1.SHIGA TOXINS INE.COLI O104 H4 Dr.T.V.Rao MDDR.T.V.RAO MD1

2. WHAT ARE SHIGA TOXINSShiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, whose genes are considered to be part of the genome of lambdoid prophages ] The toxins are named for Kiyoshi Shiga , who first described the bacterial origin of dysentery caused by Shigella dysenteriae. The most common sources for Shiga toxin are the bacteria S. dysenteriae and the Shigatoxigenic group of Escherichia coli (STEC), which includes serotype O157:O7 and other enterohemorrhagic E. coli (EHEC).DR.T.V.RAO MD2 3. SHIGA-LIKE TOXINSTRUCTURE The toxin has two subunitsdesignated A and Band isone of the AB 5 toxins. The Bsubunit is a pentamer thatbinds to specific glycolipidson the host cell, specificallyglobotriaosylceramide (Gb3).Following this, the A subunit isinternalised and cleaved intotwo parts. The A1 componentthen binds to the ribosome,disrupting protein synthesis.Stx-2 has been found to beapproximately 400 times moretoxic (as quantified by LD50 inmice) than Stx-1DR.T.V.RAO MD3 4. SITE 1 OF SLT-IB:GB3 COMPLEX Gb3 is, for unknown reasons,present in greater amounts in renal epithelial tissues, to which the renal toxicity of Shiga toxin may be attributed. Gb3 is also found in CNS neurons and endothelium, which may lead to neurotoxicity.[. Stx-2 is also known to increase the expression of its receptor GB3 and cause neuronal dysfunctions.DR.T.V.RAO MD 4 5. SIDE CHAINS CONSERVED IN SHIGA-LIKE TOXIN FAMILY SIDE CHAINS THAT VARY IN SHIGA-LIKE TOXIN FAMILYDR.T.V.RAO MD 5 6. SHIGA-LIKE TOXINS Shiga toxin family Shigella dysenteriae-1: Shiga toxin Escherichia coli: Shiga-like toxins (SLTs) SLT-I - nearly identical to Shiga toxin SLT-II variants - ~60% identity to SLT-I AB5 subunit structure A-subunit attacks ribosome enzymatically related to ricin B-subunit binds to cell-surface glycolipid: Gb3 or Gb4 Drug target: A or B?DR.T.V.RAO MD6 7. MAJOR TYPES OF SHIGA TOXINS DIFFERS IN SHIGELLA AND E.COLI Shiga toxin (Stx) - trueShiga toxin is produced by Shigella dysenteriae. Shiga-like toxin 1 and 2 (SLT-1 and 2 or Stx-1 and 2) - the Shiga toxins produced by some E. coli strains. Stx-1 differs from Stx by only 1 amino acid. Stx-2 shares 56% sequence homology with Stx-1.DR.T.V.RAO MD 7 8. SHIGA TOXINS - HOW IT ACTS SHIGA TOXIN S.DYSENTERIAE ANDE.COLI O157 TWO PART TOXIN PART BBINDS TO CELL ANDINJECTS PART A WHICHCLEAVES A SPECIFICADENINE RESIDUE INTHE 60S RIBOSOMEPREVENTING PROTEINSYNTHESIS ANDCAUSING CELL DEATHDR.T.V.RAO MD8 9. SHIGELLA TOXINS AFFECTS SEVERAL ANIMALS The toxin requires highlyspecific receptors on thecells surface in order toattach and enter the cell;species such as cattle,swine, and deer which donot carry these receptorsmay harbor toxigenicbacteria without any illeffect, shedding them intheir feces, from where theymay be spread to humans.DR.T.V.RAO MD9 10. SHIGA TOXIN TARGETS KIDNEY Once shiga toxin reaches atarget organ such as thekidney, it binds to receptorson cell membranes knownas globotriaosylceramide orGB3. The toxin is thenbrought inside the cell andtransported to the Golgiapparatus, endoplasmicreticulum and finally to thenuclear membrane.DR.T.V.RAO MD 10 11. DR.T.V.RAO MD 11 12. E. COLI THAT CAUSE HUMAN GASTROINTESTINAL ILLNESS Enteropathogenic(EPEC) Enterotoxigenic (ETEC) Enteroinvasive (EIEC) Other types, less wellcharacterizedShigatoxin-producing(STEC), also calledEnterohemorrhagic(EHEC)DR.T.V.RAO MD 12 13. PATHOGENIC MECHANISMS OFE.COLIDR.T.V.RAO MD 13 14. E. COLI THAT CAUSE HUMAN GASTROINTESTINAL ILLNESS Shiga toxin-producing (STEC),also called Enterohemorrhagic(EHEC) E. coli O157 Serogroup Non-O157 Serogroups Enteropathogenic (EPEC) Enterotoxigenic (ETEC) Enteroinvasive (EIEC) Other types, less wellcharacterizedDR.T.V.RAO MD 14 15. BASIC PATHOLOGY Small infectious dose(oral transmission, may occur in high-risksettings like day care centers and nursing homes.Further studies are being done to better understand themodes of transmission.DR.T.V.RAO MD 27 28. DYNAMICS OF SHIGA TOXINS Shiga toxins act to inhibit protein synthesis within target cells by a mechanism similar to that of ricin toxin produced by Ricinus communis.[After entering a cell, the protein functions as an N- glycosidase, cleaving a specific adenine nucleobase from the 28S RNA of the 60S subunit of the ribosome, thereby halting protein synthesis.DR.T.V.RAO MD 28 29. HOW THE INFECTED MANIFEST.. Asymptomatic Mild/moderate illness (non-bloody watery diarrhea,abdominal pain, rarelyvomiting, fever usually absent) Hemorrhagic colitis (grosslybloody diarrhea, severeabdominal pain) Hemolytic uremic syndrome(HUS) Thrombotic thrombocytopenicpupura(TTP)DR.T.V.RAO MD 29 30. DR.T.V.RAO MD 30 31. CLINICAL DIAGNOSIS SUPPORTED BYLABORATORY TESTING Gram-negative, rod shaped Clinical samples (typicallystool) Food samples Culture Identification of the organism Routine culture for 0157 doesnot detect non-0157 STEC Enzyme Immunoassay (EIA) Detection of shigatoxin (Stx1,Stx2)DR.T.V.RAO MD 31 32. E.COLI O104 H4 A TOXIGENICBACTERIADR.T.V.RAO MD 32 33. E.COLI O104 H4 AN EMERGINGINFECTION Although rare, E. coli O104:H4 has been identifiedbefore, in 2009 in the Republic of Georgia, culture ofspecimens from two patients who were part of a clusterof diarrheal illness yielded an E. coli O104:H4 strainthat was similar to the current outbreak strain. Thatstrain produced Shiga toxin, but had a differentmolecular fingerprint and was less resistant toantibiotics than the current outbreak strain in Germany.No clear outbreak was identified in the Republic ofGeorgia, and no food was identified as a source ofinfectionsDR.T.V.RAO MD33 34. SHIGA TOXIN-PRODUCINGESCHERICHIA COLI (STEC)CURRENT OUTBREAK Shiga toxin-producingEscherichia coli (STEC) cancause severe enteric infectionsand the potentially lifethreatening hemolytic uremicsyndrome (HUS). Promptdiagnosis of these infections isimportant to implement earlyclinical management thatminimizes the likelihood ofdeveloping HUS, to reduce therisk of transmitting the infectionto others, and to detect outbreakCommonly consumed vegetables are source of spread.DR.T.V.RAO MD 34 35. NEW REPORT ON E.COLI 0104 H4 OUTBREAKLarge outbreak of Shiga toxin- producing Escherichia coli O104:H4 (STEC O104:H4) infections ongoing in Germany. The responsible strain shares virulence characteristics with enter aggregative E. coli (EAEC). As of June 2, 2011, case counts confirmed by Germanys Robert Koch Institute* include 520 patients with hemolytic uremic syndrome (HUS) a type of kidney failure that is associated with E. coli or STEC infections and deaths.DR.T.V.RAO MD 35 36. VEGETABLES AS SOURCE OF E.COLI INFECTIONS While suspicion has fallen on rawtomatoes, cucumbers and lettuceas the source of the germ,researchers have been unable topinpoint the food responsible.The outbreak is considered thethird-largest involving E. coli inrecent world history, and it isalready the deadliest. Twelvepeople died in a 1996 Japaneseoutbreak that reportedly sickenedmore than 9,000, and seven diedin a Canadian outbreak in 2000.DR.T.V.RAO MD 36 37. E.COLI 0104: H4 RESEMBLESE. COLI SEROTYPE O157:H7E. coli serotype O157:H7 is a rare variety of E. coli that produces toxins which are capable of inflicting damage to the lining of the intestine. These toxins are closely related or identical to the toxin produced by Shigella dysenteriae and are referred to as Shiga toxins. In very rare instances, the infection can progress to hemolytic uremic syndrome ("HUS") and kidney failure. E. coli O157:H7 can survive at low temperatures as well as under acidic conditions, and the infectious dose is relatively small.DR.T.V.RAO MD37 38. E.COLI 0104:H4 PICKED UP NEW GENESts observed that E. coli O104:H4 has picked up some new genes, almost certainly through horizontal gene transfer, in which stretches of DNA are picked up from other E. coli strains, or possibly different species entirely. Once incorporated into the genome, the new genes can provide the bacteria with entirely novel properties. In the case of E. coli O104:H4, tests have shown that it now carries a gene for shigatoxin, which is commonly found in other disease-causing strains of this species.DR.T.V.RAO MD 38 39. GENOME OF A KILLER: GERMAN AND CHINESE SCIENTISTSCRACKED THE GENETIC CODE BEHIND THE STRAIN OF ESCHERICHIA COLIDR.T.V.RAO MD39 40. NEED FOR INVESTIGATION OF CASESGOAL: CONTROL SPREAD OF DISEASEDetermine if case is a threat to spread diseaseFood handlerDaycare attendee or workerInvolved in direct patient careDetermine potential exposures/sourcesFood historyTravel historyRecreational water exposureAnimal exposureDR.T.V.RAO MD 40 41. HANDING WASHING THE MOST ESSENTIAL STEP WASH HANDS thoroughly after using the bathroom or changing diapers and before preparing or eating food. WASH YOUR HANDS after contact with animals or their environments (at farms, petting zoos, fairs, even your own backyard).DR.T.V.RAO MD 41 42. AVOID AVOID raw milk,unpasteurized dairyproducts, andunpasteurized juices(like fresh apple cider). AVOID swallowing waterwhen swimming orplaying in lakes, ponds,streams, swimmingpools, and backyardkiddie pools.DR.T.V.RAO MD 42 43. SUPPORTIVE CARE IS THE PRIMARY NEED Antibiotics might increase the risk for HUS in patients infected with O157 STEC, and antidiarrheal medications might worsen the illness. True with 0104:H4DR.T.V.RAO MD43 44. DELAYED DIAGNOSIS LEADS TO OUTBREAKS Delayed diagnosis of STECinfections might lead tosecondary transmission inhomes, child-care settings,nursing homes, and foodservice establishments andmight delay detection ofmultistate outbreaks related towidely distributed foods .Outbreaks caused by STEC withmultiple Serogroups or PFGEpatterns have been documented.DR.T.V.RAO MD 44 45. WHY DRUGS ARE DANGEROUS Use of antibiotics otherAntidiarrheal treatments "canactually make the situationworse." Thats because killingtoxin-producing bacteria, such asthe ones responsible for thisoutbreak, can actually causethem to release more toxins. canactually make the situationworse." Thats because killingtoxin-producing bacteria, such asthe ones responsible for thisoutbreak, can actually causethem to release more toxins.DR.T.V.RAO MD 45 46. POSSIBLE PREVENTION OF E.COLI O104 H4COOK meats and poultry thoroughly. Ground beef should reach at least 155 degrees F (until the meat is no longer pink and juices run clear). DO NOT consume raw milk orunpasteurized dairy products. WASH YOUR HANDS afterusing the bathroom orchanging diapers and beforepreparing or eating food.DR.T.V.RAO MD46 47. VEGETABLES TOO ARE INFECTIOUS DO BELIEVE IT ???DR.T.V.RAO MD47 48. FOLLOW ME FOR ARTICLES OF INTEREST ONINFECTIOUS DISEASES AND MICROBIOLOGY ..DR.T.V.RAO MD 48 49. CDC MONITORING EVENTS CDC is monitoring a largeoutbreak of Shiga toxin-producing Escherichia coliO104:H4 (STEC O104:H4)infections ongoing inGermany. The responsiblestrain shares virulencecharacteristics withenteroaggregative E. coli(EAEC).DR.T.V.RAO MD49 50. Created by Dr.T.V.Rao MD for e learning resources for Medical Professionals in the Development World Email doctortvrao@gmail.comDR.T.V.RAO MD 50