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 antibla-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.

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