Abstract
OBJECTIVES
In this study, the commercially available AID AmpC line probe assay (LPA) was evaluated for detection of plasmid-mediatedbla$_{AmpC}$ β-lactamase genes in Enterobacterales as well as chromosomal mutations in the bla$_{AmpC}$ promoter/attenuator regions in Escherichia coli.
METHODS
Accuracy of the AID AmpC probes was assessed using Enterobacterales clinical isolates harbouring diverse plasmid-mediated AmpC enzymes (ACC, ACT, DHA, FOX, CMY and MOX) and E. coli clinical isolates with mutations in the chromosomal bla$_{AmpC}$ promoter/attenuator regions. The diagnostic performance of the AID AmpC LPA for bla$_{AmpC}$ detection directly from clinical specimens was determined using 99 clinical urine specimens with bacterial cell counts >10$^{5}$CFU/mL and the results were compared with culture-based phenotypic drug susceptibility testing (DST).
RESULTS
Detection of bla$_{AmpC}$ genes in Enterobacterales clinical isolates showed 100% congruence with phenotypic DST results. The AID AmpC LPA showed 100% specificity [95% confidence interval (CI) 96-100%] and 100% sensitivity (95% CI 75-100%) for detection of plasmid-meditated bla$_{AmpC}$ and E. coli genomic bla$_{AmpC}$ promoter/attenuator mutations directly from clinical urine specimens. The AID AmpC LPA detected three AmpC-producers in urine specimens with bacterial cell counts >10$^{5}$CFU/mL that were missed by culture-based phenotypic DST, thereby displaying higher diagnostic sensitivity.
CONCLUSION
The AID AmpC LPA is an accurate, sensitive and easy-to-use test that can be readily implemented in any diagnostic laboratory for molecular detection of bla$_{AmpC}$ genes in Enterobacterales.
Wagner, Karoline