Association Between agr Type, Virulence Factors, Biofilm Formation and Antibiotic Resistance of Staphylococcus aureus Isolates From Pork Production

Abstract

Livestock-associated <i>Staphylococcus aureus</i> colonization and/or infections exist in pigs and people in frequent contact with pigs. In this study, a total of 130 <i>S. aureus</i> isolates obtained from different stages of pork production were subjected to antimicrobial susceptibility, biofilm formation, as well as PCR screening to identify virulence genes, and the accessory gene regulator alleles (<i>agr</i>). Among all 130 <i>S. aureus</i> isolates, 109 (83.8%, 109/130) isolates were positive for <i>agr</i>. All swine farms isolates belonged to <i>agr</i> IV, whereas <i>S. aureus</i> isolated from slaughterhouse and retail indicated diverse <i>agr</i> types. All isolates exhibited biofilm formation ability, and raw meat isolates (belonging to <i>agr</i> I) exhibited a greater ability to form strong biofilms than swine farms isolates (belonging to <i>agr</i> IV). <i>agr</i>-positive isolates were associated with more virulence genes than <i>agr</i>-negative isolates. Most biofilm-producing isolates were positive for microbial surface component recognizing adhesive matrix molecule (MSCRAMM), capsule type and <i>ica</i> group genes. The results illustrate a significant association between the prevalence rate of MSCRAMM, capsule type and <i>ica</i> group genes among isolates producing weak, moderate and strong biofilms. The high prevalence of resistance to ciprofloxacin, gentamicin, tetracycline, clarithromycin, clindamycin, and trimethoprim-sulfamethoxazole were mainly observed in moderate and weak biofilm producers. Our findings indicate that <i>S. aureus</i> isolates from pork production displayed diverse molecular ecology.