J Vet Sci.  2019 Mar;20(2):e13. 10.4142/jvs.2019.20.e13.

Antimicrobial resistance profiles of vancomycin-resistant Enterococcus species isolated from laboratory mice

• Yamanaka H
• Kadomatsu
• Takagi T
• Ohsawa M
• Yamamoto N
• Kubo N
• Takemoto T
• Ohsawa K

• KMID: 2454015
• DOI: http://doi.org/10.4142/jvs.2019.20.e13

Abstract

Isolates of 24 enterococci, 5 Enterococcus casseliflavus and 19 Enterococcus gallinarum, possessing vanC genes and showing low-level resistance to vancomycin were obtained from mice from commercial mouse breeding companies. Since some of these isolates showed resistance to other antibiotics, the purpose of this study was to clarify the resistant profiles of these isolates. One E. casseliflavus isolate showed resistance to erythromycin with a minimal inhibitory concentration (MIC) of 8 μg/mL and also showed apparent resistance to fluoroquinolones with an MIC of 32 μg/mL for ciprofloxacin. The MICs of 2 other fluoroquinolone-resistant E. casseliflavus and E. gallinarum isolates were 3 and 6 μg/mL, respectively. These 3 resistant isolates showed an absence of macrolide- and fluoroquinolone-resistant genes, including amino acid substitutions in the quinolone resistance determining regions of DNA gyrase and topoisomerase IV. Resistance to tetracycline was detected in 2 E. gallinarum isolates that were highly resistant, exhibiting MICs of 48 and 64 μg/mL and possessing tet(O) genes. The results indicate that antibiotic-resistant enterococci are being maintained in some laboratory mouse strains that have never been treated with an antibiotic.

Keyword

Antibiotic resistance; Enterococcus; laboratory mice

MeSH Terms

Amino Acid Substitution
Animals
Anti-Bacterial Agents
Breeding
Ciprofloxacin
DNA Gyrase
DNA Topoisomerase IV
Drug Resistance, Microbial
Enterococcus*
Erythromycin
Fluoroquinolones
Mice*
Tetracycline
Vancomycin
Anti-Bacterial Agents
Ciprofloxacin
DNA Gyrase
DNA Topoisomerase IV
Erythromycin
Fluoroquinolones
Tetracycline
Vancomycin