Clostridium

• What are the main infections associated with Clostridia species?

  Tetanus, Clostridial myonecrosis, Pseudomembranous colitis
• What should students be able to do by the end of the lecture on Clostridia species?

  • Describe general characteristics of anaerobes
  • Describe their classification
  • List organisms, infections, and diseases
  • Discuss clinically important Clostridia species
  • Discuss microbiology, pathogenesis, clinical manifestations, and treatment options
• What defines anaerobes in terms of oxygen tolerance?

  Anaerobes cannot survive in the presence of oxygen
• What do anaerobes lack that contributes to their intolerance of oxygen?

  They lack catalase and superoxide dismutase
• What is the typical habitat of anaerobes in the human body?

  Anaerobes are typically found in the mouth, upper respiratory tract, gastrointestinal tract, and urogenital tract
• What are some problems in identifying anaerobic infections?

  Air in the sample, no growth, and sample contamination can complicate identification
• What are clues to anaerobic infections?

  Foul smelling discharge, gas in tissues, presence of pus, and necrotic tissue
• What are some predisposing factors for anaerobic infections?

  Trauma, foreign body, impaired blood supply, and presence of other organisms
• How are anaerobes classified based on sporing?

  • Sporing: Gram-positive bacilli (Clostridium spp.)
  • Non-sporing:
  • Gram-positive bacilli (Bifidobacterium, Propionibacterium, Lactobacillus, Actinomyces)
  • Gram-positive cocci (Peptostreptococcus, Peptococcus)
  • Gram-negative bacilli (Bacteroides, Fusobacterium, Porphyromonas, Prevotella)
  • Gram-negative cocci (Veillonella)
• What is the natural habitat of Clostridia species?

  Soil or intestinal tract of humans and animals
• What is the pathogenicity of Clostridium tetani?

  Clostridium tetani is non-invasive and causes toxemia through exotoxins
• What are the effects of tetanospasmin on the nervous system?

  Tetanospasmin binds to ganglioside receptors and blocks normal postsynaptic inhibition of motor neurons
• What are the types of tetanus?

  Classical, neonatal, and localized tetanus
• What are the clinical manifestations of generalized tetanus?

  Severe muscle spasms, lockjaw, and autonomic nervous system involvement
• How is tetanus diagnosed?

  Diagnosis is primarily clinical
• What is the treatment for tetanus?

  • Local debridement
  • Tetanus immunoglobulin
  • Tetanus toxoid
  • Antibiotics
  • Sedatives
  • Respiratory assistance
• What is the vaccination schedule for tetanus prevention?

  Booster shots every 10 years
• What is Clostridium perfringens known for?

  Causing gas gangrene and food poisoning
• What is the Nagler reaction used for?

  Identification of the alpha toxin of Clostridium perfringens
• What are the serologic types of Clostridium perfringens?

  Type A, B, C, D, and E
• What is the epidemiology of Clostridium perfringens type A?

  Found in the intestinal tract of humans and animals, soil, and water contaminated with feces
• What is the significance of the toxins produced by Clostridium perfringens?

  They are responsible for the pathogenicity of the organism
• What are the clinical manifestations of Clostridium perfringens infections?

  • Gas gangrene: rapid tissue necrosis, gas formation
  • Food poisoning: abdominal cramps, diarrhea
• What type of bacteria is C. perfringens?

  Large Gram-positive bacilli
• What conditions favor sporulation in C. perfringens?

  Sporulation is favored by alkaline medium and rarely occurs at pH <6.6
• How is C. perfringens identified in the laboratory?

  By the Nagler reaction
• What is the function of the alpha toxin produced by C. perfringens?

  It is a lecithinase that hydrolyzes lecithin in media containing egg yolk
• What type of hemolysis does C. perfringens produce on blood agar?

  Double zone of beta hemolysis
• What are the heat-resistant and heat-labile spores associated with C. perfringens responsible for?

  Heat-resistant spores cause food poisoning, while heat-labile spores cause gas gangrene
• How many serologic types is C. perfringens divided into?

  Five serologic types
• Which serologic type of C. perfringens is most common and pathogenic for humans?

  Type A
• What is the primary clinical infection caused by C. perfringens type A?

  Gas gangrene
• What happens during clostridial myonecrosis when C. perfringens is inoculated into muscle?

  It leads to secretion of exotoxins that degrade and destroy adjacent muscle
• What are the signs and symptoms of gas gangrene?

  Fever, pain in infected tissue, local tissue necrosis, and gas bubbles
• What laboratory identification features are associated with C. perfringens?

  Boxcar-shaped gram-positive rods and double-zone hemolysis on blood agar
• What is the role of MALDI-TOF MS in laboratory identification of C. perfringens?

  It is a rapid and sensitive method for identification
• What is the effective antibiotic therapy for C. perfringens infections?

  Penicillin, metronidazole, and aminoglycoside in combination
• What is the primary cause of antibiotic-associated diarrhea related to C. difficile?

  Disturbance of normal colonic flora due to broad-spectrum antibiotics
• What are the two exotoxins produced by C. difficile?

  Toxin A and Toxin B
• What is the clinical presentation of pseudomembranous colitis?

  Abdominal pain, watery severe diarrhea, and leukocytosis