The preliminary study on carbapenem resistance specifically mediated by cphA in Aeromonas veronii
Objective To investigate the effect of cphA on β-lactam resistance in Aeromonas veronii and to elucidate the function of this gene.Methods A.veronii C4 was used as the research object,and a cphA gene knockout strain was constructed using the homologous recombination method.The growth curve was determined by measuring the turbidity,the minimum inhibitory concentrations of different β-lactam antibiotics against the strains were detected using the microdilution method,and the expression of cphA in response to antibiotic exposure was determined using real-time quantitative PCR.The important active sites of the CphA enzyme were analyzed through molecular docking.Results The cphA gene knockout strain was successfully constructed.It was found that the absence of cphA did not affect the growth of A.veronii.Although the expression of cphA increased significantly in response to the exposure of both carbapenem and penicillin,the lack of cphA specifically made the strain sensitive to carbapenem antibiotics while having no effects on the resistance phenotypes of other types of β-lactams.In addition,the results of molecular docking indicated that the amino acid residues Thr135,His174,and Asn201 of the CphA enzyme constitute the active sites that form hydrogen bond interactions with the imipenem molecule.Conclusion The cphA in A.veronii specifically mediated carbapenem resistance.This study provides a theoretical basis for further improving the research on drug resistance in A.veronii and the functional research on β-lactamases.
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