Detection of Extended-spectrum Beta-lactamases in AMPC Co-producing Bacteria by Disc Diffusion Method in Clinical Isolates of Enterobacteriacae

Extended-spectrum beta-lactamases (ESBL) may not always be detected in routine susceptibility tests. This study reports the performance of the cefepime-clavulanate compared with cefotaxime–clavulanate disc diffusion method for the detection of extended-spectrum β-lactamases in AmpC coproducing Enterobacteriaceae.

Consecutive non-duplicate isolates of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis isolated from clinical samples were tested for ESBL by both the standard CLSI double-disk diffusion method using ceftazidime and cefotaxime disks and compared with cefepime/cefepime-clavulanate. Isolates were also tested for the presence of AmpC beta-lactamase by AmpC disk test and MBL was detected by EDTA disc potentiation test.

Among the 100 clinical isolates tested, ESBL production was seen in 34 (34%), Amp C production in 36 (36%), ESBL in Amp C coproduction in 24 (24%) of the isolates, MBL production in 8 (8%) isolates.

The study emphasizes the high prevalence of multidrug resistant enterobacteriacae producing beta-lactamase enzymes of diverse mechanisms. Thus proper antibiotic policy and measures to restrict the indiscriminative use of cephalosporins and carbapenems should be taken to minimize the emergence of this multiple beta-lactamase producing pathogens.