Abstract
In November 2025, an outbreak of Enterococcus cecorum in two commercial broiler flocks in southern Bulgaria were investigated. Clinical signs, including lameness and recumbency, appeared at approximately 20 days of age, and mortality reached 2.8% and 3.7%. Necropsy revealed systemic and osteoarticular lesions, including fibrinous pericarditis, hepatitis, splenomegaly, and osteomyelitis. E. cecorum was isolated in pure culture from 11 of 13 examined birds and confirmed by sodA-targeted PCR. The isolates carried the virulence-associated genes psaA, gelE, and ace, five tetracycline resistance genes (tetM, tetK, tetC, tetS, and tetT), and the macrolide resistance gene ermB. This study documents early-onset systemic E. cecorum disease in Bulgarian broilers and highlights the need for further phenotypic and genomic investigation of antimicrobial resistance.