Food poisoning caused by microbial entry: Secretory (Watery ) diarrheal diseases: Causative agents: 1-Vibrionaceae. 2-Enterobacteriaceae. Cholera: is a watery diarrheal disease caused by ingestion of sea food or water contaminated by Vibrio cholera species. Vibrio cholera O1 El Tor has been responsible for yearly epidemics in India for centuries, and for at least the last two centuries, periodic global pandemics.

N Vibrio cholera O1 El Tor rapidly spread in Asia from Indonesia, reaching Europe and other countries. Infections with new strain (Vibrio cholera O139 El Tor) appeared in Bangladesh in 1990 and have spread to India and other countries causing the eighth pandemic of cholera.

Pathogenesis and microbial virulence: Transmission: -Foodborne ; Contaminated sea food or shellfish. -Waterborne. -Reservoir: Human carriage (colon) is reported in some cases for months after treatment; so Fecal-Oral route could be involved in transmission. Pathogenesis: - Pathogenic dose: CFU/ml. - In the duodenum near the ampulla of vater; surviving organisms are bathed in bicarbonate-buffered pancreatic juice (pH can be as high as 9).

n -Vibrios reach the epithelial surface of the small intestine due to: 1- Motility. 2- Protease activity that hydrolyses mucus. -Adhesion to mucosal surface of the intestinal tract: mediated by Type 1 common pili (colonization factor antigen Cfa) to mannose-containing protein and lipids. -Colonization of mucosal surface due to Toxin-coregulated pilus (TCP); formation of micro-colonies.

N -Cholera toxin (Ctx) binds to a cell surface receptor (GM1 ganglioside) and is internalized within a vesicle. -The active subunit A of toxin modify the Gs regulatory protein of the cellular enzyme adenylate cyclase complex. -Increased cellular cAMP production.

N -Increased cAMP inhibits sodium absorption by small bowel villous cells and increase chloride secretion by enterocytes. -Passive secretion of Water; severe watery diarrhea.

Diagnosis of Cholera: Clinical presentation: -Sever diarrhea and vomiting of clear fluid ;(untreated person may produce liters of fluid a day). -Life-threatening dehydration and electrolytes imbalance -Dry mouth and skin; decreased skin turgor. -Deep breathing pattern due to acidosis associated with: 1-Stool bicarbonate loss. 2-Hypotension; poor perfusion; lactic acidosis. -Rapid peripheral pulse, coma (Na, Cl loss), death.

N Laboratory diagnosis: Clinical specimens: vomitus, stool. Cultural characteristics: -Vibrio cholera species are non-Halophilic. -They grow on different media at high pH ( ) as alkaline peptone water. - TCBS is a selective medium. - On MacConkey's agar : non- lactose fermenting colonies. - On blood agar: Usually beta haemolytic. -All Vibrio species are : Facultative anaerobic.

N Microscopy: Vibrios are gram-negative curved bacilli, motile with a single polar flagellum;( 2*0.5 micrometer diameter). Serogroup O1 is non-capsulated while O139 is capsulated.

N Biochemical identification: -All pathogenic Vibrio species are oxidase and indole positive. -All pathogenic Vibrio species reduce nitrite to nitrate. -The production of nitrose-indole compound in alkaline peptone water form the basis of "cholera red reaction", as the addition of H 2 SO 4 to the medium result in a red color.

Differentiation of V. cholerae El Tor and V. cholerae classic : N V. cholerae El TorV. cholerae classic Hemolysis of sheep red blood cellsHemolyticNon-hemolytic Resistance to Polymyxin B (50 I.U)ResistantSensitive Agglutination of chicken RBCsYesNo Voges-Proskauer ReactionPositiveNegative Susceptibility to IV phageNot-susceptibleSusceptible

Vibrio parahaemolyticus and other non-cholera Vibrios: Vibrio parahaemolyticus: -High Halophilic microbes. -Transmission: consumption of undercooked or raw seafood; shellfish, and crustaceans. -Disease: Gastroenteritis/ diarrhea. : watery diarrhea with abdominal pain due to invasive Enteritis. Vibrio vulnificus : -Invasive enteritis; Endotoxic lipopolysaccharide. -It is associated with high mortality bacteremia and septicemia.

Pathogenic E.coli: 1- Enteropathogenic E. coli: -Adherence to epithelial cells by Cfa pilus. -Insertion of exotoxin Tir by Type III secretion system. -Polymerization of cytoskeleton actin into filamentous actin. -Damage of brush border microvilli; lesions formation and watery diarrhea. 2- Enterotoxigenic E. coli: (the causative agent for traveler’s diarrhea). A- Heat Labile enterotoxin (LT): activate adenylate cyclase; elevation of cAMP. (Similar effect of cholera toxin). B-Heat stable enterotoxin (ST): activate guanylate cyclase.

N Other causative agents for Food poisoning caused by microbial entry: 1-Campylobacter species 2-Salmonella species. 3-Other Pathogenic E.coli. Management of Watery diarrheal illness: 1-Electrolyte-replacement intravenous fluid; severe dehydration. 2-Oral-Electrolyte-glucose solution. 3-In invasive diseases; antibiotic therapy should be used.