Staphylococcus aureus is an opportunistic pathogen and a leading cause of healthcare-associated infections, with heightened risk in surgical settings. The study examined isolates obtained from healthy orthopedic surgical personnel to define antibiotic resistance patterns, quantify biofilm formation, and detect selected virulence and resistance genes. The authors aimed to assess colonization characteristics that could contribute to silent nosocomial transmission from healthcare workers to patients.
Sampling targeted healthy orthopedic surgical staff; nasal and hand swabs were collected and yielded a total of 63 S. aureus isolates. Isolates were phenotypically categorized as methicillin-resistant (MRSA) or methicillin-susceptible (MSSA) using cefoxitin resistance for MRSA identification and oxacillin testing by broth microdilution as required. Antimicrobial susceptibility testing employed the Kirby–Bauer disk diffusion method, with oxacillin MICs determined by broth microdilution.
Biofilm formation was quantified using the tissue culture plate assay. Molecular detection of selected resistance and virulence determinants used PCR. The analysis compared biofilm biomass across isolate sources (nasal versus hand) and phenotypes (MRSA versus MSSA), and examined associations between antimicrobial resistance phenotypes and biofilm strength.
From the collected swabs, 63 S. aureus isolates were recovered: 52 (82.5%) were MRSA and 11 were MSSA. All isolates produced biofilm in the tissue culture plate assay. Nasal isolates accounted for the highest proportion of strong biofilm producers, although the difference in strong-producer frequency between sites was not statistically significant.
High resistance rates were recorded for penicillin and ampicillin across the collection. Erythromycin resistance showed a significant association with moderate biofilm formation. Among MRSA isolates, 40.4% exhibited a multidrug-resistant (MDR) phenotype and 1.9% were classified as extensively drug-resistant (XDR). Notably, all isolates remained susceptible to vancomycin and chloramphenicol.
MRSA isolates produced significantly greater biofilm biomass than MSSA isolates, indicating a linkage between methicillin resistance and enhanced biofilm production in this cohort.
Molecular testing identified the mecA gene in all MRSA isolates, consistent with the phenotypic methicillin-resistance profile. The icaA gene, implicated in biofilm formation, was detected exclusively among MRSA isolates and showed a strong correlation with increased biofilm biomass.
The accessory gene regulator (agr) system was typed, and three agr types were identified in the sample set; agrI was the predominant type. The study highlights the co-occurrence of resistance determinants and biofilm-associated genes among colonizing strains carried by surgical personnel.
Every S. aureus isolate in this dataset produced biofilm by the tissue culture plate assay, demonstrating widespread biofilm-forming capacity among colonizing strains. The greater biomass among MRSA isolates and the exclusive presence of icaA in MRSA suggest a genetic basis for enhanced biofilm production in these strains.
An observed significant association between erythromycin resistance and moderate biofilm formation indicates that particular antimicrobial-resistance phenotypes may correlate with distinct biofilm-strength categories. However, the higher proportion of strong producers among nasal isolates did not reach statistical significance, so site-specific differences in biofilm strength were not definitive.
The convergence of potent virulence determinants, multidrug resistance, and robust biofilm formation—especially among MRSA isolates recovered from healthy orthopedic surgical staff—raises concern for silent nosocomial transmission in surgical environments. Biofilm-forming carriers may serve as reservoirs for strains that are both difficult to eradicate and capable of resisting multiple antibiotic classes.
Authors emphasize the need for enhanced infection-control measures targeting healthcare-worker colonization, routine surveillance where appropriate, and strengthened antimicrobial stewardship to limit dissemination of MDR and XDR strains. The finding that all isolates remained susceptible to vancomycin and chloramphenicol suggests retained options for treatment, but also highlights the importance of preserving those agents through appropriate stewardship.
Ethical approval for sample collection and use was obtained from the Ethics Committee of Islamic Azad University of Medical Sciences, Tehran, Iran (IR.IAU.TMU.REC.1397.308). All procedures involving human participants complied with institutional standards and the 2013 Declaration of Helsinki. Written informed consent was obtained from participating healthcare personnel. The authors declared no conflicts of interest.
In this study of S. aureus colonizing healthy orthopedic surgical personnel, MRSA predominated and was associated with stronger biofilm formation and exclusive carriage of icaA, while mecA was present in all MRSA isolates. Substantial rates of resistance to penicillin and ampicillin were observed; 40.4% of MRSA were MDR and 1.9% were XDR, yet all isolates remained susceptible to vancomycin and chloramphenicol. These findings support targeted infection-control strategies and antimicrobial stewardship to reduce the risk of silent transmission from colonized staff to surgical patients.