Setting: Three referral hospitals in central Thailand.
Objective: To determine the population structure of Mycobacterium tuberculosis isolated from the referral hospitals.
Design: Study of 211 isolates of the bacteria received from the hospitals in central Thailand by Southern hybridization, with IS6110 probe and other probes when indicated.
Results: In 43 isolates only one copy of IS6110 was observed. These could be further differentiated by DR- and PGRS-specific probes. Two large groups of isolates with similar hybridization patterns were identified. The Beijing family, comprising 80 isolates, was previously reported to be commonly found in China, Mongolia, Thailand and Korea. The Nonthaburi group, comprising 29 isolates, were local strains. The age, sex and HIV status of the patients did not significantly correlate with the chance of being infected by isolates of any particular hybridization pattern. However, clustered isolates were found more commonly among the members of both the Beijing family and the Nonthaburi group.
Conclusion: Southern hybridization with IS6110 was found to be useful in studying the epidemiology of tuberculosis in Thailand. The existence of the Beijing family was confirmed. The unusually wide spread of the Beijing family in several countries in Asia merits further investigation.