Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/17/2003
Publication Date: 7/1/2003
Citation: GAST, R.K., PETTER, J.G., HOLT, P.S. EFFECT OF PRIOR SERIAL IN VIVO PASSAGE ON THE FREQUENCY OF SALMONELLA ENTERITIDIS CONTAMINATION IN EGGS FROM EXPERIMENTALLY INFECTED LAYING HENS. AVIAN DISEASES. 2003. 47:633-639. Interpretive Summary: Experimental infections of chickens with Salmonella enteritidis can provide valuable information for understanding and preventing the deposition of this human pathogen inside eggs. Hens are often inoculated orally in such studies to simulate naturally occurring S. enteritidis infections. However, oral infection tends to result in relatively low frequencies of egg contamination. The present study assessed whether repeatedly passing an S. enteritidis strain through groups of chickens by oral inoculation could affect its ability to cause egg contamination. The incidence of egg contamination was determined in groups of hens inoculated orally with either a parent S. enteritidis strain or with passaged isolates that were obtained by three successive rounds of infection and re-isolation from tissues of hens. Passaged S. enteritidis isolates recovered from reproductive tissues of hens (ovaries and oviducts) caused significantly more frequent egg contamination than did the parent strain, but passaged isolates recovered from livers and spleens did not. Therefore, the passage of S. enteritidis through reproductive tissues of chickens may be a useful route for improving the ability of experimental infection studies to produce egg contamination.
Technical Abstract: Experimental infection models are valuable tools for understanding and preventing the deposition of Salmonella enteritidis inside eggs. Oral inoculation is believed to closely simulate naturally occurring S. enteritidis infections of chickens, but oral infection studies have often generated relatively low frequencies of egg contamination. The present study assessed whether repeated in vivo passage of an S. enteritidis strain could affect its ability to cause egg contamination in experimentally infected hens. The incidence of egg contamination was determined in groups of hens inoculated orally with either a phage type 13a S. enteritidis strain or with derivatives of this parent strain that were obtained by three successive rounds of passage and re-isolation from tissues of infected hens. Passaged S. enteritidis isolates recovered from ovaries and oviducts induced a significantly higher incidence of egg contamination (16.97%) than was attributed to the parent strain (8.27%). However, passaged S. enteritidis isolates recovered from livers and spleens were not associated with a significantly increased frequency of deposition in eggs. By either inducing or selecting for the expression of relevant microbial properties, passage of S. enteritidis through reproductive tissues of chickens may be useful for improving the efficiency at which experimental infection models produce egg contamination.