Vancomycin resistant enterococci in farm animals – occurrence and importance

Abstract

The view on enterococci has over the years shifted from harmless commensals to opportunistic but important pathogens mainly causing nosocomial infections. One important part of this development is the emergence of vancomycin resistance enterococci (VRE). The term VRE includes several combinations of bacterial species and resistance genes of which the most clinically important is Enterococcus faecium with vanA type vancomycin resistance. This variant is also the most common VRE among farm animals. The reason for VRE being present among farm animals is selection by extensive use of the vancomycin analog avoparcin for growth promotion. Once the use of avoparcin was discontinued, the prevalence of VRE among farm animals decreased. However, VRE are still present among farm animals and by spread via food products they could potentially have a negative impact on public health. This review is based on the PhD thesis Vancomycin Resistant Enterococci in Swedish Broilers – Emergence, Epidemiology and Elimination and makes a short summary of VRE in humans and food producing animals. The specific situation regarding VRE in Swedish broiler production is also mentioned.

Antimicrobial resistance in Enterococcus spp. isolated from laying hens of backyard poultry floks

“…In the gastrointestinal habitat, enterococci are in a suitable position to acquire resistance genes from other commensals, which may further transfer to other more pathogenic bacteria [3]. The clinically most important species in human beings are E. faecalis and E. faecium that can be involved in urinary tract infections, endocarditis, wound infections, sepsis and neonatal infections [4,5]. E. faecalis is the most pathogenic species and E. faecium and is the most involved in the acquisition and transfer of antimicrobial resistance [5].…”

“…The clinically most important species in human beings are E. faecalis and E. faecium that can be involved in urinary tract infections, endocarditis, wound infections, sepsis and neonatal infections [4,5]. E. faecalis is the most pathogenic species and E. faecium and is the most involved in the acquisition and transfer of antimicrobial resistance [5].…”

Antimicrobial resistance of Enterococcus faecalis isolated from meat

“…Their ability to survive in different environmental conditions, innate resistance to many antibiotics, and ability to acquire, accumulate, and transfer genetic determinants of resistance are reasons for their increased significance as human and animal pathogens (6,18,22,24,27). Many authors have indicated a possible transfer of the resistant enterococci from animals to humans via the food chain; however, opinions on this matter are divided (1,3,4,10,12,14,15,(18)(19)(20)(21)(22)(23)25). In Poland, there are no available data about the antimicrobial resistance of enterococci isolated from meat; therefore, the aim of the study was the evaluation of this phenotypic feature among strains of Enterococcus faecalis.…”

<strong>Review on Usage of Vancomycin in Livestock and Humans: Maintaining its Efficacy, Prevention of Resistance and Alternative Therapy</strong>

“…When the use of avoparcin was discontinued, the prevalence of VRE among farm animals had been reduced [46,47,48].In vanA type of resistant, D-alanyl-D-alanyl part of bacterial cell wall alters to D-alanyl-D-lactate, thereby it prevents biding of vancomycin to the bacterial cell wall [5]. …”