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J Antimicrob Chemother. 1996 Jul;38(1):133-7.

A mechanism of rifamycin inhibition and resistance in Pseudomonas aeruginosa.

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University of Pittsburgh Graduate School of Public Health, Department of Infectious Diseases and Microbiology, Pennsylvania 15261, USA.


We sought to study the nature of rifampicin resistance in Pseudomonas aeruginosa. We hypothesized that the rifamycin regions of RNA polymerase are conserved in P. aeruginosa and that rifampicin resistance is mediated by a mutation in the rpoB gene encoding the beta subunit of RNA polymerase. Transcription assays showed that 50 nM of rifampicin inhibited transcription > 99% in a clinical isolate (MIC = 32 mg/L) and only < 40% in the rifampicin resistant mutant (MIC = 1000 mg/L). DNA sequencing revealed that the rifampicin regions are conserved in P. aeruginosa and the rifampicin regions of the rifampicin-resistant strain contained a mutation. Sodium hexametaphosphate lowered rifamycin MIC in a rifamycin-resistant mutant four-fold and in the clinical isolate 32-fold, suggesting that P. aeruginosa has a natural membrane barrier to rifamycins.

[Indexed for MEDLINE]

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