Analysis of drug susceptibility in Mycobacterium tuberculosis isolated from Thiruvananthapuram using Alamar Blue assay

Tuberculosis (TB) is caused by Mycobacterium tuberculosis and the control o f the disease is hampered by widespread emergence of drug resistance in thi s pathogen. An early information on drug susceptibility would greatly facil itate an effective treatment of TB. Seventy-eight isolates of M. tuberculos is were obtained from TB patients from Thiruvananthapuram over a period of about 18 months. Resistance and susceptibility of these isolates to four fr ontline drugs were assayed using Alamar Blue, an oxidation-reduction dye, T hirty-six per cent of the isolates were susceptible to all the four drugs u sed, 21.8% were resistant to isoniazid, 8.9% to ethambutol and 2.6% to rifa mpicin. None was found resistant to streptomycin atone. Multidrug resistanc e (resistance to at least rifampicin and isoniazid) was found in 7.7% of th e isolates. The remaining ones were resistant to combinations of two or mor e of the drugs. Alamar Blue-based assay promises to be an economical and fa st method to determine drug susceptibility and resistance of M. tuberculosi s to aid effective drug therapy.