[Emergence of AmpC enzyme and antibiotics resistance in gram-negative bacilli]

To investigate the relationship between emergence of AmpC enzyme and drug resistance in the gram-negative bacilli in Xiangya Hospital and to provide information for the treatment of antibiotics.

The bacteria were identified; the susceptibility was determined by Microscan microbiological identification system; and the AmpC enzyme was detected by disc diffusion method.

Of the 204 gram-negative strains, the positive rate of AmpC enzyme was 19.61%; AmpC-positive strains resisted to ceftriaxone, piperacillin, ceftazidime, cefotaxime, cefoperazone, aztreonam, piperacillin/tazobactam, cefuroxime, ceftazidime/clavulanic, and cefotaxime/clavulanic. But AmpC-negative strains were susceptible to those antibiotics. There were significant differences, between the two groups (All P < 0.05). Both groups were susceptible to cefepime, imipenem, meropenem, cefoperazone/sulbactam, levofloxacin, and amikacin.

The detection of AmpC enzyme is helpful to the screen of drug resistant strains. Most bacilli with AmpC enzyme show the resistance to third-generation cephosporins, aztreonam, and the beta-lactamase inhibitors, but susceptible to imipenem, cefepime, meropenem, cefoperazone/sulbactam, levofloxacin, and amikacin, which provides the information for the antibiotic therapy.