Characterization of Escherichia coli strains isolated from raw vegetables

Abstract

Vegetables are an important part of the human diet. Sometimes, contamination by pathogenic Escherichia coli can be underestimated; moreover there is a risk of antibiotic resistance spreading via the food chain. The purpose of this study was to examine the prevalence of Escherichia coli in fresh vegetables sold in retail market in the Czech Republic and to evaluate the risk to human health. Antibiotic resistance against 12 antibiotics, the presence of 12 virulence and 15 resistance genes were determined among 15 isolated strains. Most of tested strains belonged to B1 phylogenetic group, less frequently represented was B2 and D phylogroup. These results indicate that most strains are probably of human origin. All E. coli strains were resistant to at least one of twelve tested antibiotics. A multidrug resistance was observed in four strains. In this study, the presence of virulence factors Einv and papC and also genes encoding toxins (CNF1, CNF2) was detected. Nevertheless, none strain can be considered as STEC or EHEC. The widespread appearance of a growing trend associated with the prevalence of antibiotic resistance among enterobacterial isolates is undeniable and the possibility of transfer to humans cannot be ignored. Nevertheless, these results indicate that raw vegetables sold in the retail market can constitute a potential health risk for consumers.

Contamination of Fresh Produce with Antibiotic-Resistant Bacteria and Associated Risks to Human Health: A Scoping Review

“…Mcr-1 positive E. coli were also isolated from carrot, pak choi, lettuce, tomato, spinach and cucumber, and were resistant to colistin (CST), AMP, GEN, NA, TET, CIP, cefotaxime (CTX), kanamycin (KAN), levofloxacin (LVX), doxycycline (DOX) and fosfomycin (FOS) [ 44 , 45 , 46 ]. A study in the Czech Republic found that the majority of E. coli isolates (13 of 15) from 108 raw vegetable samples were positive for one or multiple ARGs, including qac , sul1 , tetA , int , sul1 , sul3 , mer and tetB [ 10 ]. One study in Germany reported that 7 out of 245 vegetable samples were positive for extended-spectrum β-lactamase (ESBL)-producing E. coli , and all ESBL-producing isolates were positive for bla CTX-M genes conferring resistance to third generation cephalosporins (3GC) [ 11 ] ( Table S4 ).…”

“…Another article mentioned that Rahnella aquatilis, P. agglomerans, E. cloacae, and C. freundii might contribute to the spread of ARGs to resident bacteria [ 27 ]. The public health risks associated with exposure to ARB, especially 3GC-resistant Enterobacteriaceae are diverse, ranging from risk of difficult-to-treat diseases, to colonization and asymptomatic carriage, to mere passage through human intestines by environmental species [ 6 , 10 ]. Only three articles discussed the fact that gut colonization by resistant bacteria can pose a risk of complicated infection among infants, the elderly or individuals with weakened immune systems [ 25 , 31 , 37 ].…”

“…Among all foodborne pathogens in fresh produce, E. coli was predominant due to its ubiquity in nature and ease of detection and isolation [ 10 , 23 ]. However, there was a significant variation in the prevalence of contamination between low- and high-income countries.…”

“…Multidrug-resistant E. coli and Salmonella spp. on vegetables have been linked with disease outbreaks in Germany, the United States, Canada, Australia and Finland [ 9 , 10 , 11 , 12 , 13 ]. Additionally, opportunistic microorganisms previously considered non-pathogenic are present in fresh produce, and can cause serious infections in an immune-compromised host.…”

Identification and Characterization of Antibiotic-Resistant, Gram-Negative Bacteria Isolated from Korean Fresh Produce and Agricultural Environment

“…Multidrug-resistant E. coli and Salmonella spp. in vegetables have also often been reported as causative agents of foodborne outbreaks in Europe and North America [ 17 , 18 , 19 , 20 , 21 ]. These cases demonstrate the importance of regularly monitoring antibiotic-resistant bacteria in agricultural products and controlling the usage of antibiotics in the agricultural environment.…”