Drug Susceptibility Pattern Of Mycobacterium Tuberculosis Isolates In Addis Ababa

Background:-Addis Ababa, the capital city of Ethiopia, hasrnan estimated population of 3.5 - 4 million. Previous reportsrnon anti-TB drug resistance suggested an increasing trendrnof anti-TB drug resistance despite differences in thernmethodology. A study in previously treated individuals alsornsuggested an increased incidence of Rifampicin (RMP) andrnIsoniazid (INH) resistance in individuals treated with fixedrndose combination (FDC) anti-TB drugs.rnObjectives:-To determine the prevalence of resistance tornthe four first line anti-TB drugs and to see whether there isrnassociation between HIV and drug resistance.rnMethods: - A cross-sectional survey on anti-TB drugrnresistance was done in 19 health centres (out of 21) and 3rnhospitals in Addis Ababa. Sputum and serum was collectedrnfrom each patient. Sputum was digested andrndecontaminated using Petroff’s method with 4% NaOH andrninoculated on to Lowenstein Jensen media. Proportionrnmethod with Middlebrook 7H10 media & 10% OADCrnenrichment was used for drug sensitivity determination.rnHIV testing was also done for each patient with rapidrnassays (Determine®, Capillus® and Unigold®). Speciesrnidentification was done with a combination of Thiophene-2-rnCarboxylic acid Hydrazide (TCH) test and species specificrnPCR amplification (pncA gene)rnResults & Discussion :-269 (242 new and 27 previouslyrntreated) patients were included in the study. Out of these,rn75% were culture positive. Sensitivity result was availablernfor 173 isolates from new cases and 19 isolates fromrnpreviously treated patients. Among the isolates from newrnpatients 78.6% were sensitive to all drugs tested and 21.4%rnwere resistant to any one drug while these figures inrnpreviously treated patients were 47.4% and 52.6%rnrespectively. Prevalence of MDR-TB among new cases wasrn0.6% (1 isolate). Resistance to RMP, INH, Streptomycinrn(STM) and Ethambutol (EMB) was 1.2%, 13.3%, 16.8 andrn3.5% respectively. In previously treated patients RMP, INH,rnSTM and EMB resistance was 5.3%, 36.9%, 52.6% andrn11.1% respectively. The prevalence of resistance in arnsimilar survey conducted in 1998 was lower and thernincrease in the current study was statistically significantrnfor any type of resistance, any EMB resistance, any STMrnresistance and resistance to multiple drugs. However thernprevalence of RMP resistance and multidrug-resistantrn(MDR) TB was not changed. There was also no associationrnobserved between drug resistance among new cases andrnHIV.rnConclusion:- Multidrug-resistance did not show increase inrnthe city particularly in the last six years, compared to thernprevious reports. However non-MDR type of drugrnresistance, precursor of MDR, is on the rise.

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