Primary drug resistance in newly diagnosed smear positive tuberculosis patients in Addis Ababa, Ethiopia.

BACKGROUND: Drug resistance monitoring is an important aspect of tuberculosis (TB) control.

OBJECTIVE: To determine the sensitivity of mycobacterial isolates from newly diagnosed pulmonary TB patients to first line anti-TB drugs in Addis Ababa.

METHODS: A survey on primary anti-tuberculosis drug resistance was conducted on smear positive pulmonary TB patients visiting 19 health centers and 3 hospitals in Addis Ababa from September 2004 to December 2005. Sputum was digested and decontaminated using Petroff's method and inoculated on Lowenstein-Jensen (LJ) media. Mycobacterial isolates were tested for sensitivity to isoniazid, rifampicin, ethambutol and streptomycin on Middlebrook 7H10 media using the standard indirect proportion method.

RESULTS: Among the M. tuberculosis strains isolated from 173 patients, 21.4% were resistant to at least one drug. Single drug resistance to streptomycin was observed in 16.2%, to isoniazid in 13.3%, to rifampicin in 1.2% and to ethambutol in 3.5% of the isolates. The prevalence of resistance to at least one drug was 15.7% and 23.7% among patients with and without HIV co-infection, respectively (p > 0.05). Only one patient (0.6%) had a multidrug resistant (MDR) strain. However, the prevalence of resistance to more than one drug was 10.4%.

CONCLUSION: Although the prevalence of MDR was low in this study, the precursors of MDR are accumulating in Addis Ababa.