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. 1995 Sep;39(9):1948–1953. doi: 10.1128/aac.39.9.1948

Role of mexA-mexB-oprM in antibiotic efflux in Pseudomonas aeruginosa.

X Z Li 1, H Nikaido 1, K Poole 1
PMCID: PMC162861  PMID: 8540696

Abstract

We have earlier described mexA-mexB-oprK, an operon involved in pyoverdine export in Pseudomonas aeruginosa, and suggested that the products of these genes also contribute to the active efflux of several antibiotics (K. Poole, K. Krebes, C. McNally, and S. Neshat, J. Bacteriol. 175:7363-7372, 1993). Recently the outer membrane component of this efflux system was shown to be OprM, rather than OprK (N. Gotoh and K. Poole, unpublished results). In the present study, the conclusion concerning the efflux activity of this system was confirmed and extended by the measurement of drug accumulation in intact cells. Thus, the steady-state accumulation levels of tetracycline and norfloxacin were increased in mexA and oprM null mutants. mexA and oprM null mutants also showed an increase in susceptibility to a wide variety of beta-lactam antibiotics and an increase in the steady-state accumulation level of benzylpenicillin, indicating that the MexA-MexB-OprM pump also effluxes beta-lactams. Furthermore, deenergization of the cytoplasmic membrane with a proton conductor always produced a strong increase in the accumulation level. Finally, a single-step mutant over-producing MexAB-OprM accumulated less tetracycline and chloramphenicol than the parent strain and was more resistant to a wide range of antimicrobial compounds, including beta-lactams. These results support the notion that these proteins contribute to the intrinsic resistance of P. aeruginosa through the multidrug active efflux process.

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Selected References

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  1. Angus B. L., Carey A. M., Caron D. A., Kropinski A. M., Hancock R. E. Outer membrane permeability in Pseudomonas aeruginosa: comparison of a wild-type with an antibiotic-supersusceptible mutant. Antimicrob Agents Chemother. 1982 Feb;21(2):299–309. doi: 10.1128/aac.21.2.299. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Dinh T., Paulsen I. T., Saier M. H., Jr A family of extracytoplasmic proteins that allow transport of large molecules across the outer membranes of gram-negative bacteria. J Bacteriol. 1994 Jul;176(13):3825–3831. doi: 10.1128/jb.176.13.3825-3831.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Fath M. J., Kolter R. ABC transporters: bacterial exporters. Microbiol Rev. 1993 Dec;57(4):995–1017. doi: 10.1128/mr.57.4.995-1017.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Gotoh N., Itoh N., Tsujimoto H., Yamagishi J., Oyamada Y., Nishino T. Isolation of OprM-deficient mutants of Pseudomonas aeruginosa by transposon insertion mutagenesis: evidence of involvement in multiple antibiotic resistance. FEMS Microbiol Lett. 1994 Oct 1;122(3):267–273. doi: 10.1111/j.1574-6968.1994.tb07179.x. [DOI] [PubMed] [Google Scholar]
  5. Jacobs C., Huang L. J., Bartowsky E., Normark S., Park J. T. Bacterial cell wall recycling provides cytosolic muropeptides as effectors for beta-lactamase induction. EMBO J. 1994 Oct 3;13(19):4684–4694. doi: 10.1002/j.1460-2075.1994.tb06792.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Li X. Z., Livermore D. M., Nikaido H. Role of efflux pump(s) in intrinsic resistance of Pseudomonas aeruginosa: resistance to tetracycline, chloramphenicol, and norfloxacin. Antimicrob Agents Chemother. 1994 Aug;38(8):1732–1741. doi: 10.1128/aac.38.8.1732. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Li X. Z., Ma D., Livermore D. M., Nikaido H. Role of efflux pump(s) in intrinsic resistance of Pseudomonas aeruginosa: active efflux as a contributing factor to beta-lactam resistance. Antimicrob Agents Chemother. 1994 Aug;38(8):1742–1752. doi: 10.1128/aac.38.8.1742. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Lomovskaya O., Lewis K. Emr, an Escherichia coli locus for multidrug resistance. Proc Natl Acad Sci U S A. 1992 Oct 1;89(19):8938–8942. doi: 10.1073/pnas.89.19.8938. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Ma D., Cook D. N., Alberti M., Pon N. G., Nikaido H., Hearst J. E. Genes acrA and acrB encode a stress-induced efflux system of Escherichia coli. Mol Microbiol. 1995 Apr;16(1):45–55. doi: 10.1111/j.1365-2958.1995.tb02390.x. [DOI] [PubMed] [Google Scholar]
  10. Ma D., Cook D. N., Hearst J. E., Nikaido H. Efflux pumps and drug resistance in gram-negative bacteria. Trends Microbiol. 1994 Dec;2(12):489–493. doi: 10.1016/0966-842x(94)90654-8. [DOI] [PubMed] [Google Scholar]
  11. Masuda N., Ohya S. Cross-resistance to meropenem, cephems, and quinolones in Pseudomonas aeruginosa. Antimicrob Agents Chemother. 1992 Sep;36(9):1847–1851. doi: 10.1128/aac.36.9.1847. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Masuda N., Sakagawa E., Ohya S. Outer membrane proteins responsible for multiple drug resistance in Pseudomonas aeruginosa. Antimicrob Agents Chemother. 1995 Mar;39(3):645–649. doi: 10.1128/AAC.39.3.645. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. McMurry L., Petrucci R. E., Jr, Levy S. B. Active efflux of tetracycline encoded by four genetically different tetracycline resistance determinants in Escherichia coli. Proc Natl Acad Sci U S A. 1980 Jul;77(7):3974–3977. doi: 10.1073/pnas.77.7.3974. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Morimyo M., Hongo E., Hama-Inaba H., Machida I. Cloning and characterization of the mvrC gene of Escherichia coli K-12 which confers resistance against methyl viologen toxicity. Nucleic Acids Res. 1992 Jun 25;20(12):3159–3165. doi: 10.1093/nar/20.12.3159. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Nikaido H., Normark S. Sensitivity of Escherichia coli to various beta-lactams is determined by the interplay of outer membrane permeability and degradation by periplasmic beta-lactamases: a quantitative predictive treatment. Mol Microbiol. 1987 Jul;1(1):29–36. doi: 10.1111/j.1365-2958.1987.tb00523.x. [DOI] [PubMed] [Google Scholar]
  16. Nikaido H. Outer membrane barrier as a mechanism of antimicrobial resistance. Antimicrob Agents Chemother. 1989 Nov;33(11):1831–1836. doi: 10.1128/aac.33.11.1831. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Nikaido H. Prevention of drug access to bacterial targets: permeability barriers and active efflux. Science. 1994 Apr 15;264(5157):382–388. doi: 10.1126/science.8153625. [DOI] [PubMed] [Google Scholar]
  18. Poole K. Bacterial multidrug resistance--emphasis on efflux mechanisms and Pseudomonas aeruginosa. J Antimicrob Chemother. 1994 Oct;34(4):453–456. doi: 10.1093/jac/34.4.453. [DOI] [PubMed] [Google Scholar]
  19. Poole K., Heinrichs D. E., Neshat S. Cloning and sequence analysis of an EnvCD homologue in Pseudomonas aeruginosa: regulation by iron and possible involvement in the secretion of the siderophore pyoverdine. Mol Microbiol. 1993 Nov;10(3):529–544. doi: 10.1111/j.1365-2958.1993.tb00925.x. [DOI] [PubMed] [Google Scholar]
  20. Poole K., Krebes K., McNally C., Neshat S. Multiple antibiotic resistance in Pseudomonas aeruginosa: evidence for involvement of an efflux operon. J Bacteriol. 1993 Nov;175(22):7363–7372. doi: 10.1128/jb.175.22.7363-7372.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Purewal A. S. Nucleotide sequence of the ethidium efflux gene from Escherichia coli. FEMS Microbiol Lett. 1991 Aug 1;66(2):229–231. doi: 10.1016/0378-1097(91)90338-b. [DOI] [PubMed] [Google Scholar]
  22. Rella M., Haas D. Resistance of Pseudomonas aeruginosa PAO to nalidixic acid and low levels of beta-lactam antibiotics: mapping of chromosomal genes. Antimicrob Agents Chemother. 1982 Aug;22(2):242–249. doi: 10.1128/aac.22.2.242. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Saier M. H., Jr, Tam R., Reizer A., Reizer J. Two novel families of bacterial membrane proteins concerned with nodulation, cell division and transport. Mol Microbiol. 1994 Mar;11(5):841–847. doi: 10.1111/j.1365-2958.1994.tb00362.x. [DOI] [PubMed] [Google Scholar]
  24. Thanassi D. G., Suh G. S., Nikaido H. Role of outer membrane barrier in efflux-mediated tetracycline resistance of Escherichia coli. J Bacteriol. 1995 Feb;177(4):998–1007. doi: 10.1128/jb.177.4.998-1007.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Yoshimura F., Nikaido H. Permeability of Pseudomonas aeruginosa outer membrane to hydrophilic solutes. J Bacteriol. 1982 Nov;152(2):636–642. doi: 10.1128/jb.152.2.636-642.1982. [DOI] [PMC free article] [PubMed] [Google Scholar]

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