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Steven Glynn McBride
Date of Award
Master of Science (MS)
Department of Biology
The United States Environmental Protection Agency’s National Water Quality Inventory and the Commonwealth of Virginia’s 305(b)/303(d) Water Quality Assessment Integrated Report show fecal bacteria to be the most common cause of impairment for both streams and estuaries. Human and animal sources have both been identified as significant contributors of pathogenic bacteria to surface waters. In this study, turkey litter from a farm in Shenandoah County, VA was surveyed for total culturable bacteria and total culturable enterococci before and after a transition to organic rearing practices. The enterococci were identified to species phenotypically using the Biolog Microbial Identification System and resistance to twelve antibiotics (ampicillin, doxycycline, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, linezolid, quinipristin/dalfopristin, rifampin, streptomycin, tetracycline, vancomycin) was determined using the Kirby-Bauer disc diffusion method with automated image analysis using a BiomicTM plate reader. The effect of temperature (5◦C, 30◦C) and moisture (2O, ~35% H2O) on the survival of Enterococcus faecium in turkey litter was determined by inoculating sterilized turkey litter with a stock culture of bacteria and quantifying colony forming units over time. The transition to organic rearing practices resulted in a reduction in the proportion of enterococci resistant to doxycycline, gentamicin, and tetracycline, and an increase in the proportion of enterococci resistant to ciprofloxacin, erythromycin, and streptomycin. Enterococci isolated from the litter of organically raised birds were resistant to fewer antibiotics than enterococci isolated from the litter of conventionally raised birds. There was an interaction between moisture and temperature on the survival of E. faecium in turkey litter, with bacteria levels dropping most quickly in warm and dry conditions. The transition to organic practices has an immediate effect on antibiotic resistance patterns in enterococci, including an overall reduction from 4.02 to 3.45 antibiotic resistance phenotypes. Results of this study indicate that when applying turkey litter to land, fecal bacteria will likely survive for prolonged periods especially in cool moist conditions; therefore, it is recommended that prior to land application bacteria loads in litter should be reduced by composting or other treatment.
McBride, Steven Glynn II, "Occurrence, antibiotic resistance, and survival of fecal enterococci in turkey litter" (2016). Masters Theses. 469.