Abstract

The increasing incidence of β-lactam resistance due to AmpC β-lactamases in Egypt necessitated this study which aimed to evaluate four different phenotypic methods for detection of AmpC β-lactamases among some clinical isolates of Enterobacteriaceae and compare these results with those obtained using polymerase chain reaction. The distribution of five AmpC β-lactamases genes (AmpC, CIT-M, Fox-1, ACC-1, ACT-1) were determined among the clinical isolates. Among 180 clinical isolates of Enterobacteriaceae, only 57 isolates were AmpC producers by phenotypic methods and 108 were AmpC producers by polymerase chain reaction. Phenotypic methods adapted in this study gave variable results with the most discriminatory results given by direct inoculation of both the enzyme extract and the bacterial culture in the wells. Of these, the best results were given by enzyme inoculation methods where 43 isolates exhibited positive result by this method. The distribution of AmpC β-lactamases gene among the clinical isolates showed that AmpC gene predominated in Escherichia coli. Fox gene was predominantly present in Enterobacter cloacae and E. coli isolates. ACT-1 predominated in E. cloacae. In contrast, enzymes from CIT-M and ACC-1 group were rarely present in Enterobacteriaceae.

Key words: Betalactam resistance, Enterobacteriaceae, AmpC betalactamases, polymerase chain reaction.