The Epidemiology of Tuberculosis in San Francisco -- A Population-Based Study Using Conventional and Molecular Methods

Abstract

Despite an efficient tuberculosis-control program, nearly a third of new cases of tuberculosis in San Francisco are the result of recent infection. Few of these instances of transmission are identified by conventional contact tracing.

The epidemiology, pathogenesis, transmission, diagnosis, and management of multidrug-resistant, extensively drug-resistant, and incurable tuberculosis

“…45,50 This definition of a cluster can be flexible to allow for minor variation in the IS6110 RFLP or MIRU-VNTR patterns and evolutionary events. 51,52 Within the context of drug-resistant tuberculosis, supporting the definition of a cluster with resistance-conferring SNP data is crucial.…”

Estimating change rates of genetic markers using serial samples: applications to the transposon IS6110 in Mycobacterium tuberculosis

“…4) derives from a database of IS6110 genotypes of M. tuberculosis patients from San Francisco. New genotypes are continually added to the database, maintained by the laboratory of Peter Small, and findings are periodically reported (Small et al, 1994;Yeh et al, 1998;Jasmer et al, 1999;Rhee et al, 1999). As of April 2001, the database included genotypes for 320 independent time intervals from 260 patients.…”

Pulmonary Tuberculosis and Mycobacterium Tuberculosis: Modern Molecular Epidemiology and Perspectives

“…Molecular epidemiology by genotyping with resolvent markers can fill this gap concerning the chain of TB transmission. Indeed, isolates from patients who were infected by a common source or belonged to the same chain of transmission have identical or closely related genotypes (considering genotyping with the most resolvent markers); in other words, clustering is assumed to reflect recent transmission within a population [150,164]. In contrast, MTB isolates from patients with epidemiologically unrelated TB present a broad variability of genotypes.…”

“…For example, Torrea et al [196] identified several chains of transmission (familial or geographical cases) in French Polynesia using a detailed molecular study. Nevertheless, Daley [40] explained on the basis of several studies [164,203] that a relatively small proportion of TB cases presenting identical genotypes were named as a contact by the source case [41].This may be attributable to unsuspected transmission not easily detected by conventional contact tracing investigations. Indeed, transmission can occur through only short and casual contact, difficult to pinpoint [207].…”