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.
Description
Keywords
Mycobacterium Tuberculosis Isolates