Transmission patterns of tuberculosis in Taiwan: Analysis by restriction fragment length polymorphism

Global dissemination of the Mycobacterium tuberculosis W-Beijing family strains

A large, genetically related group of Mycobacterium tuberculosis strains, variously called W or Beijing, is distinguished by specific molecular markers and referred to as the W-Beijing family strains. Molecular epidemiological studies suggest that these strains are highly prevalent throughout Asia and the countries of the former Soviet Union and they have also been reported in several other geographical regions, including North America. Although the spread of W-Beijing family strains in diverse populations is well documented, the underlying host-pathogen factors accounting for their continued dissemination and burden of disease have yet to be determined.

Molecular epidemiology of tuberculosis in Prague: analysis by restriction fragment length polymorphism

OBJECTIVES

To characterize by restriction fragment length polymorphism (RFLP) patterns, the distribution of different Mycobacterium tuberculosis strains isolated consecutively from 75 tuberculosis patients who resided in Prague and had culture-confirmed cases during a 4-month period in 1995.

METHODS

The insertion sequence IS6110-based RFLP analysis of M. tuberculosis isolates was carried out.

RESULTS

There were a total of 75 patients with various forms of tuberculosis (54 males; 21 females). The sources of M. tuberculosis isolates were sputum (n = 64), pleura or lymph node drainage (n = 8), and urine (n = 3). Fifty-three of the patients (70.7%) had isolates with unique RFLP patterns, while 22 (29.3%) had isolates that belonged to seven clusters of related RFLP patterns. The seven clusters consisted of four groups of two patients, two groups of four patients, and one group of six patients. Most of the patients whose isolates fell within a clustered RFLP pattern lived in different quarters of the city and had no identifiable contacts with other patients whose isolates had the same pattern.

CONCLUSIONS

The finding that isolates from most patients (70.7%) had unique rather than clustered RFLP patterns suggests that endogenous reactivation rather than exogenous transmission is the major determinant of most of the tuberculosis cases in Prague. The occurrence of seven distinct clusters comprising 29.3% of the isolates suggests that approximately one third of cases developed active tuberculosis from recent exogenous transmission.