ABSTRACT
To evaluate the current incidence of multidrug-resistant tuberculosis [MDR-TB] among positive sputum culture isolates in two commercial laboratories in Karachi, Pakistan. In this laboratory-based study eighty four AFB smear-positive sputum culture isolates grown on routine Lowenstein-Jensen [LJ] medium in two separate diagnostic labs during 12 months ending August 2011 were identified and subjected to antimicrobial susceptibility testing using LJ medium and anti-TB First-Line drugs [FLD]. MICs of the control H37RV-NCTC strain 7416 were compared with the test strains inoculated with the batch tested. Results were evaluated by the traditional resistance ratio method. The sputa expectorated by 45 females [53.57%] and 39 males [46.43%] aged 15-58 years yielded 84 M. tuberculosis isolates. The percentages of FLD resistance were Rifampicin [48.8%], Streptomycin [28.57%], Ethambutol [7.14%], and Isoniazid [4.76%]. Kanamycin [28.57%] was also tested. Only 12 [14.28%] of these were sensitive to all the FLDs, and 4 [4.76%] were MDR-TB strains [indifferent to Rifampicin and Isoniazid]. The sparse labs in Karachi that do AFB-cultures should periodically assess and publicize the frequency of MDR-TB isolates to guide empirical therapy. Rifampicin, a consistent part of the initial drug regimen for empirical prescription, was currently least effective on the strains encountered