Interactions of Shiga toxin-producing Escherichia coli with leafy green vegetables

Abstract

Shiga toxin-producing Escherichia coli (STEC) are important foodborne pathogens responsible for a wide spectrum of diseases including diarrhea, bloody diarrhea, and hemolytic uremic syndrome (HUS). A considerable number of outbreaks and sporadic cases of HUS have been associated with ingestion of fresh ready-to-eat products. Maintenance and persistence of STEC in the environment and foods can be related to its ability to form biofilm. A non-O157 STEC strain isolated from bovine feces was distinguished by its great ability to form biofilm in abiotic surfaces. In the present study, we aimed to investigate the ability of this strain to adhere to rocket leaves (Eruca sativa). Adherence assays were carried out for 3 h at 28°C and analyzed by scanning electron microscopy. The non-O157 STEC strain adhered to leaf surface and inside the stomata forming several bacterial aggregates. The number of adherent bacteria per square millimeter of leaf was eightfold higher compared with an O157 STEC strain. Deletion of the STEC autotransporter protein contributing to biofilm (Sab) reduced the adherence ability of the non-O157 strain in almost 50%, and deletion of antigen 43 (Ag43) almost abolished this interaction. Very few bacteria were seen on the leaf surface, and these differences were statistically significant, suggesting the role of both proteins and especially Ag43 in the interaction of the non-O157 STEC strain with leaves. The risk posed by non-O157 STEC adherence to leaves on fresh produce contamination should not be neglected, and measures that effectively control adherence should be included in strategies to control non-O157 STEC.

Shiga Toxin-Associated Hemolytic Uremic Syndrome: Specificities of Adult Patients and Implications for Critical Care Management

“…The preponderance of raw beef and hamburger meat as a source of contamination seems to have declined nowadays in favor of fresh products such as leafy greens, lettuce [ 50 ], or sprouts [ 12 , 70 ], which are now recognized as the second most common source of foodborne transmission [ 71 ]. In comparison to O157 E. coli , non-O157 strains display enhanced biofilm formation attributes as well as increased adherence to green leaves, which may account for the rising role of these strains [ 72 , 73 ]. In France, contaminated raw milk cheese consumption was the source of a major outbreak in 2018, and this argues for the avoidance of non-pasteurized cheese in children under six years of age [ 45 ].…”

Genomic Epidemiology of Shiga Toxin-Producing Escherichia coli Isolated from the Livestock-Food-Human Interface in South America

“…In this context, in the USA serogroups O26, O45, O103, O111, O121, and O145 (also known as "the big six"), alongside O157 have been considered adulterants in raw, non-intact ground beef products since 2011 [13]. Nevertheless, the presence of STEC in soil, water, and animal manure are factors associated with the contamination of other foods such as vegetables [14,15].…”

Adhesion to and survival of foodborne pathogens in produce and strategies for their biocontrol

“…The most studied serovar from pathogenic E. coli is O157:H7, which harbors genes that encodes for the Shiga toxin, and it could produce hemolytic uremic syndrome in humans. However, it has also been described that non‐O157 E. coli strains, can also cause diarrheal infections and hemolytic uremic syndrome in humans by auto‐transported proteins (Abe et al, 2020). In produce, it has been reported that STEC serovar O157:H7 can adhere to carrots and cilantro in different manners; in the study, E. coli O157:H7 shows a recovered average between 3.7 log 10 and 4.3 log 10 viable cells from carrots and cilantro, respectively (Sai et al, 2019).…”

“…Also, for the same strain it has been reported that adherence to the surface of leafy vegetables occurs through a type of fimbria known as curli, which is also involved in the formation of biofilm, since a knockout mutant in csgA , a gene involved in the formation of curli, is unable to colonize the leafy surface of lettuces (Fink et al, 2012). Furthermore, for the strain E. coli serovar O105:H18, it has been observed that the sab gene is partially required for the adherence of this strain to the surface of rocket leaves (Abe et al, 2020). In contrast, in lettuce roots from Valerianella locusta , it was observed that the genes associated to adherence and colonization, iha (enterobactin siderophore receptor) and hcpA (pilin subunit of type IV pilus), are not involved in the adhesion from EHEC O157H7 strain Sakai (wild type [WT]), since isogenic mutant strains in those genes do not show reduced adhesion, compared to what was observed with the WT strain, to lettuce roots (Eissenberger et al, 2018).…”