Research Information System
Turkish Journal of Pharmaceutical Sciences, vol.22, no.2, pp.131-139, 2025 (ESCI)
Objectives: The aim of this study was to determine the development of in vitro resistance and changes in biofilm forming abilities in methicillin-resistant Staphylococcus aureus (MRSA) isolates exposed to sub-minimal inhibitory concentrations (sub-MICs) of daptomycin and linezolid; and to investigate the presence of the methicillin resistance gene (mecA) and the biofilm-associated genes (icaA, icaD) by polymerase chain reaction. Materials and Methods: This study was carried out with thirty-two MRSA isolates. The susceptibility of the isolates to daptomycin and linezolid was investigated by the broth microdilution method, and MIC values were determined (1st MIC). After serial passages, the 2nd MIC and the 3rd MIC values were similarly detected. Before and after serial passages, the biofilm-forming abilities of MRSA isolates were examined using the microtiter plate (MTP) method. Results: When the daptomycin and linezolid 1st MIC and 3rd MIC values of the isolates were compared, there was a 2-8 fold increase in linezolid (p<0.05) and a 4-32 fold increase in daptomycin (p<0.05). According to the MTP method, 20 (62.5%) of the 32 isolates formed biofilm at various levels, while 12 (37.5%) did not form biofilm. After the second series of passages, biofilm formation was observed in 19 (59.4%) isolates with daptomycin (p>0.05) and in 16 (50%) isolates with linezolid (p>0.05). The mecA gene was found in all isolates. Also, icaA and icaD genes were detected in 31 (96.9%) of 32 MRSA isolates. Conclusion: MRSA isolates exposed to sub-MICs of the antibiotics daptomycin and linezolid were observed to form biofilms at varying levels or to lose their ability to form biofilms. The induction, reduction or eradication of biofilm depended on the type of antibiotic and the MRSA isolate.