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.
Insights
An efflux pump inhibition assay can reliably rule out overexpression in Acinetobacter baumannii strains. However, confirmatory testing is needed for positive results to combat antimicrobial resistance (AMR).
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance Research
Background:
- Antimicrobial resistance (AMR) in ESKAPE pathogens, particularly carbapenem-resistant Acinetobacter baumannii, is a major global health threat.
- Efflux pump overexpression is a key mechanism driving multidrug resistance (MDR) in A. baumannii, complicating treatment.
- Identifying strains with efflux pump overexpression is challenging.
Purpose of the Study:
- To evaluate the performance of an efflux pump inhibition assay compared to RT-qPCR for detecting efflux pump overexpression in clinical A. baumannii strains.
- To assess the reliability of the inhibition assay in identifying MDR A. baumannii.
Main Methods:
- Compared an efflux pump inhibition assay with RT-qPCR using 60 MDR and 1 wild-type A. baumannii clinical strains.
- Analyzed agreement using Cohen's kappa statistic.
- Investigated the association between gpi alleles and efflux pump overexpression.
Main Results:
- The inhibition assay showed fair agreement with RT-qPCR (Cohen's kappa = 0.37).
- Inhibition by 1-(1-NaphthylMethyl)-Piperazine (NMP) demonstrated moderate agreement (Cohen's kappa = 0.41), unlike Phenylalanine-Arginine-β-Naphthylamide (PaβN).
- RT-qPCR identified significant efflux pump overexpression in 16.7% of strains negative by the inhibition assay.
Conclusions:
- An NMP-based efflux pump inhibition assay can reliably exclude efflux pump overexpression in A. baumannii.
- Confirmatory molecular testing (e.g., RT-qPCR) is essential for strains testing positive with the inhibition assay.
- Genetic diversity, indicated by gpi alleles, may correlate with efflux pump overexpression.
