The status of drug resistance and ampC gene expression in Enterobacter cloacae.
OBJECTIVE
To investigate the status of the drug resistance and the ampC gene expression of Enterobacter cloacae.


METHODS
Disk diffusion tests were made for detecting the susceptibility of antimicrobial agents against Enterobacter cloacae. AmpC gene was amplified by polymerase chain reaction (PCR) and verified by DNA sequencing. AmpC gene expression was analyzed according to antimicrobial agent sensitive phenotype.


RESULTS
The sensitivity rates of 144 strains to imipenam, cefepime and cefoperazone/sulbactam were 98.61%, 65.97% and 63.89%, respectively. The sensitivity rates of 144 strains to other antimicrobial agents were lower. Among the 144 strains 120 were found to be positive by PCR for ampC. The PCR product showed high homology to the GenBank ampC sequence. Stably derepressed strains, hyperinducible strains and unexpressing or lower level expressing strains accounted for 30.0% (36/120), 37.5% (45/120), and 32.5% (39/120), respectively. Fifty-six out of 120 strains (46.67%) also produced extended spectrum beta-lactamases (ESBLs). The hyperinducible strains were highly sensitive to all the antimicrobial agents except amoxicillin/clavulanic acid and cefuroxime, while the stably derepressed strains were only sensitive to imipenam and cefepime. However, sensitivity to cefepime decreased if the strains also produced ESBLs.


CONCLUSIONS
The drug resistant status of Enterobacter cloacae is severe. Clearing out the expressive status of ampC gene will be helpful in selection of antimicrobial agents in the treatment of clinical infection.
Zhou
Zhihui
Z
Department of Infectious Diseases, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China. orangezhou@sina.com
Li
Lanjuan
L
Yu
Yunsong
Y
Ma
Yilin
Y
D002438:Cefoperazone / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D016972:Enterobacter cloacae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D015870:Gene Expression; D005798:Genes, Bacterial / Q000235:genetics*; D015378:Imipenem / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D013407:Sulbactam / Q000494:pharmacology; D001618:beta-Lactamases / Q000032:analysis
D015378:Imipenem; D002438:Cefoperazone; D001618:beta-Lactamases; D013407:Sulbactam