Surveys of Salmonella enteritidis in Unpasteurized Liquid Egg and Spent Hens at Slaughter

Abstract

In a 1995 national survey of 937 unpasteurized liquid egg samples collected in breaker plants, 179 of 937 samples (19%) were Salmonella enterica serotype Enteritidis (S. Enteritidis) positive. The proportion of unpasteurized liquid egg samples positive for S. Enteritidis was highest in the Northern Region where 106 of 267 samples collected (40%) were S. Enteritidis-positive. These Northern Region results were over three times the S. Enteritidis prevalence detected from the other three regions, whose results ranged between 10% and 12% S. Enteritidis-positive samples. In a 1995 national survey of spent hens at slaughter, 136 of 305 flocks (45%) had at least one S. Enteritidis-positive pooled sample detected. Flock prevalence was highest in the Northern and Central Regions (64% and 40%, respectively); Southeastern and Western Regional flock prevalence levels were much lower (17% and 23%, respectively). A comparison of the 1991 and 1995 unpasteurized liquid egg and spent hen results suggest there has been no decline in S. Enteritidis occurrence in the commercial egg industry between 1991 and 1995. Salmonella Enteritidis phage type 4 was detected in the 1995 surveys of both spent hens and unpasteurized liquid egg but was not found in either survey in 1991. With the exception of one liquid egg sample from the Southeastern Region, S. Enteritidis phage type 4 was found only in the Western Region of the U.S. S. Enteritidis phage type 4 has emerged in the egg industry in the Western U.S. concurrently with an increase in the number of sporadic human phage type 4 isolates in California and Utah.