Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/15/2009
Publication Date: 1/19/2010
Citation: Guard, J.Y., Gast, R.K., Guraya, R. 2010. Colonization of avian reproductive tract tissues by variant subpopulations of Salmonella Enteritidis. Avian Diseases. 54:857-861. Interpretive Summary: Information about how strains of Salmonella cooperate within an infected host is lacking. These experiments infected birds in three different ways to better understand how the bacterium colonizes tissues within the chicken. One group of birds was infected with Salmonella enterica serovar Enteritidis that can both form biofilm and contaminate the internal contents of eggs. Another was infected with a mixture that was 90% biofilm-forming only and 10% egg-contaminating. A third group was infected with a culture that was 10% biofilm-forming and 90% egg-contaminating. Results suggest that different mixtures of S. Enteritidis strains result in different patterns of infection within reproductive tract organs. However, mixtures may be good at getting past the reproductive tract organs to the egg in different ways. Overall, the spleen and liver were much better for giving positive test results for S. Enteritidis following infection. The spleen is especially useful for culturing, because it would be the least expensive to process given its small size compared to the liver.
Technical Abstract: Leghorn hens were infected with Salmonella Enteritidis cultures to determine their comparative ability to colonize the avian reproductive tract. Group 1 received PT4 22079, which was previously shown to contaminate eggs and to form biofilm. Group 2 received a 90:10 mixture of PT13a strains 21027 and 21046, which were previously shown to either produce biofilm or contaminate eggs, respectively. Group 3 received a 10:90 mixture of the same two PT13a strains, respectively. Trials were repeated 3 times and a total of 30 hens per treatment group were infected. Dosage was by oral gavage and was calculated as 8.6 +/- 2.01 x 107 CFU per hen. Liver, spleen and 3 different sections of oviduct (ovary, upper oviduct and lower oviduct) were cultured per bird. Results were that all three groups had livers and spleens that were mostly positive (90.0% and 94.4% of 270 hens cultured, respectively). Reproductive tract organs yielded 75 positives from 270 hens (27.8%) and treatment groups ranged from a low of 6.7% to a high of 76.7% positive cultures in any one trial. There was no significant difference between the numbers of positive reproductive tract samples between treatment groups due to the variance. These results suggest that the status of the reproductive tract at the time of infection may impact recovery of culture positive tissue and contribute to variance. It is suggested that S. Enteritidis cultures that vary in subpopulation composition have subtle differences in colonization of reproductive tissue that contribute to egg contamination. Culture of non-reproductive tract organs such as the liver and spleen was overall more reliable for detection of infected hens. The spleen was especially useful for detection due to its small size. Further research is needed to determine how sex hormones influence the infection pathway that results in egg contamination.