Drug-resistant tuberculosis in Egyptian children using Etest

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.

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.

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%.

Etest appears to be a good alternative method for testing susceptibility of Mycobacterium tuberculosis.