Bacteriological and molecular study of Salmonella species associated with central nervous system manifestation in chicken flocks

Abstract

Background and Aim: Salmonella species often cause systemic health problems in poultry flocks, sometimes including nervous systems manifestations. This impact of Salmonella has rarely been studied. This study aimed to define an alternative pathogenic pathway for Salmonella spp. invasion of brain tissue in chicken flocks. Brain infection produces neurological manifestations; Salmonella strains isolated from brain tissue showed the presences of two virulence genes. Confirmation of the pathway of isolates from intestinal mucosa through the blood–brain barrier was attained using experimental infections in specific pathogen-free (SPF)-day-old chicks through two routes of inoculation. Materials and Methods: Isolation of Salmonella spp. from five chicken flocks that showed signs of the central nervous system (CNS) effects were isolated. Isolates were characterized by serotyping, and antimicrobial assays. In addition, virulence profiles were described using detection of virulence plasmid spvC, and Salmonella plasmid sopB. A pathogenicity study of isolates in specific pathogen-free (SPF)-day-old chicks through oral and intracerebral administration performed, and experimental infection in SPF embryonated chicken eggs through intra-yolk and intra-allantoic administration was investigated. Supporting histopathology and immunohistopathology against Salmonella antigen in brain tissue were performed for flock and experimental infections. Results: Three serotypes of Salmonella were isolated from the brains of five flocks (two Salmonella Virchow, two Salmonella Kentucky, and one Salmonella Enteritidis isolates). Phage related gene sopB and plasmid-mediated operon spvC were identified in all isolated strains. The Salmonella strains were re-isolated and identified from the brain and internal organs of post-experimental infected chicks. Infected chicks showed nervous manifestations associated with Salmonella infection. The presence of positively stained Salmonella antigen in brain tissues indicates penetration of the blood–brain barrier by the Salmonella species. Conclusion: Our results indicate that some virulent systemic strains of Salmonella spp. can induce CNS manifestations in chicken hosts.