AmpC β-lactamases in Gram-negative bacilli from clinical isolates in a Colombian tertiary hospital

Abstract

Introduction: AmpC β-lactamases are enzymes with hydrolytic activity. They may be either constitutive or inducible. No standardized method is available for their phenotypical determination by international standards. Their detection by molecular biology could be a useful alternative for the surveillance and control of the spread of clones circulating in hospital environments.

Objective: Determine the resistance phenotype and genes expressed in the production of AmpC β-lactamases in Gram-negative bacilli from clinical isolates in a hospital.

Methods: An observational descriptive cross-sectional study was conducted. A total 78 bacterial strains were selected as carriers of AmpC β-lactamases. Disc approximation tests were performed. The strains testing positive were selected for DNA extraction and multiplex PCR for detection of six AmpC gene families. Determination was made of the frequency per sample type, service and comparison with the susceptibility profile.

Results: Of the strains selected with AmpC phenotype, 57.6% (45/78) were considered to be AmpC β-lactamase confirmed cases, due to their positive confirmatory test. The molecular technique used confirmed the presence of AmpC genes in 40% (18/45) of the cases. The gene most commonly obtained was MIR n= 9 (20%), followed by DHA n= 7 (15%).

Conclusions: Timely detection of genes encoding for AmpC β-lactamases makes it possible to set up strategies to prevent plasmid-mediated circulation in hospitals, as well as apply better therapeutic options that do not induce other resistance mechanisms.