oa Molecular Diagnosis and Vaccines - Multi-drug resistant mycobacterium tuberculosis from Abbasia Chest Hospital, Cairo, Egypt: molecular identification by DNA based methods of mutations associated with antituberculosis drug resistance
From a collection of 155 Mycobacterium tuberculosis isolates from patients in Abbasia Chest hospital, Cairo, Egypt in 1999, 25 (16%) had multidrug resistance (MDR), to at least rifampin (RIF) and isoniazid (INH), with additional resistance to streptomycin (STR), ethambutol (EMB) and pyrazinamide (PZA) in 18, 16, and 2 of them respectively. Thirteen (10.74%) MDR isolates were from newly diagnosed untreated cases and 12 (35.29 %) were re-treated cases (p<0.05). Restriction fragment length polymorphism (RFLP) analysis revealed that the MDR isolates were unique types (strains). We further evaluated the MDR strains for mutations associated with resistance in rpoB, katG, rpsL, and embB by single strand conformational polymorphism (SSCP) and DNA sequence analyses. Mutations in studied genes did not account for all RIFr, INHr, STRr, and EMBr strains, since 24%, 53%, 44.5%, and 63.7% of the strains respectively were wild-type respectively. All INHr strains were resistant to between 0.2 and 1 ?g/ml INH, none were resistant to 5 ?g/ml and 47.1% of them showed katG315 amino acid substitutions. All STRr strains were resistant to between 2 and10 ?g/ml, and 22.2 % and 33.3 % of them showed rpsL43 43 and rspL88 amino acid substitutions respectively. No major differences were found in the frequency of mutation or type of amino acid substitution between newly diagnosed untreated cases and re-treated cases. The sensitivity of SSCP was 100% when compared to DNA sequence analysis. A silent mutation was found in one RIFr strain. Our data underscore the need for continuous drug resistance monitoring due to recent increases in MDR-TB in Egypt. Early detection of resistance and characterization of resistance mechanisms in M. tuberculosis may facilitate the control of tuberculosis in Egypt.
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