[Epidemiological study of microepidemics of tuberculosis by restriction fragment length polymorphism analysis]

Restriction fragment length polymorphism (RFLP) analysis was performed with 13 events considered as microepidemics of tuberculosis occurred in Osaka prefecture from July 1995 to July 1998. In 7 out of 13 events, isolates from patients involved in each event showed identical RFLP patterns, hence these events were verified as microepidemics. Out of 7 microepidemics, three were intrafamily infection, the other three occurred in work places and the remaining one was in a school occurred among students. The total number of patients who were involved in microepidemics was 19 and their ages distributed in the wide range from 18 to 69 years old, but 11 were at twenties or forties. The total delay in case-finding was 2 months in the shortest case, and more than 14 months in the longest. In the remaining 6 of 13 events, the isolates from patients were showed different RFLP patterns, although they were suspected as microepidemics. Furthermore, in the 2 microepidemics, one isolate showed different RFLP pattern from the other isolates involved in each events. These facts suggest that there could be many overlooked sources of tuberculosis infection in Osaka.