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Advisory Committee Chair

Dale A Dickinson

Advisory Committee Members

Terje Dokland

Julia M Gohlke

Document Type

Thesis

Date of Award

2015

Degree Name by School

Master of Science in Public Health (MSPH) School of Public Health

Abstract

Bovine mastitis is inflammation of the mammary gland that occurs in cattle, as a result of invading bacteria. Staphylococcus aureus, a causative agent of bovine mastitis, produces toxins such as the toxic shock syndrome toxin (TSST-1) and the staphylococcal enterotoxins (SEs). The genes for these toxins are coded on S. aureus pathogenicity islands (SaPIs), which are mobile genetic elements associated with virulence factors. SaPIs can be mobilized by bacteriophages, resulting in the production of transducing particles that can spread virulence factors throughout a bacterial population. This research assessed the role and prevalence of SaPIs among bovine mastitis samples. In this study, 75 S. aureus bacterial isolates were characterized. Phenotypic and genotypic tests were used to confirm the identity of bacterial isolates and characterize the presence of SaPIs by: PCR detection of the toxic shock syndrome toxin gene (tst) and staphylococcal enterotoxin C (sec), as well as SaPI related genes, such as primase (pri) and the master repressor, stl from SaPI1, SaPI2, SaPIbov1, and SaPIbov2. The results showed a significant number of S. aureus samples (50/75) had at least one SaPI-related gene, which can be mobilized and result in the spread of virulence genes. This was demonstrated by infection of a mastitis sample harboring a SaPIbov1-like element with bacteriophage 80 alpha, which resulted in the mobilization of and transfer of a SaPI gene (pri) to recipient strain RN4220.

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