Drug Susceptibility Pattern of Mycobacterium Tuberculosis Isolates In Addis Ababa

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Date

2005-07

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Addis Ababa University

Abstract

Background:-Addis Ababa, the capital city of Ethiopia, has an estimated population of 3.5 - 4 million. Previous reports on anti-TB drug resistance suggested an increasing trend of anti-TB drug resistance despite differences in the methodology. A study in previously treated individuals also suggested an increased incidence of Rifampicin (RMP) and Isoniazid (INH) resistance in individuals treated with fixed dose combination (FDC) anti-TB drugs. Objectives:-To determine the prevalence of resistance to the four first line anti-TB drugs and to see whether there is association between HIV and drug resistance. Methods: - A cross-sectional survey on anti-TB drug resistance was done in 19 health centres (out of 21) and 3 hospitals in Addis Ababa. Sputum and serum was collected from each patient. Sputum was digested and decontaminated using Petroff’s method with 4% NaOH and inoculated on to Lowenstein Jensen media. Proportion method with Middlebrook 7H10 media & 10% OADC enrichment was used for drug sensitivity determination. HIV testing was also done for each patient with rapid assays (Determine®, Capillus® and Unigold®). Species identification was done with a combination of Thiophene-2- Carboxylic acid Hydrazide (TCH) test and species specific PCR amplification (pncA gene) Results & Discussion :-269 (242 new and 27 previously treated) patients were included in the study. Out of these, 75% were culture positive. Sensitivity result was available for 173 isolates from new cases and 19 isolates from previously treated patients. Among the isolates from new patients 78.6% were sensitive to all drugs tested and 21.4% were resistant to any one drug while these figures in previously treated patients were 47.4% and 52.6% respectively. Prevalence of MDR-TB among new cases was 0.6% (1 isolate). Resistance to RMP, INH, Streptomycin (STM) and Ethambutol (EMB) was 1.2%, 13.3%, 16.8 and 3.5% respectively. In previously treated patients RMP, INH, STM and EMB resistance was 5.3%, 36.9%, 52.6% and 11.1% respectively. The prevalence of resistance in a similar survey conducted in 1998 was lower and the increase in the current study was statistically significant for any type of resistance, any EMB resistance, any STM resistance and resistance to multiple drugs. However the prevalence of RMP resistance and multidrug-resistant (MDR) TB was not changed. There was also no association observed between drug resistance among new cases and HIV. Conclusion:- Multidrug-resistance did not show increase in the city particularly in the last six years, compared to the previous reports. However non-MDR type of drug resistance, precursor of MDR, is on the rise.

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Mycobacterium Tuberculosis Isolates

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