PATHOLOGY OF SALMONELLA ASSOCIATED PORCINE GASTROENTERITIS IN MOUSE MODEL
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Date
2017-10-04
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College of Veterinary and animal Science,Mannuthy
Abstract
The present study was mainly envisaged on the identification of gross and histopathology of GIT of piglets with gastroenteritis, Salmonella isolation from gastroenteritic cases of piglets, identification of isolates by biochemical test and PCR, multiplex PCR to differentiate different Salmonella serovars, if more than one serovar is isolated and gross and histopathologic lesions of experimental Salmonella infection in mice. Ninety samples either of ileum, caecum and colon with gastroentritic lesion were collected from piglet carcasses for microbiological and histopathology work. The gross lesions in piglets were enlargement of mesenteric lymph nodes, hemorrhagic mucosa and multifocal diphtheritic ulcers in stomach. Catarrhal to diphtheritic enteritis was observed in small intestine. Moderate to diffuse yellow colored diphtheritic and fibrino-necrotic deposits with varying degrees of ulcers were predominant in mucosa of caecum and colon. Necrosis in liver; subpleural hemorrhages and consolidation in lungs and petechial hemorrhages in the cortical area in kidney were observed. Histopathology revealed vascular and inflammatory changes in different segments of intestines; lungs; liver and degenerative changes in kidney. Twelve out of fourteen bacterial isolates were identified by conventional method, spvC based Salmonella genus specific PCR and SCH_4349 and 4350 gene based Salmonella Choleraesuis specific PCR and confirmed as Salmonella Choleraesuis. Amplicon from genus specific PCR revealed 100 per cent similarity to Salmonella Choleraesuis after nucleotide blast. Phylogenetic tree analysis revealed that, Salmonella Choleraesuis had evolved a different group when compared to other selected standard Salmonella serovars Typhimurium, Dublin and Enteritidis. Salmonella Choleraesuis with infective dose of 2.7 x 107 CFU/ml were administered orally for pathogenicity study to 48 mice based on the pilot study along with a control group of six mice. Six mice each were sacrificed by cervical dislocation at 6, 12, 24, 36, 48, 60, 72 and 96h, post-inoculation. Detailed postmortem examination revealed severe catarrhal enteritis, hepatic degeneration and pulmonary emphysema at varying intervals. Histopathological sections of infected mice GIT revealed
denudation of villi epithelium and submucosal glandular hypertrophy in stomach at 6h PI. At 24h PI and 48h PI, mononuclear infiltration in submucosa with edema and mild submucosal congestion and fusion of villi were observed. At 36h PI, erosion of villi epithelium was noted in ileum. At 36h PI, caecum showed congestion and mononuclear infiltration in submucosa. Colon revealed glandular hypertophy at 6h PI. Liver showed diffuse cloudy swelling of hepatocytes, centrilobular necrosis, inflammatory changes in 24h and 96h PI. Diffuse tubular congestion was observed in the kidney at 96h PI. At 12h PI lung showed interstitial haemorrhage. This study showed that porcine Salmonella infection in mice were comparable with that of natural salmonellosis in pigs and also revealed that mice would be a good model for pathogenicity studies.
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