Investigation of biofilm in methicillin resistant Staphylococcus aureus isolates by genotypic and phenotypic methods

Objective: Staphylococcus aureus is an opportunistic human pathogen isolated from clinical specimens. Antimicrobial resistance and biofilm production are significant factors of pathogenicity. This study aimed to investigate the biofilm production, genotypic and phenotypic characteristics of S. aureus and to determine the effect of glycopeptide antibiotics on biofilm-producing strains. Materials and Methods: The study included 130 methicillin-resistant S. aureus (MRSA) isolated from clinical specimens sent to Ondokuz Mayıs University Medical Microbiology Department between April 2020 and December 2022. MIC values for vancomycin and teicoplanin was determined by broth microdilution method, biofilm formation by the microtitration plate method. Biofilm inhibitory concentration (BIC) was investigated for strong biofilm-producers. mecA, pvl, icaA, icaD and bap genes were examined using polymerase chain reaction (PCR). Results: Vancomycin and teicoplanin MIC values ranged from 0,5-2 μg/ml and 0,25-2 μg/ml, respectively. Biofilm production was negative in 37.69% and strong in 23.07% of the isolates. The BIC90 values for vancomycin and teicoplanin in strong biofilm-producing isolates were 512 times higher than the MIC90 values. While the mecA gene was detected in 96,15% of the isolates, pvl in 1,53%, icaA in 73,84%, and icaD in 76,92%, the bap gene wasn't detected. The relationship between biofilm and icaA and icaD gene was found to be significant (p<0,05). Conclusion: It was determined that biofilm formation is influenced by genetic and environmental factors, plays an important role in the development of antibiotic resistance. Biofilm-forming bacteria were found to be more resistant to antibiotics. KEYWORDS: Virulence factors, Biofilm, Polymerase chain reaction