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United States Department of Agriculture

Agricultural Research Service

Research Project: INTERVENTIONS TO REDUCE FOODBORNE PATHOGENS IN SWINE AND CATTLE

Location: Food and Feed Safety Research

Title: Comparison of antimicrobial susceptibility among Clostridium difficile isolated from an integrated human and swine population in Texas

Authors
item Norman, Keri -
item Scott, H -
item Harvey, Roger
item Norby, Bo -
item Hume, Michael

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2013
Publication Date: April 4, 2014
Repository URL: http://handle.nal.usda.gov/10113/58657
Citation: Norman, K.N., Scott, H.M., Harvey, R.B., Norby, B., Hume, M.E. 2014. Comparison of antimicrobial susceptibility among Clostridium difficile isolated from an integrated human and swine population in Texas. Foodborne Pathogens and Disease. 11:257-264.

Interpretive Summary: Clostridium difficile (Cd) is a bacterium that causes disease and death in humans, and historically, the infection was acquired during hospital stays. Recently, more virulent strains that are community-acquired have emerged. Although the origin of the new strains is unknown, some speculate they could have come from animals or meat. In the present study, we sampled human wastewater and swine feces from an integrated population of humans and swine and tested them for the presence of Cd isolates. We tested 523 Cd isolates for susceptibility to eleven antibiotics commonly used in human hospitals. We found that swine isolates had less antibiotic resistance than human ones and that resistance in swine workers was no different than non-swine workers. This is important because it provides evidence that Cd was not transferred from swine to humans, and swine are not the source of Cd antibiotic resistance in humans.

Technical Abstract: Clostridium difficile can be a major problem in hospitals because the bacterium primarily affects individuals with an altered gut flora, which largely occurs through prolonged antibiotic use. Proposed sources of increased community-acquired infections are food animals and retail meats. The objective of this study was to compare the antimicrobial resistance patterns of C. difficile isolated from a closed, integrated population of humans and swine. Swine fecal samples were collected from a vertically flowing swine population consisting of farrowing, nursery, breeding, and grower/finisher production groups. Human wastewater samples were collected from swine worker and non-worker occupational group cohorts. Antimicrobial susceptibility testing was performed on 523 C. difficile strains from the population using commercially available agar diffusion Epsilometer test (Etest) for 11 different antimicrobials. All of the swine and human strains were susceptible to amoxicillin/clavulanic acid, piperacillin/tazobactam, and vancomycin. In addition, all the human strains were susceptible to chloramphenicol. The majority of the human and swine strains had decreased susceptibility to cefoxitin and ciprofloxacin. Statistically significant differences in antimicrobial susceptibility were found among the swine production groups for ciprofloxacin, tetracycline, amoxicillin/clavulanic acid, and clindamycin. No significant differences in antimicrobial susceptibility were found across human occupational group cohorts. We found that 8.3% of the swine strains and 13.3% of the human strains exhibited decreased susceptibility to metronidazole. The finding of differences in susceptibility patterns provides some evidence that transmission between host species in this integrated population is unlikely.

Last Modified: 7/22/2014
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