Investigation of the relationship between biofilm formation and antibiotic resistance of staphylococcus aureus isolates

In our study, we aimed to investigate the relationship between biofilm formation and antibiotic resistance in Staphylococcus aureus isolates. 50 methicillin-resistant S.aureus (MRSA) and 50 methicillin-susceptible S.aureus (MSSA) isolates were included in the study. MIC values of the isolates for vancomycin and teicoplanin were determined by broth microdilution method and susceptibility tests for other antimicrobials were determined by disk diffusion test (DDT) method. Isolates found positive in hVISA screening were confirmed by population profile analysis-area under the curve (PAP-AUC) method. Biofilm formation of the isolates was evaluated as phenotypic on Congo Red Agar (CRA). The icaA, icaD, eno and IS256 gene regions associated with biofilm formation were investigated by Polymerase Chain Reaction (PCR) method. Penicillin, tetracycline, ciprofloxacin, levofloxacin, erythromycin, rifampicin, gentamicin, amikacin, clindamycin, iMLSB, ceftaroline, trimethoprim-sulfamethaxazole resistance rates of S.aureus isolates were determined as 87%, 51%, 44%, 42%, 38%, 36%, 35%, 35%, 32%, 29%, 20%, 6% respectively. No isolates resistant to chloramphenicol and linezolid were found. While vancomycin and teicoplanin MIC values of the isolates were found to be sensitive between 0.25-1 μg / ml for vancomycin and 0.125-2 μg / ml for teicoplanin, no resistant isolate was found. As a result of hVISA screening, 11 MRSA and 7 MSSA isolates were detected as hVISA. As a result of the PAP-AUC method, 2 MRSA and 2 MSSA isolates (4%) were found as hVISA. 98% of the isolates phenotypically produced biofilms in the CRA medium. (93% positive + 5% borderline) Biofilm production was not observed in 2% of the isolates. There was no significant difference between MRSA and MSSA isolates in terms of biofilm production (p> 0.05). The ratio of isolates having biofilm related genes was found to be %99 icaA, %100 icaD, %100 eno and %35 for IS256. Antibiotic resistance rates of biofilm producing isolates was penicillin 86.7%, tetracycline 52%, ciprofloxacin 44.8%, levofloxacin 42.8%, erythromycin 38.7%, rifampin 36.7%, amikacin and gentamicin 35.7%, clindamycin 32.6% , and SXT 6.1%. Two isolates that did not produce biofilm were sensitive to antimicrobials other than penicillin. The resistance rates of S.aureus isolates with IS256 penicillin, rifampicin, erythromycin, clindamycin, iMLSB, tetracycline, levofloxacin, ciprofloxacin, gentamicin and amikacin resistance rates were found to be significantly higher than the group without IS256 (p <0.02-0.0001).