Biofilm Production, Distribution of ica Genes, and Antibiotic Resistance in Clinical Coagulase-Negative Staphylococci Isolates

<b>Backgrounds/Objectives:</b> This study aimed to quantify biofilm production and characterize the distribution of the biofilm-associated <i>ica</i> genes (<i>icaA</i>, <i>icaD</i>, <i>icaB</i>, <i>icaC</i>, <i>icaR</i>) in coagulase-negative staphylococci (CoNS) isolates, and to assess the association between these genes and antibiotic resistance profiles. <b>Methods:</b> A total of 121 CoNS isolates collected at Ümraniye Training and Research Hospital between 1 January and 30 August 2024 were identified by VITEK 2 Compact and MALDI-TOF MS. Biofilm production was quantified using the microtiter plate assay, and the presence of <i>ica</i> genes was determined by quantitative real-time PCR (qPCR). Antimicrobial susceptibility testing (AST) was performed with the VITEK 2 Compact (bioMérieux), and minimum inhibitory concentrations (MICs) were interpreted according to EUCAST criteria. <b>Results:</b><i>S. epidermidis</i> was found to have the highest biofilm production capacity among the CoNS isolates, followed by <i>S. haemolyticus</i>. The <i>icaA</i> gene was detected in 99.17% of isolates, followed by <i>icaR</i> (70.24%), <i>icaD</i> (55.37%), and both <i>icaB</i> and <i>icaC</i> (28.92% each). The highest resistance rates were observed for oxacillin (85.8%) and erythromycin (85.1%), while all isolates remained susceptible to linezolid, daptomycin, and vancomycin. <b>Conclusions:</b> The high prevalence of <i>ica</i> genes in CoNS isolates indicates that biofilm formation plays a critical role in the pathogenesis of these species. The findings reveal that CoNS have a strong biofilm production potential, which is a decisive factor in their pathogenicity. However, the high methicillin resistance rates emerge as one of the main factors limiting the effectiveness of current treatment options. Therefore, future studies need to focus on the development of anti-biofilm approaches and alternative therapeutic strategies.