Longitudinal study on the occurrence in pigs of colistin‐resistant Escherichia coli carrying mcr‐1 following the cessation of use of colistin

Abstract

The results suggest that cessation of colistin use may help over time to reduce or possibly eliminate mcr-1 E. coli on pig farms where it occurs.

Characterizing Antimicrobial Resistant Escherichia coli and Associated Risk Factors in a Cross-Sectional Study of Pig Farms in Great Britain

“…Thus, ciprofloxacin plates enabled detection not only of ciprofloxacin resistant E. coli, most often with QRDR mutations, but additional AMR genes. Furthermore, these MDR E. coli were less likely to be detected on other plates because they probably represented a small percentage of the total E. coli, as previously shown for mcr-harboring E. coli isolated from pig farms (Randall et al, 2018). QRDR mutations in Salmonella can confer protection against other antimicrobials (Webber et al, 2013) and the presence of double-serine QRDR mutations (GyrA83Ser and ParC80Ser) confers a selective advantage in lineages of several bacterial pathogens (Fuzi et al, 2017).…”

Whole Genome Sequencing and Characteristics of mcr-1–Harboring Plasmids of Porcine Escherichia coli Isolates Belonging to the High-Risk Clone O25b:H4-ST131 Clade B

“…Some studies have proved that stopping using colistin in positive mcr-1 carriers porcine farms has resulted in the disappearance of the resistance (Randall et al, 2018). However, because of the MDR profile of our ST131 isolates, this might not be that easy, due to coselection by other antimicrobials and host fitness adaptation.…”

Resistance to colistin and production of extended-spectrum β-lactamases and/or AmpC enzymes in Salmonella isolates collected from healthy pigs in Northwest Spain in two periods: 2008–2009 and 2018

“…Indeed, in vitro studies on Pseudomonas aeruginosa have shown that colistin-resistant phenotypes may become susceptible to colistin after a series of passages in colistin-free medium (Lee et al, 2016), which may also occur for E. coli and Salmonella. In addition, some field epidemiological studies also suggest that cessation of colistin use may help over time to reduce the frequency of detectable colistin resistance, and of mcr-1 gene, carried by Enterobacteriaceae in pigs (Randall et al, 2018;Wang et al, 2020), likely because its presence would be associated with a significant biological fitness cost (Nang et al, 2018). However, considering that the mcr-1 gene has been also detected in colistin-susceptible Enterobacteriaceae (Ovejero et al, 2017;Pham Thanh et al, 2016), and that we only tested the presence of mcr genes on those isolates with MIC >1 mg/L, it is possible that we may have somewhat overlooked the presence of dormant mcr-1 genes in some of the susceptible isolates.…”