In total, 120 Escherichia coli isolates positive for one of the gentamicin resistance (GEN(R)) genes aac(3)-II, aac(3)-IV or ant(2 '')-I were tested for gentamicin susceptibility by the agar dilution method. Isolates positive for aac(3)-IV or ant(2 '')-I had an MIC distribution of 8-64 mg/L, whereas isolates positive for aac(3)-II had MICs of 32 to > 512 mg/L, suggesting a relationship between the distribution of MICs and the specific GEN(R) mechanism. The MIC distribution, regardless of the GEN(R) mechanism, was 8 - > 512 mg/L, which supports the clinical breakpoint of MIC > 4 mg/L suggested by EUCAST and questions the breakpoint recommended by the CLSI (>= 16 mg/L).
- susceptibility tests
- resistance genes
- MIC distribution
- Escherichia coli
Jakobsen, L., Sandvang, D., Jensen, V. F., Seyfarth, A. M., Frimødt-Møller, N., & Hammerum, A. M. (2007). Gentamicin susceptibility in Escherichia coli related to the genetic background: problems with breakpoints. Clinical Microbiology and Infection, 13(8), 830-832. https://doi.org/10.1111/j.1469-0691.2007.01751.x