Clostridium

• CLOSTRIDIUM


  A genus of bacteria that includes several pathogenic species
• Characteristics of Clostridium

  • Gram positive large rods
  • Occurring singly or in pairs
  • Forms endospores
  • Obligate anaerobes
  • Usually found in soil and intestinal tract of animals and humans
  • Toxin formation
• Medically important clostridia

  • Clostridium botulinum
  • Clostridium tetani
  • Clostridium perfringens
  • Clostridium difficile
• C. tetani


  • Forms terminal spores giving a drumstick appearance
  • Forms small colonies that spread on the agar surface giving a swarming appearance
  • Causes tetanus
• Tetanus is a wound infection
• Wound types favouring tetanus

  • Deep punctured wounds
  • Septic abortions
  • Umbilical stumps
  • Dental caries
• Sources of C. tetani in wound infections

  • Soil
  • Dust
  • Animal and human faeces
  • Rusty scissors
  • Nails
  • Pins
• Factors facilitating germination of C. tetani spores

  • Necrotic tissues
  • Pyogenic infections
  • Calcium ions
  • Poor blood supply in the wounds
• Pathogenesis of C. tetani

  1. At wound sites spores germinate into vegetative cells

  2. Vegetative cells produce tetanospasmin

  3. TSN is carried intra-axonally to the CNS

  4. TSN binds to ganglioside receptors which block the release of mediators at synapses
• Tetanospasmin (TSN)


  A neurotoxin acting on the CNS solely responsible for tetanus
• Clinical manifestations of C. tetani

  • Incubation period is 4-5 days but may run into weeks
  • Muscular spasms first at area of injury
  • Locked jaw/trismus
  • Breathing may be affected
  • Contraction of back muscles resulting in opisthotonos
  • Mortality rate is very high
• Control and prevention of C. tetani

  Neutralisation of the toxin using tetanus immune globulin<|>Administration of penicillin or metronidazole<|>Surgical debridgement to remove necrotic tissues<|>Immunization with DPT<|>Providing muscle relaxants, sedation assisted ventilation
• C. botulinum


  • Has the usual features of Clostridium spp.
  • Spores are subterminal and highly resistant to heat
  • Production of neurotoxins
• Types of botulinum toxins

  • A
  • B
  • E
  • C
  • D
• Types A, B, E are common in human disease
• Types C and D are usually associated with animals
• C. botulinum Disease

  Botulism
• Types of botulism

  • Food botulism
  • Wound botulism
  • Infant botulism
• Pathogenesis of C. botulinum

  • Botulinum toxin is absorbed from the gut
  • Binds to receptors of presynaptic membranes of motor neurons
  • Results in blockage of acetylcholine leading to flaccid paralysis
• Clinical manifestations of C. botulinum

  • Incubation period is 18-24 hours
  • Visual disturbances
  • Difficulty in swallowing
  • Speech difficulty
  • Respiratory paralysis
• Diagnosis/Treatment of C. botulinum

  • Diagnosis is mainly clinical
  • Toxin can be identified in serum or food by injecting mice
  • Food sample can be cultured for bacteria and toxin type detected by neutralization
• Treatment for C. botulinum

  Administration of antitoxin (ABE)<|>Adequate ventilation
• C. difficile

  • Normal flora of the gut of less than 5% of adults
  • Causes antibiotic associated diarrhoea
  • Causes pseudomembranous colitis
• Antibiotic associated diarrhoea

  • Broad spectrum antibiotics clear the gut flora leading to proliferation of C. difficile
  • Produces enterotoxin
  • Diarrhoea may be watery or bloody
  • Abdominal cramps
• C. perfringens morphology and physiology

  • Large, rectangular bacilli (rod)
  • Staining gram-positive
  • Spores rarely seen in vitro or in clinical specimens
  • Non-motile but rapid spreading growth on blood agar
  • Aerotolerant
  • Grow at temperature of 20-50°C (optimum 45°C) and pH of 5.5-8.0
• Pathogenicity determinants of C. perfringens

  • Four major lethal toxins (alpha, beta, epsilon, and iota toxins)
  • Six minor toxins (delta, theta, kappa, lambda, mu, nu toxins)
• C. perfringens types

  • A
  • B
  • C
  • D
  • E
• C. perfringens Type A


  • Only major lethal toxin is alpha toxin
  • Responsible for histotoxic and enterotoxigenic infections in humans
• C. perfringens Type C

  • Causes necrotizing enteritis (not in U.S.)
• Identification of C. perfringens

  • Direct smear and Gram stain
  • Culture takes advantage of rapid growth in chopped meat media at 45°C
  • Gas from glucose fermentation
• Diagnosis/Treatment of systemic infection due to C. perfringens

  • Early diagnosis and aggressive treatment essential
  • Removal of necrotic tissue
  • Penicillin G in high doses if more serious infection
• Administration of antitoxin and hyperbaric oxygen are of poorly defined clinical value
• C. perfringens infections

  • Show evidence of tissue necrosis
  • Bacteremia
  • Gas gangrene (clostridial myonecrosis)
• Alpha toxin


  The toxin involved in gas gangrene that disrupts normal cellular function