Characterization of Mycobacterium tuberculosis isolates from patients in Houston, Texas, by spoligotyping

Mycobacterium tuberculosis isolates (n = 1,429) from 1,283 patients collect ed as part of an ongoing population-based tuberculosis epidemiology study i n Houston, Texas, were analyzed by spoligotyping and IS6110 profiling. The isolates were also assigned to one of three major genetic groups on the bas is of nucleotide polymorphisms located at codons 463 and 95 in the genes (k atG and gyrA) encoding catalase-peroxidase and the A subunit of DNA gyrase, respectively. A total of 225 spoligotypes were identified in the 1,429 iso lates. There were 54 spoligotypes identified among 713 isolates (n = 623 pa tients) assigned to 73 IS6110 clusters. In addition, among 716 isolates (n = 660 patients) with unique IS6110 profiles, 200 spoligotypes were identifi ed. No changes were observed either in the IS6110 profile or in the spoligo type for the 281 isolates collected sequentially from 133 patients. Five in stances in which isolates with slightly different spoligotypes had the same IS6110 profile were identified, suggesting that in rare cases isolates wit h different spoligotypes can be clonally related. Spoligotypes correlated e xtremely well with major genetic group designations. Only three very simila r spoligotypes were shared by isolates from genetic groups 2 and 3, and non e was shared by group 1 and group 2 organisms or by group 1 end group 3 org anisms. All organisms belonging to genetic groups 2 and 3 failed to hybridi ze with spacer probes 33 to 36, Taken together, the results support the exi stence of three distinct genetic groups of ill. tuberculosis organisms and provide new information about the relationship between IS6110 profiles, spo ligotypes, and major genetic groups of hi. tuberculosis.