Vancomycin-Resistant, Thermotolerant Enterococcus faecalis and Enterococcus faecium in Ready-to-Eat Beef Luncheon and Sausage

Abstract

This study investigated the prevalence, antimicrobial resistance profiles, virulence determinants, and heat tolerance of Enterococcus faecalis and Enterococcus faecium isolated from ready-to-eat (RTE) beef luncheon and sausage in Egypt. A total of 150 samples were analyzed, yielding 514 Enterococcus isolates, with contamination detected in all samples. Molecular identification revealed a predominance of E. faecium (71.2%) over E. faecalis (28.8%). High frequencies of virulence genes were detected, particularly gelE (95.7%) and ace (60.7%), indicating strong pathogenic potential. Antimicrobial susceptibility testing demonstrated widespread multidrug resistance, with high resistance rates to β-lactams, tetracycline (94%), vancomycin (62.5%), and rifampin (91%). Notably, 100% of E. faecalis and E. faecium isolates were classified as multidrug-resistant, with some strains exhibiting extensive or pandrug resistance. Vancomycin resistance genes (vanA and vanB) were detected in the majority of isolates, with vanA being predominant. Heat treatment experiments showed minimal reduction in bacterial counts after microwave heating (8.2 vs. 8.9 log10 CFU/g of the control), although boiling of the cooked RTE sausage for 5 min achieved a significant (p < 0.01) but incomplete reduction in the Enterococcus count by 3.8 logs (5.1 vs. 8.9 log10 CFU/g), indicating notable thermotolerance. Surviving isolates retained resistance and virulence traits. These findings highlight RTE meat products collected from Mansoura city as potential reservoirs of thermotolerant, multidrug-resistant enterococci, raising a potential public health concern and emphasizing the need for improved food safety measures and further nationwide studies. Although direct epidemiological links between foodborne isolates and clinical infections were not established, the presence of such strains raises a potential public health concern and underscores the need for improved food safety measures and further epidemiological investigations.