The Prevalence of Antibiotic Resistance in Clostridium Isolated from Horses
Authors:Angelica Castaneda, Kun Ho Lee
- Shelton Murinda, Associate Professor of Animal and Veterinary Sciences, California State Polytechnic University Pomona
- Wei-Jen Lin, Associate Professor of Microbiology, California State Polytechnic University Pomona
Clostridium species have been indicated as a major contributor to the death of young horses due to severe colic and bloody diarrheal infections. As a result, it is important to understand the antibiotic susceptibility of Clostridium in order to treat the horses and prevent death. Clostridium species were isolated from horse fecal samples during 4 seasons beginning in Fall 2008 and ending in Summer 2009 from three horse farms in Southern California: Cal Poly Pomona, Mt. SAC, and a private farm in Glendora. A total of 188 Clostridium isolates were collected during these four seasons. To determine the antibiotic resistance of the isolates, a modified NCCLS agar dilution method was used to screen the isolates for antibiotic resistance. The antibiotics tested were ampicillin, tetracycline, metronidazole, and vancomycin. These were selected using a NCCLS guideline that provides a comprehensive list of antimicrobial agents that should be considered when doing routine testing in veterinary microbiology. The initial screening revealed that of the 188 Clostridium isolates tested, 17 were resistant to ampicillin, 14 were resistant to tetracycline, 4 were resistant to metronidazole, and none were resistant to vancomycin. Biochemical testing revealed that of the isolates resistant to ampicillin, 15 are C.beijerinckii/butyricum and 2 are C. ramosum. Of the isolates resistant to tetracycline, 5 are beijerinckii/butyricum 3 are C. paraoutrificum, 3 are C. septicum, 2 are C. baratii, and 1 is C. botulinum/sporogenes. Of those resistant to metronidazole, 3 are C. beijerinckii/butyricum and 1 is C. ramosum. None of the isolates were resistant to more than one antibiotic. Future studies will include 16S ribosomal DNA sequencing for species confirmation and gene specific PCR for identification of their modes of antibiotic resistance. Geographical and seasonal distributions of these resistant traits among the isolates will be further analyzed.