Production of Shiga toxin by Shiga toxin-expressing Escherichia coli (STEC) in broth media: from divergence to definition

Abstract

Aims: To determine the suitability of eight different commercial broth media for Shiga toxin (Stx) production. Methods and Results: Shiga toxin‐producing Escherichia coli (STEC) strains producing Stx1 or Stx2 were grown at 37°C (250 rev min−1) for 24 h in brain heart infusion broth, E. coli broth, Evans medium, Luria‐Bertani broth, Penassay broth, buffered‐peptone water, syncase broth and trypticase soy broth. Toxin production was measured by enzyme‐linked immunosorbent assay (ELISA) in polymyxin‐treated cell pellets and/or supernatants of cultures, ELISA optical densities reached 1 when isolates were grown for 2–4 h in E. coli broth in the presence of antibiotic. Besides, a collection of STEC‐expressing Stx strains was evaluated and the Stx production was assayed in the supernatants and in polymyxin‐treated pellets of bacterial growth after 4 h of cultivation in E. coli broth in the presence of antibiotic. Conclusions: The most suitable medium for Stx production was E. coli broth when the bacterial isolates were grown for 4 h in the presence of ciprofloxacin and the Stx production is detected in the supernatant. Significance and Impact of the Study: This study presents the first comprehensive comparison of different broth media with regard to Stx production to establish optimal culture conditions for STEC detection in routine diagnostic laboratories.

Diversity of Shiga toxin-producing Escherichia coli in sheep flocks of Paraná State, southern Brazil

“…STEC supernatants were prepared as described previously (Rocha and Piazza, 2007), and 1:10 dilutions were tested in duplicates on Vero cells. Supernatants of E. coli O157:H7 (EDL933) and K-12 (DH5a) strains were used as positive and negative controls, respectively.…”

The ability of haemolysins expressed by atypical enteropathogenic Escherichia coli to bind to extracellular matrix components

“…To detect haemolytic activity, all bacteria were taken from stock cultures and spotted onto blood agar plates. Data regarding toxin expression or secretion are associated with the composition of the culture media in which the bacteria are grown (Vilhena-Costa et al 2006, Rocha & Piazza 2007. We investigated whether the haemolytic profile of aEPEC isolates was dependent on media components.…”

A Rapid Immunoassay for Detection of Shiga Toxin-Producing Escherichia coli Directly from Human Fecal Samples and Its Performance in Detection of Toxin Subtypes

“…It has been well documented that in vitro Shiga toxin production varies depending on the culture conditions and isolate (28, 36, 55, 56). Our results indicate that Stx2 phages in the strains studied are generally more susceptible to induction with ciprofloxacin than are Stx1 phages.…”