Enterococcus cecorum and Enterococcus hirae can cause locomotor problems, septicaemia, and endocarditis in broiler chickens. Understanding transmission routes and resistance patterns are essential for effective treatment. The aim of this study was to follow the same animals from the breeder flock to the hatchery and up to 14-day-old broiler chickens on the farm to find the source of E. cecorum and E. hirae. During the production cycle, only faeces and organs of broilers were E. hirae positive in all three sampled farms in which recurrent enterococcal infections were previously confirmed. None of the isolates possessed virulence genes. Based on resistance profiles, a variety of different strains were present in faeces and organs of different broilers' ages. Samples from the breeder flock and hatchery were negative. Faecal shedding on the farm and tolerance of enterococci to the environmental conditions enable persistence of pathogenic enterococci in farm dust; therefore, adequate cleaning and disinfection after depopulation of the farms could prevent disease recurrence in the new cycle. Susceptibility testing of E. hirae isolates showed no resistance to the drugs of choice for the treatment of enterococcal infections in poultry.
Keywords: Enterococcus cecorum; Enterococcus hirae; antimicrobial resistance; broiler chicken; route of infection; virulence genes.