Abstract

Antibiotic resistance is an important issue in human and veterinary medicine, because it can render many previously treatable diseases untreatable. In the United States and other developed countries, antibiotic resistance is increasing at an alarming rate, both in prevalence and also in the number of antibiotics affected.^2,6,9 Given this trend, it is crucial that practitioners be especially vigilant about how they administer many of the “last-resort” antibiotics, such as cephalosporins and fluoroquinolones, which are necessary to maintain control over disease. While antibiotic resistance has been well-documented in food and companion animals, thus far few studies of antibiotic resistance have been done in zoos.^5,7,8 In the few studies that have investigated antibiotic resistance in zoo animals, the prevalence of antibiotic resistance has been rather high.^1,3,4 The goal of this study was to investigate the association between the administration of cephalosporin and fluoroquinolone antibiotics to apes and exotic felids at Lincoln Park Zoo, and the risk of corresponding antibiotic resistance in their commensal enteric bacteria. It was hypothesized that animals administered antibiotics would be at higher risk for colonization by antibiotic-resistant bacteria. In a cross-sectional design in 2004, fecal samples were collected from gorillas (Gorilla gorilla gorilla) (n=14) and exotic felids (Panthera leo krugeri, Uncia uncia, Leptailurus serval, Puma concolor californica, Panthera tigris altaica, Panthera pardus orientalis, Panthera pardus, Panthera pardus saxicolor, Acinonyx jubatus) (n=20) as soon after defecation as possible and shipped overnight on ice to Dr. Boyle-Vavra at the University of Chicago. There, samples were selectively plated to identify bacterial species, and commensal E. coli and enterococci isolates were subjected to Vitek 2 (bioMerieux Inc.; Durham, NC) susceptibility testing. Results were categorized as resistant, partially resistant, or susceptible. Odds ratios were calculated to compare antibiotic resistance between animals that were administered cephalosporins or fluoroquinolones over the past 10 years and those that were not exposed to these antibiotics. Interestingly, 12.5% of gorillas and 22% of felids were found to have E. coli partially resistant to cephalosporins, while 10% of gorillas and 35% of felids were found to have enterococci resistant to fluoroquinolones. Though not statistically significant, enrofloxacin use did predict increased fluoroquinolone resistance in ape enterococci but not in felids. Cephalosporin use did not increase resistance in apes or felids. Behavioral and husbandry variables (dominance, gender, age, specific habitat, and being housed with other animals) were tested and did not predict bacterial resistance to cephalosporins or fluoroquinolones in either group.

Acknowledgments

We would like to thank the Grant Health Care Foundation for funding this work, as well as the animal keeper staff at Lincoln Park Zoo for the collection of samples, and Drs. Jennifer Liang and Craig Miller and Mrs. Cecilia Simon for their considerable time and effort.

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