Resistance and virulence distribution in enterococci isolated from broilers reared in two farming systems

Area of Science:

• Veterinary Microbiology
• Food Safety
• Antimicrobial Resistance

Background:

• Enterococci pose growing human health risks due to antimicrobial resistance.
• Poultry meat consumption is a potential transmission route for resistant enterococci.
• Enterococci are significant opportunistic pathogens in both human and animal infections.

Purpose of the Study:

• To compare antimicrobial resistance profiles of enterococci from Portuguese conventional and free-range broiler farms.
• To evaluate and contrast the prevalence of virulence genes in enterococci from these two farming systems.
• To assess potential differences in resistance gene acquisition between farming methods.

Main Methods:

• Antibiotic susceptibility testing was performed on enterococci isolates.
• Molecular methods were used to detect specific virulence genes (tet(M), erm(B), aac(6')-Ie-aph(2″)-Ia, pbp5, gelE, esp, agg, cylA).
• Phenotypic tests assessed hemolytic and gelatinase activities.

Main Results:

• High resistance to tetracycline, erythromycin, and gentamicin was observed in both farming systems.
• No vancomycin-resistant enterococci were identified; penicillin resistance was least common.
• Prevalence of tet(M), erm(B), aac(6')-Ie-aph(2″)-Ia, and pbp5 genes did not differ between systems, though pbp5 associated with genetic clusters.
• Hemolytic and gelatinase activities were present in 26.47% and 50% of isolates, respectively; gelE was common, esp and agg were rare, and cylA was absent.

Conclusions:

• Similar antimicrobial resistance patterns and virulence gene profiles exist in conventional and free-range broiler farms.
• Enterococci in free-range environments may be less likely to acquire additional resistance genes.
• Findings highlight the importance of monitoring enterococci in poultry production for public health.