Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/27/2011
Publication Date: 12/15/2011
Citation: Hannah, J.F., Wilson, J.L., Cox Jr, N.A., Richardson, L.J., Cason Jr, J.A., Buhr, R.J. 2011. Colonization of a marker and field strain of Salmonella Enteritidis and a marker strain of Salmonella Typhimurium in vancomycin pretreated and non-pretreated laying hens. Avian Diseases. 55:588-592. Interpretive Summary: This study evaluated the effects of pre-treating table egg laying hens with the antibiotic vancomycin (which suppresses Gram-positive bacteria within the intestinal tract that compete with Salmonella) on the hen’s susceptibility to colonization/infection by three Salmonella strains. The ability of marker (nalidixic acid-resistant) S. Enteritidis (SE-M), field S. Enteritidis (SE-F), and marker S. Typhimurium (ST-M) strains to colonize within the intestinal and reproductive tracts were compared in hens at 26, 33, and 76 weeks of age. Two weeks post-inoculation, hens were euthanized and the ceca, spleen, liver/gall bladder, reproductive tracts, and ovarian follicles were aseptically collected, and analyzed for the presence of Salmonella. Hen age (26, 33, and 76 wk-of-age) and vancomycin pretreatment to reduce established intestinal microflora had no affect on Salmonella colonization and dissemination. Both SE-F and ST-M colonized the ceca, spleen, and liver/gall bladder at significantly higher rates than SE-M, and were recovered from environmental and eggshell samples, while SE-M was not. Because the SE-M strain did not colonize well within the laying hen and was not recovered from the environmental or eggshell samples, this suggests that when in competition for nutrients during culture, this SE-M is difficult to recover. Since the poor colonization of SE-M cannot be attributed to the presence of established intestinal microflora following vancomycin pre-treatment, the poor colonization ability of SE-M may be associated with the induction of antibiotic resistance and repeated lab culture.
Technical Abstract: This study was conducted to evaluate the effects of a vancomycin pre-treatment on the ability of marker (nalidixic acid-resistant) S. Enteritidis (SE-M), field S. Enteritidis (SE-F), and marker S. Typhimurium (ST-M) strains to colonize within the intestinal and reproductive tracts and translocate to other organs of Leghorn laying hens. In each of three trials, caged hens (76, 26, and 33 wk-of-age) were divided into 6 groups designated to receive SE-M, SE-F, or ST-M, and half were pretreated with vancomycin (n=12). Vancomycin-treated hens received 10mg/kg body weight for 5 d to inhibit Gram-positive bacteria within the intestines. On day 6, all hens were challenged orally, intravaginally and intracolonally with Salmonella and placed into separate floor pens by Salmonella strain. Two wk post-inoculation, all hens were euthanized and the ceca, spleen, liver/gallbladder (LGB), upper (URT) and lower (LRT) reproductive tracts, and ovarian follicles were aseptically collected, and analyzed for Salmonella. Results for the three hen’s ages were not different and therefore, were combined, and Chi-square and Fisher’s exact test were used to identify significant differences (P<0.05) in colonization. The vancomycin pretreatment had no significant effect on the colonization ability of SE-M, SE-F, or ST-M. The marker strain of S. Enteritidis was recovered from 21% of ceca, 4% of LGB, and 9% of LRT samples. The field strain of S. Enteritidis was recovered from 88% of ceca, 96 % of spleen, 92% of LGB, 30% of LRT, 4% of URT and 13% of follicle samples. S. Typhimurium was recovered from 100% of ceca, 74 % of spleen, 91% of LGB, 30% of LRT, 9% of URT and 9% of follicle samples. Among ceca, spleen and LGB samples, SE-F and ST-M colonization was significantly greater than SE-M colonization. Overall prevalence of Salmonella in the reproductive tracts of challenged hens was relatively low, ranging from 4-30%.