INFLUENCE OF SUBINHIBITORY CONCENTRATIONS OF ANTIBIOTICS ON SURFACE HYDROPHOBICITY OF SALMONELLA-ENTERITIDIS

The effects of subinhibitory concentrations (sub-MICs) of quinolones c iprofloxacin (CAS 85721-33-1), enoxacin (CAS 74011-58-8), norfloxacin (CAS 70458-96-7), ofloxacin (CAS 82419-36-1), pefloxacin (CAS 70458-92 -3), aminoglycosides amikacin (CAS 37517-28-5), gentamicin (CAS 1403-6 6-3), netilmicin (CAS 563911-56-1), tobramycin (CAS 32986-56-4), and b eta-lactam antibiotics imipenem (CAS 64221-86-9) and meropenem (CAS 96 036-02-2) on the surface hydrophobicity of a clinical isolate of Salmo nella enteritidis were studied. Cell hydrophobicity on the tested stra in was determined by the method of bacterial adherence to hydrocarbone -xylene (BATH) and on the basis of salt aggregation test of ammonium s ulphate (SAT). From the quinolones tested, the highest inhibition of a dherence was shown by ciprofloxacin (40%) and enoxacin (38%) at 1/4 of MIC. Aminoglycoside antibiotics stimulated the adherence, having no a ppreciable effect on the SAT values. The only significant effect on th e adhesion was that of gentamicin, 1/4 of MIC of which lowered its val ue to 2.5%. The decrease of adherence also was accompanied by a drop o f hydrophobicity of the bacterial strain in the SAT test. The results obtained in both tests show that sub-MICs of beta-lactams cause a sign ificant inhibition of the hydrophobicity of the studied strain and tha t the effect of imipenem is more pronounced than that of meropenem. Th e levels of the inhibition of adherence induced by 1/8 and 1/16 of MIC were 22% and 20%, respectively, as compared to the control value. The influence exerted by the sub-MICs of antibiotics on the cell surface hydrophobicity might be seen as an interference with the pathogenic po tential of Salmonella enteritidis.