Association of Ct Values from Real-Time PCR with Culture in Microbiological Clearance Samples for Shiga Toxin-Producing Escherichia coli (STEC).

Michael Bording-Jorgensen,Binal Shah-Gandhi,Brendon D Parsons,Gillian A.M Tarr,Linda Chui,Colin Lloyd

doi:10.3390/microorganisms8111801

Abstract

Shiga toxin-producing Escherichia coli (STEC) are associated with acute gastroenteritis worldwide, which induces a high economic burden on both healthcare and individuals. Culture-independent diagnostic tests (CIDT) in frontline microbiology laboratories have been implemented in Alberta since 2019. The objectives of this study were to determine the association between gene detection and culture positivity over time using STEC microbiological clearance samples and also to establish the frequency of specimen submission. Both stx genes’ amplification by real-time PCR was performed with DNA extracted from stool samples using the easyMAG system. Stools were inoculated onto chromogenic agar for culture. An association between gene detection and culture positivity was found to be independent of which stx gene was present. CIDT can provide rapid reporting with less hands-on time and technical expertise. However, culture is still important for surveillance and early cluster detection. In addition, stool submissions could be reduced from daily to every 3–5 days until a sample is negative by culture.

Highlights

There are approximately 4 million reported cases annually of food-borne illness in Canada, with an estimated 4000 from 30 known and another 7600 from unknown etiologies, some of which will result in hospitalization [1]
The detection of clearance, based on the first negative sample, in this investigation was found to be an average of 18 days or 22 days, with the shortest being 3 days (Patient G) and the longest being 38 days (Patients D and J) (Table 2)
Serotypes included O157 and non-O157 shiga toxin-producing Escherichia coli (STEC) belonging to both “BIG 6” (O26, O103, O111 and O121) and non-top 6 (O118 and O186) (Table 2)

Summary

Introduction

There are approximately 4 million reported cases annually of food-borne illness in Canada, with an estimated 4000 from 30 known and another 7600 from unknown etiologies, some of which will result in hospitalization [1]. The average economic cost of food-borne acute gastroenteritis (AGE) is over CAD 1000 per case, CAD 514 million (British Columbia) [3], CAD 400 million (Alberta), and an estimated total Canadian cost of CAD 3.7 billion [4]. These costs include diagnostic testing, loss of productivity, hospitalization if required, medications, and clinic visits [3]. Those under the age of 5 years, are most at risk for developing complications when infected, and there are long-term sequelae such as the possibility of developing irritable bowel syndrome even 8 years post-infection [7]

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Conclusion