Relations between emergence of constitutive high expression AmpC β-lactamase and therapy of antibiotics.

OBJECTIVE To investigate the influence of antibiotics to produce constitutive high expressed AmpC β-lactamases by Gram-negative bacilli.METHODS Selecting the bacilli which were resistant to cefoxitin and negative in three-dimention test from the patients with nosocomial infections.Collecting the same patients'samples for three-dimention test until they were positive.Recording the bacteria species,underlying diseases,the sorts and dosage of antibiotics.RESULTS Of 152 strains,68 was positive.Twelve strains of Enterobacter cloacae were all changed(100%).The bacteria from the cerebral patients were prone to turn into the constitutive high expression(P0.05),the positive rate was 83.3%(10/12,OR=7.1).used penicillins plus β-lactamase inhibitors(128.8/276.0)and carbapenem plus β-lactams(58.9/82.3)were positively related with the dosage of antibiotics,while cephalosporins(95.3/64.6)and peptide(18.9/15.5)were negatively related.CONCLUSIONS High dose penicillins+β-lactamase inhibitors and carbapenem+β-lactams may promote the producetion of durative high expressed AmpC β-lactamases.