Prevalence of Enterococcus faecalis and Escherichia coli in nonviable embryonated broiler eggs

     

Enterococcus faecalis is considered a normal inhabitant of the poultry gastrointestinal tract. Although it has been known to be an opportunistic poultry pathogen, high levels of this organism can be recovered from the intestinal tract of normal, healthy birds with no known disease issues. More recently, an increasing number of poultry veterinarians and diagnostic laboratories have been reporting that E. faecalis is being isolated from yolks of unhatched embryonated eggs or from yolk sacs of morbid chicks shortly after hatch. Escherichia coli, which is known to be associated with embryonic and early chick mortality, has also been isolated from these cases. Recent studies have suggested that coinfection with E. faecalis and E. coli may enhance the virulence of both organisms, resulting in decreased hatchability and poor chick quality. To better understand this issue and the potential role of co-infection of embryonated eggs with E. faecalis and E. coli, a survey was conducted to determine the prevalence of E. faecalis and E. coli in hatch residue. A total of 405 hatch residue samples that had evidence of early embryonic mortality were selected for sampling. Ten different samplings were taken from 6 hatcheries. Samples were collected by opening eggs aseptically and swabbing the yolk area. Standard microbiological methods were used to determine the presence of E. faecalis and E. coli. Of the 405 samples tested, 174 (43%) were found to be positive for both bacteria, whereas E. faecalis alone was recovered from 54 samples (13%) and E. coli alone was recovered from 53 samples (13%). Neither bacterial species was recovered from the remaining 124 samples (31%), possibly indicating that these embryonic mortalities may not have been a result of infection with pathogenic bacteria. The results indicated that E. faecalis and E. coli were frequently isolated from cases of early embryonic mortality and that co-infection was far more common than either organism isolated alone. The results suggested that co-infection with E. faecalis and E. coli may enhance virulence of the bacteria, leading to early embryonic mortality, which has not been previously reported.

Key Words: Enterococcus, E. coli, broiler.