Molecular epidemiology of tuberculosis in foreign-born persons living in San Francisco

Vitamin D and the risk of latent tuberculosis infection: a systematic review and meta-analysis

Objective

Latent tuberculosis infection (LTBI) may be a risk of developing tuberculosis (TB) and thus a health hazard. The aim of this meta-analysis is to explore the association between vitamin D and LTBI.

Methods

Databases including PubMed, Embase, Scopus, and ProQuest were electronically searched to identify observational or interventional studies that reported the association between vitamin D and LTBI. The retrieval time is limited from inception to 30 September 2021. Two reviewers independently screened literature, extracted data, and assessed risk bias of included studies. Meta-analysis was performed by using STATA 12.0 software.

Results

A total of 5 studies involving 2 case–control studies and 3 cohort studies were included. The meta-analysis result showed that the risk of LTBI among individuals was not associated with high vitamin D level (OR 0.51, 95% CI 0.05–5.65, P = 0.58). The result from cohort studies also suggested that relatively high vitamin D level was not a protective factor for LTBI (RR = 0.56, 95%CI 0.19–1.67, P = 0.300).

Conclusions

Our meta-analysis suggested that serum vitamin D levels were not associated with incidence of LTBI, and relatively high serum vitamin D level was not a protective factor for LTBI. Further RCTs are needed to verify whether sufficient vitamin D levels and vitamin D supplementation reduces the risk of LTBI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01830-5.

Association between vitamin D and latent tuberculosis infection in the United States: NHANES, 2011-2012

Background

Latent tuberculosis infection (LTBI) is a precursor of active tuberculosis diseases and an important issue in the United States and worldwide. The association between vitamin D deficiency and LTBI is poorly understood.

Methods

From 2011 to 2012, the National Health and Nutrition Examination Survey (NHANES) assessed LTBI (according to tuberculin skin testing and QuantiFERON^®-TB Gold In-Tube) and measured serum levels of vitamin D. We evaluated the association between LTBI and vitamin D using multivariate logistic regression models adjusted for known confounders.

Results

The LTBI group had a lower 25-hydroxyvitamin D [25(OH)D] level than the non-LTBI group (p=0.0012). The adjusted risk of LTBI was significantly higher among participants with serum 25(OH)D levels <12 ng/ml (adjusted OR [aOR], 2.27; 95% CI, 1.40-3.66) and 12-19 ng/ml (aOR, 1.75; 95% CI, 1.25-2.46) compared to those with a level ≥30 ng/ml. The higher risk of LTBI among the participants with serum 25(OH)D levels <12 ng/ml and 12-19 ng/ml remained unchanged in both male and summer season subgroups.

Conclusions

A low serum 25(OH)D level was significantly associated with the risk of LTBI in this US cohort.

The Prevalence of Latent Tuberculosis Infection in the United States

RATIONALE

Individuals with latent tuberculosis infection (LTBI) represent a reservoir of infection, many of whom will progress to tuberculosis (TB) disease. A central pillar of TB control in the United States is reducing this reservoir through targeted testing and treatment.

OBJECTIVES

To estimate the prevalence of LTBI in the United States using the tuberculin skin test (TST) and an IFN-γ release assay.

METHODS

We used nationally representative data from the 2011-2012 National Health and Nutrition Examination Survey (n = 6,083 aged ≥6 yr). LTBI was measured by both the TST and QuantiFERON-TB Gold In-Tube test (QFT-GIT). Weighted population, prevalence, and multiple logistic regression were used.

MEASUREMENTS AND MAIN RESULTS

The estimated prevalence of LTBI in 2011-2012 was 4.4% as measured by the TST and 4.8% by QFT-GIT, corresponding to 12,398,000 and 13,628,000 individuals, respectively. Prevalence declined slightly since 2000 among the U.S. born but remained constant among the foreign born. Earlier birth cohorts consistently had higher prevalence than more recent ones. Higher risk groups included the foreign born, close contact with a case of TB disease, and certain racial/ethnic groups.

CONCLUSIONS

After years of decline, the prevalence of LTBI remained relatively constant between 2000 and 2011. A large reservoir of 12.4 million still exists, with foreign-born persons representing an increasingly larger proportion of this reservoir (73%). Estimates and risk factors for LTBI were generally similar between the TST and QFT-GIT. The updated estimates of LTBI and associated risk groups can help improve targeted testing and treatment in the United States.

Methodological and Clinical Aspects of the Molecular Epidemiology of Mycobacterium tuberculosis and Other Mycobacteria

Molecular typing has revolutionized epidemiological studies of infectious diseases, including those of a mycobacterial etiology. With the advent of fingerprinting techniques, many traditional concepts regarding transmission, infectivity, or pathogenicity of mycobacterial bacilli have been revisited, and their conventional interpretations have been challenged. Since the mid-1990s, when the first typing methods were introduced, a plethora of other modalities have been proposed. So-called molecular epidemiology has become an essential subdiscipline of modern mycobacteriology. It serves as a resource for understanding the key issues in the epidemiology of tuberculosis and other mycobacterial diseases. Among these issues are disclosing sources of infection, quantifying recent transmission, identifying transmission links, discerning reinfection from relapse, tracking the geographic distribution and clonal expansion of specific strains, and exploring the genetic mechanisms underlying specific phenotypic traits, including virulence, organ tropism, transmissibility, or drug resistance. Since genotyping continues to unravel the biology of mycobacteria, it offers enormous promise in the fight against and prevention of the diseases caused by these pathogens. In this review, molecular typing methods for Mycobacterium tuberculosis and nontuberculous mycobacteria elaborated over the last 2 decades are summarized. The relevance of these methods to the epidemiological investigation, diagnosis, evolution, and control of mycobacterial diseases is discussed.

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.

Molecular epidemiology of Mycobacterium tuberculosis complex in Singapore, 2006-2012

Background

Tuberculosis remains common in Singapore, increasing in incidence since 2008. We attempted to determine the molecular epidemiology of Mycobacterium tuberculosis complex (MTC) isolates locally, identifying major circulating genotypes and obtaining a glimpse of transmission dynamics.

Methodology

Non-duplicate MTC isolates archived between 2006 and 2012 at the larger clinical tuberculosis laboratory in Singapore were sampled for spoligotyping and MIRU-VNTR typing, with case data obtained from the Singapore Tuberculosis Elimination Program registry database. Isolates between 2008 and 2012 were selected because of either multidrug-resistance or potential epidemiological linkage, whereas earlier isolates were randomly selected. Separate analyses were performed for the early (2006-2007) and later (2008-2012) study phases in view of potential selection bias.

Principal Findings

A total of 1,612 MTC isolates were typed, constituting 13.1% of all culture-positive tuberculosis cases during this period. Multidrug-resistance was present in 91 (5.6%) isolates – higher than the national prevalence in view of selection bias. The majority of isolates belonged to the Beijing (45.8%) and EAI (22.8%) lineages. There were 347 (30.7%) and 133 (27.5%) cases clustered by combined spoligotyping and MIRU-VNTR typing from the earlier and later phases respectively. Patients within these clusters tended to be of Chinese ethnicity, Singapore resident, and have isolates belonging to the Beijing lineage. A review of prior contact investigation results for all patients with clustered isolates failed to reveal epidemiological links for the majority, suggesting either unknown transmission networks or inadequate specificity of the molecular typing methods in a country with a moderate incidence of tuberculosis.

Conclusion

Our work demonstrates that Singapore has a large and heterogeneous distribution of MTC strains, and with possible cross-transmission over the past few years based on our molecular typing results. A universal MTC typing program coupled with enhanced contact investigations may be useful in further understanding the transmission dynamics of tuberculosis locally.

Molecular epidemiology of tuberculosis in foreign-born persons living in San Francisco

RATIONALE

In San Francisco, 70% of the tuberculosis cases occur among foreign-born persons, mainly from China, the Philippines, and Mexico. We postulate that there are differences in the characteristics and risk factors for tuberculosis among these populations.

OBJECTIVES

To determine the clinical, epidemiological and microbiological characteristics of tuberculosis caused by recent infection and rapid evolution in the major groups of foreign-born and the U.S.-born populations.

METHODS

We analyzed data from a 20-year prospective community-based study of the molecular epidemiology of tuberculosis in San Francisco. We included all culture-positive tuberculosis cases in the City during the study period.

MEASUREMENTS AND MAIN RESULTS

We calculated and compared incidence rates, clinical and microbiological characteristics, and risk factors for being a secondary case between the various foreign-born and U.S.-born tuberculosis populations. Between 1991 and 2010, there were 4,058 new cases of tuberculosis, of which 1,226 (30%) were U.S.-born and 2,832 (70%) were foreign-born. A total of 3,278 (81%) were culture positive, of which 2,419 (74%) had complete data for analysis. The incidence rate, including the incidence rate of tuberculosis due to recent infection and rapid evolution, decreased significantly in the U.S.-born and the major foreign-born populations. The clinical and microbiological characteristics and the risk factors for tuberculosis due to recent infection differed among the groups.

CONCLUSIONS

There are differences in the characteristics and the risk factors for tuberculosis due to recent transmission among the major foreign-born and U.S.-born populations in San Francisco. These differences should be considered for the design of targeted tuberculosis control interventions.