Contribution of resistance-nodulation-division efflux pump operon smeU1-V-W-U2-X to multidrug resistance of Stenotrophomonas maltophilia

Chao Hsien Chen, Chiang Ching Huang, Tsao Chuen Chung, Rouh Mei Hu, Yi Wei Huang, Tsuey Ching Yang

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KJ09C, a multidrug-resistant mutant of Stenotrophomonas maltophilia KJ, was generated by in vitro selection with chloramphenicol. The multidrug-resistant phenotype of KJ09C was attributed to overexpression of a resistance nodulation division (RND)-type efflux system encoded by an operon consisting of five genes: smeU1, smeV, smeW, smeU2, and smeX. Proteins encoded by smeV, smeW, and smeX were similar to the membrane fusion protein, RND transporter, and outer membrane protein, respectively, of known RND-type systems. The proteins encoded by smeU1 and smeU2 were found to belong to the family of short-chain dehydrogenases/ reductases. Mutant KJ09C exhibited increased resistance to chloramphenicol, quinolones, and tetracyclines and susceptibility to aminoglycosides; susceptibility to β-lactams and erythromycin was not affected. The expression of the smeU1-V-W-U2-X operon was regulated by the divergently transcribed LysR-type regulator gene smeRv. Overexpression of the SmeVWX pump contributed to the acquired resistance to chloramphenicol, quinolones, and tetracyclines. Inactivation of smeV and smeW completely abolished the activity of the SmeVWX pump, whereas inactivation of smeX alone decreased the activity of the SmeVWX pump. The enhanced aminoglycoside susceptibility observed in KJ09C resulted from SmeX overexpression.

Original languageEnglish
Pages (from-to)5826-5833
Number of pages8
JournalAntimicrobial Agents and Chemotherapy
Issue number12
Publication statusPublished - Dec 2011


ASJC Scopus subject areas

  • Pharmacology (medical)
  • Pharmacology
  • Infectious Diseases

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