Drug susceptibility of Mycobacterium avium and Mycobacterium simiae isolated in a rural hospital in central India.

Drug susceptibility testing of nontuberculous mycobacterial species has gained importance after their increased isolation from AIDS patients and the fact that their treatment not only differs from Mycobacterium tuberculosis but also among themselves. Drug susceptibility testing was performed for 3 clinical and 4 environmental isolates of Mycobacterium avium and 4 clinical isolates of Mycobacterium simiae by macrodilution method using BACTEC 460TB system and microtitre broth dilution method using Middlebrook 7H9 medium. Six drugs including Streptomycin, Isoniazid, Rifampicin, Ethambutol, Ofloxacin and Kanamycin were tested. In addition, Azithromycin was tested against Mycobacterium avium only by BACTEC 460TB system. All clinical isolates of Mycobacterium avium and Mycobacterium simiae were resistant to all the drugs tested while environmental isolates were relatively sensitive. All Mycobacterium avium isolates whether clinical or environmental were sensitive to azithromycin. Total concordance between macro and microdilution methods was observed. To the best of our knowledge, this is the first report of drug susceptibility of Mycobacterium simiae in AIDS patients from India.