Doctor of Philosophy (PhD)
Veterinary Medical Sciences - Pathobiological Sciences
There are many contradictory reports in the literature involving the culture of Spiroplasma mirum, its resistance to disinfectants and antibiotics, and its potential role in Transmissible Spongiform Encephalopathies (TSEs). These contradictions led to an interest in a possible link between spiroplasma and TSEs and the development of a research plan to elucidate this connection. It was hypothesized that Spiroplasma was associated with a neurodegenerative disease such as TSE. In this work we further characterized S. mirum laboratory strains and continued to evaluate the possible correlations they have with TSE infections and the prion. To optimize recovery of S. mirum from experimental infections, we established reproducible culture conditions in M1D media, embryonated eggs, and SP4 plates. Overall, results indicated that SP4 plates are the most accurate quantitative method for S. mirum. However, plate counts should be accompanied by qualitative assessments of cultures in liquid M1D as well. A susceptibility profile for physical and environmental disinfectants and antibiotics for spiroplasma was also determined. The three species of Spiroplasma tested were susceptible to minimal dilutions of common laboratory disinfectants. They were also susceptible to many of the antibiotics in use for other mollicutes. Although Spiroplasma and prions, the presumed infectious agent of TSEs, may both persist in neurologic tissues for extended periods of time, the two do not share the same properties of resistance. Experimental neonatal goat infections with a S. mirum laboratory strain SMCA using three different inoculation routes did not result in pathology, clinical signs, or an immune response over a two year time period. In addition, the organism was not detected via PCR or culture. The same strain did cause minimal clinical signs in one animal when inoculated into five month old white-tailed deer and was recovered from the cortex of the clinically-affected deer after multiple passages in culture. Although the goat experiments did not result in TSE-like disease, an improved methodology for a spiroplasmosis animal model was developed, and further research should be conducted using similar methods in neonatal white-tailed deer.
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French, Hilari Maree, "Characterization of Spiroplasma mirum and its role in transmissible spongiform encephalopathies" (2011). LSU Doctoral Dissertations. 3012.