Antibiotic Resistance and Distribution of Virulence Genes in MDRSA Isolated from Clinically Healthy Domestic Animals

The emergence of multidrug-resistant (MDR) bacteria in domestic animals has become a great global concern. Veterinarian often face a challenge in treating multidrug-resistant Staphylococcus aureus (MDRSA) infections due to their resistance to various classes of antibiotics. The success of S. aureus is related to the remarkable ability of this pathogen to acquire resistance towards multiple antibiotics used in veterinary practice over the years, coupled with its extensive virulence factors. Therefore, the objectives for this study would to determine the antibiotic resistant pattern and characterize the virulence profiles of MDRSA isolated from clinically healthy domestic animals in east coast regions of Malaysia. Thirty-six (36) MDRSA isolates from clinically healthy pets and livestock from the east coast regions of Malaysia were characterized in this study. S. aureus isolates were confirmed using PCR with primers specific for nuc gene. The antibiogram of S. aureus against 18 various antibiotics from 10 different antimicrobial groups was determined using Kirby–Bauer method. All 36 S. aureus isolates have demonstrated to be resistant towards more than 3 antimicrobial groups and were considered to be MDRSA. Molecular detections of 16 virulence genes (scn, chp, sak, sea, sep, fnbA, iccA, clfA, clfB, sdrC, sdrD, sdrE, eta, etb, luk-PV and tst) which associated in human immune evasion, adhesins, biofilm-formation and toxin-encoding genes were carried out using PCR. Agr typing was done to determine the distribution of agr types among the isolated MDRSA. Antibiogram has revealed that MDRSA showed high resistance rate against clindamycin (88.5%), penicillin (84.6%), tetracycline (76.9%), erythromycin (73.1%) and chloramphenicol (73.1%) antibiotics. PCR screening of various virulence genes have revealed the presence of several immune evasion cluster (IEC) genes (scn, chp and sak), adhesin (fnbA, iccA, clfA and clfB) and biofilm formation (sdrC and sdrE) encoding genes among the MDRSA. 88.5% of the MDRSA were classified as agr type I while the rest were categorized as type II (11.5%). This study has demonstrated that animal origin MDRSA harbored virulence genes which enable the pathogen to colonize the human host, form biofilm and evade human immune system.