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 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.

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