INTESTINAL COLONIZATION AND ORGAN INVASION IN CHICKS EXPERIMENTALLY INFECTED WITH SALMONELLA ENTERITIDIS PHAGE TYPE 4 AND OTHER PHAGE TYPES ISOLATED FROM POULTRY IN THE UNITED STATES

Authors: Gast, Richard; Benson, Steven

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Salmonella enteritidis (SE) contamination of eggs is an important public health problem in the U.S. and in many other nations. In the U.S., SE strains of a variety of phage types have been associated with egg- transmitted illness. In Europe, however, nearly all SE isolates from both humans and poultry during the past decade have been phage type (PT) 4. Although previously reported only very rarely, PT4 SE strains have recently been isolated from both poultry and humans in the U.S. The widespread prevalence of PT4 strains in European poultry raises questions about whether PT4 SE strains might be more infectious for chickens than other PT's and if control strategies for SE in U.S. poultry need to be revised to account for the presence of PT4. The present study evaluated the ability of SE isolates of various phage types found in the U.S. (including PT4) to colonize the intestinal tract and invade to reach internal organs in experimentally infected chicks. Groups of chicks were infected with various oral doses of three PT4 isolates and three isolates of other PT's. Although significant differences in the ability to infect chicks were observed between individual SE isolates, no overall pattern of differences was evident between PT4 isolates and isolates of other PT's. This suggests that strategies developed for controlling other SE PT's should still be applicable if PT4 becomes prevalent in the U.S.

Technical Abstract: The transmission of Salmonella enteritidis (SE) to humans by contaminated eggs is a significant public health problem on several continents. Phage type 4 SE strains have only recently been isolated from poultry and humans in the U.S., although this phage type predominates in many other countries. The unusually high prevalence of phage type 4 strains in poultry in Europe has led to speculation about the relative abilities of the various phage types to infect chickens and about whether the current strategies for controlling SE in laying flocks in the U.S. are adequate for addressing the appearance of phage type 4. The present study assessed the ability of SE isolates of various phage types found in the U.S. (including phage type 4) to colonize the intestinal tract and invade to reach internal organs in experimentally infected chicks. Groups of five- day-old single-comb white leghorn chicks were inoculated with a range of oral doses of three phage type 4 isolates and three isolates of other phage types. Although some significant differences were observed between individual SE isolates in the frequencies at which they colonized the intestinal tracts and invaded to reach the spleens of inoculated chicks, no consistent overall pattern differentiated phage type 4 isolates from isolates of other phage types.