Understanding Salmonella enterica serovar Dublin as a cause of abortion in cattle

Franklin, Jemma May (2023) Understanding Salmonella enterica serovar Dublin as a cause of abortion in cattle. PhD thesis, University of Nottingham.

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Salmonella enterica serovar Dublin (S. Dublin) is a host-adapted non-typhoidal Salmonella serovar associated with disease predominantly in cattle as well as a variety of other species including humans. S. Dublin is one of the most common infectious causes of bovine abortion in the UK and is the most commonly isolated Salmonella serovar from cattle. S. Dublin can persist in the environment and reside in sub-clinically infected animals, making it extremely difficult to eradicate on farm. Infection in cattle is acquired via the faecal oral route, and the bacterium can be shed in faeces, urine and milk. As a zoonotic disease, S. Dublin also poses a risk to human health and food security, with many cases in humans being found to be associated with consumption of contaminated dairy and beef products. Additionally, an abortion in a dairy herd in the UK is estimated to cost upwards of £630 (Cabell, 2007).

Compared to serovars like S. Typhimurium and S. Paratyphi, S. Dublin is a relatively under-researched serovar. Little is known about its virulence in host specific tissues and niches and the process of infection and dissemination in cattle is unknown. Furthermore, research into S. Dublin infection as a cause of abortion is scarce, with the host response to the pathogen during pregnancy currently unknown.

16 S. Dublin isolates from cases of clinical disease in cattle in the UK were phenotypically characterised for their growth and virulence in the Bovine Caruncular Epithelial cell line (BCECs). The comparison of the whole genome sequences of these 16 isolates to those of 250 other S. Dublin strains from the UK isolated between 2001 and 2019 from various origins of isolation confirmed that these 16 isolates were representative of the circulating population. Virulence factors were identified in the 266 total S. Dublin isolates using bioinformatic analysis, and a phylogenetic alignment of the accessory genomes of these isolates revealed distinct clustering of isolates from similar origins of isolation.

The survival of 4 of the 16 S. Dublin isolates was assessed in fresh bovine whole blood, and infection of BCECs was carried out to understand the expression of CXCL8, TNFα and PGE2 via qPCR and ELISA. S. Dublin were able to survive in bovine blood for up to 2 hours and invaded and persisted in BCECs for up to 24 hours. BCECs up-regulated expression of CXCL8 and TNFα mRNA and PGE2 in response to infection with S. Dublin over the course of 24 hours.

The work presented here is the first of its kind to identify the virulence factors of a large cohort of S. Dublin isolates and detail the survival of S. Dublin in bovine blood. Additionally, this is the first time that S. Dublin have been shown to infect cells from the placentomes of pregnant cattle and the first time that the host response to infection with S. Dublin has been investigated in a placentome-derived cell line.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Totemeyer, Sabine
Keywords: Salmonella; Microbiology; Bovine abortion
Subjects: S Agriculture > SF Animal culture
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Veterinary Medicine and Science
Item ID: 73234
Depositing User: Franklin, Jemma
Date Deposited: 31 Jul 2023 04:40
Last Modified: 31 Jul 2023 04:40
URI: https://eprints.nottingham.ac.uk/id/eprint/73234

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