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Category: Food Microbiology
Shiga Toxin-Producing Escherichia coli, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555819972/9781555819965.ch11-1.gif /docserver/preview/fulltext/10.1128/9781555819972/9781555819965.ch11-2.gifAbstract:
This chapter summarizes the latest information available for Shiga toxin-producing Escherichia coli (STEC). STEC was first recognized as a human pathogen in 1982, when E. coli O157:H7 was identified as the cause of two outbreaks of hemorrhagic colitis. Since then, many other serogroups of E. coli, such as O26, O111, O145, O45, O113, O121, and sorbitol-fermenting O157:NM, have also been associated with cases of hemorrhagic colitis and have been classified as STEC. However, serotype O157:H7 is the predominant cause of STEC-associated disease in the United States and many other countries. Production of Shiga toxins (Stxs) by E. coli O157:H7 was subsequently associated with a severe and sometimes fatal condition, hemolytic-uremic syndrome. E. coli organisms of many different serotypes can produce Stxs, with more than 600 serotypes being identified so far, including approximately 160 O serogroups and 50 H types. However, only strains that cause hemorrhagic colitis are considered enterohemorrhagic E. coli (EHEC), and there are at least 130 EHEC serotypes that have been recovered from human patients. Major non-O157 EHEC serogroups identified in the United States include O26, O45, O103, O111, O121, and O145. Here, we discuss many aspects of their biology, reservoirs, virulence, genomics, and antimicrobial resistance, as well as some recommendations for reduction of their numbers in different foods. We also present some web tools that could help us identify other uncommon causes or vehicles and track down the source of contamination in the future.
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Snapshot of the two freely available databases containing all genomes as well as historical metadata (MLST) available for E. coli and Shigella and the web tool for in silico determination of virulence genes, serotyping, and MLST for E. coli. (A) NCBI pathogen detection; (B) EnteroBase; (C) DTU web tool.
Neighbor-joining phylogenetic tree of 59 E. coli genomes available at NCBI using a custom-made core genome MLST analysis showing stx distribution on those genomes. The species-based phylogeny was inferred using 820 conserved core genome loci. The two EHEC lineages are shown as well as strains belonging to the German outbreak of E. coli O104:H4 in 2011 (stx 2 EAEC). The colors represent the presence and type of stx gene.
Number of cases of STEC disease in the United States by year, 2010 to 2014 (https://www.cdc.gov/ecoli/surveillance.html). Unk, unknown.
Electron microscopy image of an A/E lesion and schematic illustration of A/E lesion formation in EHEC. Effector proteins undergo A/E translocation through the T3SS, which forms a pore through the membranes of EHEC. EHEC translocates a number of proteins: EspB and EspD, which form a translocon in the plasma membrane; the cytoplasmic proteins EspF, EspG, and Map; the translocated intimin receptor Tir, which inserts into the plasma membrane; and other unidentified effectors. Formation of the EHEC pedestal is also shown. EHEC intimately attaches to the host cell through intimin-Tir binding. The binding triggers the formation of actin-rich pedestals beneath adherent bacteria after Wiskott-Aldrich syndrome protein and the heptameric actin-related protein Arp2/3 are recruited to the pedestal tip. Reproduced from reference 117 with permission.
Genetic organization of the EHEC LEE and EHEC prophages CP-933U, CP-933K, and CP-933P. Reproduced from reference 121 .
T3SS apparatus of EHEC. The basal body of the T3SS is composed of the secretin EscC, the inner membrane proteins EscR, EscS, EscT, EscU, and EscV, and the EscJ lipoprotein, which connects the inner and outer membrane ring structures. EscF constitutes the needle structure, whereas EspA subunits polymerize to form the EspA filament. EspB and EspD form the translocation pore in the host cell plasma membrane, connecting the bacteria with the eukaryotic cell via EspA filaments. The cytoplasmic ATPase EscN provides the energy to the system by hydrolyzing ATP molecules into ADP. SepD and SepL are represented as cytoplasmic components of the T3SS. Reproduced from reference 121 .
Comparison of D values for E. coli O157:H7 and Salmonella spp. in ground beef
Vehicles of foodborne outbreaks and associated cases of E. coli O157 infections in the United States between 2011 and 2015 a
Representative foodborne and waterborne outbreaks of E. coli O157:H7 and other STEC infections a
Nomenclature and biological characteristics of Stxs a