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Abstract
S. aureus and S. epidermidis are common pathogens in biofilm related infections of indwelling medical devices. The aim of this study was to assess the efficacy of vancomycin and clindamycin alone and in combination with hamamelitannin as a quorum sensing inhibitor in preventing biofilm formation by S. aureus and S. epidermidis. The frequency of biofilm formation and its strength of 21 S. aureus and 26 S. epidermidis strains isolated by blood culture from patients admitted to ICUs of Fayoum and Cairo university hospitals was assessed by modified microtitre plate method. The MICs of vancomycin and clindamycin against 22 strains (11 MRSA and 11 methicillin - Resistant S. epidermidis) was assessed by microdillution method in a concentrations ranging from 512 ug/ml to 0.25ug / ml and the ability of vancomycin, clindamycin alone and in combination with hamamelitannin as a quorum sensing inhibitor to prevent biofilm formation. The presence of icaA and icaD genes was determined by PCR technique. 63.8% were strong biofilm producers, 25.5% were moderate and 10.6% were non biofilm producers. The MIC50 and MIC90 of vancomycin were 2 ug/ml and 4 ug/ml respectively against planktonic and Sessile cells while those of clindamycin were 0.5 ug/ml and 8 ug/ml respectively against planktonic cells and 4 ug/ml and 32 ug/ml respectively against Sessile cells