Differentiation of Pathogenic from Nonpathogenic Enterococcus cecorum Field Isolates Based on the Detection of the...

The clinical presentation of Enterococcus cecorum (EC)-associated systemic disease in broiler chickens is characterized by septicemia, lameness, and sometimes paralysis, typically affecting birds older than 4 wk of age. During the past few years, the incidence of this disease has increased worldwide. The detection of the cpsO gene was recently reported to successfully differentiate between pathogenic and commensal EC strains. This study aimed to evaluate the use of cpsO gene detection to differentiate pathogenic and nonpathogenic EC field isolates and to assess its association with macroscopic lesions observed in affected birds. Enterococcus spp. isolates (n = 348) recovered from necropsy cases submitted to the Mississippi State University's Poultry Research and Diagnostic Laboratory during 2023 were analyzed. Isolates originating from broiler breeders, layer breeders, hatcheries, and broiler chickens were included in this study. One hundred EC isolates were selected for phenotypic characterization and cpsO gene detection by PCR. EC was recovered from samples of the heart, joints, ovary, testicles, midgut, and ceca. The cpsO gene was detected in a high percentage (65%) of EC isolates recovered from broiler chickens, mainly from heart and femoral head lesions. In contrast, cpsO was detected infrequently in isolates from broiler breeders (10%) and was not detected in isolates recovered from intestinal samples or hatchery submissions. The presence of this gene was significantly associated with EC isolated from lesions observed in clinical disease cases, providing support for the pathogenic classification of these isolates. According to multiple literature reports, EC has been reported as a multidrug-resistant bacterium. However, in this study only a small percentage of isolates (3.4%) showed resistance to three or more classes of antimicrobials, and a high percentage of isolates (57%) were susceptible to all antimicrobials tested.