Attempts to utilize bacteriophage to combat Salmonella enterica serovar Enteritidis infection in chickens

Bacteriophage capable of lysing a nalidixic acid-resistant Salmonella enterica serovar Enteritidis strain (SeE Nal(r)) 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 Nal(r), but average SeE Nal(r) counts of between 10(5) and 10(7) cfu of SeE Nal(r) per g of cecum were obtained even from phage-treated 14-day old birds and even when more than 10(7) plaque forming units of phage were present per gram of cecal content The average cecal SeE Nal(r) 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 Nal(r) 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 Nal(r) counts.