Molecular and virulence characteristics of methicillin-resistant Staphylococcus aureus in burn patients

Objective

This work was to investigate the drug resistance, molecular and virulence characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in burn patients and provide empiric antibiotic therapy for clinical treatment.

Methods

A total of 365 non duplicate Staphylococcus strains, including 85 MRSA and 280 methicillin-susceptible Staphylococcus aureus (MSSA), were collected from burn patients from 2008 to 2015. The susceptibility tests of antibacterial agents were performed by the Kirby-Bauer disk diffusion method. Polymerase chain reaction (PCR) and gel electrophoresis amplification technology were used to identify the mecA, qacA/B, and virulence genes, such as staphylococcal enterotoxin A (sea), staphylococcal enterotoxin B (seb), panton-valentine leukocidin (PVL), hemolysin A (hla), fibronectin-binding protein A (fnbA) of MRSA. Pulsed field gel electrophoresis (PFGE) was performed to analysis nucleotide homology of MRSA isolates.

Results

The resistance rates of MRSA to commonly-used antimicrobial agents were significantly higher than that of MSSA. The PCR assay results showed that all MRSA were mecA-positive and qacA/B-positive strains. The prevalence of virulence gene sea, seb, PVL, hla and fnbA were 70%, 60%, 90%, 85%, 5% in MRSA strains, respectively. Also, the prevalence of virulence genes sea, seb, pvl, hla and fnbA were 40%, 33.3%, 93.3%, 100%, and 20% in MSSA strains, respectively. According to the PFGE analysis, sixteen of MRSA isolates were classified into A, B, and C types and corresponding amounts were 13 (81.25%), 2 (12.5%), and 1 (6.25%), respectively.

Conclusions

The burn patients who infected MRSA have a higher drug resistance, and further recognition the molecular characteristics of MRSA is necessary to find better treatment options.