Objective: To identify multiple infections of Mycobacterium tuberculosis in tuberculosis patients.
Methods: From the clinical isolates of M. tuberculosis during 1999 to 2004 stored at Shanghai Municipal Center for Disease Control and Prevention, cases who had two isolates with different drug resistance patterns in the same treatment episode were selected. The first isolate from the selected patients was inoculated onto Middlebrook 7H11 agar plates, and 30 single colonies from each isolate were picked and genotyped by the 7 loci Variable Number Tandem Repeat (VNTR) method.
Results: Two out of 22 isolates had two different genotypes among their 30 single colonies, and the proportions of the two genotype colonies were 24:6 and 29:1. The other 20 isolates showed identical genotype pattern among their 30 single colonies.
Conclusion: Multiple infections of M. tuberculosis occurred in tuberculosis patients in Shanghai.