Status of First-Line Anti-TB drugs: An Audit of 84 Clinical Sputum AFB Isolates in Karachi
Abstract
Objective: To evaluate the current incidence of multidrug-resistant tuberculosis (MDR-TB) among positive sputum culture isolates in two commercial laboratories in Karachi, Pakistan.
Methodology: 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.
Results: 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).
Conclusion: 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.
Methodology: 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.
Results: 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).
Conclusion: 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.
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