Role of smeU1VWU2X operon in alleviation of oxidative stresses and occurrence of sulfamethoxazole-trimethoprim-resistant mutants in stenotrophomonas maltophilia

Chao Jung Wu, Tsu Ting Chiu, Yi Tsung Lin, Yi Wei Huang, Li Hua Li, Tsuey Ching Yang

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Overexpression of resistance-nodulation-division (RND)-type efflux pumps is an important mechanism for bacteria to combat antimicrobials. RND efflux pumps are also critical for bacterial physiology, such as oxidative stress tolerance. Stenotrophomonas maltophilia, a multidrug-resistant opportunistic pathogen, harbors eight RND-type efflux pump operons. Of these, the smeU1VWU2X operon is unique for its possession of two additional genes, smeU1 and smeU2, which encode proteins of the short-chain dehydrogenase/reductase (SDR) family. Overexpression of the SmeVWX pump is known to contribute to the acquired resistance to chloramphenicol, quinolone, and tetracycline; however, SmeU1 and SmeU2 are little involved in this phenotype. In the study described in this article, we further linked the smeU1VWU2X operon to oxidative stress alleviation and sulfamethoxazole-trimethoprim (SXT)resistant mutant occurrence. The smeU1VWU2X operon was inducibly expressed upon challenge with menadione (MD), plumbagin (PL), and hydrogen peroxide (H 2 O 2 ), as verified by the use of the chromosomal smeU1VWU2X-xylE transcriptional fusion construct and quantitative real-time PCR (qRT-PCR). The MD-mediated smeU1VWU2X upexpression was totally dependent on SoxR and partially relied on SmeRv but was less relevant to OxyR. SmeRv, but not SoxR and OxyR, played a regulatory role in the H 2 O 2 -mediated smeU1VWU2X upexpression. The significance of smeU1VWU2X upexpression was investigated with respect to oxidative stress alleviation and SXT-resistant mutant occurrence. Overexpression of the smeU1VWU2X operon contributed to the alleviation of MD-mediated oxidative stress. Of the encoded proteins, the SmeVWX pump and SmeU2, rather than SmeU1, participated in MD tolerance. Furthermore, we also demonstrated that the MD-mediated expression of the smeU1VWU2X operon decreased the SXT resistance frequency when S. maltophilia was grown in a reactive oxygen species (ROS)-rich environment.

Original languageEnglish
Article numbere02114-17
JournalAntimicrobial Agents and Chemotherapy
Volume62
Issue number2
DOIs
Publication statusPublished - Feb 2018
Externally publishedYes

Keywords

  • Efflux pumps
  • Oxidative stress

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases

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