Molecular typing of mycobacterium tuberculosis by using nine novel variable-number tandem repeats across the Beijing family and low-copy-number IS6110 isolates

Molecular epidemiological tools for genotyping clinical isolates of Mycobacterium tuberculosis have been developed and used to help track and contain transmission of tuberculosis. We identified 87 short sequence repeat loci within the genome of the M. tuberculosis H37Rv strain. Nine tandem repeats were found to be variable (variable-number tandem repeats (VNTRs)) in a set of 91 isolates. Fifty-seven of the isolates had only four IS6110 bands. The other 34 isolates were members of the Beijing strain family. The number of alleles of each these nine VNTRs was determined by examining each isolate. Six of the loci (Mtb-v1, -v4, -v10, -v15, -v18, and -v20) were able to differentiate the Beijing spoligotype identical isolates into seven distinct genotypes. Five of the loci (Mtb-v3, -v5, -v6, -v10, and -v15) were informative in discriminating the four-band IS6110 restriction fragment length polymorphism isolates from each other. The Nei's diversity values of each marker ranged from 0.02 to 0.59, with the number of alleles ranging from two to eight across the entire strain set. These nine loci provide a useful, discriminatory extension of VNTR typing methods for application to molecular epidemiologic studies of M. tuberculosis

Using GIS technology to identify areas of tuberculosis transmission and incidence

BACKGROUND: Currently in the U.S. it is recommended that tuberculosis screening and treatment programs be targeted at high-risk populations. While a strategy of targeted testing and treatment of persons most likely to develop tuberculosis is attractive, it is uncertain how best to accomplish this goal. In this study we seek to identify geographical areas where on-going tuberculosis transmission is occurring by linking Geographic Information Systems (GIS) technology with molecular surveillance. METHODS: This cross-sectional analysis was performed on data collected on persons newly diagnosed with culture positive tuberculosis at the Tarrant County Health Department (TCHD) between January 1, 1993 and December 31, 2000. Clinical isolates were molecularly characterized using IS6110-based RFLP analysis and spoligotyping methods to identify patients infected with the same strain. Residential addresses at the time of diagnosis of tuberculosis were geocoded and mapped according to strain characterization. Generalized estimating equations (GEE) analysis models were used to identify risk factors involved in clustering. RESULTS: Evaluation of the spatial distribution of cases within zip-code boundaries identified distinct areas of geographical distribution of same strain disease. We identified these geographical areas as having increased likelihood of on-going transmission. Based on this evidence we plan to perform geographically based screening and treatment programs. CONCLUSION: Using GIS analysis combined with molecular epidemiological surveillance may be an effective method for identifying instances of local transmission. These methods can be used to enhance targeted screening and control efforts, with the goal of interruption of disease transmission and ultimately incidence reduction

Does directly observed therapy (DOT) reduce drug resistant tuberculosis?

<p>Abstract</p> <p>Background</p> <p>Directly observed therapy (DOT) is a widely recommended and promoted strategy to manage tuberculosis (TB), however, there is still disagreement about the role of DOT in TB control and the impact it has on reducing the acquisition and transmission of drug resistant TB. This study compares the portion of drug resistant genotype clusters, representing recent transmission, within and between communities implementing programs differing only in their directly observed therapy (DOT) practices.</p> <p>Methods</p> <p>Genotype clusters were defined as 2 or more patient members with matching IS<it>6110 </it>restriction fragment length polymorphism (RFLP) and spoligotype patterns from all culture-positive tuberculosis cases diagnosed between January 1, 1995 and December 31, 2001. Logistic regression was used to compute maximum-likelihood estimates of odds ratios (ORs) and 95% confidence intervals (CIs) comparing cluster members with and without drug resistant isolates. In the universal DOT county, all patients received doses under direct observation of health department staff; whereas in selective DOT county, the majority of received patients doses under direct observation of health department staff, while some were able to self-administer doses.</p> <p>Results</p> <p>Isolates from 1,706 persons collected during 1,721 episodes of tuberculosis were genotyped. Cluster members from the selective DOT county were more than twice as likely than cluster members from the universal DOT county to have at least one isolate resistant to isoniazid, rifampin, and/or ethambutol (OR = 2.3, 95% CI: 1.7, 3.1). Selective DOT county isolates were nearly 5 times more likely than universal DOT county isolates to belong to clusters with at least 2 resistant isolates having identical resistance patterns (OR = 4.7, 95% CI: 2.9, 7.6).</p> <p>Conclusions</p> <p>Universal DOT for tuberculosis is associated with a decrease in the acquisition and transmission of resistant tuberculosis.</p

An Analysis of the International and Domestic Health Hazards Posed by the 2014 West African Ebola Virus Disease Outbreak

An epidemic of "ebolavirus" in West Africa, which was first identified in March 2014, is now the largest Ebola Virus Disease (EVD) outbreak on record. The West African epidemic will only be quelled through widespread adherence of public health initiatives promoting barrier-nursing techniques, health education, and the rapid identification of cases. The ongoing EVD outbreak in West Africa is unlikely to affect public health in the U.S. significantly