A Study on the AmpC Production Amongst the Urinary Enterobacteriaceae Isolates.

The AmpC β-lactamases are clinically important because they confer resistance to the narrow-, expandedand the broad-spectrum cephalosporins, the β-lactam-β-lactamase inhibitor combinations and aztreonam. The clinical microbiology laboratories should be able to detect the bacterial strains which produce AmpC, since these strains may appear to be susceptible to a particular β-lactam antibiotic in vitro, but may show no clinical response, resulting in a treatment failure with this β-lactam antibiotic [1]. The chromosomally mediated β-lactamase production takes place mainly through the expression of the AmpC gene which is either constitutive or inducible. In most of the genera of the family Enterobacteriaceae, AmpC is inducible [2]. The plasmid-encoded AmpC enzymes are almost always expressed constitutively [3].The Clinical and Laboratory Standards Institute (CLSI) does not describe methods for their detection. This study was aimed at detecting inducible and constitutive AmpC production amongst the urinary Enterobacteriaceae isolates by using different phenotypic methods.