Master of Science (MS)
Veterinary Medical Sciences - Pathobiological Sciences
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.
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Boudreaux, Charles Mitchell, "A novel strategy of controlling bovine pneumonic pasteurellosis: transfecting the upper respiratory tract of cattle with a gene coding for the antimicrobial peptide cecropin B" (2004). LSU Master's Theses. 645.