Detecting AmpC β-lactamases from nosocomial Klebsiella pneumoniae infection and their resistance in ICU patients

Objective To explore cephalosporinase from nosocomial Klebsiella pneumoniae infection and their drug-resistant characteristics among the ICU patients so as to provide an instruction for rational clinical medication.Methods 67 samples were identified with VITEK-60 automated system.The strains producing AmpC β-lactamases were screened with cefoxitin disk diffusion method recommended by the CLSI,and confirmed by cefoxitin three-dimensional test.AmpC β-lactamase genotype was differentiated by PCR-sequencing and susceptibility tests which were done with the Kirby-Bauer method recommended by the CLSI.Results In the 67 isolates of Klebsiella pneumoniae,11 strains(16.4％) were found to produce AmpC β-lactamases.The drug-resistant genotype for all the 11 AmpC-positive strains was DHA-1.AmpC-producing strains developed multi-drug resistance,especially for broadspectrum β-lactam antibiotics and enzyme inhibitors.β-lactamases-producing strains were more resistant than non-producing ones.Conclusion Klebsiella pneumoniae in ICU patients has a higher proportion of producing AmpC β-lactamase strains,which are all of DHA-1 genotype and have multi-drug resistance. Key words: Nosocomial infection;  Klebsiella pneumoniae;  Cephalosporinase;  Resistance