Drug resistance of Mycobacterium tuberculosis isolates from tuberculosis lymphadenitis patients in Ethiopia

BACKGROUND & OBJECTIVES: The emergence of drug resistance tuberculosis (TB) is a significant challenge for TB control and prevention programmes, and the major problem is multidrug resistant tuberculosis (MDR-TB). The present study was carried out to determine the frequency of drug resistant Mycobacterium tuberculosis isolates among newly and retreated TB lymphadenitis patients and risk factors for acquiring this infection. METHODS: Two hundred twenty five M. tuberculosis isolates from TB lymphadenitis patients who were diagnosed as new and retreated tuberculosis cases between April 2012 and May 2012 were included in this study. Isolates were tested for susceptibility to isoniazed (INH), rifampicin (RMP), streptomycin (SM), ethambutol (EMB) and pyrazinamide (PZA) using the BacT/AlerT 3D system protocol. RESULTS: Among 225 isolates, 15 (6.7%) were resistant to at least one first line anti-TB drug. Three (1.3%) were MDR-TB. Resistance to INH, RMP, SM, and EMB was found in 8 (3.6%), 4 (1.8%), 10 (4.4%), and 4 (1.8%) isolates, respectively. Of the 212 new TB lymphadenitis cases three (1.4%) were MDR-TB. A rifampicin resistant M. tuberculosis isolate was diagnosed from smear and culture negative newly treated cases. All isolates were susceptible to PZA. Matted cervical lymph nodes were the prominent sites involved. Newly treated TB lymphadenitis patients had a greater risk for presenting resistance to anti-TB drugs (P=0.046). INTERPRETATION & CONCLUSIONS: Our study showed that TB lymphadenitis patients harboured drug resistant TB and MDR-TB, although at a low rate. Resistance was not associated with age, sex, patients’ education and contact history. Further research is required to determine transmission dynamics of drug resistant strains.