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Rifampicin reduces susceptibility to ofloxacin in rifampicin-resistant Mycobacterium tuberculosis through efflux

dc.contributor.authorLouw G.E.
dc.contributor.authorWarren R.M.
dc.contributor.authorGey Van Pittius N.C.
dc.contributor.authorLeon R.
dc.contributor.authorJimenez A.
dc.contributor.authorHernandez-Pando R.
dc.contributor.authorMcEvoy C.R.E.
dc.contributor.authorGrobbelaar M.
dc.contributor.authorMurray M.
dc.contributor.authorVan Helden P.D.
dc.contributor.authorVictor T.C.
dc.date.accessioned2011-10-13T16:59:22Z
dc.date.available2011-10-13T16:59:22Z
dc.date.issued2011
dc.identifier.citationAmerican Journal of Respiratory and Critical Care Medicine
dc.identifier.citation184
dc.identifier.citation2
dc.identifier.citationhttp://www.scopus.com/inward/record.url?eid=2-s2.0-80051572614&partnerID=40&md5=edb776caf6a5a250c89f1083db5b6ba0
dc.identifier.issn1073449X
dc.identifier.other10.1164/rccm.201011-1924OC
dc.identifier.urihttp://hdl.handle.net/10019.1/17086
dc.description.abstractRationale: Central dogma suggests that rifampicin resistance in Mycobacterium tuberculosis develops solely through rpoB gene mutations. Objective: To determine whether rifampicin induces efflux pumps activation in rifampicin resistant M. tuberculosis strains thereby defining rifampicin resistance levels and reducing ofloxacin susceptibility. Methods: Rifampicin and/or ofloxacin minimum inhibitory concentrations (MICs) were determined in rifampicin resistant strains by culture in BACTEC 12B medium. Verapamil and reserpine were included to determine their effect on rifampicin and ofloxacin susceptibility. RT-qPCR was applied to assess expression of efflux pump/ transporter genes after rifampicin exposure. To determine whether verapamil could restore susceptibility to first-line drugs, BALB/cmice were infected with aMDR-TB strain and treated with first-line drugs with/without verapamil. Measurements and Main Findings: Rifampicin MICs varied independently of rpoB mutation and genetic background. Addition reserpine and verapamil significantly restored rifampicin susceptibility (p = 0.0000). RT-qPCR demonstrated that rifampicin induced differential expression of efflux/transporter genes in MDR-TB isolates. Incubation of rifampicin mono-resistant strains in rifampicin (2 mg/ml) for 7 days induced ofloxacin resistance (MIC > 2 μg/ml) in strains with an rpoB531 mutation. Ofloxacin susceptibility was restored by exposure to efflux pump inhibitors. Studies in BALB/c mice showed that verapamil in combination with first-line drugs significantly reduced pulmonary CFUs after 1 and 2 months treatment (p < 0.05). Conclusion: Exposure of rifampicin resistant M. tuberculosis strains to rifampicin can potentially compromise the efficacy of the secondline treatment regimens containing ofloxacin, thereby emphasising the need for rapid diagnostics to guide treatment. Efflux pump inhibitors have the potential to improve the efficacy of antituberculosis drug treatment.
dc.titleRifampicin reduces susceptibility to ofloxacin in rifampicin-resistant Mycobacterium tuberculosis through efflux
dc.typeArticle
dc.description.versionArticle


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