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Background: Fluoroquinolones are broad-spectrum antibiotics that are recommended, and increasingly important, for the treatment of multidrug-resistant tuberculosis (MDR-TB). Resistance to fluoroquinolones is caused by mutations in the Quinolone Resistance Determining Region (QRDR) of gyrA and gyrB genes of Mycobacterium tuberculosis. In this study, we characterized the phenotypic and genotypic resistance to fluoroquinolones for the first time in northeast Iran.Methods: A total of 123 Mycobacterium tuberculosis isolates, including 111 clinical and 12 collected multidrug-resistant isolates were studied. Also, 19 WHO quality control strains were included in the study. The phenotypic susceptibility was determined by the proportion method on Löwenstein-Jensen medium. The molecular cause of resistance to the fluoroquinolone drugs ofloxacin and levofloxacin was investigated by sequencing of the QRDR region of the gyrA and gyrB genes.Results: Among 123 isolates, six (4.8%) were fluoroquinolone-resistant according to phenotypic methods, and genotypically three of them had a mutation at codon 94 of the gyrA gene (Asp→ Gly) which was earlier reported to cause resistance. All three remaining phenotypically resistant isolates had a nucleotide change in codon 95. No mutations were found in the gyrB gene. Five of the 19 WHO quality control strains, were phenotypically fluoroquinolone-resistant, four of them were genotypically resistant with mutations at codon 90, 91 of the gyrA gene and one resistant strain had no detected mutation.Conclusions: Mutation at codon 94 of the gyrA gene, was the main cause of fluoroquinolone resistance among M. tuberculosis isolates in our region. In 3/6 fluoroquinolone-resistant isolates, no mutations were found in either gyrA or gyrB. Therefore, it can be concluded that various other factors may lead to fluoroquinolone resistance, such as active efflux pumps, decreased cell wall permeability, and drug inactivation. [ABSTRACT FROM AUTHOR]

Background: Due to side-effects and low efficacy of common drugs on new resistant strains of Mycobacterium tuberculosis (Mtb), investigation on novel drugs and natural compounds from rich sources of endemic plants is required. Thus, in the present study, the anti-mycobacterial effects of 22 Iranian endemic or rare plant extracts on multi-drug resistance (MDR) and extensively-drug resistance (XDR) Mtb isolates were evaluated., Methods: Twenty-two Iranian endemic and rare plant species from 9 families were collected and extracted by methanol. Their inhibitory-effects were then evaluated against Mtb H37Rv strain, seven clinical MDR-TB, and two XDR-TB isolates using the resazurin microtiter assay (REMA) method. The best of them were then fractionalized by five different polar solvents (Petroleum- Ether, Dichloromethane, Ethyl-Acetate, n-butanol, and water). To find anti-mycobacterial fractions, the inhibitory effect of isolated fractions was tested on Mtb H37Rv., Results: Out of the 22 plants, 14 plant extracts demonstrated anti-mycobacterial activity with minimum inhibitory concentration (MIC) ranging from 4 to 30μg/mL against Mtb H37Rv. Eight plant extracts also exhibited anti-mycobacterial activity against MDR and XDR clinical strains of Mtb by MICs, i.e., 15-60μg/ml. Crinitaria grimmii and Linum album were the best antimycobacterial plants. Among fractions of Crinitaria grimmii, dichloromethane and n-butanol, and for Linum album, dichloromethane and Ethyl-Acetate fractions displayed more anti-mycobacterial effect as compared to crude extract on Mtb., Conclusion: The present study confirms the potential role of some plants to treat respiratory diseases as our results have demonstrated that these plants exhibit anti-mycobacterial activity in the acceptable range against Mtb. Thus, these plants could be good sources and alternatives of plant metabolites for anti-TB-drug development., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)