]> 2026-07-31T09:40:02+00:00 WBR293 0 en ADP-ribosylation of the Gs alpha subunit proteins Cholera toxin involves ADP-ribosylation of the Gs alpha subunit proteins. ADP-ribosylation of elongation factor 2 (EF-2) Exotoxin A from Pseudomonas aeruginosa involves ADP-ribosylation of elongation factor 2 (EF-2). Cleavage of N-glycoside bond of adenine in 28S ribosomal RNA Shiga-like toxin-1 (SLT-1) of EHEC cleaves N-glycoside bond of adenine in 28S rRNA of the 60S ribosome unit to prevent EF-1-dependent aminoacyl tRNA binding, thereby inhibiting protein synthesis. Attachment of epithelium and effacement of microvilli In EPEC, attachment of epithelium and effacement of microvilli is mediated via phosphorylation of Tir and subsequent intimin binding. Local invasion of colonic mucosa In EIEC, diarrhea is caused by local invasion of colonic mucosa. ''Escherichia coli'' O157:H7 (EHEC) is an enterohemorrhagic strain of ''Escherichia coli''. Infection may lead to hemorrhagic diarrhea and subsequent development of hemolytic-uremic syndrome (HUS). Transmission is via the fecal-oral route, and the majority of cases are associated with ingestion of undercooked, contaminated ground beef or pork. ''E. coli'' O157:H7 is negative for invasiveness (Sereny test), adheres through the E. coli common pilus (ECP), and does not produce heat-stable or heat-labile toxins. In addition, ''E. coli'' O157:H7 is usually sorbitol negative, whereas other ''E. coli'' ferment sorbitol. ''E. coli'' O157:H7 also lacks the ability to hydrolyze 4-methylumbelliferyl-β-D-glucuronide (MUG) and does not grow at 45 °C in the presence of 0.15% bile salts (cannot be isolated by using standard fecal coliform methods that include incubation at 45 °C). Among the virulence factors are periplasmic catalase and shiga-like toxins. Shiga-like toxin (SLT-1) is an iron-regulated toxin that catalytically inactivates 60S ribosomal subunits of eukaryotic cells. It cleaves N-glycoside bond of adenine in 28S rRNA of the 60S ribosome unit to prevent EF-1-dependent aminoacyl tRNA binding, thereby inhibiting protein synthesis.<br/> '''Educational Objective:''' ''Escherichia coli'' O157:H7 (EHEC) is an enterohemorrhagic strain of ''Escherichia coli''. Transmission is via the fecal-oral route, and the majority of cases are associated with ingestion of undercooked, contaminated ground beef or pork. Shiga-like toxin-1 (SLT-1) of EHEC cleaves N-glycoside bond of adenine in 28S rRNA of the 60S ribosome unit to prevent EF-1-dependent aminoacyl tRNA binding, thereby inhibiting protein synthesis.<br/> '''References:''' First Aid 2015 page 138. Microbiology A 27-year-old man presents to the clinic with abdominal cramps, general malaise, fever, and diarrhea 5 hours after consuming hamburgers. He has dry mucosa and decreased skin turgor. Few leukocytes are found in his fecal specimen. Growth of colorless colonies on sorbitol-MacConkey agar is noted. Which of the following descriptions best explains the pathogenesis of the organism responsible for this patient's condition? C Gastrointestinal 2020-10-28T03:01:55Z 2459150.626331 WBR293