SURVIVAL AND FITNESS OF MCR-1-HARBOURING ESCHERICHIA COLI ON SELECTED PRODUCE

Abstract

Antimicrobial resistance is a global public health concern. Colistin, also referred to as polymyxin E, is a last resort antibiotic used to treat complicated bacterial infections caused by Gram-negative bacteria when other antibiotics are proven ineffective. It was believed that colistin resistance was chromosomally mediated; however, Liu et al. have discovered the mobile colistin resistance gene in the year of 2016. Following this discovery, the mobile colistin resistance gene, mcr-1, has been detected in several niches in more than 40 countries. Lebanon, a developing country, suffers a serious antimicrobial resistance issue with the dissemination and spread of the mobile colistin gene mcr-1 in several matrices. Foodborne outbreaks related to consuming raw vegetables have been increasing with Escherichia coli reported the most common pathogen behind these outbreaks. Multidrug resistance mcr-1-harbouring E.coli has been detected in fresh produce in several countries. The sources of contamination of fresh produce include soil, irrigation water, manure, domestic and wild animals, insects, processing methods and handling. Hence, the aim of this study is to quantify the survival and fitness of mcr-1-harbouring Escherichia coli on selected fresh produce, lettuce, and spinach. The study also aims to assess the potential changes of Antimicrobial resistance (AMR) profiles of these E.coli on fresh produce. The isolates used are from various sources, sewage water, poultry, river water, and pigeon fecal matter. Results of this study show that all used isolates survived on both lettuce and spinach for up to 72 hours at room temperature and up to 7 days at 4°C. The final bacterial load was evaluated to assess the survival potential of these isolates on the fresh produce samples used. The PCR analysis showed that all the tested isolates from the last time points retained the mobile colistin resistance gene mcr-1. The disc diffusion method showed that the survived isolates of sewage source (WB3) and that of river water source (Waz3(1)) retrieved from the last time point did not exhibit any changes in their AMR profiles when compared to those of the original corresponding isolates. The other survived isolates showed minor changes in their AMR profiles when compared to their corresponding original isolates. This is the first study to evaluate the survival of multidrug resistant mcr-1-harboring Escherichia coli in lettuce and spinach. The findings of this study highlight the urge to act to ban colistin use and limit its use to therapeutical purposes to stop the spread of colistin resistance genes from different matrices to humans.