Abstract
AmpC genes are encoded on the chromosome of Enterobacter cloacae. Excessive production of AmpC β-lactamases is induced by an antimicrobial agent. We examined the excessive production of AmpC β-lactamases using the E. cloacae strain that had been isolated from a clinical specimen by two methods. Consequently, AmpC β-lactamases were detected in 3.7% of the strains by the Cica β test, which is a third-generation cephem antibiotics susceptibility test in which AmpC genes were induced by the disc diffusion method. Additionally, for induction, the cells were cultured in CAZ Sub-MIC liquid culture medium with shaking, and the results showed 80% positivity for the lactamases. It is considered that there is a possibility that strains excessively producing AmpC β-lactamases exist in vivo, even when AmpC β-lactamases are not detected by clinical isolation because it is considered that a newer method is closer to the in vivo environment in terms of conditions. Moreover, this result shows that it is very important in antibiotic therapy to follow the dosage regimen, because antibiotic therapy with insufficient dosage promotes the excessive production of AmpC β-lactamases, and the patient may acquire an intractable infectious disease.
