Development of an In Vivo Model for Study of Intestinal Invasion bySalmonella entericain Chickens

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Abstract
An in vivo loop test model for the investigation of the invasiveness ofSalmonella entericain chickens was developed. Ten jejunal loops were made in 10- to 12-week-old Lohman Brown chickens under isofluoran anaesthesia.Salmonellaat 5.0 × 107CFU was inoculated into each loop and left for 2 h, followed by a 1-h incubation with gentamicin in order to kill noninvading bacteria. After euthanasia,Salmonellainvasiveness was measured as tissue-associated counts relative to a reference strain. The ability ofSalmonellainvasion was 1 log10CFU higher per 42-mm2mucosal tissue in the anterior than in the posterior part of jejunum. A statistically significant (P< 0.001) sixfold difference in invasiveness was observed between a wild-typeS. entericaserotype Typhimurium strain and the correspondinginvHmutant. The model was shown to be able to show small differences in invasive capability and allows for comparison of strains tested in different animals, provided that the same reference strain is present in all animals.