Polyether ionophore resistance in a one health perspective

Abstract

Antimicrobial resistance is a major threat to human health and must be approached from a One Health perspective. Use of antimicrobials in animal husbandry can lead to dissemination and persistence of resistance in human pathogens. Polyether ionophores (PIs) have antimicrobial activities and are among the most extensively used feed additives for major production animals. Recent discoveries of genetically encoded PI resistance mechanisms and co-localization of resistance mechanisms against PIs and antimicrobials used in human medicine on transferrable plasmids, have raised concerns that use of PIs as feed additives bear potential risks for human health. This review summarizes the current knowledge on PI resistance and discusses the potential consequences of PI-usage as feed additives in a One Health perspective.

Keywords: anticoccidials; antimicrobial resistance; coccidiostats; growth promoters; one health; polyether ionophore; vancomycin resistance.

Figure 1

Proposed effects of monensin-mediated ion gradient disruption in Eimeria tenella (Smith and Galloway, 1983) parasites (A) and in gram-positive Streptococcus bovis (Russell, 1987) bacteria (B). Encircled numbers represent suggested sequence of ion transport events. Red arrows indicate direction of change in cystosolic ion concentrations. Cation gradients across a bilayer is displayed by triangles.

Figure 2

Comparison of the proportion of polyether ionophore resistant isolates from conventionally reared broilers of Enterococcus faecium and Enterococcus faecalis in four European countries sorted by year. The data were retrieved from the reports of the surveillance programs of each country (MARAN, The Netherlands; DANMAP, Denmark; SVARM, Sweden; NORM-VET, Norway). Cut-off values used were > 4 mg/L for salinomycin, and > 2 mg/L for narasin. Note that these cut-off values are higher than the values proposed to correlate with the narAB resistance genes by Pikkemaat et al. (2022) and Nilsson et al. (2016) and the results likely underestimate the true prevalence of PI resistant isolates in broiler populations.