Introduction: Enterococcus faecalis is an important pathogen often implicated in nosocomial infections and poses a major public health risk. However, little is known about phenotypic antimicrobial resistance (AMR) and AMR/virulence gene composition in E. faecalis isolated from commercial pork plants.
Purpose: To characterize AMR phenotypes in E. faecalis isolated from commercial pork processing plant, to analyze AMR and virulence genes and to describe statistical associations between AMR phenotypes, resistance and virulence genotypes.
Methods: A total of 200 samples were randomly obtained from carcasses after bleeding (BC; 50), pasteurization (PC; 100) and from retail pork products (RP; 50). One isolate from each positive sample was analysed for antimicrobial susceptibility and characterized using an enterococcal DNA microarray for analysis of resistance and virulence genes.
Results: Resistance to clinically important drugs, ciprofloxacin (one isolate each from BC and RP samples) and daptomycin (one isolate each from PC and RP samples) was found. Multiresistance (≥5 antimicrobials) was more common in E. faecalis isolated from BC (77.4% of isolates) samples than those from PC (25%) and RP (37.6%) samples. The most common resistance genes (> 5% prevalence) found in E. faecalis were aminoglycosides (aac(6), aphA3, aadE,), macrolides-lincosamide (ermB, ermA, sat(4), linB) and tetracyclines (tetL, tetM, tetO). The virulence genes expressing adhesion (ace, efaAfs, agrBfs), gelatinase (gelE) and pheromone (cAM, ccF10, cob, cpd1) factors were frequently found and isolates carrying these genes were more likely to be statistically associated with genes conferring resistance to aminoglycoside, tetracycline, erythromycin and lincomycin.
Significance: These data underscore the importance of E. faecalis isolates from pork plants as a reservoir of resistance and virulence genes that may pose food safety and public health risks. Statistical associations found between virulence and resistance genes suggest their possible linkage on a common genetic element, raising concerns about their potential for co-transfer to other enterococci.