Identifier

etd-07012004-101913

Degree

Master of Science (MS)

Department

Veterinary Medical Sciences - Pathobiological Sciences

Document Type

Thesis

Abstract

The very potent antibacterial activity of cecropin B makes it a likely candidate to prevent and/or treat Mannheimia haemolytica 1:A infection in the upper respiratory tract (URT) of cattle. The purpose of this study was to ascertain if the URT could be transfected with a gene coding for the antimicrobial peptide cecropin B. By transfecting cattle with a gene coding for cecropin B, this study attempted to inhibit colonization of a virulent strain of M. haemolytica 1:A in the URT while investigating any possible changes in the indigenous and transient nasal flora. In this study the antibacterial efficacy of cecropin B for a virulent strain of M. haemolytica 1:A was determined. In vitro results showed that cecropin B was very effective in inhibiting this virulent strain of M. haemolytica 1:A within 20 minutes of incubation at 37°C. No inhibition of its activity was observed by incubating cecropin B in pooled bovine nasal secretions. The nasal passages of calves were aerosolized with different amounts of plasmid DNA containing a gene coding for cecropin B. Results of this study show that calves transfected with 50 or 100 μg of plasmid DNA per nostril were able to express cecropin B at the mRNA and peptide level. Detection of the cecropin B gene in control calves may indicate the possibility of native bovine cecropin. After challenge with a virulent strain of M. haemolytica 1:A, all calves were stressed by transportation in a crowded trailer 100 miles for 3 hours. Seven out of the 8 control calves yielded detectible levels of M. haemolytica 1:A in nasal aspirates throughout the weeks following challenge. All 4 calves given 25 μg of plasmid DNA per nostril and two of the 4 calves given 50 μg of plasmid DNA per nostril yielded detectible levels of M. haemolytica 1:A in nasal aspirates following challenge. However, M. haemolytica 1:A was not detected in any calf given 100 μg of plasmid DNA per nostril. There appeared to be no change in the normal bacterial nasal flora.

Date

2004

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Richard Corstvet

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