Prevalence of Biofilm Formation and Multidrug Resistance in Clinical Isolates of Staphylococcus Aureus

Abstract Background The biofilm mode of growth significantly enhances the resistance of Staphylococcus aureus (S. aureus) to antibiotics, rendering standard treatment less effective and contributing to the global crisis of antimicrobial multidrug resistance (AMR). Thus, this study determined the prevalence of multidrug resistance (MDR) and biofilm formation among clinical S. aureus isolates and assessed their relationship. Methods A cross-sectional study was conducted to investigate the characteristics of S. aureus clinical isolates. Conventional biochemical tests were used for the presumptive identification of S. aureus, and the detection of S. aureus species-specific 16S rRNA via polymerase chain reaction (PCR) served as the confirmatory test.Biofilm formation was qualitatively assessed via the use congo red agar and quantitatively measured via the microtiter plate method. Antibiotic susceptibility test (AST) was performed using the modified Kirby–Bauer disc diffusion method, and the minimum inhibitory concentration (MIC) of vancomycin was determined via the macro broth dilution method. Logistic regression was used to predict biofilm formation by specimen type, whereas Fisher exact test was used to assess its association with MDR. Biofilm-forming isolates were molecularly characterized for the presence of the cna and icaA genes via PCR. Results A total of 280 non-duplicate Staphylococcus species isolates were collected, 33 isolates were confirmed as S. aureus. Qualitatively, 72.7% of the isolates were biofilm formers, whereas 66.7% of the isolates were weak biofilm formers. PCR characterization revealed that 6.7% of the biofilm formers harbor the cna gene, but the icaA gene was not detected in the biofilm formers. Gentamicin had the lowest resistance rate at 27.3%, whereas ciprofloxacin had the highest level of resistance at 66.7%. Additionally, 54.6% of the isolates were cefoxitin resistant, whereas 45.5% were resistant to vancomycin. Multidrug resistance was observed in 75.8% of the isolates. Conclusion This study revealed the prevalence of MDR Staphylococcus aureus and biofilm formation, but no significant association between them, likely due to the small sample size. The specimen type does not predict biofilm formation. Further research is needed to explore their independent mechanisms and to inform effective control strategies.