Clinically-relevant Shiga toxin 2 subtypes from environmental Shiga toxin-producing Escherichia coli identified by top-down/middle-down proteomics and DNA sequencing

Using Nanospray Liquid Chromatography and Mass Spectrometry to Quantitate Shiga Toxin Production in Environmental Escherichia coli Recovered from a Major Produce Production Region in California

“…Given that only truncated forms of the A subunit are produced, they are not detected by the A subunit specific antibodies. In the present study, the IS did not prevent expression of the B subunits in the O157:H7 strains (Table ), and these observations were in agreement with a recent report that employed a top-down/middle-down mass spectrometry method for detecting Stx expression in STEC strains . Reports have documented that B-subunits have their own promoter, and in the examined STEC strains, the B subunit promoter seemed to be weaker than the promoter for the A subunit because the expression levels are much lower than that observed for an intact stx operon.…”

Top-down proteomic identification of plasmid and host proteins produced by pathogenic Escherichia coli using MALDI-TOF-TOF tandem mass spectrometry

“…Mitomycin-C (MMC) and ciprofloxacin are antibiotics that are commonly used to elicit the SOS response in bacteria and have been shown to be particularly effective at inducing the production of Shiga toxin in many (although not all) STEC strains [ 26 , 27 , 47 , 48 ]. The antimicrobial mode-of-action of these antibiotics is damage of bacterial DNA by cross-linking or otherwise interfering with DNA replication.…”

“…Previously, we have identified different types and subtypes of Shiga toxin (Stx) from Shiga toxin-producing E . coli (STEC) using antibiotic induction, MALDI-TOF-TOF-MS/MS and top-down proteomic analysis [ 26 , 27 ]. This approach has been quite successful in Stx identification as well as demonstrating the strain-dependent nature of Stx production across STEC strains.…”

Draft Genome Sequences of Shiga Toxin-Producing Escherichia coli O157:H7 Strains Recovered from a Major Production Region for Leafy Greens in California

“…Using a robust isolation method, STEC O157:H7 strains were recovered from cattle in a major agricultural region for leafy greens and were identified based on a typical STEC colony morphology on selective chromogenic medium and positive PCR tests for a stx gene (5). Further proteomic analyses indicated that all O157:H7 cattle strains were found to express the toxin receptor binding B-subunit (6, 7), but some were found not to have a functional toxin (7). The genome sequencing of nine O157:H7 cattle strains with various levels of toxin activity is reported here.…”