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1.  Epidemiology of Isoniazid Resistance Mutations and Their Effect on Tuberculosis Treatment Outcomes 
Isoniazid resistance is highly prevalent in Vietnam. We investigated the molecular and epidemiological characteristics and the association with first-line treatment outcomes of the main isoniazid resistance mutations in Mycobacterium tuberculosis in codon 315 of the katG and in the promoter region of the inhA gene. Mycobacterium tuberculosis strains with phenotypic resistance to isoniazid from consecutively diagnosed smear-positive tuberculosis patients in rural Vietnam were subjected to Genotype MTBDRplus testing to identify katG and inhA mutations. Treatment failure and relapse were determined by sputum culture. In total, 227 of 251 isoniazid-resistant strains (90.4%) had detectable mutations: 75.3% in katG codon 315 (katG315) and 28.2% in the inhA promoter region. katG315 mutations were significantly associated with pretreatment resistance to streptomycin, rifampin, and ethambutol but not with the Beijing genotype and predicted both unfavorable treatment outcome (treatment failure or death) and relapse; inhA promoter region mutations were only associated with resistance to streptomycin and relapse. In tuberculosis patients, M. tuberculosis katG315 mutations but not inhA mutations are associated with unfavorable treatment outcome. inhA mutations do, however, increase the risk of relapse, at least with treatment regimens that contain only isoniazid and ethambutol in the continuation phase.
doi:10.1128/AAC.00077-13
PMCID: PMC3719713  PMID: 23689727
2.  Comparative Study of IS6110 Restriction Fragment Length Polymorphism and Variable-Number Tandem-Repeat Typing of Mycobacterium tuberculosis Isolates in the Netherlands, Based on a 5-Year Nationwide Survey 
Journal of Clinical Microbiology  2013;51(4):1193-1198.
In order to switch from IS6110 and polymorphic GC-rich repetitive sequence (PGRS) restriction fragment length polymorphism (RFLP) to 24-locus variable-number tandem-repeat (VNTR) typing of Mycobacterium tuberculosis complex isolates in the national tuberculosis control program in The Netherlands, a detailed evaluation on discriminatory power and agreement with findings in a cluster investigation was performed on 3,975 tuberculosis cases during the period of 2004 to 2008. The level of discrimination of the two typing methods did not differ substantially: RFLP typing yielded 2,733 distinct patterns compared to 2,607 in VNTR typing. The global concordance, defined as isolates labeled unique or identically distributed in clusters by both methods, amounted to 78.5% (n = 3,123). Of the remaining 855 cases, 12% (n = 479) of the cases were clustered only by VNTR, 7.7% (n = 305) only by RFLP typing, and 1.8% (n = 71) revealed different cluster compositions in the two approaches. A cluster investigation was performed for 87% (n = 1,462) of the cases clustered by RFLP. For the 740 cases with confirmed or presumed epidemiological links, 92% were concordant with VNTR typing. In contrast, only 64% of the 722 cases without an epidemiological link but clustered by RFLP typing were also clustered by VNTR typing. We conclude that VNTR typing has a discriminatory power equal to IS6110 RFLP typing but is in better agreement with findings in a cluster investigation performed on an RFLP-clustering-based cluster investigation. Both aspects make VNTR typing a suitable method for tuberculosis surveillance systems.
doi:10.1128/JCM.03061-12
PMCID: PMC3666783  PMID: 23363841
3.  Inferring patient to patient transmission of Mycobacterium tuberculosis from whole genome sequencing data 
BMC Infectious Diseases  2013;13:110.
Background
Mycobacterium tuberculosis is characterised by limited genomic diversity, which makes the application of whole genome sequencing particularly attractive for clinical and epidemiological investigation. However, in order to confidently infer transmission events, an accurate knowledge of the rate of change in the genome over relevant timescales is required.
Methods
We attempted to estimate a molecular clock by sequencing 199 isolates from epidemiologically linked tuberculosis cases, collected in the Netherlands spanning almost 16 years.
Results
Multiple analyses support an average mutation rate of ~0.3 SNPs per genome per year. However, all analyses revealed a very high degree of variation around this mean, making the confirmation of links proposed by epidemiology, and inference of novel links, difficult. Despite this, in some cases, the phylogenetic context of other strains provided evidence supporting the confident exclusion of previously inferred epidemiological links.
Conclusions
This in-depth analysis of the molecular clock revealed that it is slow and variable over short time scales, which limits its usefulness in transmission studies. However, the superior resolution of whole genome sequencing can provide the phylogenetic context to allow the confident exclusion of possible transmission events previously inferred via traditional DNA fingerprinting techniques and epidemiological cluster investigation. Despite the slow generation of variation even at the whole genome level we conclude that the investigation of tuberculosis transmission will benefit greatly from routine whole genome sequencing.
doi:10.1186/1471-2334-13-110
PMCID: PMC3599118  PMID: 23446317
Mycobacterium tuberculosis; Molecular clock; Whole genome sequencing; Transmission; Epidemiology
4.  Clustering of Beijing genotype Mycobacterium tuberculosis isolates from the Mekong delta in Vietnam on the basis of variable number of tandem repeat versus restriction fragment length polymorphism typing 
Background
In comparison to restriction fragment length polymorphism (RFLP) typing, variable number of tandem repeat (VNTR) typing is easier to perform, faster and yields results in a simple, numerical format. Therefore, this technique has gained recognition as the new international gold standard in typing of Mycobacterium tuberculosis. However, some reports indicated that VNTR typing may be less suitable for Beijing genotype isolates. We therefore compared the performance of internationally standardized RFLP and 24 loci VNTR typing to discriminate among 100 Beijing genotype isolates from the Southern Vietnam.
Methods
Hundred Beijing genotype strains defined by spoligotyping were randomly selected and typed by RFLP and VNTR typing. The discriminatory power of VNTR and RFLP typing was compared using the Bionumerics software.
Results
Among 95 Beijing strains available for analysis, 14 clusters were identified comprising 34 strains and 61 unique profiles in 24 loci VNTR typing ((Hunter Gaston Discrimination Index (HGDI = 0.994)). 13 clusters containing 31 strains and 64 unique patterns in RFLP typing (HGDI = 0.994) were found. Nine RFLP clusters were subdivided by VNTR typing and 12 VNTR clusters were split by RFLP. Five isolates (5%) revealing double alleles or no signal in two or more loci in VNTR typing could not be analyzed.
Conclusions
Overall, 24 loci VNTR typing and RFLP typing had similar high-level of discrimination among 95 Beijing strains from Southern Vietnam. However, loci VNTR 154, VNTR 2461 and VNTR 3171 had hardly added any value to the level of discrimination.
doi:10.1186/1471-2334-13-63
PMCID: PMC3568002  PMID: 23375050
5.  Mixed Tuberculosis Infections in Rural South Vietnam 
Journal of Clinical Microbiology  2012;50(5):1586-1592.
Tuberculosis patients may be infected with or have disease caused by more than one Mycobacterium tuberculosis strain, usually referred to as “mixed infections.” These have mainly been observed in settings with a very high tuberculosis incidence and/or high HIV prevalence. We assessed the rate of mixed infections in a population-based study in rural Vietnam, where the prevalences of both HIV and tuberculosis are substantially lower than those in previous studies looking at mixed infections. In total, 1,248 M. tuberculosis isolates from the same number of patients were subjected to IS6110 restriction fragment length polymorphism (RFLP) typing, spoligotyping, and variable-number-tandem-repeat (VNTR) typing. We compared mixed infections identified by the presence of (i) discrepant RFLP and spoligotype patterns in isolates from the same patient and (ii) double alleles at ≥2 loci by VNTR typing and assessed epidemiological characteristics of these infections. RFLP/spoligotyping and VNTR typing identified 39 (3.1%) and 60 (4.8%) mixed infections, respectively (Cohen's kappa statistic, 0.57). The number of loci with double alleles in the VNTR pattern was strongly associated with the proportion of isolates with mixed infections according to RFLP/spoligotyping (P < 0.001). Mixed infections occurred more frequently in newly treated than in previously treated patients, were significantly associated with minor X-ray abnormalities, and were almost significantly associated with lower sputum smear grades. Although the infection pressure in our study area is lower than that in previously studied populations, mixed M. tuberculosis infections do occur in rural South Vietnam in at least 3.1% of cases.
doi:10.1128/JCM.00434-12
PMCID: PMC3347091  PMID: 22378903
7.  First Worldwide Proficiency Study on Variable-Number Tandem-Repeat Typing of Mycobacterium tuberculosis Complex Strains 
Journal of Clinical Microbiology  2012;50(3):662-669.
Although variable-number tandem-repeat (VNTR) typing has gained recognition as the new standard for the DNA fingerprinting of Mycobacterium tuberculosis complex (MTBC) isolates, external quality control programs have not yet been developed. Therefore, we organized the first multicenter proficiency study on 24-locus VNTR typing. Sets of 30 DNAs of MTBC strains, including 10 duplicate DNA samples, were distributed among 37 participating laboratories in 30 different countries worldwide. Twenty-four laboratories used an in-house-adapted method with fragment sizing by gel electrophoresis or an automated DNA analyzer, nine laboratories used a commercially available kit, and four laboratories used other methods. The intra- and interlaboratory reproducibilities of VNTR typing varied from 0% to 100%, with averages of 72% and 60%, respectively. Twenty of the 37 laboratories failed to amplify particular VNTR loci; if these missing results were ignored, the number of laboratories with 100% interlaboratory reproducibility increased from 1 to 5. The average interlaboratory reproducibility of VNTR typing using a commercial kit was better (88%) than that of in-house-adapted methods using a DNA analyzer (70%) or gel electrophoresis (50%). Eleven laboratories using in-house-adapted manual typing or automated typing scored inter- and intralaboratory reproducibilities of 80% or higher, which suggests that these approaches can be used in a reliable way. In conclusion, this first multicenter study has documented the worldwide quality of VNTR typing of MTBC strains and highlights the importance of international quality control to improve genotyping in the future.
doi:10.1128/JCM.00607-11
PMCID: PMC3295139  PMID: 22170917
8.  Increased Transmission of Mycobacterium tuberculosis Beijing Genotype Strains Associated with Resistance to Streptomycin: A Population-Based Study 
PLoS ONE  2012;7(8):e42323.
Background
Studies have shown that the Mycobacterium tuberculosis Beijing genotype is an emerging pathogen that is frequently associated with drug resistance. This suggests that drug resistant Beijing strains have a relatively high transmission fitness compared to other drug-resistant strains.
Methods and Findings
We studied the relative transmission fitness of the Beijing genotype in relation to anti-tuberculosis drug resistance in a population-based study of smear-positive tuberculosis patients prospectively recruited and studied over a 4-year period in rural Vietnam. Transmission fitness was analyzed by clustering of cases on basis of three DNA typing methods. Of 2531 included patients, 2207 (87%) were eligible for analysis of whom 936 (42%) were in a DNA fingerprint cluster. The clustering rate varied by genotype with 292/786 (37%) for the Beijing genotype, 527/802 (67%) for the East-African Indian (EAI) genotype, and 117/619 (19%) for other genotypes. Clustering was associated with the EAI compared to the Beijing genotype (adjusted odds ratio (ORadj) 3.4: 95% CI 2.8–4.4). Patients infected with streptomycin-resistant strains were less frequently clustered than patients infected with streptomycin-susceptible strains when these were of the EAI genotype (ORadj 0.6, 95% CI 0.4–0.9), while this pattern was reversed for strains of the Beijing genotype (ORadj 1.3, 95% CI 1.0–1.8, p for difference 0.002). The strong association between Beijing and MDR-TB (ORadj 7.2; 95% CI 4.2–12.3) existed only if streptomycin resistance was present.
Conclusions
Beijing genotype strains showed less overall transmissibility than EAI strains, but when comparisons were made within genotypes, Beijing strains showed increased transmission fitness when streptomycin-resistant, while the reverse was observed for EAI strains. The association between MDR-TB and Beijing genotype in this population was strongly dependent on resistance to streptomycin. Streptomycin resistance may provide Beijing strains with a fitness advantage over other genotypes and predispose to multidrug resistance in patients infected with Beijing strains.
doi:10.1371/journal.pone.0042323
PMCID: PMC3418256  PMID: 22912700
9.  Rapid Test for Identification of a Highly Transmissible Mycobacterium tuberculosis Beijing Strain of Sub-Saharan Origin 
Journal of Clinical Microbiology  2012;50(2):516-518.
The development of a rapid test to identify Mycobacterium tuberculosis Beijing isolates and specifically strain GC1237, coming from a sub-Saharan country, is needed due to its alarming wide spread on Gran Canaria Island (Spain). A rapid test that detects IS6110 present between dnaA and dnaN in the Beijing strains and in a specific site for GC1237 (Rv2180c) has been developed. This test would be a useful tool in the surveillance of subsequent cases.
doi:10.1128/JCM.06314-11
PMCID: PMC3264144  PMID: 22116140
10.  Epidemiology of tuberculosis in WHO European Region and public health response 
European Spine Journal  2012;22(Suppl 4):549-555.
Purpose
To provide an overview of the tuberculosis (TB) and multi-drug resistant tuberculosis (MDR-TB) in the WHO European Region and evolution of public health response with focus on extra-pulmonary tuberculosis and Pott’s disease.
Methods
Authors reviewed regional strategic documents related to TB. The epidemiologic data were reviewed and analyzed.
Results
In the absence of associated pulmonary TB, Pott’s disease is reported as extra-pulmonary TB (up to 47 % of all TB cases in some settings). Due to limitations of the surveillance system, the epidemiology of Pott’s disease and its treatment success are unknown. The Stop TB Strategy and Consolidated Action Plan to Prevent and Combat M/XDR-TB provide comprehensive roadmaps to address all types of TB.
Conclusions
There is a need to further analyze country data to document the extent of Pott’s disease and develop specific guidelines for timely diagnosis and treatment of Pott’s disease.
doi:10.1007/s00586-012-2339-3
PMCID: PMC3691406  PMID: 22565803
Pott’s disease; Extra-pulmonary tuberculosis; Multi-drug resistant tuberculosis; European Region; Action Plan
11.  Drug Susceptibility of Mycobacterium tuberculosis Beijing Genotype and Association with MDR TB 
Emerging Infectious Diseases  2012;18(4):660-663.
To determine differences in the ability of Mycobacterium tuberculosis strains to withstand antituberculosis drug treatment, we compared the activity of antituberculosis drugs against susceptible Beijing and East-African/Indian genotype M. tuberculosis strains. Beijing genotype strains showed high rates of mutation within a wide range of drug concentrations, possibly explaining this genotype’s association with multidrug-resistant tuberculosis.
doi:10.3201/eid1804.110912
PMCID: PMC3309663  PMID: 22469099
multidrug-resistant tuberculosis; MDR TB; Beijing genotype strains; antituberculosis drugs; emergence; resistance; antimicrobial resistances; Mycobacterium tuberculosis; tuberculosis and other mycobacteria
12.  Pre-Existing Isoniazid Resistance, but Not the Genotype of Mycobacterium Tuberculosis Drives Rifampicin Resistance Codon Preference in Vitro 
PLoS ONE  2012;7(1):e29108.
Both the probability of a mutation occurring and the ability of the mutant to persist will influence the distribution of mutants that arise in a population. We studied the interaction of these factors for the in vitro selection of rifampicin (RIF)-resistant mutants of Mycobacterium tuberculosis. We characterised two series of spontaneous RIF-resistant in vitro mutants from isoniazid (INH)-sensitive and -resistant laboratory strains and clinical isolates, representing various M. tuberculosis genotypes. The first series were selected from multiple parallel 1 ml cultures and the second from single 10 ml cultures. RIF-resistant mutants were screened by Multiplex Ligation-dependent Probe Amplification (MLPA) or by sequencing the rpoB gene. For all strains the mutation rate for RIF resistance was determined with a fluctuation assay. The most striking observation was a shift towards rpoB-S531L (TCG→TTG) mutations in a panel of laboratory-generated INH-resistant mutants selected from the 10-ml cultures (p<0.001). All tested strains showed similar mutation rates (1.33×10−8 to 2.49×10−7) except one of the laboratory-generated INH mutants with a mutation rate measured at 5.71×10−7, more than 10 times higher than that of the INH susceptible parental strain (5.46–7.44×10−8). No significant, systematic difference in the spectrum of rpoB-mutations between strains of different genotypes was observed. The dramatic shift towards rpoB-S531L in our INH-resistant laboratory mutants suggests that the relative fitness of resistant mutants can dramatically impact the distribution of (subsequent) mutations that accumulate in a M. tuberculosis population, at least in vitro. We conclude that, against specific genetic backgrounds, certain resistance mutations are particularly likely to spread. Molecular screening for these (combinations of) mutations in clinical isolates could rapidly identify these particular pathogenic strains. We therefore recommend that isolates are screened for the distribution of resistance mutations, especially in regions that are highly endemic for (multi)drug resistant tuberculosis.
doi:10.1371/journal.pone.0029108
PMCID: PMC3250395  PMID: 22235262
13.  Investigation on Mycobacterium tuberculosis Diversity in China and the Origin of the Beijing Clade 
PLoS ONE  2011;6(12):e29190.
Background
Investigation of the genetic diversity of Mycobacterium tuberculosis in China has shown that Beijing genotype strains play a dominant role in the tuberculosis (TB) epidemic. In order to examine the strain diversity in the whole country, and to study the evolutionary development of Beijing strains, we sought to genotype a large collection of isolates using different methods.
Methodology/Principal Findings
We applied a 15-loci VNTR typing analysis on 1,586 isolates from the Beijing municipality and 12 Chinese provinces or autonomous regions. The data was compared to that of 900 isolates from various other worldwide geographic regions outside of China. A total of 1,162/1,586 (73.2%) of the isolates, distributed into 472 VNTR types, were found to belong to the Beijing genotype family and this represented 56 to 94% of the isolates in each of the localizations. VNTR typing revealed that the majority of the non-Beijing isolates fall into two genotype families, which represented 17% of the total number of isolates, and seem largely restricted to China. A small number of East African Indian genotype strains was also observed in this collection. Ancient Beijing strains with an intact region of difference (RD) 181, as well as strains presumably resembling ancestors of the whole Beijing genotype family, were mainly found in the Guangxi autonomous region.
Conclusions/Significance
This is the largest M. tuberculosis VNTR-based genotyping study performed in China to date. The high percentage of Beijing isolates in the whole country and the presence in the South of strains representing early branching points may be an indication that the Beijing lineage originated from China, probably in the Guangxi region. Two modern lineages are shown here to represent the majority of non-Beijing Chinese isolates. The observed geographic distribution of the different lineages within China suggests that natural frontiers are major factors in their diffusion.
doi:10.1371/journal.pone.0029190
PMCID: PMC3248407  PMID: 22220207
14.  SNP/RD Typing of Mycobacterium tuberculosis Beijing Strains Reveals Local and Worldwide Disseminated Clonal Complexes 
PLoS ONE  2011;6(12):e28365.
The Beijing strain is one of the most successful genotypes of Mycobacterium tuberculosis worldwide and appears to be highly homogenous according to existing genotyping methods. To type Beijing strains reliably we developed a robust typing scheme using single nucleotide polymorphisms (SNPs) and regions of difference (RDs) derived from whole-genome sequencing data of eight Beijing strains. SNP/RD typing of 259 M. tuberculosis isolates originating from 45 countries worldwide discriminated 27 clonal complexes within the Beijing genotype family. A total of 16 Beijing clonal complexes contained more than one isolate of known origin, of which two clonal complexes were strongly associated with South African origin. The remaining 14 clonal complexes encompassed isolates from different countries. Even highly resolved clonal complexes comprised isolates from distinct geographical sites. Our results suggest that Beijing strains spread globally on multiple occasions and that the tuberculosis epidemic caused by the Beijing genotype is at least partially driven by modern migration patterns. The SNPs and RDs presented in this study will facilitate future molecular epidemiological and phylogenetic studies on Beijing strains.
doi:10.1371/journal.pone.0028365
PMCID: PMC3230589  PMID: 22162765
15.  Preferential Deletion Events in the Direct Repeat Locus of Mycobacterium tuberculosis▿ 
Journal of Clinical Microbiology  2011;49(4):1318-1322.
The “Harlingen” IS6110 restriction fragment length polymorphism (RFLP) cluster has linked over 100 tuberculosis cases in The Netherlands since 1993. Four Mycobacterium tuberculosis isolates that were epidemiologically linked to this cluster had different spoligotype patterns, as well as slightly divergent IS6110 profiles, compared to the majority of the isolates. Sequencing of the direct repeat (DR) locus revealed sequence polymorphisms at the putative deletion sites. These deletion footprints provided evidence for independent deletions of the central region of the DR locus in three isolates, while the different genotype of the fourth isolate was explained by transmission. Our finding suggests that convergent deletions in the DR locus occur frequently. However, deletion footprints are not suitable to detect convergent deletions in the DR because they seem to be exceptional. Deletion footprints in the DR were not described previously, and we did not observe them in any public M. tuberculosis complex sequences. We conclude that preferential deletions in the DR loci of closely related strains are usually an unnoted event that interferes with clustering of closely related strains.
doi:10.1128/JCM.01848-10
PMCID: PMC3122804  PMID: 21325559
16.  African 2, a Clonal Complex of Mycobacterium bovis Epidemiologically Important in East Africa▿ †  
Journal of Bacteriology  2010;193(3):670-678.
We have identified a clonal complex of Mycobacterium bovis isolated at high frequency from cattle in Uganda, Burundi, Tanzania, and Ethiopia. We have named this related group of M. bovis strains the African 2 (Af2) clonal complex of M. bovis. Af2 strains are defined by a specific chromosomal deletion (RDAf2) and can be identified by the absence of spacers 3 to 7 in their spoligotype patterns. Deletion analysis of M. bovis isolates from Algeria, Mali, Chad, Nigeria, Cameroon, South Africa, and Mozambique did not identify any strains of the Af2 clonal complex, suggesting that this clonal complex of M. bovis is localized in East Africa. The specific spoligotype pattern of the Af2 clonal complex was rarely identified among isolates from outside Africa, and the few isolates that were found and tested were intact at the RDAf2 locus. We conclude that the Af2 clonal complex is localized to cattle in East Africa. We found that strains of the Af2 clonal complex of M. bovis have, in general, four or more copies of the insertion sequence IS6110, in contrast to the majority of M. bovis strains isolated from cattle, which are thought to carry only one or a few copies.
doi:10.1128/JB.00750-10
PMCID: PMC3021238  PMID: 21097608
17.  A Multi-Country Non-Inferiority Cluster Randomized Trial of Frontloaded Smear Microscopy for the Diagnosis of Pulmonary Tuberculosis 
PLoS Medicine  2011;8(7):e1000443.
Luis Cuevas and colleagues report findings from a multicenter diagnostic clinical trial in tuberculosis, showing that the sensitivity and specificity of a “front-loaded” diagnostic scheme is not inferior to that of a standard diagnostic scheme.
Background
More than 50 million people around the world are investigated for tuberculosis using sputum smear microscopy annually. This process requires repeated visits and patients often drop out.
Methods and Findings
This clinical trial of adults with cough ≥2 wk duration (in Ethiopia, Nepal, Nigeria, and Yemen) compared the sensitivity/specificity of two sputum samples collected “on the spot” during the first visit plus one sputum sample collected the following morning (spot-spot-morning [SSM]) versus the standard spot-morning-spot (SMS) scheme. Analyses were per protocol analysis (PPA) and intention to treat (ITT). A sub-analysis compared just the first two smears of each scheme, spot-spot and spot-morning.
In total, 6,627 patients (3,052 SSM/3,575 SMS) were enrolled; 6,466 had culture and 1,526 were culture-positive. The sensitivity of SSM (ITT, 70.2%, 95% CI 66.5%–73.9%) was non-inferior to the sensitivity of SMS (PPA, 65.9%, 95% CI 62.3%–69.5%). Similarly, the specificity of SSM (ITT, 96.9%, 95% CI 93.2%–99.9%) was non-inferior to the specificity of SMS (ITT, 97.6%, 95% CI 94.0%–99.9%). The sensitivity of spot-spot (ITT, 63.6%, 95% CI 59.7%–67.5%) was also non-inferior to spot-morning (ITT, 64.8%, 95% CI 61.3%–68.3%), as the difference was within the selected −5% non-inferiority limit (difference ITT = 1.4%, 95% CI −3.7% to 6.6%). Patients screened using the SSM scheme were more likely to provide the first two specimens than patients screened with the SMS scheme (98% versus 94.2%, p<0.01). The PPA and ITT analysis resulted in similar results.
Conclusions
The sensitivity and specificity of SSM are non-inferior to those of SMS, with a higher proportion of patients submitting specimens. The scheme identifies most smear-positive patients on the first day of consultation.
Trial Registration
Current Controlled Trials ISRCTN53339491
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Every year, nearly 10 million people develop tuberculosis—a contagious bacterial infection that usually affects the lungs (pulmonary tuberculosis)—and about 1.7 million people die from the disease. Mycobacterium tuberculosis, which causes tuberculosis, is spread in airborne droplets when people with the disease cough or sneeze. Thus, to control tuberculosis, it is essential that infected individuals are rapidly identified and treated. The “gold standard” diagnostic test for tuberculosis is mycobacterial culture, in which laboratory staff try to grow M. tuberculosis from sputum (mucus brought up from the lungs by coughing). However, although this test is sensitive (it detects most patients with tuberculosis) and has a high specificity (a low rate of false-positive results), it is too slow to produce results and too complex for routine use in the low- and middle-income countries where tuberculosis mainly occurs. In these countries, patients are usually investigated using direct sputum smear microscopy, a cheaper but less sensitive test in which multiple sputum samples treated with the acid-fast Ziehl-Neelsen stain are examined for the presence of M. tuberculosis bacilli.
Why Was This Study Done?
In most national tuberculosis control programs, patients provide an “on the spot” specimen during their initial consultation, a specimen collected at home the next morning, and another on-the-spot specimen when they bring their morning specimen to the clinic (a “spot-morning-spot,” or SMS, collection scheme). Unfortunately, patients often fail to return with their morning sample. Furthermore, the examination of three samples strains the limited laboratory resources of developing countries. Based on several recent reviews, the World Health Organization recently recommended that only two samples need be examined, a policy change that reduces the laboratory workload but does not avoid the problems of collecting a morning sample and patient drop-out during the diagnostic process. In this non-inferiority, cluster randomized trial, the researchers compare the sensitivity and specificity of a spot-spot-morning (SSM; two on-the-spot specimens collected during the first clinic visit an hour apart, and a third specimen collected at home the next morning) scheme for tuberculosis diagnosis with those of the standard SMS scheme. A non-inferiority trial investigates whether an intervention is not worse than a control intervention; a cluster randomized trial randomly assigns groups of patients rather than individual patients to the test and control interventions.
What Did the Researchers Do and Find?
The researchers enrolled 6,627 patients in Ethiopia, Nepal, Nigeria, and Yemen who had had a cough for more than two weeks (a characteristic symptom of tuberculosis). A quarter of the patients had culture-positive tuberculosis. The centers participating in the study were randomly assigned each week for a year to use either the SMS or the SSM sample collection scheme. Compared to mycobacterial culture, the sensitivities of the SSM and SMS schemes were 70.2% and 65.9%, respectively, which indicates that the new scheme was non-inferior to the SMS scheme. Similarly, the specificity of SSM (96.9%) was non-inferior to that of SMS (97.6%). Importantly, the sensitivity of diagnosis using just the first two samples collected in the SSM scheme was also non-inferior to the sensitivity of diagnosis using the first two samples collected in the SMS scheme (63.6% versus 64.8%; the researchers defined non-inferiority of SSM as a difference in its sensitivity compared to that of SMS of less than −5%). Finally, patients tested using the SSM scheme were more likely to provide the first two samples than patients tested using the SMS scheme (98% versus 94.2%).
What Do These Findings Mean?
These findings suggest that a sputum collection scheme in which two samples are collected one hour apart followed by a morning specimen could identify as many smear-positive patients as the standard SMS scheme. Importantly, they also indicate that examination of the first two specimens alone identifies most smear-positive patients independently of which scheme is used. These findings suggest that the SSM scheme might be more suitable for tuberculosis diagnosis than the SMS scheme in locations where patients are likely to drop out of the diagnosis process (for example, in low- and middle-income countries, where patients often live a long way from clinics). However, for an SSM scheme to work effectively, an on-site laboratory with a same-day turn-around service will be essential, and tuberculosis clinics will need to minimize contact between patients waiting to provide their second on-the-spot specimen.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000443.
A related PLoS Medicine Research Article by Cuevas et al. uses LED fluorescence microscopy for the diagnosis of pulmonary tuberculosis
The World Health Organization provides information on all aspects of tuberculosis, including information on tuberculosis diagnostics and on the recommendation to reduce the number of smears for diagnosis to two; the Stop TB Partnership provides information on global tuberculosis control (some information in several languages)
The US Centers for Disease Control and Prevention has information about tuberculosis, including information on the diagnosis of tuberculosis disease
The US National Institute of Allergy and Infectious Diseases also has detailed information on all aspects of tuberculosis
MedlinePlus has links to further information about tuberculosis (in English and Spanish)
A new Web site dedicated to the discussion and optimization of smear microscopy has recently been launched
doi:10.1371/journal.pmed.1000443
PMCID: PMC3134460  PMID: 21765808
18.  The use of microbead-based spoligotyping for Mycobacterium tuberculosis complex to evaluate the quality of the conventional method: Providing guidelines for Quality Assurance when working on membranes 
BMC Infectious Diseases  2011;11:110.
Background
The classical spoligotyping technique, relying on membrane reverse line-blot hybridization of the spacers of the Mycobacterium tuberculosis CRISPR locus, is used world-wide (598 references in Pubmed on April 8th, 2011). However, until now no inter-laboratory quality control study had been undertaken to validate this technique. We analyzed the quality of membrane-based spoligotyping by comparing it to the recently introduced and highly robust microbead-based spoligotyping. Nine hundred and twenty-seven isolates were analyzed totaling 39,861 data points. Samples were received from 11 international laboratories with a worldwide distribution.
Methods
The high-throughput microbead-based Spoligotyping was performed on CTAB and thermolyzate DNA extracted from isolated Mycobacterium tuberculosis complex (MTC) strains coming from the genotyping participating centers. Information regarding how the classical Spoligotyping method was performed by center was available. Genotype discriminatory analyses were carried out by comparing the spoligotypes obtained by both methods. The non parametric U-Mann Whitney homogeneity test and the Spearman rank correlation test were performed to validate the observed results.
Results
Seven out of the 11 laboratories (63 %), perfectly typed more than 90% of isolates, 3 scored between 80-90% and a single center was under 80% reaching 51% concordance only. However, this was mainly due to discordance in a single spacer, likely having a non-functional probe on the membrane used. The centers using thermolyzate DNA performed as well as centers using the more extended CTAB extraction procedure. Few centers shared the same problematic spacers and these problematic spacers were scattered over the whole CRISPR locus (Mostly spacers 15, 14, 18, 37, 39, 40).
Conclusions
We confirm that classical spoligotyping is a robust method with generally a high reliability in most centers. The applied DNA extraction procedure (CTAB or thermolyzate) did not affect the results in this study. However performance was center-dependent, suggesting that training is a key component in quality assurance of spoligotyping. Overall, no particular spacer yielded a higher degree of deviating results, suggesting that errors occur randomly either in the process of re-using membranes, or during the reading of the results and transferring of data from the film to a digital file. Last, the performance of the microbead-based method was excellent as previously shown by Cowan et al. (J. Clin. Microbiol. 2004) and Zhang et al. (J. Med. Microbiol. 2009) and demonstrated the proper detection of spacer 15 that is known to occasionally give weak signals in the classical spoligotyping.
doi:10.1186/1471-2334-11-110
PMCID: PMC3107175  PMID: 21527037
19.  High-Resolution Typing by Integration of Genome Sequencing Data in a Large Tuberculosis Cluster▿  
Journal of Clinical Microbiology  2010;48(9):3403-3406.
To investigate whether genome sequencing yields more useful markers than those currently used to study the epidemiology of tuberculosis, it was applied to three Mycobacterium tuberculosis isolates of the Harlingen outbreak. Our findings suggest that single nucleotide polymorphisms can be used to identify transmission chains in restriction fragment length polymorphism clusters.
doi:10.1128/JCM.00370-10
PMCID: PMC2937716  PMID: 20592143
20.  Phylogeny of Mycobacterium tuberculosis Beijing Strains Constructed from Polymorphisms in Genes Involved in DNA Replication, Recombination and Repair 
PLoS ONE  2011;6(1):e16020.
Background
The Beijing family is a successful group of M. tuberculosis strains, often associated with drug resistance and widely distributed throughout the world. Polymorphic genetic markers have been used to type particular M. tuberculosis strains. We recently identified a group of polymorphic DNA repair replication and recombination (3R) genes. It was shown that evolution of M. tuberculosis complex strains can be studied using 3R SNPs and a high-resolution tool for strain discrimination was developed. Here we investigated the genetic diversity and propose a phylogeny for Beijing strains by analyzing polymorphisms in 3R genes.
Methodology/Principal Findings
A group of 3R genes was sequenced in a collection of Beijing strains from different geographic origins. Sequence analysis and comparison with the ones of non-Beijing strains identified several SNPs. These SNPs were used to type a larger collection of Beijing strains and allowed identification of 26 different sequence types for which a phylogeny was constructed. Phylogenetic relationships established by sequence types were in agreement with evolutionary pathways suggested by other genetic markers, such as Large Sequence Polymorphisms (LSPs). A recent Beijing genotype (Bmyc10), which included 60% of strains from distinct parts of the world, appeared to be predominant.
Conclusions/Significance
We found SNPs in 3R genes associated with the Beijing family, which enabled discrimination of different groups and the proposal of a phylogeny. The Beijing family can be divided into different groups characterized by particular genetic polymorphisms that may reflect pathogenic features. These SNPs are new, potential genetic markers that may contribute to better understand the success of the Beijing family.
doi:10.1371/journal.pone.0016020
PMCID: PMC3024326  PMID: 21283803
21.  Human T cell epitopes of Mycobacterium tuberculosis are evolutionarily hyperconserved 
Nature genetics  2010;42(6):498-503.
Mycobacterium tuberculosis is an obligate human pathogen capable of persisting in individual hosts for decades. To determine whether antigenic variation and immune escape contribute to the success of M. tuberculosis, we determined and analyzed 22 genome sequences representative of the global diversity of the M. tuberculosis complex (MTBC). As expected, we found that essential genes in MTBC were more evolutionarily conserved than non-essential genes. Surprisingly however, most of 491 experimentally confirmed human T cell epitopes showed little sequence variation and exhibited a lower ratio of non-synonymous to synonymous changes than essential and non-essential genes. These findings are consistent with strong purifying selection acting on these epitopes, and imply that MTBC might benefit from recognition by human T cells.
doi:10.1038/ng.590
PMCID: PMC2883744  PMID: 20495566
22.  Human T cell epitopes of Mycobacterium tuberculosis are evolutionarily hyperconserved 
Nature genetics  2010;42(6):498-503.
Mycobacterium tuberculosis is an obligate human pathogen capable of persisting in individual hosts for decades. To determine whether antigenic variation and immune escape contribute to the success of M. tuberculosis, we determined and analyzed 22 genome sequences representative of the global diversity of the M. tuberculosis complex (MTBC). As expected, we found that essential genes in MTBC were more evolutionarily conserved than non-essential genes. Surprisingly however, most of 491 experimentally confirmed human T cell epitopes showed little sequence variation and exhibited a lower ratio of non-synonymous to synonymous changes than essential and non-essential genes. These findings are consistent with strong purifying selection acting on these epitopes, and imply that MTBC might benefit from recognition by human T cells.
doi:10.1038/ng.590
PMCID: PMC2883744  PMID: 20495566
23.  Genome structure in the vole bacillus, Mycobacterium microti, a member of the Mycobacterium tuberculosis complex with a low virulence for humans 
Microbiology (Reading, England)  2004;150(Pt 5):1519-1527.
Mycobacterium microti, a member of the Mycobacterium tuberculosis complex, is phylogenetically closely related to M. tuberculosis, differing in a few biochemical properties. However, these species have different levels of virulence in different hosts; most notably M. microti shows lower virulence for humans than M. tuberculosis. This report presents genomic comparisons using DNA microarray analysis for an extensive study of the diversity of M. microti strains. Compared to M. tuberculosis H37Rv, 13 deletions were identified in 12 strains of M. microti, including the regions RD1 to RD10, which are also missing in Mycobacterium bovis BCG. In addition, four new deleted regions, named MiD1, RD1β, MiD2 and MiD3, were identified. DNA sequencing was used to define the extent of most of the deletions in one strain. Although RD1 of M. bovis BCG and M. microti is thought to be crucial for attenuation, in this study, three of the four M. microti strains that were isolated from immunocompetent patients had the RD1 deletion. In fact, only the RD3 deletion was present in all of the strains examined, although deletions RD7, RD8 and MiD1 were found in almost all the M. microti strains. These deletions might therefore have some relation to the different host range of M. microti. It was also noticeable that of the 12 strains studied, only three were identical; these strains were all isolated from immunocompetent humans, suggesting that they could have arisen from a single source. Thus, this study shows that it is difficult to ascribe virulence to any particular pattern of deletion in M. microti.
PMCID: PMC2964484  PMID: 15133113
24.  Mycobacterium tuberculosis Spoligotypes in Monterrey, Mexico▿  
Journal of Clinical Microbiology  2009;48(2):448-455.
Although tuberculosis is still a public health problem in Mexico, there is little information about the genetic characteristics of the isolates. In the present study, we analyzed by spoligotyping 180 Mycobacterium tuberculosis clinical isolates from the urban area of Monterrey, Mexico, including drug-susceptible and drug-resistant isolates. The spoligotype patterns were compared with those in the international SITVIT2 spoligotyping database. Four isolates presented spoligotype patterns not found in the database (orphan types); the rest were distributed among 44 spoligo international types (SITs). SIT53 (clade T1) and SIT119 (clade X1) were predominant and included 43 (23.8%) and 28 (15.5%) of the isolates, respectively. In order to determine if there was a dominant spoligotype in the group of multidrug-resistant isolates, 37 of them were analyzed by IS6110-based restriction fragment length polymorphism assays, and scarce clustering of strains with more than five bands was observed. Fourteen isolates of this multidrug-resistant group presented four bands or less and were distributed in four SITs: SIT53 (n = 8), SIT92 (n = 3), SIT70 (n = 2), and SIT3038 (n = 1). When the molecular detection of mutations in the katG and rpoB genes were analyzed in these isolates with low copy numbers of IS6110, only two isolates shared the same IS6110, spoligotyping, and mutations patterns. When the distribution of the spoligotypes was analyzed by age cohort, SIT119 was predominantly found in patients 0 to 20 years old, especially in males, accounting for up to 40% of the isolates. In contrast, SIT53 was more prevalent in older females. This analysis demonstrates the variability of M. tuberculosis isolates in Monterrey and the partial dominance of SIT53 and SIT119 in that area of Mexico.
doi:10.1128/JCM.01894-09
PMCID: PMC2815641  PMID: 19940048
25.  Validation of the GenoType® MTBDRplus assay for diagnosis of multidrug resistant tuberculosis in South Vietnam 
BMC Infectious Diseases  2010;10:149.
Background
To control multidrug resistant tuberculosis (MDR-TB), the drug susceptibility profile is needed to guide therapy. Classical drug susceptibility testing (DST) may take up to 2 to 4 months. The GenoType® MTBDRplus test is a commercially available line-probe assay that rapidly detects Mycobacterium tuberculosis (MTB) complex, as well as the most common mutations associated with rifampin and isoniazid resistance.
We assessed sensitivity and specificity of the assay by using a geographically representative set of MTB isolates from the South of Vietnam.
Methods
We re-cultured 111 MTB isolates that were MDR, rifampin-resistant or pan-susceptible according to conventional DST and tested these with the GenoType® MTBDRplus test.
Results
By conventional DST, 55 strains were classified as MDR-TB, four strains were rifampicin mono-resistant and 52 strains were susceptible to all first-line drugs. The sensitivity of the GenoType® MTBDRplus was 93.1% for rifampicin, 92.6% for isoniazid and 88.9% for the combination of both; its specificity was 100%. The positive predictive value of the GenoType® MTBDRplus test for MDR-TB was 100% and the negative predictive value 90.3%.
Conclusions
We found a high specificity and positive predictive value of the GenoType® MTBDRplus test for MDR-TB which merits its use in the MDR-TB treatment program in Vietnam.
doi:10.1186/1471-2334-10-149
PMCID: PMC2901356  PMID: 20525271

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