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Antimicrobial susceptibility of Erysipelothrix rhusiopathiae isolated from pigs in Southern Japan with a modified
Takehisa Chuma1, Toshio Kawamoto, Francis Shahada
1Laboratory of Veterinary Public Health, Department of Veterinary Medicine, Faculty of Agriculture, Kagoshima University, Korimoto, Kagoshima890-0065, Japan.
Abstract:
The determination of antimicrobial minimum inhibitory concentration (MIC) in Erysipelothrix rhusiopathiae by using the agar dilution method has not been covered by the Clinical and Laboratory Institute (CLSI). Only the broth microdilution method has been outlined. This report describes a modification of the agar dilution procedure for E. rhusiopathiae using Trypto-soy agar supplemented with 0.1% Tween 80 and incubation in ambient air at 37 degrees C for 24 hr. The MICs of the assay were in agreement with those of the broth microdilution method recommended by the CLSI. Antimicrobial susceptibility test was performed using this method for 149 E. rhusiopathiae isolates from 2 meat processing plants in Kagoshima Prefecture during the period of April 2004 to March 2005. The number of strains resistant to oxytetracycline, erythromycin, lincomycin, ofloxacin and enrofloxacin were 56 (37.6%), 4 (2.7%), 18 (12.1%), 21 (14.1%) and 19 (12.8%), respectively. All strains were susceptible to ampicillin.
Insights
A modified agar dilution method for determining antimicrobial minimum inhibitory concentration (MIC) in Erysipelothrix rhusiopathiae was developed. This validated method showed agreement with CLSI standards, aiding antimicrobial susceptibility testing.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Clinical Laboratory Science
Background:
- The Clinical and Laboratory Standards Institute (CLSI) has not established an agar dilution method for Erysipelothrix rhusiopathiae.
- Only the broth microdilution method is currently outlined by CLSI for this bacterium.
Purpose of the Study:
- To develop and validate a modified agar dilution method for determining antimicrobial minimum inhibitory concentrations (MICs) in Erysipelothrix rhusiopathiae.
- To assess the antimicrobial susceptibility profile of E. rhusiopathiae isolates from meat processing plants.
Main Methods:
- A modified agar dilution procedure was developed using Trypto-soy agar supplemented with 0.1% Tween 80.
- Incubation was performed in ambient air at 37°C for 24 hours.
- The modified method was validated against the CLSI-recommended broth microdilution method.
Main Results:
- The modified agar dilution method yielded MICs consistent with the CLSI-recommended broth microdilution method.
- Antimicrobial susceptibility testing of 149 E. rhusiopathiae isolates revealed resistance to oxytetracycline (37.6%), lincomycin (12.1%), ofloxacin (14.1%), and enrofloxacin (12.8%).
- All tested strains were susceptible to ampicillin, with low resistance rates observed for erythromycin (2.7%).
Conclusions:
- The modified agar dilution method is a reliable alternative for determining E. rhusiopathiae MICs.
- The study highlights significant resistance to certain antimicrobials in E. rhusiopathiae from meat processing environments.
- Ampicillin demonstrates consistent efficacy against E. rhusiopathiae isolates.
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