title: Genotypic and phenotypic characteristics of tunisian isoniazid-resistant Mycobacterium tuberculosis strains.
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.
authors: Microbiology Laboratory, Rabta University Hospital, Tunis, 1007, Tunisia. alya_soudani@yahoo.fr
authors: Alya
authors: A
authors: Soudani
authors: Sondess
authors: S
authors: Hadjfredj
authors: Meriem
authors: M
authors: Zribi
authors: Feriel
authors: F
authors: Messaadi
authors: Taieb
authors: T
authors: Messaoud
authors: Afef
authors: A
authors: Masmoudi
authors: Mohamed
authors: M
authors: Zribi
authors: Chedlia
authors: C
authors: Fendri
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002374:Catalase / Q000235:genetics* / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005838:Genotype; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D010641:Phenotype; D017422:Sequence Analysis, DNA; D018088:Tuberculosis, Multidrug-Resistant / Q000382:microbiology; D014416:Tunisia
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D002374:Catalase; C480353:katG protein, Mycobacterium tuberculosis; D007538:Isoniazid