Aim: Etest (AB Biodisk, Solna, Sweden) is a new rapid and accurate alternative for susceptibility testing. It also can measure the minimal inhibitory concentration. The aim of this study was to assess the prevalence of drug-resistant Mycobacterium TB (MT) in newly diagnosed tuberculous Egyptian children, and to determine the effectiveness of the Etest to detect drug-resistant MT.
Methods: This prospective study included 150 newly diagnosed pulmonary and extrapulmonary tuberculous children. The organism was isolated and identified after decontamination. Antimicrobial susceptibility testing was performed by proportion method using Lowenstein-Jensen medium (PMLJ) and Etest. Minimal inhibitory concentration for both first and second line anti tuberculous drugs was determined by Etest. Comparison between the two methods was done.
Results: Age range was 6 months - 15 years (mean of 7.4+/-3.3). Pulmonary tuberculosis (TB) and extrapulmonary cases were 85/150 (55.3%) and 67/150 (44.7%) respectively. Seventy three isolates of MT were obtained from patients or contacts. Using Etest, the over all drug resistant of MT was 24.7% which is resistance to one drug (any drug). Resistance to first-line drugs; isoniazid, rifampicin, streptomycin and ethambutol was 5.4%, 2.7%, 6.8% and 1.4% respectively. Rifampicin resistance strongly correlated with isoniazid resistance. The prevalence of multi-drug resistance was 2.7%. Resistance to second line was 2.7% for amikacin and 1.4% for ciprofloxacin. Etest showed an overall specificity of 97.89 and sensitivity of 81.8. Overall agreement of Etest with reference proportion method range was 94.5-100%.
Conclusion: Etest appears to be a good alternative method for testing susceptibility of Mycobacterium tuberculosis.