In vitro activity of levofloxacin against planktonic and biofilm Stenotrophomonas maltophilia lifestyles under conditions relevant to pulmonary infection in cystic fibrosis, and relationship with SmeDEF multidrug efflux pump expression

作者：Pompilio Arianna; Crocetta Valentina; Verginelli Fabio; Di Bonaventura Giovanni^*

来源：FEMS Microbiology Letters, 2016, 363(14): fnw145.

DOI：10.1093/femsle/fnw145

• biofilm
• cystic fibrosis
• levofloxacin
• lung infection
• multidrug efflux pump
• Stenotrophomonas maltophilia

The activity of levofloxacin against planktonic and biofilm Stenotrophomonas maltophilia cells and the role played by the multidrug efflux pump SmeDEF were evaluated under conditions relevant to the cystic fibrosis (CF) lung. MIC, MBC and MBEC of levofloxacin were assessed, against five CF strains, under 'standard' (CLSI-recommended) and 'CF-like' (pH 6.8, 5% CO2, in a synthetic CF sputum) conditions. Levofloxacin was tested against biofilms at concentrations (10, 50 and 100 mu g mL(-1)) corresponding to achievable serum levels and sputum levels by aerosolisation. smeD expression was evaluated, under both conditions, in planktonic and biofilm cells by RT-PCR. The bactericidal effect of levofloxacin was decreased, in three out of five strains tested, under 'CF-like' conditions (MBC: 2-4 vs 8-16 mu g mL(-1), under 'standard' and 'CF-like' conditions, respectively). Biofilm was intrinsically resistant to levofloxacin, regardless of conditions tested (MBECs >= 100 mu g mL-1 for all strains). Only under 'CF-like' conditions, smeD expression increased during planktonic-to-biofilm transition, and in biofilm cells compared to stationary planktonic cells. Our findings confirmed that S. maltophilia biofilm is intrinsically resistant to therapeutic concentrations of levofloxacin. Under conditions relevant to CF, smeD overexpression could contribute to levofloxacin resistance. Further studies are warranted to define the clinical relevance of our findings.

• 出版日期2016-7