Title Genotypic and Phenotypic Characteristics of Tunisian Isoniazid-Resistant Mycobacterium tuberculosis Strains
Author Alya Soudani1* Sondess Hadjfredj2, Meriem Zribi1, Feriel Messaadi3, Taieb Messaoud2, Afef Masmoudi1, Mohamed Zribi3, and Chedlia Fendri1
Address 1Microbiology Laboratory, Rabta University Hospital, Tunis 1007, Tunisia, 2Biochemistry and Molecular Laboratory, Children Hospital, Tunis 1007, Tunisia, 3Hygiene Laboratory, Hedi Chaker Hospital, Sfax 3000, Tunisia
Bibliography Journal of Microbiology, 49(3),413-417, 2011,
Key Words M. tuberculosis, isoniazid resistance, new katG326 mutation, katG315 and mabA -15C→T mutations, phenotypic properties
Abstract Forty three isoniazid (INH)-resistant Mycobacterium tuberculosis isolates were characterized on the basis of the most common INH associated mutations, katG315 and mabA -15C→T, and phenotypic properties (i.e. MIC of INH, resistance associated pattern, and catalase activity). Typing for resistance mutations was performed by Multiplex Allele-Specific PCR and sequencing reaction. Mutations at either codon were detected in 67.5% of isolates: katG315 in 37.2, mabA -15C→T in 27.9 and both of them in 2.4%, respectively. katG sequencing showed a G insertion at codon 325 detected in 2 strains and leading to amino acid change T326D which has not been previously reported. Distribution of each mutation, among the investigated strains, showed that katG S315T was associated with multiple-drug profile, high-level INH resistance and loss or decreased catalase activity; whereas the mabA -15C→T was more prevalent in mono-INH resistant isolates, but it was not only associated with a low-level INH resistance. It seems that determination of catalase activity aids in the detection of isolates for which MICs are high and could, in conjunction with molecular methods, provide rapid detection of most clinical INH-resistant strains.