Abstract
Acute gastroenteritis caused by Shiga toxin-producing Escherichia coli (STEC) affects more than 4 million individuals in Canada. Diagnostic laboratories are shifting towards culture-independent diagnostic testing; however, recovery of STEC remains an important aspect of surveillance programs. The objective of this study was to compare common broth media used for the enrichment of STEC. Clinical isolates including O157:H7 as well as non-O157 serotypes were cultured in tryptic soy (TSB), MacConkey (Mac), and Gram-negative (GN) broths and growth was compared using culture on sheep’s blood agar and real-time PCR (qPCR). In addition, a selection of the same isolates was spiked into negative stool and enriched in the same three broths, which were then evaluated using culture on CHROMagarTM STEC agar and qPCR. TSB was found to provide the optimal enrichment for growth of isolates with and without stool. The results from this study suggest that diagnostic laboratories may benefit from enriching STEC samples in TSB as a first line enrichment instead of GN or Mac.
Highlights
Acute gastroenteritis (AGE), which is defined as vomiting and/or diarrhea for less than 7 days, affects more than 4 million individuals in Canada [1]
Shiga toxin-producing Escherichia coli (STEC) isolates (n = 52) were grown in Tryptic Soy Broth (TSB), Gram-negative Broth (GN), and MacConkey Broth (Mac) broth to determine if broth composition would influence growth
E. coli regarded as a non-fastidious organism that grows well in most conditions; as is usually regarded as a non-fastidious organism that grows well in most conditions; howillustrated in our data, we have found both GN and Mac broths are limited in their ability to ever, as illustrated in our data, we have found both GN and Mac broths are limited in their support the growth of certain STEC, as expected
Summary
Acute gastroenteritis (AGE), which is defined as vomiting and/or diarrhea for less than 7 days, affects more than 4 million individuals in Canada [1]. Escherichia coli (STEC) are one of the pathogens responsible for major outbreaks. Their primary reservoir is ruminants, there have been recent outbreaks involving contaminated food items such as flour, clover sprouts, and cheese [2]. STEC infections are associated with hemorrhagic colitis with the possibility of developing hemolytic uremic syndrome [3] This potentially deadly consequence is due to the production of Shiga toxins (Stx) 1 and/or 2, with Stx 2 having a higher association [4]. There have been over 200 serotypes of E. coli identified to contain the Shiga toxin and cause diarrheal disease in humans [7]. E. coli O157:H7 was the first serotype identified in 1982, causing AGE-related morbidity involved in several outbreaks in the United States of America. This is achieved through surveillance programs, which rely on the ability to culture microorganisms9030503
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