Laboratory Detection and Neutralizing Activity of Exocellular AmpC β-lactamases by Anti bla-CMY

Adel Attia,Eman Fatah,Gamal El-Mowalid

doi:10.21608/zvjz.2017.7886

Abstract

Detection of AmpC β-lactamases (AmpC-bls) is important for infection control purposes and therapeutic options. Here, we provided a diagnostic anti β-lactamase neutralization test (bla-NT); modified from broth microdilution (BM) for the detection of bls-AmpC, CMY, in multidrug resistant Escherichia coli and Klebsiella pneumoniae. Anti-bla neutralizing activity against these two bacteria was tested. Anti bla-CMY was prepared in rabbits and used in: bla-NT; investigating effect on bacterial colony forming unit (CFU); and in ELISA. In bla-NT, the anti-bla-CMY neutralized exocellular bls produced by the tested bacterial strains and resulted in an increase in the bacterial sensitivity to the tested antimicrobials and reduction in minimum inhibitory concentration. Interestingly, the anti-bla-CMY decreased the CFU and its morphology when added to the tested bacteria. ELISA-OD was significantly correlated with the drop in minimum inhibitory concentration and CFU counts at P-value ≤ 0.05 and 0.01, respectively. It could be concluded that, bla-NT could detect bls-AmpC and run parallel to BM in microbiology laboratory. Investigations are running to develop the test for quantitative detection of bls-AmpC.

Highlights

AmpC β-lactamases is β-lactmase antibiotics destroying enzyme that has a special clinical interest since late 1980s
We provide bla-NT as modified test from broth microdilution test for accurate detection of bls-AmpC and for determining the possible activity on the multidrug resistant bacterial strains
E. coli and K. pneumoniae were resistant to amoxicillin, amoxicillin/ clavulanate, aztreonam, cephalexin, cefuroxime, cefotaxime, ceftriaxone and cefoxitin, with variable resistance to piperacillin and cefepime according to disc diffusion

Summary

Introduction

AmpC β-lactamases is β-lactmase antibiotics destroying enzyme that has a special clinical interest since late 1980s. It is associated with multiple antibiotic resistance to cephalothin, cefazolin, cefoxitin, most penicillins and bla- inhibitor/β-lactam combinations. Bls enzymes over expression confer resistance to broad-spectrum cephalosporins including cefotaxime, ceftazidime, and ceftriaxone [1]. Escherichia coli and Klebsiella pneumoniae have a great concern when produce Extended Spectrum β-Lactamases (ESBLs) associated with plasmid mediated bls-AmpC, which should be taken seriously and should be early diagnosed in clinical laboratory. It is essential that clinical laboratories accurately detect strains producing bls-AmpC [5]. There are presently no Clinical and Laboratory Standards Institute (CLSI) or other approved criteria for bls-AmpC detection [6]

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