Gram negative rods 5


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Gram negative rods 5

  1. 1. Gram negative Rods related to animal sources
  2. 2. Brucella Small gram neg rods. Without capsule. B.melitensis(goats and sheep). B.abortus(cattle) B.suis(pigs) Are human pathogens Cause Brucellosis or undulant fever(rise and fall pattern) B.melitensis infections more severe and prolonged whereas B.abortus infections are self limited. Treatment: Tetracycline Prevention: Pasteurization of milk.
  3. 3. Francisella F.tularensis causes Tularemia. Small pleomorphic gm neg rods. Granuloma infection due to endotoxin. Most of them are ulceroglandular, the site of entry (usually the skin)ulcerates and the regional lymph nodes are swollen and painful. Treatment: Streptomycin Prevention: avoid bitten by ticks(insect vector) and handling wild animals.
  4. 4. Yersinia Y.pestis cause Plague also known as black death. Is a small gm neg rod that exhibits bipolar staining (resembles a safety pin). Freshly isolated samples possess a polysaccharide-protein complex capsule. These may be lost. Virulence is lost as well. One of the most virulent bacteria known. Even 1-10 orgs can cause disease. Rat flea is the vector and endemic in wild rodents. The orgs at the time of the bite spread to the regional lymph nodes, which swell and become tender. They are known as buboes and hence the name Bubonic plague.
  5. 5. The orgs, reach high concentrations in blood 9bacteremia) and disseminate to form abscesses in many organs. The endotoxin related symptoms including DIC and cutaneous haemorrhages lead to the name Black death. Several virulent factors. They have an envelope capsular antigen called F-1 which protects against phagocytosis. Endotoxin, an exotoxin and 2 special proteins V and Wantigens that allow the org to survive and grow intracellularly. Mode of action of these antigens and of the exotoxin is unknown. A group of virulent factors called “Yops” (yersinia outer proteins). These are injected into the human cell by the typeIII secretion system and inhibit phagocytosis and cytokine production by macrophages and neutrophils.
  6. 6. One of the Yops proteins is a protease(YopJ), that cleaves 2 signal transduction pathway proteins required for the induction of TNF synthesis. This inhibits the action of host defense and contribute to the ability of the org to replicate rapidly.
  7. 7. Clinical findings: Bubonic plague is the most frequent form. It begins with pain and swelling of the lymph nodes and systemic symptoms such as high fever, myalgias and prostration. The affected nodes become large and exquisitely tender. The buboes are early characteristic finding. Septic shock and pneumonia are the main life threatening events subsequently. Pneumonic plague arises from inhalation of an aerosol or from septic emboli that reaches the lungs. Untreated bubonic plague fatal in half the cases, and pneumonic plague is 100% fatal.
  8. 8. Lab findings: Smear and culture of blood or pus from the bubo is the best diagnostic procedure. Care should be taken during aspiration or doing the culture not to create an aerosol that might transmit the infection. Giemsa or Wayson stain reveals the typical safety pin appearance better than gm stain. Fluorescent antibody staining to identify orgs in tissues.
  9. 9.  Treatment:  A combination of Streptomycin and Tetracycline. Streptomycin can be used alone.  As disease progresses rapidly should not wait for bacteriological culture.  Incision and drainage of the buboes not usually necessary.  Prevention:  Control the spread of rats and avoid rat flea bites.  A patient with plague should be kept in strict isolation for 72 hours after starting treatment.  Reporting cases is mandatory.  A formalin killed organism vaccine is available but offers only partial protection against bubonic plague but not pneumonic plague.
  10. 10. Pasteurella P.multocida causes wounds (rapidly spreading cellulitis at the site of animal bite) associated with cat and dog bites. Treatment of choice is Penicillin G. Prevention: Cat bite cases should be given Ampicillin to prevent infection. Cat bites especially should not be sutured.
  11. 11. Bartonella B.henselae cause of cat-scratch disease (CSD), especially in immunocompetent people. Characterized by fever, and tender enlarged lymph nodes typically on the same side as the scratch. In immunocompromised cases such as AIDS, B.henselae can cause bacillary angiomatosis(BA)characterized by cherry red vascular lesions in the skin and visceral organs. CSD no antibiotics required.For BA: Doxycycline or Erythromycin.