Master's Theses

Document Type

Thesis

Date of Award

Spring 2014

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Dr. Rob Channell

Abstract

Antibiotic resistance is a growing concern in medical and veterinary settings. Resistance can be worsened by misuse and overuse of antibiotics. Such situations can give rise to highly resistant organisms. Ciprofloxacin, a synthetic, broad-spectrum antibiotic used to treat gram-positive and gram-negative infections in humans, has similar chemical structure to enrofloxacin, which is used to treat animals. Cross-resistance might arise because of that similarity. This research describes the dispersal and prevalence of bacteria that exhibit ciprofloxacin resistance in relation to feedlots in the central Great Plains region. Six times in 2013, six feedlots were sampled for airborne bacterial communities at, upwind of, and downwind of the feedlot. The samples were grown on exposed Mueller Hinton agar plates infused with a clinical dose of ciprofloxacin. After incubation, bacterial colonies were counted, indicating the prevalence of resistant bacteria. Other variables were measured and analyzed, including wind speed, air temperature, and relative humidity. Colony prevalence was higher on the feedlots than at any of the locations upwind and downwind of the lots. Wind speed, relative humidity, and distance from the feedlot significantly influenced the number of colonies that were detected. Some colonies from among the samples were isolated, gram-stained, tested for minimum inhibitory concentrations of ciprofloxacin, and sequenced for species identification. 21 bacterial isolates represented eight species in four genera: Enterococcus, Cellulomonas, Arthrobacter, and Microbacterium. Though species richness in this study was somewhat low, the bacterial isolates showed high levels of ciprofloxacin resistance. Because the prevalence of ciprofloxacin-resistant bacterial colonies seemed to decline sharply with increased distance from the feedlots, this study suggested that the feedlots have a relatively small effect on the dispersal of ciprofloxacin resistant bacteria on the surrounding landscape.

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Rights

© 2014 Jennifer R. Pfannenstiel-Klaus

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