Contamination of Marek's disease vaccine suspensions with Enterococcus faecalis and its possible role in amyloid arthropathy

Samples of hatchery air (hatcher and processing room), Marek's disease vaccine suspensions and injection needles collected during chick processing, revealed variable levels (<500 to 10(6) colony forming units (cfu)/m(3) air, < 10 to 106 cfu/ml vaccine suspension, and 9500 to 61 000 cfu/needle) of Enterococcus faecalis contamination. This observation suggests a possible infection route in 1-day-old chickens through intramuscular vaccination of Marek's disease vaccine contaminated with arthropathic and amyloidogenic E. faecalis, which could lead to amyloid arthropathy. Pulsed-field gel electrophoresis (PFGE) DNA restriction endonuclease fragment analysis of E. faecalis strains obtained from two hatcheries revealed a predominant PFGE pattern in one hatchery, while one isolate with an almost identical PFGE pattern to an amyloid arthropathy inducing isolate was found.