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.

Phage type 4 Salmonella enteritidis strains have only recently been isolated from poultry and humans in the United States, although this phage type predominates in many other countries. The present study assessed the ability of S. enteritidis isolates of various phage types found in the United States (including phage type 4) to colonize the intestinal tract and invade to reach internal organs in experimentally infected chicks. Groups of 5-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 S. enteritidis 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.