This research was performed to ascertain the ubiquity of bacterial pathogens which hyper-produced AmpC β-lactamase enzymes in adult catfish cultured in the Nigerian catfish grow-out pond systems. Phenotypic and molecular methods were used to isolate and identify bacterial pathogens that hyper-produced AmpC β-lactamase enzymes. The AmpC β-lactamase enzymes produced by the bacterial pathogens were subsequently characterized by BLASTX and RPS-BLAST bioinformatics software as well as with the Cn3D molecular modelling software. Findings from the present study indicated that pathogenic bacterial strains which hyper-produced the AmpC β-lactamase enzymes were isolated from 49 catfish samples out of the 54 catfish samples which were examined. The pathogenic bacterial strains were mainly identified as Citrobacter freundii MGH 150, Enterobacter cloacae NG 14, and Enterobacter cloacae subspecies dissolvens HKE 15. The AmpC β-lactamase enzymes produced by the bacterial pathogens were also respectively identified as cephalosporinase hydrolyzing class C CMY-LAT-MOX-ACT-MIR-FOX, CMY2/MIR/ACT/EC family class C beta-lactamase, and CMY2/MIR/ACT/EC family class C beta-lactamase. The presence of AmpC enzymes that are hyper-produced by bacterial pathogens which were isolated from almost all the catfish examined calls for urgent monitoring/surveillance of the Nigerian catfish ponds by the relevant regulatory agencies.
