Presence of Shiga Toxin-Producing Escherichia coli (STEC) in Fresh Beef Marketed in 13 Regions of ITALY (2017).

Bianca Varcasia,Paola De Santis,Laura De Santis,Francesco Tomassetti,Sarah Lovari,Fabiola Di Giamberardino,Stefano Bilei

doi:10.3390/microorganisms6040126

Abstract

The aim of this study was to determine the prevalence of Shiga toxin-producing Escherichia coli in fresh beef marketed in 2017 in 13 regions of Italy, to evaluate the potential risk to human health. According to the ISO/TS 13136:2012 standard, 239 samples were analysed and nine were STEC positive, from which 20 strains were isolated. The STEC-positive samples were obtained from Calabria (n = 1), Campania (n = 1), Lazio (n = 2), Liguria (n = 1), Lombardia (n = 1) and Veneto (n = 3). All STEC strains were analysed for serogroups O26, O45, O55, O91, O103, O104, O111, O113, O121, O128, O145, O146 and O157, using Real-Time PCR. Three serogroups were identified amongst the 20 strains: O91 (n = 5), O113 (n = 2), and O157 (n = 1); the O-group for each of the 12 remaining STEC strains was not identified. Six stx subtypes were detected: stx1a, stx1c, stx2a, stx2b, stx2c and stx2d. Subtype stx2c was the most common, followed by stx2d and stx2b. Subtype stx2a was identified in only one eae-negative strain and occurred in combination with stx1a, stx1c and stx2b. The presence in meat of STEC strains being potentially harmful to human health shows the importance, during harvest, of implementing additional measures to reduce contamination risk.

Highlights

Shiga toxins (Stx) are potent cytotoxins encoded by lambdoid phages and integrated into the bacterial chromosome of a large and complex group of pathogenic Escherichia coli (STEC) strains that cause disease in humans [1,2]
Some studies have suggested that Shiga toxin-producing Esherichia coli (STEC) strains producing Stx2f can cause diarrhoea in humans [18]; recently, STEC strains carrying the stx2f gene have been isolated from patients with hemolytic uremic syndrome (HUS) [18,19]
Enrichment cultures are essential to augment sensitivity, thereby promoting the isolation of STEC strains needed to confirm the presence of the stx genes in the live cell, while excluding the presence of free DNA or free prophages in the cultures [28]

Summary

Introduction

Shiga toxins (Stx) are potent cytotoxins encoded by lambdoid phages and integrated into the bacterial chromosome of a large and complex group of pathogenic Escherichia coli (STEC) strains that cause disease in humans [1,2]. Epidemiological studies [3,4,5] have shown that some Stx and Stx subtypes often are associated with severe human STEC illnesses [4]. Subtypes Stx2a, Stx2c and Stx2d are associated with STEC infections in humans [11,15,16,17], while Stx2e, Stx2f, Stx2g are mainly found in animals [2,10,11]. Some studies have suggested that STEC strains producing Stx2f can cause diarrhoea in humans [18]; recently, STEC strains carrying the stx2f gene have been isolated from patients with hemolytic uremic syndrome (HUS) [18,19]

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