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Category: Clinical Microbiology
Escherichia coli O104:H4 Pathogenesis: An Enteroaggregative E. coli/Shiga Toxin-Producing E. coli Explosive Cocktail of High Virulence, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818791/9781555818784_Chap26-1.gif /docserver/preview/fulltext/10.1128/9781555818791/9781555818784_Chap26-2.gifAbstract:
In May 2011, an outbreak caused by Escherichia coli of serotype O104:H4 spread throughout Germany ( 1 ). The next month, France also reported a cluster of E. coli O104:H4 infections ( 2 ). A total of 46 deaths, 782 cases of hemolytic-uremic syndrome (HUS), and 3,128 cases of acute gastroenteritis were officially attributed to this new clone of enterohemorrhagic E. coli (EHEC) (last update from European Centre for Disease Prevention and Control, 27 July 2011). Most or all victims (although diagnosed in different countries in Europe) became infected in Germany or France. The phenotypic and genotypic characterization of the E. coli O104:H4 indicated that the isolates from the French and German outbreaks were common to both incidents. Fenugreek seeds imported from Egypt, from which sprouts were grown, were implicated as a common source. However, there is still much uncertainty about whether this is truly the common cause of the infections, as tests on the seeds did not allow the detection of any E. coli isolate of serotype O104:H4.
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Hybrid characteristics of E. coli O104:H4 outbreak strain (EAEC/STEC). Schematic representation of the genes harbored by E. coli O104:H4; the main genes from EAEC or STEC are highlighted: stx2 (coding for Stx 2), pic, sigA, and sepA (coding for the SPATE proteins); Pic, protein involved in intestinal colonization; SigA, a homolog of Pet, with cytotoxic activity; SepA, a colonization factor of Shigella), set1AB (coding for ShET1, a holotoxin AB5), iha (coding for Iha, a STEC adhesin that is an IrgA homolog), aggR, aggABCD, aap, aatPABCD (genes from EAEC plasmids coding for transcription regulator, AAF/I, dispersin, and dispersin transporter, respectively), lpf1-2 (coding for Lpf of STEC), terZABCDEF (coding for a cluster for Tellurite resistance), CTX-M15 and TEM-1 (antibiotic resistance genes). SigA and SepA are SPATEs detected mainly in Shigella sp.
Adherence patterns of EAEC, STEC, and E. coli O104:H4 outbreak strain to epithelial cells. Subconfluent epithelial cell cultures are infected with the different bacterial strains. Cells are fixed and stained with Giemsa stain. From Scalesky et al. 1999. Infect Immun 67:3410; Paton et al. 2001. Infect Immun 69:6999; and Martina Bielaszewska. http://ecdc.europa.eu/en/press/events/Documents/22-231111-Breakthroughs-in-molecular-epidemiology-Bielaszewska.pdf.
Transmission electron microscopy (TEM) of Stx2 phage (P13374) induction from lysogenic strain E. coli K-12 strain TPE2364 (C600) infected with phage lysates of E. coli O104:H4 strain CB13374. (A, B) Ultrathin sections of two bacterial cells (TPE2364) with maturating virion particles within the cytoplasm indicated by arrows (bars, 500 nm). (C) TEM of CsCl-purified, negatively stained phage (P13374) particles released by strain TPE2364 (bar, 100 nm). Short tails (arrows) and a hexagonal head are shown. From Beutin et al. 2012. J Virol 86:10444.
Schematic representation of E. coli O104:H4 virulence factors and their targets on the mucosal epithelium. The targets and virulence factors are extrapolated from their known function in other pathogens, and the action mechanism for ShET1 is hypothetical.