Abstract
BackgroundThe impact of enterococci in human health has been growing for the last decades, mainly due to their resistance to several antimicrobial agents. Human consumption of contaminated meat, especially poultry, has been identified as a possible route of transmission. The aim of the present study was to evaluate and compare the antimicrobial resistance profiles and virulence genes of enterococci isolated from Portuguese conventional and free-range broiler farms.ResultsAntibiotic susceptibility testing showed high frequencies of resistance to tetracycline in both farming systems. Resistance to erythromycin and gentamicin were detected in about half of the isolates. Resistance to penicillin was the less frequently observed and no vancomycin resistant isolates were identified. The majority of the enterococcal isolates, from either farming systems, were resistant to more than one antibiotic, and no statistical associations were found, except for penicillin resistance which associated with the genetic clusters. No differences were found between farming systems regarding the prevalence of tet(M), erm(B), aac (6′)-Ie-aph (2″)-Ia and pbp5 genes, nevertheless pbp5 prevalence was associated with the different genetic clusters. Hemolytic activity was identified in 26.47% of all isolates and gelatinase activity in 50%. The gelE gene was identified in the majority of the isolates, whereas esp and agg genes were rarely detected. The cylA determinant was not detected in any of the isolates.ConclusionsOverall, results suggest that similar resistance patterns and virulence genes can be found in both farming systems, though enterococci in free-range conditions should be less prone to acquire further resistance genes.
Highlights
The impact of enterococci in human health has been growing for the last decades, mainly due to their resistance to several antimicrobial agents
Microbial diversity Of the 34 enterococci isolates obtained from the broiler fecal samples recovered from the two slaughterhouses, 21 were identified as E. faecium, 11 as E. faecalis, one as E. gallinarum and one as E. durans
Even though the animals from which the fecal samples were collected had been raised in different housing conditions, unlikely, if they were obtained from the same hatchery there could be an early colonization with similar enterococci before being transferred to different broiler farms
Summary
The impact of enterococci in human health has been growing for the last decades, mainly due to their resistance to several antimicrobial agents. Acquired AMR in these bacteria is of great importance Due to their ability to gain foreign genetic material, including transposons and plasmids, enterococci rapidly became resistant to additional antimicrobial agents such as erythromycin and tetracyclines, shortly after their introduction into clinical practice [6]. Owing to their characteristics, it is believed that enterococci play a pivotal role in the acquisition, conservation and dissemination of AMR genes to other related bacteria [7]
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