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Wild-type cutoff for Apramycin against Escherichia coli
Yuqi Yang1, Tianshi Xiao2, Jiarui Li2
1Pharmacology Teaching and Research Department, School of Basic Medicine, Guizhou University of Traditional Chinese Medicine, Dongqing Road, University Town, Huaxi District, Guiyang, People's Republic of China.
Background:
Apramycin is used exclusively for the treatment of Escherichia coli (E.coli) infections in swine around the world since the early 1980s. Recently, many research papers have demonstrated that apramycin has significant in vitro activity against multidrug-resistant E.coli isolated in hospitals. Therefore, ensuring the proper use of apramycin in veterinary clinics is of great significance of public health. The objectives of this study were to develop a wild-type cutoff for apramycin against E.coli using a statistical method recommended by Clinical and Laboratory Standards Institute (CLSI) and to investigate the prevalence of resistance genes that confer resistance to apramycin in E. coli.
Results:
Apramycin susceptibility testing of 1230 E.coli clinical isolates from swine were determinded by broth microdilution testing according to the CLSI document M07-A9. A total number of 310 E.coli strains from different minimum inhibitory concentration (MIC) subsets (0.5-256 μg/mL) were selected for the detection of resistance genes (aac(3)-IV; npmA; apmA) in E. coli by PCR. The percentage of E. coli isolates at each MIC (0.5, 1, 2, 4, 8, 16, 32, 64, 128, and 256 μg/mL) was 0.08, 0.08, 0.16, 2.93, 31.14, 38.86, 12.85, 2.03, 1.46, and 10.41%. The MIC50 and MIC90 were 16 and 64 μg/mL. All the 310 E.coli isolates were negative for npmA and apmA gene, and only the aac(3)-IV gene was detected in this study.
Conclusions:
The wild-type cutoff for apramycin against E.coli was defined as 32 μg/mL. The prevelance of aac(3)-IV gene mainly concentrated in these MIC subsets 'MIC ≥ 64 μg/ mL', which indicates that the wild-type cutoff established in our study is reliable. The wild-type cutoff offers interpretion criteria of apramycin susceptibility testing of E.coli.
Insights
This study establishes a wild-type cutoff of 32 μg/mL for apramycin against E. coli in swine, crucial for monitoring antimicrobial resistance. The aac(3)-IV gene was prevalent in resistant strains, validating the new cutoff for veterinary use.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Molecular Diagnostics
Background:
- Apramycin has been a key treatment for swine E. coli infections since the 1980s.
- Emerging multidrug-resistant E. coli necessitates proper apramycin use and susceptibility testing.
- This study addresses the need for reliable interpretive criteria for apramycin in veterinary medicine.
Purpose of the Study:
- To establish a wild-type cutoff for apramycin against E. coli using CLSI guidelines.
- To determine the prevalence of apramycin resistance genes in swine E. coli isolates.
- To provide reliable interpretive criteria for apramycin susceptibility testing.
Main Methods:
- Broth microdilution testing was performed on 1230 E. coli clinical isolates from swine.
- PCR was used to detect resistance genes (aac(3)-IV, npmA, apmA) in 310 selected E. coli strains.
- Statistical analysis based on CLSI document M07-A9 was employed to define the wild-type cutoff.
Main Results:
- The minimum inhibitory concentration (MIC) distribution showed MIC50 and MIC90 values of 16 and 64 μg/mL, respectively.
- The aac(3)-IV gene was the only detected resistance gene, found predominantly in isolates with MICs ≥ 64 μg/mL.
- A wild-type cutoff for apramycin against E. coli was determined to be 32 μg/mL.
Conclusions:
- The established wild-type cutoff of 32 μg/mL for apramycin against E. coli is reliable.
- The prevalence of the aac(3)-IV gene supports the validity of the new cutoff.
- This wild-type cutoff provides essential interpretive criteria for apramycin susceptibility testing in E. coli.
