Biofilm Formation in Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus Strains

Abstract

Background: The combination of methicillin resistance (MR) and the ability of biofilm formation of Staphylococcus aureus (SA) makes treatment difficult. Biofilm is formed by distinct genetic mechanisms in MRSA and methicillin-sensitive SA (MSSA), and hence, there is difference in the prevalence of biofilms in them. This study investigated the biofilm production in SA and analyzed its correlation with MR. Materials and methods: A total of 261 consecutive Staphylococcus aureus isolated from various clinical samples from January to April 2019 were included in the study. Antibiotic sensitivity was carried out as per Clinical and Laboratory Standards Institute guidelines and cefoxitin disk was used for screening for MR. Total of 147 MSSA and 114 MRSA were taken for further processing. Biofilm formation was determined by tube and microtiter plate methods in all the isolates. The data were analyzed for statistical significance using Microsoft excel software. Results: Resistance to erythromycin, clindamycin, gentamicin, cotrimoxazole, and inducible clindamycin resistance was significantly higher in all the MR Staphylococcus strain including biofilm forming MRSA strains. The biofilm formation was significantly higher in MSSA isolates by both the tube (78.2%) and microtiter plate methods (64.9%). Discussion: Although the antimicrobial resistance was higher in MRSA, the ability to form biofilms was significantly higher in MSSA. Biofilms of MSSA are usually less prevalent than MRSA probably because of the distinct genetic mechanisms involved in the formation of biofilms. The higher biofilm forming ability of MSSA in our study highlights the need for determination of other genes involved in biofilm formation and virulence mechanisms in SA.