Detection and analysis of AmpC-producing Gram-negative bacilli by three-dimensional extract tests

Objective To investigate the distribution of AmpC-producing gram-negative bacilli isolated in our hospital between September 2004 and August 2006.Methods The clinical isolates were reidentified by VITEK2,and three dimensional test was used to detect AmpC enzyme.Results Of 572 clinical isolates identified,204 were AmpC positive by three-dimensional tests(35.7%),including 148(25.9%) of single AmpC beta-lactamase producers and 56(9.8%) producing both AmpC beta-lactamase and ESBLs.Phenotype screening test showed that 173 out of 572 isolates were highly AmpC beta-lactamases producing strains,of which,148 tested positive by three-dimensional test with the coincidence rate as 85.5%.Conclusion High isolation rate of AmpC-producing gram-negative bacilli was shown in our hospital.Despite its complicated use,three-dimensional test appears reliable to detect AmpC enzyme.Phenotype screening test remains useful as a routine method for AmpC enzyme detection in laboratory practices.