient and hospital-based surveillance we prospectively enrolled 172 patients, 23 with mild disease (outpatient) and 149 with severe leptospirosis (hospitalized). Circulating concentrations of pro- and anti-inflammatory cytokines at the time of patient presentation were measured using a multiplex bead array assay. Concentrations of IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-17A, and TNF-α were significantly higher (P<0.05) in severe disease compared to mild disease. Among severe patients, levels of IL-6 (P<0.001), IL-8 (P = 0.0049) and IL-10 (P<0.001), were higher in fatal compared to non-fatal cases. High levels of IL-6 and IL-10 were independently associated (P<0.05) with case fatality after adjustment for age and days of symptoms. IL-6 levels were higher (P = 0.0519) among fatal cases who developed SPHS than among who did not.
This study shows that severe cases of leptospirosis are differentiated from mild disease by a “cytokine storm” process, and that IL-6 and IL-10 may play an immunopathogenic role in the development of life-threatening outcomes in human leptospirosis.
Leptospirosis is a tropical bacterial disease that is transmitted to humans from infected animals. Leptospirosis symptoms can range from mild fever to fatal disease forms, such as massive bleeding into the lungs, called Severe Pulmonary Hemorrhage Syndrome (SPHS). It is not known what determines the severity of leptospirosis, but we hypothesized that it may be influenced by differences in the type and concentration of signaling proteins called cytokines that are produced by the immune system in response to infection. We collected blood from patients with mild and severe leptospirosis, and compared the concentration of eight different cytokines circulating in the blood. We found that patients with severe leptospirosis had higher levels of most cytokines. Among patients who had severe forms, higher levels of specific cytokines called IL-6 and IL-8 were predictive of death even after statistical adjustment for age and number of days of symptoms prior to hospitalization. IL-6 was higher in patients who died from SPHS compared to those who died of other leptospirosis complications. This knowledge suggests that severe forms of leptospirosis may be due to a specific kind of immune response, which may lead to targeted therapies to reduce the impact of this disease.
Leptospirosis is a zoonotic disease which has emerged as a major cause of morbidity and mortality among impoverished populations. One centenary after the discovery of the causative spirochaetal agent, little is understood of Leptospira pathogenesis, which in turn has hampered the identification of new intervention strategies to address this neglected disease. However the recent availability of complete genome sequences for Leptospira and discovery of genetic tools to transform the pathogen has led to major insights into the biology and pathogenesis of this pathogen. We discuss the life cycle of the bacterium and the new advances that have been made and their implications for the future prevention of this disease.
This study describes the serotype distribution and antibiotic resistance patterns among 397 S. pneumoniae meningitis case isolates recovered in Salvador, Brazil, during the period of 2000-2007, before introduction of the 10-valent pneumococcal conjugate vaccine.
The active hospital-based surveillance showed a decline in the annual incidence rates of pneumococcal meningitis during the period of study, from 1.12 cases to 0.83 cases/100,000 persons for all age groups (P <0.001), with an overall case-fatality rate of 28.6 % (113 of 395) for all patients and 41.9% (57 of 136) for those <5 years of age. Serotypes 14 (n= 55; 13.9%), 3 (n= 32; 8.1 %), 23F (n=32; 8.1 %), 19F (n=31; 7.8%), 6B (n=30; 7.6%), 18C (n=28; 7.1 %), and 6A (n=20; 5%) were the most prevalent serotypes. In patients < 5 years the estimated projected coverage of 7-, 10- and 13-valent conjugate vaccines was 74.3%, 75.7% and 83.1%, respectively. Antimicrobial susceptibility testing revealed that 22.1% (n=88) of isolates were non-susceptible to penicillin, 56% were non-susceptible to trimethoprim/sulfamethoxazole, and 29.6% were non-susceptible to tetracycline. Nonsusceptibility to penicillin and cefotaxime was detected solely among serotype 14 isolates (n=4; 1%). This study provides an important baseline to assess the impact of conjugate vaccine implantation on the epidemiology of meningitis due to Streptococcus pneumoniae in Salvador, Brazil.
Streptococcus pneumoniae; Vaccine; Antimicrobial resistance; Meningitis; Children
Following introduction of Haemophilus influenzae type b (Hib) conjugate vaccines, meningitis caused by serotypes other than Hib has gained importance. We conducted active hospital-based surveillance for meningitis over an 11-year period in Salvador, Brazil. H. influenzae isolates were serotyped and analyzed by PCR, pulsed-field gel electrophoresis and DNA sequencing to identify strains with a specific deletion (IS1016) in the bexA gene (IS1016-bexA). We identified 43 meningitis cases caused by non-type b H. influenzae: 28 (65%) were caused by type a (Hia), 9 (21%) by non-capsulated strains and 3 (7%) each by types e and f. Hia isolates clustered in two clonal groups; clonal group A strains (n=9) had the IS1016-bexA deletion. Among children <5 years, meningitis caused by Hia from clonal group A had higher case-fatality than clonal group B. Despite small numbers, these results indicate that the presence of IS1016-bexA deletion is associated with enhanced virulence in non-type b H. influenzae.
Haemophilus influenzae; non-type b H. influenzae; meningitis; Hib conjugate vaccine; virulence; IS1016-bexA deletion; molecular epidemiology
In comparison to other bacterial pathogens, our knowledge of the molecular basis of the pathogenesis of leptospirosis is extremely limited. An improved understanding of leptospiral pathogenetic mechanisms requires reliable tools for functional genetic analysis. Leptospiral immunoglobulin-like (Lig) proteins are surface proteins found in pathogenic Leptospira, but not in saprophytes. Here, we describe a system for heterologous expression of the Leptospira interrogans genes ligA and ligB in the saprophyte Leptospira biflexa serovar Patoc.
The genes encoding LigA and LigB under the control of a constitutive spirochaetal promoter were inserted into the L. biflexa replicative plasmid. We were able to demonstrate expression and surface localization of LigA and LigB in L. biflexa. We found that the expression of the lig genes significantly enhanced the ability of transformed L. biflexa to adhere in vitro to extracellular matrix components and cultured cells, suggesting the involvement of Lig proteins in cell adhesion.
This work reports a complete description of the system we have developed for heterologous expression of pathogen-specific proteins in the saprophytic L. biflexa. We show that expression of LigA and LigB proteins from the pathogen confers a virulence-associated phenotype on L. biflexa, namely adhesion to eukaryotic cells and fibronectin in vitro. This study indicates that L. biflexa can serve as a surrogate host to characterize the role of key virulence factors of the causative agent of leptospirosis.
In Brazil, Brazilian spotted fever was once considered the only tick-borne rickettsial disease. We report eschar-associated rickettsial disease that occurred after a tick bite. The etiologic agent is most related to Rickettsia parkeri, R. africae, and R. sibirica and probably widely distributed from São Paulo to Bahia in the Atlantic Forest.
Spotted fever group rickettsiosis; rickettsia; eschar; multiple-locus sequence analysis; ticks; molecular diagnosis; dispatch
The purpose of this study was to perform a 16S sequence-based quality control of two Leptospira strain collections. 16S rRNA gene sequencing was used to verify two Leptospira reference collections provided by the World Health Organization and maintained at a reference laboratory for leptospirosis in Brazil. Among the 89 serovars evaluated, four conflicting strains were identified in one of the collections. Although 16S rRNA gene sequencing cannot identify Leptospira beyond the species level, it is suitable for the identification of contamination and quality control of leptospiral reference collections. This study highlights the importance of the availability of high-quality 16S rRNA sequences in public databases. In addition, it emphasizes the need for periodical verifications and quality control of Leptospira reference collections.
Leptospirosis is a widespread zoonotic infection that primarily affects residents of tropical regions, but causes infections in animals and humans in temperate regions as well. The agents of leptospirosis comprise several members of the genus Leptospira, which also includes non-pathogenic, saprophytic species. Leptospirosis can vary in severity from a mild, non-specific illness to severe disease that includes multi-organ failure and widespread endothelial damage and hemorrhage. To begin to investigate how pathogenic leptospires affect endothelial cells, we compared the responses of two endothelial cell lines to infection by pathogenic versus non-pathogenic leptospires. Microarray analyses suggested that pathogenic L. interrogans and non-pathogenic L. biflexa triggered changes in expression of genes whose products are involved in cellular architecture and interactions with the matrix, but that the changes were in opposite directions, with infection by L. biflexa primarily predicted to increase or maintain cell layer integrity, while L. interrogans lead primarily to changes predicted to disrupt cell layer integrity. Neither bacterial strain caused necrosis or apoptosis of the cells even after prolonged incubation. The pathogenic L. interrogans, however, did result in significant disruption of endothelial cell layers as assessed by microscopy and the ability of the bacteria to cross the cell layers. This disruption of endothelial layer integrity was abrogated by addition of the endothelial protective drug lisinopril at physiologically relevant concentrations. These results suggest that, through adhesion of L. interrogans to endothelial cells, the bacteria may disrupt endothelial barrier function, promoting dissemination of the bacteria and contributing to severe disease manifestations. In addition, supplementing antibiotic therapy with lisinopril or derivatives with endothelial protective activities may decrease the severity of leptospirosis.
Leptospirosis is a widespread zoonotic infection that primarily affects residents of tropical regions, but is seen occasionally in temperate regions as well. Leptospirosis can vary in severity from a mild, non-specific illness to severe disease that includes multi-organ failure and widespread endothelial damage and hemorrhage. To investigate how pathogenic leptospires affect endothelial cells, we compared the responses of two endothelial cell lines to infection by pathogenic versus non-pathogenic leptospires. Our analyses suggested that pathogenic L. interrogans and non-pathogenic L. biflexa caused changes in expression of genes whose products are involved in cellular architecture and interactions with the matrix, but that the changes were in opposite directions, with infection by L. biflexa primarily maintaining cell layer integrity, while L. interrogans disrupted cell layers. In fact, L. interrogans caused significant disruption of endothelial cell layers, but this damage could be abrogated by the endothelial protective drug lisinopril. Our results suggest that L. interrogans binds to endothelial cells and disrupts endothelial barrier function, which may promote dissemination of the bacteria and contribute to severe disease manifestations. This disruption may be slowed by endothelial-protective drugs to decrease damage in leptospirosis.
In determining the efficacy of new vaccine candidates for leptospirosis, the primary end point is death and an important secondary end point is sterilizing immunity. However, evaluation of this end point is often hampered by the time-consuming demands and complexity of methods such as culture isolation (CI). In this study, we evaluated the use of an imprint (or touch preparation) method (IM) in detecting the presence of leptospires in tissues of hamsters infected with Leptospira interrogans serovar Copenhageni. In a dissemination study, compared to CI, the IM led to equal or improved detection of leptospires in kidney, liver, lung and blood samples collected post-infection and overall concordance was good (κ=0.61). Furthermore, in an evaluation of hamsters immunized with a recombinant leptospiral protein-based vaccine candidate and subsequently challenged, the agreement between the CI and IM was very good (κ=0.84). These findings indicate that the IM is a rapid method for the direct observation of Leptospira spp. that can be readily applied to evaluating infection in experimental animals and determining sterilizing immunity when screening potential vaccine candidates.
The newly described Streptococcus pneumoniae serotype 6C accounted for 2.3% (16/709) of meningitis cases and 3.2% (3/95) of nasopharyngeal isolates from healthy individuals in Brazil. The strains were multidrug resistant (18.8%) and genetically diverse. Despite low serotype 6C prevalence, continuous surveillance is necessary to guide vaccine strategies.
Streptococcus pneumoniae; serotype 6C; epidemiology; meningitis; carriage
The family of leptospiral immunoglobulin-like (lig) genes comprises ligA, ligB and ligC. This study used PCR to demonstrate the presence of lig genes among serovars from a collection of leptospiral strains and clinical isolates. Whilst ligA and ligC appeared to be present in a limited number of pathogenic serovars, the ligB gene was distributed ubiquitously among all pathogenic strains. None of the lig genes were detected among intermediate or saprophytic Leptospira species. It was also shown that, similar to the previously characterized secY gene, a short specific PCR fragment of ligB could be used to correctly identify pathogenic Leptospira species. These findings demonstrate that ligB is widely present among pathogenic strains and may be useful for their reliable identification and classification.
Recent serologic, immunoprotection, and pathogenesis studies identified the Lig proteins as key virulence determinants in interactions of leptospiral pathogens with the mammalian host. We examined the sequence variation and recombination patterns of ligA, ligB, and ligC among 10 pathogenic strains from five Leptospira species. All strains were found to have intact ligB genes and genetic drift accounting for most of the ligB genetic diversity observed. The ligA gene was found exclusively in L. interrogans and L. kirschneri strains, and was created from ligB by a two-step partial gene duplication process. The aminoterminal domain of LigB and the LigA paralog were essentially identical (98.5 ± 0.8% mean identity) in strains with both genes. Like ligB, ligC gene variation also followed phylogenetic patterns, suggesting an early gene duplication event. However, ligC is a pseudogene in several strains, suggesting that LigC is not essential for virulence. Two ligB genes and one ligC gene had mosaic compositions and evidence for recombination events between related Leptospira species was also found for some ligA genes. In conclusion, the results presented here indicate that Lig diversity has important ramifications for the selection of Lig polypeptides for use in diagnosis and as vaccine candidates. This sequence information will aid the identification of highly conserved regions within the Lig proteins and improve upon the performance characteristics of the Lig proteins in diagnostic assays and in subunit vaccine formulations with the potential to confer heterologous protection.
Leptospirosis; Lig; Pathogenesis; Molecular evolution; Sequence analysis
A survey was conducted to identify reservoirs for urban leptospirosis in the city of Salvador, Brazil. Sampling protocols were performed in the vicinity of households of severe leptospirosis cases identified during active hospital-based surveillance. Among a total of 142 captured Rattus norvegicus (Norwegian brown rat), 80.3% had a positive culture isolate from urine or kidney specimens and 68.1% had a positive serum sample by microscopic agglutination test (MAT) titre of ≥1:100. Monoclonal antibody-based typing of isolates identified that the agent carried by rats was L. interrogans serovar Copenhageni, which was the same serovar isolated from patients during hospital-based surveillance. Leptospira spp. were not isolated from 8 captured Didelphis marsupialis (Opossum), while 5/7 had a positive MAT titre against a saprophytic serogroup. R. rattus were not captured during the survey. The study findings indicate that the brown rat is a major rodent reservoir for leptospirosis in this urban setting. Furthermore, the high carriage rates of L. interrogans serovar Copenhageni in captured rats suggest that there is a significant degree of environmental contamination with this agent in the household environment of high risk areas, which in turn is a cause of transmission during urban epidemics.
Leptospira; Leptospirosis; Rats; Poverty Areas
Leptospira interrogans is responsible for leptospirosis, a zoonosis of worldwide distribution. LipL32 is the major outer membrane protein of pathogenic leptospires, accounting for up to 75% of total outer membrane protein. In recent times LipL32 has become the focus of intense study because of its surface location, dominance in the host immune response, and conservation among pathogenic species. In this study, an lipL32 mutant was constructed in L. interrogans using transposon mutagenesis. The lipL32 mutant had normal morphology and growth rate compared to the wild type and was equally adherent to extracellular matrix. Protein composition of the cell membranes was found to be largely unaffected by the loss of LipL32, with no obvious compensatory increase in other proteins. Microarray studies found no obvious stress response or upregulation of genes that may compensate for the loss of LipL32 but did suggest an association between LipL32 and the synthesis of heme and vitamin B12. When hamsters were inoculated by systemic and mucosal routes, the mutant caused acute severe disease manifestations that were indistinguishable from wild-type L. interrogans infection. In the rat model of chronic infection, the LipL32 mutant colonized the renal tubules as efficiently as the wild-type strain. In conclusion, this study showed that LipL32 does not play a role in either the acute or chronic models of infection. Considering the abundance and conservation of LipL32 among all pathogenic Leptospira spp. and its absence in saprophytic Leptospira, this finding is remarkable. The role of this protein in leptospiral biology and pathogenesis thus remains elusive.
Inhabitants of slum settlements represent a significant proportion of the population at risk for pneumococcal disease in developing countries.
We conducted a household survey of pneumococcal carriage among residents of a slum community in the city of Salvador, Brazil.
Among 262 subjects, 95 (36%) were colonized with S. pneumoniae. Children <5 years of age (OR, 8.0; 95%CI, 3.5-18.6) and those who attended schools (OR 2.7, 95%CI, 1.2-6.0) had significantly higher risk of being colonized. Of 94 isolates obtained from colonized individuals, 51% had serotypes included in the seven-valent pneumococcal conjugate vaccine. Overall, 10% (9 of 94 isolates) were nonsusceptible to penicillin and 28% (27 of 94 isolates) were resistant to cotrimoxazole. BOX-PCR, PFGE and MLST analysis found that 44% of the carriage isolates belonged to 14 distinct clonal groups. Strains of the same clonal group were isolated from multiple members of 9 out of the 39 study households. Nineteen carriage isolates had genotypes that were the same as those identified among 362 strains obtained from active surveillance for meningitis.
The study's findings indicate that there is significant intra and inter-household spread of S. pneumoniae in the slum community setting. However, a limited number of clones encountered during carriage among slum residents were found to cause invasive disease.
Streptococcus pneumoniae; nasopharyngeal carriage; pneumococcal conjugate vaccines; antibiotic resistance; urban slums
Leptospira interrogans is the most common cause of leptospirosis in humans and animals. Genetic analysis of L. interrogans has been severely hindered by a lack of tools for genetic manipulation. Recently we developed the mariner-based transposon Himar1 to generate the first defined mutants in L. interrogans. In this study, a total of 929 independent transposon mutants were obtained and the location of insertion determined. Of these mutants, 721 were located in the protein coding regions of 551 different genes. While sequence analysis of transposon insertion sites indicated that transposition occurred in an essentially random fashion in the genome, 25 unique transposon mutants were found to exhibit insertions into genes encoding 16S or 23S rRNAs, suggesting these genes are insertional hot spots in the L. interrogans genome. In contrast, loci containing notionally essential genes involved in lipopolysaccharide and heme biosynthesis showed few transposon insertions. The effect of gene disruption on the virulence of a selected set of defined mutants was investigated using the hamster model of leptospirosis. Two attenuated mutants with disruptions in hypothetical genes were identified, thus validating the use of transposon mutagenesis for the identification of novel virulence factors in L. interrogans. This library provides a valuable resource for the study of gene function in L. interrogans. Combined with the genome sequences of L. interrogans, this provides an opportunity to investigate genes that contribute to pathogenesis and will provide a better understanding of the biology of L. interrogans.