Levofloxacin Efflux and smeD in Clinical Isolates of Stenotrophomonas maltophilia

So Young Chong, Kyungwon Lee, Hae Sun Chung, Seong Geun Hong, Younghee Suh, Yunsop Chong

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Trimethoprim-sulfamethoxazole is the first-line antimicrobial combination for Stenotrophomonas maltophilia infections. However, allergy or intolerance and increasing resistance limit the use of trimethoprim-sulfamethoxazole. Quinolones can be used as an alternative therapeutic option, but resistance can emerge rapidly during therapy. We analyzed the contribution of SmeABC and SmeDEF efflux pumps to levofloxacin resistance in clinical isolates of S. maltophilia. Nonduplicate clinical isolates of S. maltophilia were collected in 2010 from 11 university hospitals (n = 102). Fifty-five levofloxacin nonsusceptible (minimum inhibitory concentration [MIC] ≥4 μg/ml) and 47 susceptible (MIC ≤2 μg/ml) isolates were tested for efflux pump overexpression. Real-time reverse transcription-PCR was performed for amplification and quantification of smeB, smeC, smeD, and smeF mRNA. To determine which antimicrobials were affected by smeD overexpression, the growth rates of a levofloxacin-susceptible S. maltophilia isolate were compared by measuring absorbance of antimicrobial-supplemented Luria-Bertani broth (LB) cultures with or without triclosan. Significant relationships between sme gene overexpression and resistance were observed for smeD against levofloxacin, smeC and smeF against ceftazidime, and smeC against ticarcillin-clavulanate. The mean MICs of moxifloxacin and tigecycline did not significantly differ for isolates with or without overexpression of smeB, smeC, and smeF, but were significantly higher for isolates with smeD overexpression. The mean MICs of amikacin were significantly higher for smeC or smeF overexpressing isolates. Increased growth of a levofloxacin-susceptible isolate was observed in LB with 1/2 MIC levofloxacin in the presence of triclosan. These data suggest that the expression of smeD plays a role in levofloxacin resistance in S. maltophilia.

Original languageEnglish
Pages (from-to)163-168
Number of pages6
JournalMicrobial Drug Resistance
Issue number2
StatePublished - Mar 2017

Bibliographical note

Publisher Copyright:
© Copyright 2017, Mary Ann Liebert, Inc. 2017.


  • SmeDEF pump
  • Stenotrophomonas maltophilia
  • biocide
  • levofloxacin resistance


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