1-(1-naphthylmethyl)-piperazine Inhibition assay successfully rules out efflux pump overexpression in Acinetobacter
Victor Zosim1,2, Catherine Mullie2, François Peltier2
1Laboratoire de Bactériologie-Hygiène, CHU Amiens-Picardie, Amiens, France.
Background:
Antimicrobial resistance (AMR) in Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE pathogens), notably in carbapenem-resistant Acinetobacter baumannii, is a pressing global health concern, contributing to significant AMR-associated mortality. Efflux pump overexpression plays a crucial role in the multidrug resistance (MDR) of A. baumannii, but the identification of efflux-overexpressing strains remains challenging.
Methods And Results:
We evaluated the performance of an efflux pump inhibition assay in comparison with RT-qPCR, to assess efflux pump overexpression in a collection of clinical A. baumannii strains. Sixty MDR strains and a wild one were analyzed. The inhibition assay was positive for 34 and negative for 27 strains, respectively. Results were in agreement with RT-qPCR in 67.2% of the tested strains (39/58). Cohen's kappa showed a fair agreement between inhibition assay and RT-qPCR (Cohen's kappa = 0.37). Inhibition by 1-(1-NaphthylMethyl)-Piperazine (NMP), but not by Phenylalanine-Arginine-β-Naphthylamide (PaβN), was in moderate agreement with RT-qPCR (Cohen's kappa = 0.41). Furthermore, gpi alleles were associated with efflux pump overexpression (p = 0.03), suggesting potential links between genetic diversity and efflux pump overexpression. RT-qPCR showed a significant efflux pump overexpression for 4 (16.7%) out of 24 inhibition assay negative strains.
Conclusions:
Our findings support the ability to reliably rule out efflux pump overexpression in A. baumannii strains displaying a negative result with an inhibition test relying on NMP. However, confirmatory analyses are necessary for strains that test positive.
