Gekenidis, Maria-Theresia and Qi, Weihong and Hummerjohann, Jorg and Zbinden, Reinhard and Walsh, Fiona and Drissner, David (2018) Antibiotic-resistant indicator bacteria in irrigation water: High prevalence of extendedspectrum beta-lactamase (ESBL)-producing Escherichia coli. PLoS ONE, 13 (11). ISSN 1932-6203

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Abstract

Irrigation water is a major source of fresh produce contamination with undesired microorganisms including antibiotic-resistant bacteria (ARB), and contaminated fresh produce can transfer ARB to the consumer especially when consumed raw. Nevertheless, no legal guidelines exist so far regulating quality of irrigation water with respect to ARB. We therefore examined irrigation water from major vegetable growing areas for occurrence of antibioticresistant indicator bacteria Escherichia coli and Enterococcus spp., including extendedspectrumβ-lactamase (ESBL)-producing E. coli and vancomycin-resistant Enterococcus spp. Occurrence of ARB strains was compared to total numbers of the respective species. We categorized water samples according to total numbers and found that categories with higher total E. coli or Enterococcus spp. numbers generally had an increased proportion of respective ARB-positive samples. We further detected high prevalence of ESBL-producing E. coli with eight positive samples of thirty-six (22%), while two presumptive vancomycinresistant Enterococcus spp. were vancomycin-susceptible in confirmatory tests. In disk diffusion assays all ESBL-producing E. coli were multidrug-resistant (n = 21) and wholegenome sequencing of selected strains revealed a multitude of transmissible resistance genes (ARG), with blaCTX-M-1 (4 of 11) and blaCTX-M-15 (3 of 11) as the most frequent ESBL genes. Overall, the increased occurrence of indicator ARB with increased total indicator bacteria suggests that the latter might be a suitable estimate for presence of respective ARB strains. Finally, the high prevalence of ESBL-producing E. coli with transmissible ARG emphasizes the need to establish legal critical values and monitoring guidelines for ARB in irrigation water.

Item Type:	Article
Keywords:	Antibiotic-resistant indicator; bacteria; irrigation water; High prevalence; extended-spectrum; beta-lactamase; ESBL; Escherichia coli;
Academic Unit:	Faculty of Science and Engineering > Biology
Item ID:	12669
Identification Number:	https://doi.org/10.1371/journal.pone.0207857
Depositing User:	Fiona Walsh
Date Deposited:	31 Mar 2020 12:48
Journal or Publication Title:	PLoS ONE
Publisher:	Public Library of Science
Refereed:	Yes
URI:	Publisher
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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