Antibiotic susceptibility pattern and biofilm formation in coagulase negative staphylococci.

Introduction Coagulase negative staphylococci (CoNS) are commensals of non-sterile sites in humans and become pathogenic mostly when the host is immunocompromised by prior diseases or invasive surgical or related procedures [1]. Slime or biofilm production by CoNS has been identified as an important factor in the pathogenesis of infections as bacteria organized in biofilms are protected from the action of antibiotics and the immune system [2]. Biofilm is ascribed the most important virulence factor of S. epidermidis as it enables attachment and persistence of the bacteria on foreign materials [3,4]. Other studies have indicated a correlation between antibiotic resistance and slime expression. For instance, insertion of a certain transposon influences both biofilm formation and the expression of methicillin resistance in S. epidermidis [4]. In another study methicillin resistance was found to be significantly higher in slime positive isolates (81%) than in slime negative isolates (57%) [5]. Due to the frequent recovery of CoNS in clinical infections their antibiotic susceptibility profile as well as their biofilm forming ability was investigated in this study.