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Bohomolets Microbiology Lecture #19


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By Ms. Kostiuk from Microbiology department

Published in: Health & Medicine, Technology
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Bohomolets Microbiology Lecture #19

  1. 1. Shigellosis Cholera
  2. 2. Shigella sonnei
  3. 3. Properties of Shigellae <ul><li>Gram-negative rods </li></ul><ul><li>Nonmotile (do not have flagella) </li></ul><ul><li>Nonencapsulated </li></ul><ul><li>Not fastidious to laboratory medium </li></ul><ul><li>Do not ferment lactose (during first 48 hours) </li></ul><ul><li>Do not form H 2 S </li></ul><ul><li>They produce no gas from the fermentation of sugars </li></ul><ul><li>They are human parasites </li></ul><ul><li>Low infectious dose (< 100 bacteria) </li></ul><ul><li>Reproduce in the enterocytes of colon </li></ul>
  4. 4. Antigenic structure of Shigella <ul><li>O antigen. It used to divide the genus into 4 serogroup: A, B, C, D </li></ul><ul><li>K antigen. According it shigellae are divided into serotypes </li></ul>
  5. 5. Modern classification of Shigella <ul><li>Family – Enterobacteriaceae </li></ul><ul><ul><li>Genus – Shigella </li></ul></ul><ul><ul><ul><li>Species : </li></ul></ul></ul><ul><ul><ul><ul><li>Sh. disenteriae – 12 serotypes </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Sh. flexneri – 9 serotypes </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Sh. boydii – 18 serotypes </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Sh. sonnei – 1 serotype </li></ul></ul></ul></ul>
  6. 6. Biochemical activity of shigellae - - + (after 72 hours) + (after 48 hours) + + Sh. sonnei + - - - + + Sh. boydii + - - - + + Sh. flexneri + - - - - + Sh. dysenteriae Indole H 2 S Sucrose Lactose Manitol Glucose Biochemical feature Species
  7. 7. Virulence factors of shigellae <ul><li>Adherence by pili </li></ul><ul><li>Invasion. Ipa-BCD antigen. Ensures entering of bacteria to the M-cells of large intestine, spreading to the underlying tissue, and apoptosis of phagocytes </li></ul><ul><li>Endotoxin that causes fever, general intoxication </li></ul><ul><li>Exotoxin ( Shiga toxin ) that has a number activities: </li></ul><ul><ul><li>Enterotoxic effect - inflammation of the underlying gut wall layer, degeneration of the villi, and local erosion that causes bleeding and heavy mucous secretion. </li></ul></ul><ul><ul><li>Cytotoxic effect - damage to the intestine, injury to the nerve cells, capillary endothelium, myocardial and kidney cells. </li></ul></ul>
  8. 8. Pathogenesis of shigellosis <ul><li>Reservoir of shigellae are ill humans only (not animals) </li></ul><ul><li>Mechanism of transmission is fecal-oral . The 4 F’s – fingers, flies, food, and feces – are the principal factors in transmission. </li></ul><ul><li>Infectious dose is small and depend on virulence of Shigella, for Sh.disenteriae ID is 10 cells, for Sh.sonnei – at least 10 4 cells. </li></ul><ul><li>Incubation period is 1 to 4 days. </li></ul><ul><li>Sh.dysenteriae (the most virulent among shigellae) causes the most severe disease, Sh.sonnei (the least virulent among shigellae) causes mild disease. </li></ul><ul><li>Manifestations of dysentery are fever, vomiting, frequent liquid stools containing blood and pus, abdominal cramps, and intestinal pain but unproductive urge to defecate. Less common symptoms are headache, stiff neck, convulsions. </li></ul>
  9. 9. Shigellosis <ul><li>within 2-3 days </li></ul><ul><ul><li>epithelial cell damage </li></ul></ul>Destructive effect of shigellae resembles effect of enteroinvasive E. coli
  10. 10. The appearance of large intestinal mucosa in Shigella (bacillary) dysentery
  11. 11. Diagnosis of bacillary dysentery <ul><li>Bacteriologic method – isolation of pure culture from feces and identification: </li></ul><ul><ul><ul><li>Morphology properties, Gram-staining </li></ul></ul></ul><ul><ul><ul><li>Biochemical properties </li></ul></ul></ul><ul><ul><ul><li>Antigenic properties (serological identification) </li></ul></ul></ul><ul><li>Gen diagnosis - PCR </li></ul><ul><li>Serological method - revealing of antibody titer increasing in pair serum or specific IgM exposure </li></ul><ul><li>Bacterioscopy method can not be used </li></ul>
  12. 12. Treatment <ul><li>Fluid and electrolyte replacement . </li></ul><ul><li>In severe cases antibiotics are indicated, in mild cases, non antibiotics are used. Due to multiple drug resistance (connected with plasmids) antibiotics sensitivity tests must be performed. </li></ul><ul><li>Antiperistaltic drugs are contraindicated in shigellosis, because they prolong the fever, diarrhea, excretion of the microorganisms, and can provoke ulcers formation. </li></ul>
  13. 13. Vibrio cholerae
  14. 14. Properties of Vibrio cholerae <ul><li>Gram negative motile rod </li></ul><ul><li>comma shaped </li></ul><ul><li>facultative anaerobe </li></ul><ul><li>oxidase positive </li></ul><ul><li>it has one flagellum at one end </li></ul><ul><li>it is able to tolerate strong alkaline conditions and high salt concentrations </li></ul><ul><li>readily cultivated </li></ul>
  15. 15. Vibrio cholerae. Micrograph of bacteria in tissue Curved shape and single polar flagellum
  16. 16. Genuses of Vibrionaceae that are medically important Vibrionaceae Vibrio Aeromonas Plesiomonas <ul><li>V. cholerae causes cholera </li></ul><ul><li>V. parahaemolyticus is primarily marine organism (halophilic). It causes diarrhea associated with eating raw or improperly cooked seafood </li></ul><ul><li>V. vulnificus is found in seawater (halophilic). It causes severe skin and soft tissue infections, can cause a rapidly fatal septicemia in immunocompromised people </li></ul>
  17. 17. Antigenic structure of vibrios <ul><li>O (somatic) antigen. There are 150 serogroup of vibrios </li></ul><ul><li>H (flagella) antigen. It is common antigen for all vibrios </li></ul>
  18. 18. Electron micrograph of Vibrio cholerae
  19. 19. Classification of Vibrio cholerae Ogawa , Inaba , Hikojima Serotypes Classic and El Tor Biotypes Agents of cholera belong to O1 serogroup and O139 serogroup ( a new strain of V.cholerae that appeared in India in late 1992 ) Serogroup cholerae Species Вид Vibrio Genus Vibrionaceae Family
  20. 20. Chemogroups of vibrios according to Heiberg classification (1935) V. cholerae belongs to I chemogroup - - - VI - - + V + + - IV + + + ІІІ + - - ІІ + - + І Sucrose Arabinose Mannose Fermentation of carbohydrates Chemogroup
  21. 21. Differentiation of biotypes V. cholera classic and El Tor - + Sensitivity to polymyxin + - Susceptibility to group II (El Tor) bacteriophage - + Susceptibility to group IV (C) bacteriophage + - Hemolysis + - Agglutination of chicken erythrocytes V. cholerae El Tor V. cholerae classic Feature
  22. 22. Hemolysis test Classic El Tor
  23. 23. V. cholerae classic and El Tor growth on the blood agar Classic El Tor
  24. 24. Virulence factors of V.cholerae <ul><li>Adherence to mucosa layer of small intestine by pili </li></ul><ul><li>Enzyme of virulence – mucinase, hyaluronidase. </li></ul><ul><li>Exotoxin (cholerogen). The heat labile enterotoxin that consist of an A (active) and a B (binding) subunits. The B subunit binds to a ganglioside receptor on the surface of the enterosyte. The A subunit is inserted into the cytosol, where cause activation of the enzyme adenylate cyclase. The resulting overproduction of cAMP (cyclic adenosine monophosphate) stimulates secretion of chloride ions and water, leading to a massive watery diarrhea without inflammatory cells. </li></ul><ul><li>Endotoxin cause inhibition of phagocytosis, decrease of blood pressure, general intoxication </li></ul>
  25. 25. Pathogenesis of cholera <ul><li>Sours of infection are ill humans of carries. </li></ul><ul><li>The main animal reservoirs are marine shellfish, such as shrimp and oysters. </li></ul><ul><li>Transmission fecal-oral, with feces contaminated water or food. </li></ul><ul><li>Infectious dose is approximately 1 billion of bacteria. </li></ul><ul><li>Incubation period is a few hours to a few days. </li></ul>
  26. 26. Pathogenesis of cholera <ul><li>Colonization of small intestine. Vibrio penetrate the mucous barrier of duodenum using their flagellum, adhere to the microvilli of the epithelial cells and multiply there. </li></ul><ul><li>Adherence is related to secretion of the bacterial enzyme mucinase , which dissolves the protective glycoprotein coating over the intestinal cells. </li></ul><ul><li>Visible damage intestinal epithelial cells is absence. </li></ul>Vibrios Villus surface
  27. 27. Cholera - attachment V. cholerae bacteria, unlike the shigellae, do not penetrate into the intestinal cells
  28. 28. Mechanism of infectious diarrhea Intestinal epithelium Secretion of fluids Bacteria Non-blooding diarrhea Blooding diarrhea
  29. 29. Pathogenesis of cholera. Symptoms of cholera <ul><li>Due to cholerogen symptoms of disease occur. Vomiting, secretory diarrhea, dehydration lead to muscle, circulatory, and neurological symptoms and death. </li></ul><ul><li>Watery diarrheal fluid contains flecks of mucus and therefore has been described as “rice-watery stool”. </li></ul><ul><li>Fluid losses of nearly one liter per hour ( to 20 liters a day ) have been reported in severe cases, and an untreated patient can lose up to 50% of body weight during the course of the disease. </li></ul><ul><li>The diarrhea causes loss of blood volume, acidosis from bicarbonate loss, and potassium depletion that predispose the patient to muscle cramps, and, in young children, coma and convulsions. </li></ul><ul><li>The loss of fluid and electrolytes leads to cardiac and renal failure. </li></ul><ul><li>Secondary circulatory consequences can include hypotension, tachycardia, cyanosis, and collapse from shock within 18 to 24 hours. </li></ul><ul><li>Mortality rate from cholera approaches 55%. </li></ul>
  30. 30. Diagnosis <ul><li>Material from patient – stool samples </li></ul><ul><li>Methods of diagnosis: </li></ul><ul><li>Bacterioscopy. </li></ul><ul><ul><li>Direct dark-field microscopic observation. Curved cells with darting motility. </li></ul></ul><ul><ul><li>Gram stained swab of feces. Gram negative curved rods </li></ul></ul><ul><li>Indication of specific antigen of the V. cholerae with immunofluorescence test. </li></ul><ul><li>Bacteriological method. Isolation and identification of pure culture. </li></ul><ul><li>Serological method . Detection of rising antitoxin titer in the serum </li></ul>
  31. 31. Therapy <ul><li>Replacement of water and electrolytes </li></ul><ul><li>Antimicrobial therapy – antibiotics </li></ul>
  32. 32. Prevention <ul><li>Vaccines are available, but </li></ul><ul><ul><li>partially effective </li></ul></ul><ul><ul><li>not generally used </li></ul></ul><ul><ul><li>used only for international travelers and people, living in endemic regions </li></ul></ul><ul><li>Types of vaccines: </li></ul><ul><li>Killed cholera vibrios. But it protect for only 6 months or less. </li></ul><ul><li>Oral attenuated vaccine containing live vibrios. It is more effective. </li></ul>