Occurrence of Pseudomonas spp. in Raw Vegetables: Molecular and Phenotypical Analysis of Their Antimicrobial Resistance and Virulence-Related Traits.

Lidia Ruiz-Roldán,Gabriela Chichón,Beatriz Rojo-Bezares,Carmen Torres,María López,Yolanda Sáenz,Carmen Lozano

doi:10.3390/ijms222312626

Lidia Ruiz-Roldán, Gabriela Chichón + Show 5 more

Open Access

https://doi.org/10.3390/ijms222312626

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Abstract

Pseudomonas is characterized by its great capacity to colonize different ecological niches, but also by its antimicrobial resistance and pathogenicity, causing human, animal, or plant diseases. Raw and undercooked food is a potential carrier of foodborne disease. The aim of this study was to determine the occurrence of Pseudomonas spp. among raw vegetables, analysing their antimicrobial resistance, virulence, and molecular typing. A total of 163 Pseudomonas spp. isolates (12 different species) were recovered from 77 of the 145 analysed samples (53.1%) and were classified into 139 different pulsed-field gel electrophoresis patterns. Low antimicrobial resistance levels, but one multidrug-resistant isolate, were found. Among the 37 recovered P. aeruginosa strains, 28 sequence-types and nine serotypes were detected. Eleven OprD patterns and an insertion sequence (ISPa1635) truncating the oprD gene of one imipenem-resistant strain were found. Ten virulotypes were observed, including four exoU-positive and thirty-one exoS-positive strains. The lasR gene was absent in three ST155 strains and was truncated by different insertion sequences (ISPre2, IS1411, and ISPst7) in other three strains. High biofilm, motility, pigment, elastase, and rhamnolipid production were detected. Our study demonstrated a low occurrence of P. aeruginosa (18%) and low antimicrobial resistance, but a high number of virulence-related traits in these P. aeruginosa strains, highlighting their pathological importance.

Highlights

Vegetables and fresh fruit are important products in a healthy diet
The highest prevalence was detected in lettuce (90%) and chard (70%) samples, and the lowest one was among the onion/leek samples (26.3%)
Food and the environment have been described as reservoirs of bacteria harbouring antimicrobial resistance genes that could be transferred or mobilised into human pathogens

Summary

Introduction

Vegetables and fresh fruit are important products in a healthy diet. Vegetables have become increasingly recognised as potential carriers of foodborne diseases due to various contamination sources, such as dust, soil, manure, irrigation water, or wild animal faeces [1,2]. Fresh vegetables which are grown close to the soil, are often consumed raw, exposing consumers to the risk of infection [3]. Bacteria can develop antimicrobial resistance due to spontaneous mutations or acquisition of resistance mechanisms by horizontal gene transfer. Antimicrobial resistant isolates can spread antimicrobial resistance genes to other commensal and pathogenic bacteria [5]. The role of food in human exposure to antimicrobial resistant bacteria, as well as a reservoir of resistance genes, is becoming a growing food safety issue [3]

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