A modified disc method of phenotype screening for detection of AmpC

Objective To establish and evaluate a modified disc screening test used for detecting AmpC enzyme in Escherichia coli and Klebsiella pneumoniae.Methods Of 164 strains of clinical isolation of Escherichia coli and 40 strains of Klebsiella pneumoniae resistant to the third cephalosporin, AmpC enzyme was detected by the modified disc screening test, three-dimensional extract test and multiplex PCR.Results Among the 164 isolates of Escherichia coli,AmpC enzyme-positive strains were 8,8 and 9 by the above 3 methods,respectively.At the same time,2 ESBLs-positive strains were found by the modified disc screening test in the 8 AmpC-enzyme positive strains.Among the 40 isolates of Klebsiella pneumoniae,2 strains of induced AmpC were identified by the modified disc screening test and multiplex PCR.Conclusion The modified disc screening test can not only detect AmpC-positive strains,but also the strains with induced AmpC and ESBLs.The modified disc screening test is a simple,rapid and practical method which can be used in clinical laboratories.