Resistance to extended-spectrum cephalosporin in Enterobacteriaceae is increasingly prevalent in South Korea. This study aims to explore the distribution of AmpC genes in Proteus mirabilis isolated from stray and hospital-admitted companion animals in South Korea. AmpC β-lactamases hold clinical significance due to its potential to facilitate antimicrobial resistance to cefoxitin, cefazolin, and most penicillins. A total of 163 bacterial isolates belonging to the Enterobacteriaceae family were collected from dogs (n = 158) and cats (n=5). Of them, 134 isolates were from hospital-admitted animals, while 29 isolates from stray animals. Boronic acid tests and antimicrobial susceptibility tests were conducted for an initial screening to detect AmpC β-lactamase resistant P. mirabilis. Gene-specific PCRs were conducted to identify the type of AmpC genes, which include six groups (MOXM, CITM, DHAM, ACCM, EBCM, and FOXM), in the resistant isolates. The boronic acid disk tests revealed 45 (27.6%) positive isolates out of 163 isolates tested. Of these 45 isolates, six were determined to harbor the EBCM gene, 13 for CITM, one for FOXM, and one for DHAM by single detection PCR. No isolates carried for ACCM or MOXM. Thus, a total of 21 out of 163 isolates (12.9%) were demonstrated to possess AmpC genes. No isolates contain more than one group of AmpC gene family. A significantly higher percentage of P. mirabilis was found to possess AmpC genes compared to past studies. Therefore, the increasing trend in antimicrobial resistance in P. mirabilis indicates a dire need to monitor antimicrobial prescription in the veterinary field.

INTRODUCTION
MATERIALS AND METHODS
    Ethics approval
    Study population and bacterial isolates
    Identification of isolates
    Phenotypic antimicrobial susceptibility testing
    AmpC boronic acid phenotype test
    Genotypic antimicrobial susceptibility testing
RESULTS
    Antibiotic disk tests
    Boronic acid test and PCR
DISCUSSION
CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES

• Christine Kim(Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University)
• Woo Kyung Jung(Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University) Corresponding Author
• Se Ra Shin(Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University)
• Seong Mi Noh(Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University)
• Yu Jin Yang(Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University)
• Sook Shin(Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University)
• Kun Taek Park(Department of Biotechnology, Inje University)
• Yong Ho Park(Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University) Corresponding Author