Attempts to utilize bacteriophage to combat salmonella enterica serovar enteritidis infection in chickens

Abstract

Bacteriophage capable of lysing a nalidixic acid-resistant Salmonella enterica serovar Enteritidis strain (SeE Nalr) were tested for the ability to reduce cecal Salmonella counts in young chickens infected with the bacterium. Qualitative analysis of cloacal swabs suggested that phage treatment can possibly reduce shedding of SeE Nalr, but average SeE Nalr counts of between 105 and 107 cfu of SeE Nalr per g of cecum were obtained even from phage-treated 14-day old birds and even when more than 107 plaque forming units of phage were present per gram of cecal content. The average cecal SeE Nalr counts were generally between 0.3 and 1.3 orders of magnitude lower in phage-treated chickens than in untreated controls birds. The difference in counts was statistically not significant in three animal trials, but significant in two trials using feed particles as delivery vehicles for the phage. Although some of the SeE Nalr in the cecae of phage-treated chickens had developed resistance to some of the phage used, factors other than phage resistance must have contributed to the failure of the phage to substantially reduce SeE Nalr counts.