[Effect of subinhibitory levels of aminoglycosides and fluoroquinolines on hydrophobicity and motility of Serratia marcescens].

The authors investigated the effect of subinhibitory quinolone concentrations (ciprofloxacin, enoxacin, norfloxacin, ofloxacin, pefloxacin) and aminoglycosides (amicacin, gentamicin, netilmicin, tobramycin) on the surface hydrophobicity and motility of the clinical isolate of Serratia marcescens. The hydrophobicity was evaluated by methods of adherence to the hydrocarbon xylene (BATH) in a salt-aggregation ammonium sulphate (SAT) test. The tested quinolones in subinhibitory concentrations inhibited the adherence of S. marcescens to xylene with the exception of 1/16 MIC ofloxacin where slight stimulation took place. The most marked inhibition of adherence was observed after the action of 1/4 MIC ciprofloxacin (to 13.2%) and pefloxacin (to 31.0%) as compared with the control. Among aminoglycosides netilmicin markedly inhibited the adherence over the whole range of concentrations, whereby 1/8 MIC suppressed it to 0.7%. With these data correlated also the results of the salt-aggregation test. The investigated antibiotics did not have a major effect on the motility of S. marcescens.