Other Gram Negative Bacilli

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Other Gram Negative Bacilli

  1. 1. <ul><li>Vibrios, Pseudomonas, Campylobacter, Helicobacter </li></ul>Other gram-negative bacilli
  2. 2. VIBRIOS <ul><li>Among the most common bacteria in surface waters worldwide </li></ul><ul><li>Curved, aerobic rods; motile with polar flagella </li></ul><ul><li>oxidase (+) </li></ul><ul><li>grow best on alkaline media </li></ul><ul><li>Often found in brackish water </li></ul>
  3. 3. Vibrio cholerae <ul><li>Classified based on somatic O antigen: </li></ul><ul><ul><li>V. cholerae O1 – most common cause of epidemic & pandemic cholera </li></ul></ul><ul><ul><li>V. cholerae O139 (Bengal strain) – epidemic </li></ul></ul><ul><ul><li>Non-O1 group </li></ul></ul><ul><li>Two biotypes (based on differences in biochemical reactions): </li></ul><ul><ul><li>El Tor – most common cause of epidemics and cause of 7 th pandemic </li></ul></ul><ul><ul><li>Cholerae or classical </li></ul></ul><ul><li>Three serotypes (based on antigenic differences): </li></ul><ul><ul><li>Ogawa, Inaba, Hikojima </li></ul></ul>
  4. 4. Vibrio cholerae <ul><li>MOT: fecal-oral </li></ul><ul><li>Sources of infection: humans, marine shellfish (shrimp and oysters) </li></ul><ul><li>Sensitive to gastric acid  high infective dose </li></ul><ul><li>Virulence factors: </li></ul><ul><ul><li>Mucinase – cause adherence to cells of the brush border of the gut </li></ul></ul><ul><ul><li>Choleragen – stimulate adenylyl cyclase </li></ul></ul>
  5. 5. Vibrio cholerae
  6. 6. Vibrio cholerae Cholera Toxin B subunit A subunit Binds GM1 ganglioside (surface of epithelial cells) Carried to ER (retrograde transport) Endocytosis Reduced by protein disulfide isomerase in ER Cytosol Unfolding Refolding Interact with cytosolic ADP ribosylation factors Activate G protein Stimulate adenylate cyclase Inc. cAMP Open CFTR Cl released in lumen; secretion of HCO 3 , Na + & water
  7. 7. Vibrio cholerae <ul><li>Clinical findings: </li></ul><ul><ul><li>Voluminous watery diarrhea – hallmark; “rice water” stool </li></ul></ul><ul><ul><li>Loss of fluid and electrolytes – marked dehydration </li></ul></ul><ul><ul><ul><li>“ washerwoman” hands </li></ul></ul></ul><ul><ul><ul><li>Cardiac and renal failure </li></ul></ul></ul><ul><ul><ul><li>Hypovolemic shock </li></ul></ul></ul>
  8. 8. Vibrio cholerae <ul><li>Diagnosis: </li></ul><ul><ul><li>Culture on MacConkey’s agar (slow lactose fermenter) or TCBS (Thiosulfate citrate bile salt sucrose) agar plate for selective isolation </li></ul></ul><ul><ul><li>Oxidase (+) – distinguished from the family Enterobacteriaceae </li></ul></ul><ul><ul><li>Serology </li></ul></ul><ul><li>Treatment: </li></ul><ul><ul><li>Prompt and rapid fluid and electrolyte replacement </li></ul></ul><ul><ul><li>Tetracycline – shorten duration </li></ul></ul>
  9. 9. Growth on TCBS agar plate
  10. 10. Vibrio parahaemolyticus <ul><li>Halophilic – grows on 8% NaCl solution </li></ul><ul><li>MOT: ingestion of raw or undercooked seafood, especially shellfish such as oysters </li></ul><ul><li>Mild to severe watery diarrhea, nausea and vomiting, abdominal cramps, fever  self-limited </li></ul><ul><li>No specific treatment indicated </li></ul>
  11. 12. Vibrio vulnificus <ul><li>Found in warm salt waters </li></ul><ul><li>Causes severe skin and soft tissue infections (cellulitis), especially in shellfish handlers </li></ul><ul><li>Rapid, fatal septicemia in immunocom- promised people who have eaten raw shellfish </li></ul><ul><li>Treatment: doxycycline </li></ul>
  12. 14. Pseudomonas aeruginosa <ul><li>Gram-negative rods that resemble the Enterobacteriaceae but are strict aerobes </li></ul><ul><li>Derive energy by oxidation of sugars rather than fermentation </li></ul><ul><li>Oxidase (+) </li></ul><ul><li>Able to grow in water containing only traces of nutrients </li></ul>
  13. 15. Pseudomonas aeruginosa <ul><li>Produce two pigments: </li></ul><ul><ul><li>Pyocyanin (blue) </li></ul></ul><ul><ul><li>Pyoverdin (fluorescein) – yellow green pigments that fluoresce under UVL </li></ul></ul><ul><li>Found chiefly in soil and water </li></ul><ul><li>Found on the skin in moist areas </li></ul><ul><li>Primarily opportunistic </li></ul>
  14. 16. Pseudomonas aeruginosa <ul><li>Virulence factors: </li></ul><ul><ul><li>Endotoxins – cause sepsis and shock </li></ul></ul><ul><ul><li>Exotoxin A – cause tissue necrosis; inhibits eukaryotic protein synthesis similar to diphtheria exotoxin </li></ul></ul><ul><ul><li>Enzymes </li></ul></ul><ul><ul><ul><li>Elastases and proteases </li></ul></ul></ul><ul><ul><li>Pyocyanin – damages the cilia and mucosal cells of respiratory tract </li></ul></ul>
  15. 17. Pseudomonas aeruginosa <ul><li>Clinical: </li></ul><ul><ul><li>Urinary tract infections </li></ul></ul><ul><ul><li>Pneumonia in cystic fibrosis patients </li></ul></ul><ul><ul><li>Burn wound infection </li></ul></ul><ul><ul><li>Sepsis </li></ul></ul><ul><ul><li>Ecthyma gangrenosum – black necrotic lesions on skin </li></ul></ul><ul><ul><li>Malignant external otitis </li></ul></ul><ul><ul><li>Folliculitis </li></ul></ul><ul><ul><li>Osteochondritis of the foot due to punctured wounds through the soles of gym shoes - most common cause </li></ul></ul>
  16. 19. Ecthyma gangrenosum
  17. 21. Osteochondritis of foot
  18. 23. Pseudomonas aeruginosa <ul><li>Diagnosis: </li></ul><ul><ul><li>Culture – non-lactose fermenting </li></ul></ul><ul><ul><li>Oxidase production </li></ul></ul><ul><ul><li>Biochemical reactions – confirmatory </li></ul></ul><ul><li>Treatment: </li></ul><ul><ul><li>Resistant to many antibiotics </li></ul></ul><ul><ul><li>Ticarcillin or piperacillin + aminoglycoside (gentamicin or amikacin) </li></ul></ul>
  19. 24. Production of pyocyanin, water-soluble green pigment of Pseudomonas aeruginosa. (left tube)
  20. 25. Campylobacter jejuni <ul><li>Comma- or S-shaped rods </li></ul><ul><li>Microaerophilic (5% oxygen) </li></ul><ul><li>Grows well at 42 0 C </li></ul><ul><li>Sources of infection: domestic animals </li></ul><ul><li>MOT: fecal-oral (poultry, meat, unpasteurized milk common sources) </li></ul>
  21. 27. Campylobacter jejuni <ul><li>Clinical: </li></ul><ul><ul><li>Enterocolitis – begins as watery, foul-smelling diarrhea  bloody stools </li></ul></ul><ul><ul><li>Associated with </li></ul></ul><ul><ul><ul><li>Guillain-Barre syndrome </li></ul></ul></ul><ul><ul><ul><ul><li>Most common cause of acute neuro-muscular paralysis </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Autoimmune disease </li></ul></ul></ul></ul><ul><ul><ul><li>Reactive arthritis </li></ul></ul></ul><ul><ul><ul><li>Reiter’s syndrome </li></ul></ul></ul>
  22. 28. Campylobacter jejuni <ul><li>Diagnosis: </li></ul><ul><ul><li>Culture </li></ul></ul><ul><ul><li>Oxidase (+); sensitive to nalidixic acid </li></ul></ul><ul><li>Treatment: erythromycin or ciprofloxacin </li></ul>
  23. 29. Helicobacter pylori <ul><li>Curved; gram-negative; similar in appearance to Campylobacter </li></ul><ul><li>Strongly urease positive  convert urea to ammonia  neutralize gastric acid </li></ul><ul><li>Rapidly motile – allow organism to penetrate protective mucus layer </li></ul>
  24. 34. Helicobacter pylori <ul><li>Most common cause of chronic gastritis </li></ul><ul><li>Most common cause of duodenal ulcers </li></ul><ul><li>Second most common cause of gastric ulcer </li></ul><ul><li>Associated with development of gastric CA and gastric lymphoma </li></ul>
  25. 35. Helicobacter pylori <ul><li>Diagnosis: </li></ul><ul><ul><li>Culture </li></ul></ul><ul><ul><li>Urease production  urea breath test </li></ul></ul>
  26. 38. Helicobacter pylori <ul><li>Treatment: </li></ul><ul><ul><li>Proton pump inhibitors (Omeprazole) </li></ul></ul><ul><ul><li>Antibiotics – amoxicillin, metronidazole, tetracycline </li></ul></ul><ul><ul><li>Bismuth salts </li></ul></ul>

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