Effect of Subinhibitory Aminoglycoside and Fluoroquino-lone Concentrations on the Hydrophobicity and Motility of Serratia marcescens

Overview

The authors investigated the effect of subinhibitory quinolone concentrations (ciprofloxacin, eno-xacin, norfloxacin, ofloxacin, pefloxacin) and aminoglycosides (amicacin, gentamicin, netilmicin,tobramycin) on the surface hydrophobicity and motility of the clinical isolate of Serratia marces-cens. 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 con-centrations inhibited the adherence of S. marcescens to xylene with the exception of 1/16 MICofloxacin where slight stimulation took place. The most marked inhibition of adherence wasobserved after the action of 1/4 MIC ciprofloxacin (to 13.2%) and pefloxacin (to 31.0%) as comparedwith the control. Among aminoglycosides netilmicin markedly inhibited the adherence over thewhole range of concentrations, whereby 1/8 MIC suppressed it to 0.7%. With these data correlatedalso the results of the salt-aggregation test. The investigated antibiotics did not have a major effecton the motility of S. marcescens.

Key words:
antibiotics – subinhibitory concentrations – hydrophobicity – motility – Serratia mar-cescens.