The Relationship between Biofilm Production and Antimicrobial Resistance in Methicillin-sensitive and Methicillin-resistant Staphylococcus aureus Isolates: In vitro Evaluation

Abstract

Introduction: The biofilm formation ability plays an important role in the pathogenesis of Staphylococcus aureus infections. This study aimed to investigate the biofilm production ability of methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) isolates and evaluate the relationship between their antimicrobial resistance profile and biofilm formation ability. Materials and Methods: A total of 50 MRSA and 50 MSSA isolates were examined. The antimicrobial susceptibility testing of isolates was performed using the disk diffusion method. The broth microdilution method was used to determine the minimum inhibitor concentrations (MICs) of vancomycin and teicoplanin. The biofilm formation ability of isolates was tested on Congo Red Agar. The presence of icaA, icaD, IS256, and eno genes was investigated by polymerase chain reaction. Results: Both MRSA and MSSA isolates were found susceptible to vancomycin, teicoplanin, chloramphenicol, and linezolid. Two MRSA and 2 MSSA isolates were determined as heterogeneous vancomycin-intermediate S. aureus. No significant difference was observed between the biofilm formation ability of MRSA and MSSA isolates. The eno and icaD genes were detected in 100% of both MSSA and MRSA isolates. The icaA gen was detected in all MRSA and 49 MSSA isolates. The IS256 was detected in 35 of the 50 MRSA isolates. None of the MSSA isolates were positive for the IS256. The amikacin, gentamicin, ciprofloxacin, levofloxacin, rifampin, clindamycin, and tetracycline resistance rates in IS256- positive MRSA isolates were significantly higher than those IS256-negative MRSA isolates. The mean MIC values of vancomycin and teicoplanin in IS256-positive MRSA isolates were significantly higher than those in IS256-negative MRSA isolates. Conclusion: This study revealed that the presence of the IS256 sequence was correlated with antimicrobial resistance, especially MRSA isolates.

Keywords

• methicillin-resistant s. aureus
• methicillin-sensitive s. aureus
• antimicrobial susceptibility
• biofilm formation