Decline in prevalence of tuberculosis following an intensive case finding campaign and the COVID-19 pandemic in an urban Ugandan community.

BACKGROUND: Systematic screening is a potential tool for reducing the prevalence of tuberculosis (TB) and counteracting COVID-19-related disruptions in care. Repeated community-wide screening can also measure changes in the prevalence of TB over time. METHODS: We conducted serial, cross-sectional TB case finding campaigns in one community in Kampala, Uganda, in 2019 and 2021. Both campaigns sought sputum for TB testing (Xpert MTB/RIF Ultra) from all adolescents and adults. We estimated the prevalence of TB among screening participants in each campaign and compared characteristics of people with TB across campaigns. We simultaneously enrolled and characterised community residents who were diagnosed with TB through routine care and assessed trends in facility-based diagnosis. RESULTS: We successfully screened 12 033 community residents (35% of the estimated adult/adolescent population) in 2019 and 11 595 (33%) in 2021. In 2019, 0.94% (95% CI: 0.77% to 1.13%) of participants tested Xpert positive (including trace). This proportion fell to 0.52% (95% CI: 0.40% to 0.67%) in 2021; the prevalence ratio was 0.55 (95% CI: 0.40 to 0.75)). There was no change in the age (median 26 vs 26), sex (56% vs 59% female) or prevalence of chronic cough (49% vs 54%) among those testing positive. By contrast, the rate of routine facility-based diagnosis remained steady in the 8 months before each campaign (210 (95% CI: 155 to 279) vs 240 (95% CI: 181 to 312) per 100 000 per year). CONCLUSIONS: Following an intensive initial case finding campaign in an urban Ugandan community in 2019, the burden of prevalent TB as measured by systematic screening had decreased by 45% in 2021, despite the intervening COVID-19 pandemic.

Back-to-Africa introductions of Mycobacterium tuberculosis as the main cause of tuberculosis in Dar es Salaam, Tanzania.

In settings with high tuberculosis (TB) endemicity, distinct genotypes of the Mycobacterium tuberculosis complex (MTBC) often differ in prevalence. However, the factors leading to these differences remain poorly understood. Here we studied the MTBC population in Dar es Salaam, Tanzania over a six-year period, using 1,082 unique patient-derived MTBC whole-genome sequences (WGS) and associated clinical data. We show that the TB epidemic in Dar es Salaam is dominated by multiple MTBC genotypes introduced to Tanzania from different parts of the world during the last 300 years. The most common MTBC genotypes deriving from these introductions exhibited differences in transmission rates and in the duration of the infectious period, but little differences in overall fitness, as measured by the effective reproductive number. Moreover, measures of disease severity and bacterial load indicated no differences in virulence between these genotypes during active TB. Instead, the combination of an early introduction and a high transmission rate accounted for the high prevalence of L3.1.1, the most dominant MTBC genotype in this setting. Yet, a longer co-existence with the host population did not always result in a higher transmission rate, suggesting that distinct life-history traits have evolved in the different MTBC genotypes. Taken together, our results point to bacterial factors as important determinants of the TB epidemic in Dar es Salaam.

Adherence trajectory as an on-treatment risk indicator among drug-resistant TB patients in the Philippines.

INTRODUCTION: High levels of treatment adherence are critical for achieving optimal treatment outcomes among patients with tuberculosis (TB), especially for drug-resistant TB (DR TB). Current tools for identifying high-risk non-adherence are insufficient. Here, we apply trajectory analysis to characterize adherence behavior early in DR TB treatment and assess whether these patterns predict treatment outcomes. METHODS: We conducted a retrospective analysis of Philippines DR TB patients treated between 2013 and 2016. To identify unique patterns of adherence, we performed group-based trajectory modelling on adherence to the first 12 weeks of treatment. We estimated the association of adherence trajectory group with six-month and final treatment outcomes using univariable and multivariable logistic regression. We also estimated and compared the predictive accuracy of adherence trajectory group and a binary adherence threshold for treatment outcomes. RESULTS: Of 596 patients, 302 (50.7%) had multidrug resistant TB, 11 (1.8%) extremely drug-resistant (XDR) TB, and 283 (47.5%) pre-XDR TB. We identified three distinct adherence trajectories during the first 12 weeks of treatment: a high adherence group (n = 483), a moderate adherence group (n = 93) and a low adherence group (n = 20). Similar patterns were identified at 4 and 8 weeks. Being in the 12-week moderate or low adherence group was associated with unfavorable six-month (adjusted OR [aOR] 3.42, 95% CI 1.90-6.12) and final (aOR 2.71, 95% 1.73-4.30) treatment outcomes. Adherence trajectory group performed similarly to a binary threshold classification for the prediction of final treatment outcomes (65.9% vs. 65.4% correctly classified), but was more accurate for prediction of six-month treatment outcomes (79.4% vs. 60.0% correctly classified). CONCLUSIONS: Adherence patterns are strongly predictive of DR TB treatment outcomes. Trajectory-based analyses represent an exciting avenue of research into TB patient adherence behavior seeking to inform interventions which rapidly identify and support patients with high-risk adherence patterns.

The Role of C-Reactive Protein as a Triage Tool for Pulmonary Tuberculosis in Children.

BACKGROUND: C-reactive protein (CRP) has shown promise as a triage tool for pulmonary tuberculosis (TB) in adults living with the human immunodeficiency virus. We performed the first assessment of CRP for TB triage in children. METHODS: Symptomatic children less than 15 years old were prospectively enrolled in Kampala, Uganda. We completed a standard TB evaluation and measured CRP using a point-of-care assay. We determined the sensitivity and specificity of CRP to identify pulmonary TB in children using 10 mg/L and 5 mg/L cut-off points and generated a receiver operating characteristic (ROC) curve to determine alternative cut-offs that could approach the target accuracy for a triage test (≥90% sensitivity and ≥70% specificity). RESULTS: We included 332 children (median age 3 years old, interquartile range [IQR]: 1-6). The median CRP level was low at 3.0 mg/L (IQR: 2.5-26.6) but was higher in children with Confirmed TB than in children with Unlikely TB (9.5 mg/L vs. 2.9 mg/L, P-value = .03). At a 10 mg/L cut-off, CRP sensitivity was 50.0% (95% confidence interval [CI], 37.0-63.0) among Confirmed TB cases and specificity was 63.3% (95% CI, 54.7-71.3) among children with Unlikely TB. Sensitivity increased to 56.5% (95% CI, 43.3-69.0) at the 5 mg/L cut-off, but specificity decreased to 54.0% (95% CI, 45.3-62.4). The area under the ROC curve was 0.59 (95% CI, 0.51-0.67), and the highest sensitivity achieved was 66.1% at a specificity of 46.8%. CONCLUSIONS: CRP levels were low in children with pulmonary TB, and CRP was unable to achieve the accuracy targets for a TB triage test.

Genetic diversity and primary drug resistance transmission in Mycobacterium tuberculosis in southern Mexico.

Tuberculosis is a global human health threat, especially in developing countries. The present study aimed to describe the genetic diversity of Mycobacterium tuberculosis and to measure the transmission rates of primary and acquired resistance. A total of 755 M. tuberculosis isolates from a cohort study of patients with culture-confirmed pulmonary tuberculosis in Orizaba, Veracruz, performed between 1995 and 2010 were genotyped by the 24-locus mycobacterial interspersed repetitive unit-variable number of tandem repeats (MIRU-VNTR) method. Drug susceptibility was determined. Logistic regression models were constructed to identify the variables associated with resistance and clusters. The recent transmission index (RTI), the Hunter-Gaston discrimination index (HGDI) for the MIRU-VNTR test and allelic diversity (h) were calculated. The Haarlem and LAM lineages were the most common in the population. A total of 519 isolates were grouped into 128 clusters. The overall drug resistance rate was 19%, isoniazid monoresistance (10%) was the most common, and 3.4% of the isolates were multidrug resistant. Among the 116 isolates resistant to at least one drug, the primary and acquired resistance rates were 81.9% and 18.1%, respectively. Primary resistance was associated with belonging to a cluster (aOR 4.05, 95% CI 1.5-11.2, p = 0.007). Previous treatment history (aOR 9.05, 95% CI 3.6-22.5, p < 0.001) and LAM lineage (aOR 4.25, 95% CI 1.4-12.7, p = 0.010) were associated with multidrug-resistant tuberculosis (MDR-TB). The RTI was 51.7%, and the 24-locus MIRU-VNTR HGDI was 0.98. The alleles with the greatest diversity were 4056-QUB26 (h = 0.84), 2163b-QUB11b (h = 0.79), and 424-Mtub04 (h = 0.72). Primary resistance transmission, high LAM lineage prevalence and its association with MDR-TB represent public health problems. The implementation of molecular tools is needed to improve the existing control surveillance tuberculosis program.

Local adaptation in populations of Mycobacterium tuberculosis endemic to the Indian Ocean Rim.

Background: Lineage 1 (L1) and 3 (L3) are two lineages of the Mycobacterium tuberculosis complex (MTBC) causing tuberculosis (TB) in humans. L1 and L3 are prevalent around the rim of the Indian Ocean, the region that accounts for most of the world's new TB cases. Despite their relevance for this region, L1 and L3 remain understudied. Methods: We analyzed 2,938 L1 and 2,030 L3 whole genome sequences originating from 69 countries. We reconstructed the evolutionary history of these two lineages and identified genes under positive selection. Results: We found a strongly asymmetric pattern of migration from South Asia toward neighboring regions, highlighting the historical role of South Asia in the dispersion of L1 and L3. Moreover, we found that several genes were under positive selection, including genes involved in virulence and resistance to antibiotics. For L1 we identified signatures of local adaptation at the esxH locus, a gene coding for a secreted effector that targets the human endosomal sorting complex, and is included in several vaccine candidates. Conclusions: Our study highlights the importance of genetic diversity in the MTBC, and sheds new light on two of the most important MTBC lineages affecting humans.

A Prospective Evaluation of Xpert MTB/RIF Ultra for Childhood Pulmonary Tuberculosis in Uganda.

BACKGROUND: Xpert MTB/RIF Ultra (Xpert Ultra) has improved the sensitivity to detect pulmonary tuberculosis (TB) in adults. However, there have been limited prospective evaluations of its diagnostic accuracy in children. METHODS: We enrolled children undergoing assessment for pulmonary TB in Kampala, Uganda, over a 12-month period. Children received a complete TB evaluation and were classified as Confirmed, Unconfirmed, or Unlikely TB. We calculated the sensitivity and specificity of Xpert Ultra among children with Confirmed vs Unlikely TB. We also determined the diagnostic accuracy with clinical, microbiological, and extended microbiological reference standards (MRSs). RESULTS: Of the 213 children included, 23 (10.8%) had Confirmed TB, 88 (41.3%) had Unconfirmed TB, and 102 (47.9%) had Unlikely TB. The median age was 3.9 years, 13% were HIV-positive, and 61.5% were underweight. Xpert Ultra sensitivity was 69.6% (95% confidence interval [CI]: 47.1-86.8) among children with Confirmed TB and decreased to 23.4% (95% CI: 15.9-32.4) with the clinical reference standard. Specificity was 100% (95% CI: 96.4-100) among children with Unlikely TB and decreased to 94.7% (95% CI: 90.5-97.4) with a MRS. Sensitivity was 52.9% (95% CI: 35.1-70.2) and specificity 95.5% (95% CI: 91.4-98.1) with the extended MRS. Of the 26 positive Xpert Ultra results, 6 (23.1%) were "Trace-positive," with most (5/6) occurring in children with Unconfirmed TB. CONCLUSIONS: Xpert Ultra is a useful tool for diagnosing pulmonary TB in children, but there remains a need for more sensitive tests to detect culture-negative TB.

The Spectrum of Tuberculosis Disease in an Urban Ugandan Community and Its Health Facilities.

BACKGROUND: New, sensitive diagnostic tests facilitate identification and investigation of milder forms of tuberculosis (TB) disease. We used community-based TB testing with the Xpert MTB/RIF Ultra assay ("Ultra") to characterize individuals with previously undiagnosed TB and compare them to those from the same community who were diagnosed with TB through routine care. METHODS: We offered community-based sputum Ultra testing to adult residents of a well-defined area (population 34 000 adults) in Kampala, Uganda, via door-to-door screening and venue-based testing, then used detailed interview and laboratory testing to characterize TB-positive individuals. We compared these individuals to residents diagnosed with pulmonary TB at local health facilities and a representative sample of residents without TB (controls). RESULTS: Of 12 032 residents with interpretable Ultra results, 113 (940 [95% confidence interval {CI}, 780-1130] per 100 000) tested positive, including 71 (63%) positive at the lowest (trace) level. A spectrum of TB disease was observed in terms of chronic cough (93% among health facility-diagnosed cases, 77% among residents with positive community-based Ultra results at levels above trace, 33% among trace-positive community participants, and 18% among TB-negative controls), TB symptom prevalence (99%, 87%, 60%, and 38%, respectively), and C-reactive protein (75th percentile: 101 mg/L, 28 mg/L, 6 mg/L, and 4 mg/L, respectively). Community-diagnosed cases were less likely than health facility-diagnosed cases to have human immunodeficiency virus coinfection or previous TB. The specificity of Ultra was 99.4% (95% CI, 99.2%-99.5%) relative to a single spot sputum culture. CONCLUSIONS: People with undiagnosed prevalent TB in the community have different characteristics than those diagnosed with pulmonary TB in health facilities. Newer diagnostic tests may identify a group of people with early or very mild disease.

Empiric treatment of pulmonary TB in the Xpert era: Correspondence of sputum culture, Xpert MTB/RIF, and clinical diagnoses.

BACKGROUND: Clinical tuberculosis diagnosis and empiric treatment have traditionally been common among patients with negative bacteriologic test results. Increasing availability of rapid molecular diagnostic tests, including Xpert MTB/RIF and the new Xpert Ultra cartridge, may alter the role of empiric treatment. METHODS: We prospectively enrolled outpatients age > = 15 who were evaluated for pulmonary tuberculosis at three health facilities in Kampala, Uganda. Using sputum mycobacterial culture, interviews, and clinical record abstraction, we estimated the accuracy of clinical diagnosis relative to Xpert and sputum culture and assessed the contribution of clinical diagnosis to case detection. RESULTS: Over a period of 9 months, 99 patients were diagnosed with pulmonary tuberculosis and subsequently completed sputum culture; they were matched to 196 patients receiving negative tuberculosis evaluations in the same facilities. Xpert was included in the evaluation of 291 (99%) patients. Compared to culture, Xpert had a sensitivity of 92% (95% confidence interval 83-97%) and specificity of 95% (92-98%). Twenty patients with negative Xpert were clinically diagnosed with tuberculosis and subsequently had their culture status determined; two (10%) were culture-positive. Considering all treated patients regardless of Xpert and culture data completeness, and considering treatment initiations before a positive Xpert (N = 4) to be empiric, 26/101 (26%) tuberculosis treatment courses were started empirically. Compared to sputum smear- or Xpert-positive patients with positive cultures, empirically-treated, Xpert-negative patients with negative cultures had higher prevalence of HIV (67% versus 37%), shorter duration of cough (median 4 versus 8 weeks), and lower inflammatory markers (median CRP 7 versus 101 mg/L). CONCLUSION: Judged against sputum culture in a routine care setting of high HIV prevalence, the accuracy of Xpert was high. Clinical judgment identified a small number of additional culture-positive cases, but with poor specificity. Although clinicians should continue to prescribe tuberculosis treatment for Xpert-negative patients whose clinical presentations strongly suggest pulmonary tuberculosis, they should also carefully consider alternative diagnoses.

Reference set of Mycobacterium tuberculosis clinical strains: A tool for research and product development.

The Mycobacterium tuberculosis complex (MTBC) causes tuberculosis (TB) in humans and various other mammals. The human-adapted members of the MTBC comprise seven phylogenetic lineages that differ in their geographical distribution. There is growing evidence that this phylogeographic diversity modulates the outcome of TB infection and disease. For decades, TB research and development has focused on the two canonical MTBC laboratory strains H37Rv and Erdman, both of which belong to Lineage 4. Relying on only a few laboratory-adapted strains can be misleading as study results might not be directly transferrable to clinical settings where patients are infected with a diverse array of strains, including drug-resistant variants. Here, we argue for the need to expand TB research and development by incorporating the phylogenetic diversity of the MTBC. To facilitate such work, we have assembled a group of 20 genetically well-characterized clinical strains representing the seven known human-adapted MTBC lineages. With the "MTBC clinical strains reference set" we aim to provide a standardized resource for the TB community. We hope it will enable more direct comparisons between studies that explore the physiology of MTBC beyond the laboratory strains used thus far. We anticipate that detailed phenotypic analyses of this reference strain set will increase our understanding of TB biology and assist in the development of new control tools that are broadly effective.

Whole-genome sequencing and single nucleotide polymorphisms in multidrug-resistant clinical isolates of Mycobacterium tuberculosis from the Philippines.

OBJECTIVES: Thousands of cases of multidrug-resistant tuberculosis (TB) have been observed in the Philippines, but studies on the Mycobacterium tuberculosis (MTB) genotypes that underlie the observed drug resistance profiles are lacking. This study aimed to analyse the whole genomes of clinical MTB isolates representing various resistance profiles to identify single nucleotide polymorphisms (SNPs) in resistance-associated genes. METHODS: The genomes of ten MTB isolates cultured from banked sputum sources were sequenced. Bioinformatics analysis consisted of assembly, annotation and SNP identification in genes reported to be associated with resistance to isoniazid (INH), rifampicin (RIF), ethambutol (ETH), streptomycin, pyrazinamide (PZA) and fluoroquinolones (FQs). RESULTS: The draft assemblies covered an average of 97.08% of the expected genome size. Seven of the ten isolates belonged to the Indo-Oceanic lineage/EA12-Manila clade. Two isolates were classified into the Euro-American lineage, whilst the pre-XDR (pre-extensively drug-resistant) isolate was classified under the East Asian/Beijing clade. The SNPs katG Ser315Thr, rpoB Ser450Leu and embB Met306Val were found in INH- (4/7), RIF- (3/6) and ETH-resistant (2/6) isolates, respectively, but not in susceptible isolates. Mutations in the inhA promoter and in the pncA and gyrA genes known to be involved in resistance to INH, PZA and FQs, respectively, were also identified. CONCLUSIONS: This study represents the first effort to investigate the whole genomes of Philippine clinical strains of MTB exhibiting various multidrug resistance profiles. Whole-genome data can provide valuable insights to the mechanistic and epidemiological qualities of TB in a high-burden setting such as the Philippines.

Spatial overlap links seemingly unconnected genotype-matched TB cases in rural Uganda.

INTRODUCTION: Incomplete understanding of TB transmission dynamics in high HIV prevalence settings remains an obstacle for prevention. Understanding where transmission occurs could provide a platform for case finding and interrupting transmission. METHODS: From 2012-2015, we sought to recruit all adults starting TB treatment in a Ugandan community. Participants underwent household (HH) contact investigation, and provided names of social contacts, sites of work, healthcare and socializing, and two sputum samples. Mycobacterium tuberculosis culture-positive specimens underwent 24-loci MIRU-VNTR and spoligotyping. We sought to identify epidemiologic links between genotype-matched cases by analyzing social networks and mapping locations where cases reported spending ≥12 hours over the one-month pre-treatment. Sites of spatial overlap (≤100m) between genotype-matched cases were considered potential transmission sites. We analyzed social networks stratified by genotype clustering status, with cases linked by shared locations, and compared network density by location type between clustered vs. non-clustered cases. RESULTS: Of 173 adults with TB, 131 (76%) were enrolled, 108 provided sputum, and 84/131 (78%) were MTB culture-positive: 52% (66/131) tested HIV-positive. Of 118 adult HH contacts, 105 (89%) were screened and 3 (2.5%) diagnosed with active TB. Overall, 33 TB cases (39%) belonged to 15 distinct MTB genotype-matched clusters. Within each cluster, no cases shared a HH or reported shared non-HH contacts. In 6/15 (40%) clusters, potential epidemiologic links were identified by spatial overlap at specific locations: 5/6 involved health care settings. Genotype-clustered TB social networks had significantly greater network density based on shared clinics (p<0.001) and decreased density based on shared marketplaces (p<0.001), compared to non-clustered networks. CONCLUSIONS: In this molecular epidemiologic study, links between MTB genotype-matched cases were only identifiable via shared locations, healthcare locations in particular, rather than named contacts. This suggests most transmission is occurring between casual contacts, and emphasizes the need for improved infection control in healthcare settings in rural Africa.

Mycobacterium tuberculosis lineage 4 comprises globally distributed and geographically restricted sublineages.

Generalist and specialist species differ in the breadth of their ecological niches. Little is known about the niche width of obligate human pathogens. Here we analyzed a global collection of Mycobacterium tuberculosis lineage 4 clinical isolates, the most geographically widespread cause of human tuberculosis. We show that lineage 4 comprises globally distributed and geographically restricted sublineages, suggesting a distinction between generalists and specialists. Population genomic analyses showed that, whereas the majority of human T cell epitopes were conserved in all sublineages, the proportion of variable epitopes was higher in generalists. Our data further support a European origin for the most common generalist sublineage. Hence, the global success of lineage 4 reflects distinct strategies adopted by different sublineages and the influence of human migration.

Adaptation of Mycobacterium tuberculosis to Impaired Host Immunity in HIV-Infected Patients.

BACKGROUND: It is unknown whether immunosuppression influences the physiologic state of Mycobacterium tuberculosis in vivo. We evaluated the impact of host immunity by comparing M. tuberculosis and human gene transcription in sputum between human immunodeficiency virus (HIV)-infected and uninfected patients with tuberculosis. METHODS: We collected sputum specimens before treatment from Gambians and Ugandans with pulmonary tuberculosis, revealed by positive results of acid-fast bacillus smears. We quantified expression of 2179 M. tuberculosis genes and 234 human immune genes via quantitative reverse transcription-polymerase chain reaction. We summarized genes from key functional categories with significantly increased or decreased expression. RESULTS: A total of 24 of 65 patients with tuberculosis were HIV infected. M. tuberculosis DosR regulon genes were less highly expressed among HIV-infected patients with tuberculosis than among HIV-uninfected patients with tuberculosis (Gambia, P < .0001; Uganda, P = .037). In profiling of human genes from the same sputa, HIV-infected patients had 3.4-fold lower expression of IFNG (P = .005), 4.9-fold higher expression of ARG1 (P = .0006), and 3.4-fold higher expression of IL10 (P = .0002) than in HIV-uninfected patients with tuberculosis. CONCLUSIONS: M. tuberculosis in HIV-infected patients had lower expression of the DosR regulon, a critical metabolic and immunomodulatory switch induced by NO, carbon monoxide, and hypoxia. Our human data suggest that decreased DosR expression may result from alternative pathway activation of macrophages, with consequent decreased NO expression and/or by poor granuloma formation with consequent decreased hypoxic stress.

Likelihood-based inference for discretely observed birth-death-shift processes, with applications to evolution of mobile genetic elements.

Continuous-time birth-death-shift (BDS) processes are frequently used in stochastic modeling, with many applications in ecology and epidemiology. In particular, such processes can model evolutionary dynamics of transposable elements-important genetic markers in molecular epidemiology. Estimation of the effects of individual covariates on the birth, death, and shift rates of the process can be accomplished by analyzing patient data, but inferring these rates in a discretely and unevenly observed setting presents computational challenges. We propose a multi-type branching process approximation to BDS processes and develop a corresponding expectation maximization algorithm, where we use spectral techniques to reduce calculation of expected sufficient statistics to low-dimensional integration. These techniques yield an efficient and robust optimization routine for inferring the rates of the BDS process, and apply broadly to multi-type branching processes whose rates can depend on many covariates. After rigorously testing our methodology in simulation studies, we apply our method to study intrapatient time evolution of IS6110 transposable element, a genetic marker frequently used during estimation of epidemiological clusters of Mycobacterium tuberculosis infections.

Use of 16S rRNA gene for identification of a broad range of clinically relevant bacterial pathogens.

According to World Health Organization statistics of 2011, infectious diseases remain in the top five causes of mortality worldwide. However, despite sophisticated research tools for microbial detection, rapid and accurate molecular diagnostics for identification of infection in humans have not been extensively adopted. Time-consuming culture-based methods remain to the forefront of clinical microbial detection. The 16S rRNA gene, a molecular marker for identification of bacterial species, is ubiquitous to members of this domain and, thanks to ever-expanding databases of sequence information, a useful tool for bacterial identification. In this study, we assembled an extensive repository of clinical isolates (n = 617), representing 30 medically important pathogenic species and originally identified using traditional culture-based or non-16S molecular methods. This strain repository was used to systematically evaluate the ability of 16S rRNA for species level identification. To enable the most accurate species level classification based on the paucity of sequence data accumulated in public databases, we built a Naïve Bayes classifier representing a diverse set of high-quality sequences from medically important bacterial organisms. We show that for species identification, a model-based approach is superior to an alignment based method. Overall, between 16S gene based and clinical identities, our study shows a genus-level concordance rate of 96% and a species-level concordance rate of 87.5%. We point to multiple cases of probable clinical misidentification with traditional culture based identification across a wide range of gram-negative rods and gram-positive cocci as well as common gram-negative cocci.

Genomic epidemiology of multidrug-resistant Mycobacterium tuberculosis during transcontinental spread.

The transcontinental spread of multidrug-resistant (MDR) tuberculosis is poorly characterized in molecular epidemiologic studies. We used genomic sequencing to understand the establishment and dispersion of MDR Mycobacterium tuberculosis within a group of immigrants to the United States. We used a genomic epidemiology approach to study a genotypically matched (by spoligotype, IS6110 restriction fragment length polymorphism, and mycobacterial interspersed repetitive units-variable number of tandem repeat signature) lineage 2/Beijing MDR strain implicated in an outbreak of tuberculosis among refugees in Thailand and consecutive cases within California. All 46 MDR M. tuberculosis genomes from both Thailand and California were highly related, with a median difference of 10 single-nucleotide polymorphisms (SNPs). The Wat Tham Krabok (WTK) strain is a new sequence type distinguished from all known Beijing strains by 55 SNPs and a genomic deletion (Rv1267c) associated with increased fitness. Sequence data revealed a highly prevalent MDR strain that included several closely related but distinct allelic variants within Thailand, rather than the occurrence of a single outbreak. In California, sequencing data supported multiple independent introductions of WTK with subsequent transmission and reactivation within the state, as well as a potential super spreader with a prolonged infectious period. Twenty-seven drug resistance-conferring mutations and 4 putative compensatory mutations were found within WTK strains. Genomic sequencing has substantial epidemiologic value in both low- and high-burden settings in understanding transmission chains of highly prevalent MDR strains.

Identifying locations of recent TB transmission in rural Uganda: a multidisciplinary approach.

OBJECTIVES: Targeting high Tuberculosis (TB) transmission sites may offer a novel approach to TB prevention in sub-Saharan Africa. We sought to characterise TB transmission sites in a rural Ugandan township. METHODS: We recruited adults starting TB treatment in Tororo, Uganda, over 1 year. Fifty four TB cases provided names of frequent contacts, sites of residence, health care, work and social activities, and two sputum samples. Mycobacterium tuberculosis (MTB) culture-positive specimens underwent spoligotyping to identify strains with shared genotypes. We visualised TB case social networks, and obtained, mapped and geo-coded global positioning system measures for every location that cases reported frequenting 1 month before treatment. Locations of spatial overlap among genotype-clustered cases were considered potential transmission sites. RESULTS: Six distinct genotypic clusters were identified involving 21 of 33 (64%) MTB culture-positive, genotyped cases; none shared a home. Although 18 of 54 (33%) TB cases shared social network ties, none of the genotype-clustered cases shared social ties. Using spatial analysis, we identified potential sites of within-cluster TB transmission for five of six genotypic clusters. All sites but one were healthcare and social venues, including sites of drinking, worship and marketplaces. Cases reported spending the largest proportion of pre-treatment person-time (22.4%) at drinking venues. CONCLUSIONS: Using molecular epidemiology, geospatial and social network data from adult TB cases identified at clinics, we quantified person-time spent at high-risk locations across a rural Ugandan community and determined the most likely sites of recent TB transmission to be healthcare and social venues. These sites may not have been identified using contact investigation alone.

Association between diabetes mellitus and tuberculosis in United States-born and foreign-born populations in San Francisco.

SETTING: The impact of diabetes on tuberculosis in United States and foreign-born populations in San Francisco has not been studied. OBJECTIVE: To determine the characteristics, prevalence and temporal trends of diabetes in US and foreign-born persons attending the San Francisco Tuberculosis Clinic. DESIGN: We analyzed data from individuals seeking medical attention at the San Francisco Tuberculosis Clinic. We included patients with diagnosis of tuberculosis, latent infection, or not infected with Mycobacterium tuberculosis. We assessed the temporal trend and the characteristics of individuals with and without diabetes. RESULT: Between 2005 and 2012, there were 4371 (19.0%) individuals without evidence of tuberculosis infection, 17,856 (77.6%) with latent tuberculosis, and 791 (3.4%) with tuberculosis. 66% were born in the United States, China, Mexico, and the Philippines. The prevalence of diabetes was the highest among individuals with tuberculosis and increased during the study period. Patients with tuberculosis and diabetes were more likely to be male, older than 45 years and born in the Philippines. There was a disproportionate association of TB and DM relative to LTBI and DM among Filipinos in individuals older than 45 years old. CONCLUSIONS: Our data suggest that Filipinos older than 45 years old are more likely to have tuberculosis probably due to a higher prevalence of diabetes. In San Francisco, tuberculosis-screening programs in individuals with diabetes and latent tuberculosis may be beneficial in patients older than 45 years old especially from the Philippines.

Pyrazinamide resistance, Mycobacterium tuberculosis lineage and treatment outcomes in San Francisco, California.

BACKGROUND: Pyrazinamide (PZA) is a first line agent for the treatment of active tuberculosis. PZA is also considered a potent companion drug for newer regimens under development. There are limited data on the demographic, clinical, and pathogen characteristics of PZA resistant tuberculosis. METHODS: Using a retrospective cohort study design, we evaluated all PZA resistant M. tuberculosis (M.tb) and M. bovis cases reported in San Francisco from 1991 to 2011. Demographic, clinical, and molecular data were analyzed. M.tb lineage was determined for all PZA resistant strains and compared to PZA susceptible strains. RESULTS: PZA resistance was identified in 1.8% (50 of 2,842) of mycobacterial isolates tested, corresponding to a case rate of 0.3 per 100,000 in the population. Monoresistant PZA infection was associated with the Hispanic population ([OR], 6.3; 95% [CI], 1.97-20.16) and 48% of cases were due to M. bovis. Infection with monoresistant PZA was also associated with extrapulmonary disease ([OR], 6.0; 95% [CI], 2.70-13.26). There was no statistically significant difference between treatment failure and mortality rates in patients infected with PZA monoresistance compared to pansusceptible controls (4% vs. 8%, p = 0.51), or those with PZA and MDR resistance (PZA-MDR) compared to MDR controls (18% vs. 29%, p = 0.40). PZA resistance was not associated with M.tb lineage. CONCLUSIONS: Across two decades of comprehensive epidemiologic data on tuberculosis in San Francisco County, PZA resistance was uncommon. PZA resistance caused predominantly extrapulmonary disease and was more common in Hispanics compared to other ethnicities, with nearly half the cases attributed to M. bovis. No association was found between PZA monoresistance and M.tb lineage. Treatment outcomes were not adversely influenced by the presence of PZA resistance.