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• Anaerobes


  Organisms that require a reduced oxygen tension for growth and fail to grow on solid media in the presence of oxygen
• Polymicrobic


  • Involving more than one bacterial species
• Types of Anaerobic Infections

  • Exogenous
  • Endogenous

  
• Exogenous infections

  • Food-borne botulism
  • Tetanus
  • Infant botulism

  
• Endogenous infections

  • Arise within the mouth
  • Intestinal tract
  • Female genital tract
• Pathogenesis and Spectrum of Disease for Anaerobic Bacteria

  
• Anaerobic Bacteria Classification

  • Anaerobic Cocci
  • Anaerobic Bacilli

  
• Anaerobic Bacilli

  • Gram-neg
  • Gram-pos
  • Spore-forming
  • Non-Spore-forming
• Anaerobic Cocci

  • Gram-positive
  • Gram-negative
• Gram Positive Anaerobic Bacilli

  • Clostridium botulinum
  • Clostridium difficile
  • Clostridium perfringens
  • Clostridium septicum
  • Clostridium sordellii
  • Clostridium tetani
  • Other Clostridium spp.
  • Actinomyces israelii
  • Actinomyces naeslundii
  • Actinomyces odontolyticus
  • Other Actinomyces spp.
  • Atopobium minutum
  • Atopobium parvulum
  • Bifidobacterium spp.
  • Collinsella aerofaciens
  • Eggerthella lenta
  • Eubacterium spp.
  • Lactobacillus spp.
  • Mobiluncus spp.
  • Propionibacterium spp.

  
• Gram Negative Anaerobic Bacteria

  • Bacteroides fragilis group
  • Other Bacteroides spp.
  • Bacteroides ureolyticus
  • Bilophila wadsworthia
  • Fusobacterium spp.
  • Leptotrichia spp.
  • Porphyromonas spp.
  • Prevotella spp.
  • Sutterella wadsworthensis

  
• Gram-positive Anaerobic Cocci

  • Anaerococcus prevotii
  • Anaerococcus tetradius
  • Finegoldia magna
  • Gallicola barnesae
  • Parvimonas micra
  • Peptococcus niger
  • Peptoniphilus spp.
  • Peptostreptococcus anaerobius
  • Staphylococcus saccharolyticus

  
• Gram-negative Anaerobic Cocci

  • Acidaminococcus
  • Megasphaera
  • Veillonella spp.

  
• Clostridia

  • Endospore-forming
  • Catalase (-)
  • Obligate anaerobes
  • Motile and have peritrichous flagella
  • Nonencapsulated
  • Have a single hemolytic reaction
  • Have swollen sporangia
  • Carbohydrate fermenters

  
• Clostridium Groups

  • Gas Gangrene Group
  • Clostridium tetani
  • Clostridium botulinum
  • Clostridium difficile
  • Miscellaneous clostridium
  • Clostridium perfringens
• Clostridium perfringens


  Formerly known as C. welchii, also known as bacillus aerogenes capsulatus or gas gangrene bacillus
• Clostridium perfringens


  • Most commonly isolated member of Clostridium in blood cultures
  • Nonmotile
  • Obligatory anaerobe
  • Only encapsulated clostridia
  • Spores are absent in solid media & thio

  
• Causes of Clostridium perfringens

  • Myonecrosis (gas gangrene)
  • Pork poisoning (pig bell)
• Virulence Factors of Clostridium perfringens

  • Alpha toxin
  • Beta toxin
  • Lambda toxin
  • Theta toxin
  • Kappa toxin
  • Mu toxin
  • Nu toxin
  • Epsilon and iota toxin
  • Enterotoxin
  • Neuramidase

  
• Gas gangrene is a bacterial infection that produces gas in tissues in gangrene
• C. perfringens culture

  • Double zone of hemolysis on BAP
  • Milk media: stormy fermentation
• Stormy Fermentation


  Used for the identification of Clostridium species
• Biochemical Characteristics of C. perfringens

  • Does not ferment xylose
  • Positive Lecithinase test
  • Positive Nagler reaction
  • Positive Reverse CAMP
• Gram stain of a smear of exudate from a wound that had gas bubbles shows large, boxcar-shaped, gram-positive bacilli, suggestive of clostridial disease
• Clostridium tetani


  Aka tack head bacillus, spores: terminal & swollen, drumstick/lollipop/tennis racket appearance
• Clostridium tetani


  • Swarming colonies on BAP
  • Exhibits Wasserman-Takaki phenomenon
  • Does not ferment any carbohydrates
• Clinical manifestations of Tetanus

  • Trismus (lock jaw)
  • Risus sardonic
  • Opisthotonus
• Tetanospasmin


  A neurotoxin causing spasmodic contraction
• Clostridium botulinum


  Aka Canned good bacillus or Bacillus botulinus, heat resistant spores that are oval and subterminal
• Clostridium botulinum


  • β hemolytic
  • Potential bioterrorism agent

  
• Causes of Clostridium botulinum

  • Wound botulism
  • Food botulism
  • Infant botulism

  
• Botulinum toxin


  One of the most potent exotoxins, a neurotoxin causing flaccid paralysis
• Uses of Botox

  • Temporary smoothing of facial wrinkles
  • Severe underarm sweating
  • Cervical dystonia
  • Blepharospasm
  • Strabismus
  • Overactive bladder
• Clostridium difficile

  Characteristics include oval & subterminal spores, fluoresce yellow green colonies with horse stable odor on BAP, yellow ground glass colonies on CCFA
• Clostridium difficile is a major cause of nosocomial diarrhea
• Clostridium difficile is the most common cause of antibiotic-associated diarrhea and pseudomembranous colitis
• Miscellaneous Clostridia

  • Clostridium ramosum
  • Clostridium septicum
• Actinomyces

  Branching & beaded, has sulfur granules, facultative anaerobe
• Actinomyces

  • Young cultures show “Spider-like” and “wooly” colonies, old cultures show “Raspberry” or “Molar tooth” colonies
• Actinomyces are found as normal flora on the mucosal surfaces of the human digestive tract and urogenital tract and on the skin