Enterococcal infections and antimicrobial resistance in poultry

Enterococcus species were initially regarded as primary commensal microorganisms constituting a major component of the gastrointestinal microbiota in avian and mammalian hosts. However, over the years, pathogenic Enterococcus strains have emerged as significant causes of morbidity and mortality in broiler production, frequently leading to recurrent outbreaks. Enterococcus spp. also act as opportunistic pathogens, responsible for septicemia, endocarditis, osteomyelitis, and neurological disorders in poultry and parrots. Enterococcus are particularly notable for their remarkable capacity to develop and disseminate antimicrobial resistance. Among them, vancomycin-resistant Enterococcus (VRE) pose a serious, life-threatening concern for both animal and human health. Furthermore, the routine and periodic use of antibiotics in poultry farming has promoted the emergence of multidrug-resistant strains, thereby limiting treatment options and heightening zoonotic risks. Comparative genomic analyses have demonstrated that highly pathogenic Enterococcal strains exhibit strong genetic relatedness and share numerous virulence-associated genes. These pathogenic strains typically display higher antimicrobial resistance levels than their commensal counterparts. In this state-of-the-art review, we examine the current understanding of the distribution patterns, pathogenic potential, and antimicrobial resistance profiles of Enterococcus strains derived from poultry, emphasizing the importance of multidisciplinary approaches and their global implications for animal and public health. Our conclusions emphasize the urgent need for stricter regulations governing antibiotic use in poultry production and the development of innovative strategies to mitigate the escalating threat posed by antibiotic-resistant Enterococcus strains. We further highlight the necessity of adopting a comprehensive, multidisciplinary “One Health” approach to promote effective solutions within veterinary medicine and safeguard both animal and human health.