Comparison of Six Chromogenic Agar Media for the Isolation of a Broad Variety of Non-O157 Shigatoxin-Producing Escherichia coli (STEC) Serogroups.

Bavo Verhaegen,Koen De Reu,Marc Heyndrickx,Lieven De Zutter

doi:10.3390/ijerph120606965

Bavo Verhaegen, Koen De Reu + Show 2 more

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https://doi.org/10.3390/ijerph120606965

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Abstract

The isolation of non-O157 STEC from food samples has proved to be challenging. The selection of a suitable selective isolation agar remains problematic. The purpose of this study was to qualitatively and quantitatively evaluate six chromogenic agar media for the isolation of STEC: Tryptone Bile X-glucuronide agar (TBX), Rainbow® Agar O157 (RB), Rapid E. coli O157:H7 (RE), Modified MacConkey Agar (mMac), CHROMagarTM STEC (Chr ST) and chromIDTM EHEC (Chr ID). During this study, 45 E. coli strains were used, including 39 STEC strains belonging to 16 different O serogroups and 6 non-STEC E. coli. All E. coli strains were able to grow on TBX and RB, whereas one STEC strain was unable to grow on Chr ID and a number of other STEC strains did not grow on mMac, CHROMagar STEC and Rapid E. coli O157:H7. However, only the latter three agars were selective enough to completely inhibit the growth of the non-STEC E. coli. Our conclusion was that paired use of a more selective agar such as CHROMagar STEC together with a less selective agar like TBX or Chr ID might be the best solution for isolating non-O157 STEC from food.

Highlights

The multitude of infectious diseases transmitted by microorganisms is a burden for public health.The well-known shigatoxin-producing Escherichia coli (STEC), known as verotoxin-producingE. coli (VTEC), causes human infections through direct transmission from person to person or from infected animals
The use of Tryptone Bile X-glucuronide agar (TBX) for isolation of STEC is recommended
The growth and appearance of these STEC strains was compared to some common non-STEC E. coli

Summary

Introduction

E. coli (VTEC), causes human infections through direct transmission from person to person or from infected animals. It can be indirectly transmitted via contaminated food, water, or environments contaminated with faeces [1]. STEC infections can be responsible for clinical symptoms ranging from mild to severe diarrhea, possibly complicated with hemolytic uremic syndrome (HUS) or thrombotic thrombocytopaenic purpura (TTP) [2]. Rapid detection of this pathogen is of utmost importance to ensure appropriate actions to safeguard public health.

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