Anti-adhesive and Anti-biofilm Activities in Vitro of Linezolid, Vancomycin, Tigecycline and Daptomycin against Staphylococcus Haemolyticus

Biofilm may be formed on wide variety of surfaces, including indwelling medical devices, leading to several infectious diseases, e.g., bacteremia and sepsis. The most important pathogens related with infections associated with medical devices are coagulase-negative staphylococci, including Staphylococcus haemolyticus ñ bacterial species which express quite often the multidrug resistance. The four clinical multiresistant and methicillin-resistant S. haemolyticus were included in the present study. The evaluation of drug susceptibility was performed by using disc-diffusion method and broth microdilution method according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. The biofilm formation on the Nelaton catheter and the effect of linezolid, vancomycin, tigecycline and daptomycin on the biofilm formation and disruption of mature structure was based on the method with TTC (2,3,5-triphenyltetrazolium chloride). The adhesion process of S. haemolyticus to the Nelaton catheter was inhibited by antibiotics, as follows: linezolid at concentration 0.25-0.5 ◊ MIC, vancomycin ñ concentration 0.5 ◊ MIC, tigecycline ñ concentration 0.25-4 ◊ MIC and daptomycin ñ concentration 0.06-1 ◊ MIC, depending on the isolate. Linezolid inhibited the biofilm formation at concentration between 0.5-1 ◊ MIC, vancomycin ñ 1-2 ◊ MIC, tigecycline ñ 0.5-4 ◊ MIC and daptomycin ñ 0.06-2 ◊ MIC. The concentration of linezolid eradicating the mature biofilm was found to be 1-2 ◊ MIC, vancomycin ñ 2-8 ◊ MIC, tigecycline 2-4 ◊ MIC and daptomycin ñ 0.06-2 ◊ MIC. The most active antibiotic against S. haemolyticus biofilm formation and disruption of mature structure seems to be daptomycin.