Changes in CoNS biofilm formation, composition, structure and antimicrobial resistance due to growth in sub-inhibitory concentrations of dicloxacillin

Abstract

Many studies have demonstrated that low concentrations of antibiotics can inhibit microbial adherence to medical-device surfaces. However, little is known about the changes that might occur in bacterial physiology of biofilms formed under sub-inhibitory (sub-MIC) concentrations of antibiotics. In this study, biofilms of two coagulase negative staphylococci (CoNS) species were formed with and without the presence of subMIC concentrations of dicloxacillin and changes in the ability to produce biofilms as well as in the composition of biofilm matrix were evaluated. Biofilms formed in the presence of dicloxacillin developed less amount of biomass and exhibited a different composition of the biofilm matrix. Bacterial physiological alterations triggered by biofilm formation under subMIC concentrations of antibiotics were also evaluated. The results showed that bacteria surface characteristics, like hydrophobicity and elemental composition as well as the expression of PNAG molecules were affected. Additionally, an increase in resistance to several antibiotics was observed in biofilm cells formed in the presence of dicloxacillin.