Lectures 8-11-Bacillus anthracis, B. cereus, Clostridium
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Lectures 8-11-Bacillus anthracis, B. cereus, Clostridium

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Lectures 8-11-Bacillus anthracis, B. cereus, Clostridium Lectures 8-11-Bacillus anthracis, B. cereus, Clostridium Presentation Transcript

  • ‫بسم ا الرحمن الرحيم‬ FAMILY: BACILLIACEAE Prof. Khalifa Sifaw Ghenghesh
  • 1. GENUS: BACILLUS • Gram +ve bacilli • Aerobic • Spore-Forming
  • i. Bacillus anthracis • >> Anthrax. • Large, Square - ended Rods, Arranged in Chains. • Non-Motile. • Spores: • Capsule: – Purple Stained >> McFadyan's Method (Polychrome Methylene Blue). • Colonies on BA: "Medusa Head Appearance"
  • Bacillus anthracis
  • An electron micrograph of spores from the Sterne strain of Bacillus anthracis
  • Bacillus anthracis McFaydean capsule stain, grown at 35oC, in defibrinated horse blood.
  • DISEASE: • In Animals: >> Septicaemia. • In Humans: i. Cutaneous Anthrax > Malignant pustule ii. Pulmonary Anthrax (Wool-Sorter'sDisease). iii. Gastrointestinal Anthrax.
  • Cutaneous Anthrax
  • Anthrax lesion on the skin of the forearm caused by Bacillus anthracis
  • PATHOGENESIS • Capsule > Invasiveness – D-glutamic acid • Exotoxin (Plasmid mediated) i. Protective Factor (Antigen). ii. Oedema Factor. iii. Lethal Factor. Blocks the Adenyl Cyclase Pathway > Increases vascular Permeability > Shock
  • LABORATORY DIAGNOSIS: • Specimens obtained from: a malignant pustule, sputum, blood. - Gram stain + fluorescent-antibody stain. - Motility - Capsule formation: Sodium bicarbonate +CO2 - String-of-pearls reaction: - Mouse test: - API >> Demonstration of Abs to the organism:
  • Bicarbonate agar and blood agar plate cultures of Bacillus anthracis
  • Negative encapsulation: Blood agar and bicarbonate agar plate cultures of Bacillus cereus
  • • TREATMENT – Penicillin, Ciprofloxacin • IMMUNIZATION – Animals > Live spore vaccine (Sterne strain) – Workers at Risk of Exposure > Anthrax Vaccine Absorbed (AVA) >> “Alum precipitated toxoid”
  • ii. Bacillus cereus • Food Poisoning. • Clinical Syndromes: i. Severe Nausea &Vomiting. ii. Abdominal Cramps & Diarrhoea.
  • PATHOGENICITY: >> Due to an Enterotoxin. • Also Causes Disease in Patients with Underlying Disease. • TREATMENT: >> Tetracycline, Erythromycin. • iii. B. subtilis: • iv. B. stearothermophilus.
  • 2. GENUS: CLOSTRIDIUM • Gram +ve bacilli • Anaerobic, • Spore Forming - Spores:
  • Ink Stain of Sporulating Clostridiumspores appear clear, vegetative cells dark
  • i. Clostridium perfringens • Nonmotile • Spores Not Produced in Ordinary Media. • Aerotolerant Anaerobe. • 5 Types: A - E
  • Gram stain of Clostridium perfringens
  • Exudate smear of Clostridium perfringens
  • Tissue smear of Clostridium perfringens
  • DISEASE: • Clostridial Myonecrosis. • Less Severe Wound Infections. • Food Poisoning.
  • Patient with gas gangrene
  • LABORATORY IDENTIFICATION • In Chopped Meat - Glucose Medium: • On BA: • On Egg Yolk Agar: >> Precipitation (Opalescence). • Milk Media: Stormy Formation. • Nagler Reacrion:
  • Blood agar plate with Cl. perfringens characteristic double zone of hemolysis
  • PATHOGENICITY & CLINICAL INFECTION ∀ α-Toxin: Acts on Lecithin-Containing Lipoprotein Complexes in the Cell Membrane. • Predisposing Factors: i. Trauma with Deep and Lacerated or Crush Wounds of Muscle Etc. ii. Require a Reduced Oxygen Tension and Reduced Oxidation Reduction Potential for Growth.
  • FOOD POISONING: • Cl. perfringens Type A >> Enterotoxin. > Acute Abdominal Pain and Diarrhoea.
  • LABORATORY DIAGNOSIS: • Important: Diagnosis of Clostridium Myonecrosis Should Be Rapid and Made on Clinical Grounds. i. Direct Smear and Gram Stain of Material from Deep Within the Wound. ii. Culture: Tissue Aspirates or Deep Swabs Taken from Affected Muscle.
  • TREATMENT: • Clostridium Myonecrosis: i. Surgical Removal of All Infected and Necrotic Tissue. ii. Antibiotic and Antitoxin Therapy. iii. Adminstration of Hyperbaric Oxygen. • Food Poisoning:
  • Clostridia That May Be Associated with Gas Gangrene: • • • • • Cl. perfringens Type A Cl. septicum Cl. novyi Type A Cl. histolyticum Cl. Sordellii
  • Human case of malignant edema caused by Cl. septicum
  • ii. Clostridium tetani • > Tetanus. • > Terminal Spores with Drumstick Appearance. • > Obligate Anaerobe.
  • Clostridium tetani Gram Positive Rods
  • Clostridium tetani
  • VIRULENCE FACTORS: • Tetanus Toxin (Tetanospasmin) > Neurotoxin. i. An Intercellular Toxin Released by Cellular Autolysis. ii. Inhibits the Release of Inhibitory Transmitters. iii. Toxoid.
  • CLINICAL INFECTION & PATHOGENESIS • "Tetanus is Generalized in Nature". i. Unimmunized Rural Population. ii. In Practice: Simple Puncture Wounds > Nail, Splinter or Thorn. iii. In Traumatic Wounds > Compound Fractures, Dental Extractions, Etc. iv. Tetanus Neonatrum: v. Postoperative Tetanus:
  • Drawing of a Soldier dying of Tetanus (Opisthotonos)
  • A patient presented with facial tetany. Note the contraction of the masseter and neck muscles
  • LABORATORY DIAGNOSIS: • > Diagnosis on Clinical Grounds. TREATMENT: • • • • • • • • • i. Antitoxin. ii. Debridement of Wound and Removal of any Foreign Bodies. iii. Pencillin >>> In Large Doses. iv. Mild Tetanospasm: >>> Barbiturates. v. Severe Cases: >>> Use Curare - Like Agents. >>> Tracheostomy. >>> Careful Control of the Environment.
  • PREVENTION: > Prompt and Adequate Cleaning of Wounds. i. Active Immunity. ii. Passive Immunity.
  • iii. Clostridium botulinum • > Botulism. • > Gram +ve, Spore Forming Bacilli. • > Strict Anaerobe.
  • Gram Stain of Cl. botulinum, Characteristic Long Rods
  • A photomicrograph of Clostridium botulinum type A
  • Blood Agar Plate with C. botulinum
  • VIRULENCE FACTORS • Botulinum Toxin >>> Neurotoxin. – Serologically 8 Toxins >> A, B, C1, C2, D, E, F & G. > Affect the Cholinergic System > Blocks the Release of Acetylcholine (at Points in Peripheral Nervous System).
  • DISEASE IN HUMANS 1. Food - Borne Botulism: > Incubation Period: 12-36 Hours to 8 days. 2. Infant Botulism: LABORATORY DIAGNOSIS i. Diagnosis Made Clinically. ii. Detection of Organism or Its Toxin in the Suspected Food iii. Samples of Stool or Vomit
  • TREATMENT & PREVENTION Important: Specific Treatment Should Begin as Quick as Possible. >Polyvalent Antitoxin >>> Immediately. >Physiological Support >>> ICU. >NEVER Use a Swollen or Defective Can.
  • iv. Clostridium difficile • Antibiotic Associated Colitis. • Produce Two Major Protein Toxins (A &B). • Risk Factors: – Antibiotic Exposure. – Old Age.
  • Clostridium difficile
  • Scanning electron micrograph of Clostridium difficle
  • Intestinal Smear- Close Association of Cl. difficile with Neutrophils
  • • Infection Can Be: – Endogenous or Exogenous. • Nosocomial Spread: Due to Spores. LAB DIAGNOSIS: 1. Demonstration of Cytotoxin in Stool. 2. Isolation of the Microorganism. TREATMENT: – Discontinuing Treatment. – Vancomycin.