RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM SCREENING OF MYCOBACTERIUM-TUBERCULOSIS ISOLATES - POPULATION SURVEILLANCE FOR TARGETING DISEASE TRANSMISSION IN A COMMUNITY

SETTING: Alabama State Tuberculosis Control Program, USA. OBJECTIVE: T o combine molecular screening data with routine information to assess transmission of Mycobacterium tuberculosis and improve control efforts : DESIGN: Since January 1994, samples from tuberculosis cases statewid e have been systematically analyzed by IS6110 restriction fragment len gth polymorphism (RFLP). All cases during 1994-1995 with a predominate RFLP pattern were evaluated and risk factors assessed. pTBN12 was use d to evaluate a large cluster in the Birmingham-Jefferson County (BJC) area. RESULTS: Statewide, a common two-band pattern was found, named JH2 (99/566, 17.5%). The most important risk associated with this patt ern was homelessness (odds ratio, 8.9; P < 0.001). In the BJC area, th e homeless accounted for 23% (51/175) of new cases diagnosed during th e study period. For the BJC homeless, there were 13 unique RFLP patter ns, and JH2 was predominant (29/33, 88%) among three clusters. Seconda ry analysis of the homeless JH2 cluster revealed a large group that in cluded 19 of 24 (79%) isolates analyzed. Compared with the BJC non hom eless (n = 124), the homeless were younger (P < 0.001), of male gender (P < 0.001), black race (P = 0.002), and were heavy alcohol (P < 0.00 1) and non-injection drug (P = 0.001) users. CONCLUSIONS: By screening tuberculosis cases statewide, a common two-band RFLP pattern was iden tified. Its predominance is explained by an ongoing tuberculosis epide mic among Birmingham's homeless population, highlighting RFLP as a too l for population surveillance. The pattern differences observed by pTB N12 typing clearly demonstrate that the isolates might be related but are not clonal.