Related Experiment Videos
Antimicrobial susceptibility of Arcanobacterium pyogenes isolated from cattle and pigs
H Yoshimura1, A Kojima, M Ishimaru
1National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan.
Abstract:
The minimum inhibitory concentrations (MICs) of 18 antimicrobial agents were determined for 49 Arcanobacterium pyogenes isolates (42 bovine isolates and 7 porcine isolates). Benzylpenicillin and ampicillin were the most active antibiotics, with MIC ranges of < or = 0.0125-0.05 microgram/ml for both bovine and porcine isolates. All isolates were susceptible to penicillins and cephems. MICs for 90% of the isolates of dihydrostreptomycin, gentamicin and oxytetracycline for bovine isolates were > 100 micrograms/ml, 1.56 micrograms/ml and 25 micrograms/ml, respectively. More resistance to dihydrostreptomycin appeared among porcine isolates (85.7%) than among bovine isolates (52.4%). Resistance to gentamicin occurred in only 3 (7.1%) of the bovine isolates. Resistance to oxytetracycline also appeared more frequent among porcine isolates (85.7%) than among bovine isolates (57.1%). All bovine isolates were susceptible to erythromycin, tilmocosin and lincomycin, but two porcine isolates (28.6%) were simultaneously resistant to these antibiotics. Tiamulin was as active as tilmicosin, with an MIC for 50% of the isolates (MIC50) of 0.05 microgram/ml for both bovine and porcine isolates. The MIC50s of chloramphenicol and its derivatives florfenicol and thiamphenicol were all 1.56 micrograms/ml. The fluoroquinolones enrofloxacin and ofloxacin were not so active as penicillins and macrolides, with MIC50s of 0.78 microgram/ml and 1.56 micrograms/ml, respectively, for both bovine and porcine isolates.
Insights
Arcanobacterium pyogenes shows susceptibility to penicillins and cephems. However, resistance to dihydrostreptomycin and oxytetracycline is higher in porcine isolates compared to bovine isolates.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Bacterial Pathogenesis
Background:
- Arcanobacterium pyogenes is a significant opportunistic pathogen affecting both bovine and porcine species.
- Understanding antimicrobial susceptibility patterns is crucial for effective treatment and control of A. pyogenes infections.
- Limited data exists on the comparative antimicrobial resistance profiles of A. pyogenes from different animal hosts.
Purpose of the Study:
- To determine the minimum inhibitory concentrations (MICs) of 18 antimicrobial agents against Arcanobacterium pyogenes isolates.
- To compare the antimicrobial susceptibility profiles between bovine and porcine isolates of A. pyogenes.
- To identify potential therapeutic options and highlight emerging resistance trends.
Main Methods:
- Agar dilution method was used to determine MICs for 49 Arcanobacterium pyogenes isolates (42 bovine, 7 porcine).
- Eighteen different antimicrobial agents were tested.
- MIC ranges and MIC50 values were calculated for each antibiotic and isolate group.
Main Results:
- Benzylpenicillin and ampicillin demonstrated the highest activity against all isolates.
- All isolates were susceptible to penicillins and cephems.
- Higher resistance rates to dihydrostreptomycin and oxytetracycline were observed in porcine isolates compared to bovine isolates. Some porcine isolates showed resistance to macrolides (erythromycin, tilmicosin, lincomycin).
Conclusions:
- Penicillins and cephems remain effective choices for treating Arcanobacterium pyogenes infections in cattle and pigs.
- Distinct resistance patterns between bovine and porcine A. pyogenes isolates warrant targeted antimicrobial selection.
- Continuous monitoring of antimicrobial resistance is essential for veterinary medicine.