Susceptibility of planktonic and biofilm forming isolates of Staphylococcus epidermidis to antimicrobial agents

The coagulase-negative Staphylococcus epidermidis is now well established as a major nosocomial pathogen associated with infections of indwelling medical devices. One hundered and nine (109) clinical isolates of S. epidermidis were isolated and identified from the following infection, native valve endocarditis, prosthetic joint infection, and intravascular catheter infection. Screening of isolates for biofilm formation qualitatively and quantitatively was assessed. The isolates were associated with biofilm formation, which may lead to an inability to eradicate the infection due to the intrinsic nature of biofilms to resist high levels of antibiotics. In this study, the sensitivity pattern to 11 different antimicrobial disks were determined. The data revealed that, all isolates were resistant to oxacillin and Amoxicilin-clavulinic acid except one, On the contrary, all isolates were sensitive to vancomycin. Furthermore, Minimum Inhibitory Concentrations (MICs) and Minimum bactericidal Concentrations (MBCs) for 29 isolates of S. epidermidis of strong biofilm producing and sensitive isolates were measured against three antimicrobial agents (vancomycin, chloramphenicol and clindamycin) in planktonic form and in biofilm forming. Planktonic isolates were susceptible to all agents studied,but the isolates in biofilms were resistant to high concentrations of most of these agents. The data revealed that, the MICS and MBCS of most isolates in biofilm form were increased 512 to 2048 times or more. These data provide insights into the response of S. epidermidis isolates when challenged with various levels of antımicrobial agents in clinical use.