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PowerPoint ANAEROBES AND PSEUDOMONAS OPPORTUNISTIC INFECTIONS gangrene

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					ANAEROBES AND PSEUDOMONAS -
  OPPORTUNISTIC INFECTIONS


     Faculty: Dr. Alvin Fox
         MAJOR POINTS

Overview of anaerobic bacteriology

Anaerobic non-spore formers

Anaerobic spore formers
  (clostridia)

Pseudomonas (a strict aerobe)
               KEY WORDS
• Obligate anaerobes     • C. perfringens
• Strict anaerobes       • Lecithinase
• Polymicrobic (mixed)     (phospholipase,  toxin)
  infection              • C. perfringens enterotoxin
• Spore formers          • C. botulinum
• Non-spore formers      • Botulinum toxin
• Bacteroides            • C. difficile
• B. fragilis            • C. difficile enterotoxin
• Clostridium tetani     • Pseudomonas aeruginosa
• Tetanospasmin          • Pyocyanin
                         • Fluorescein
                         • Toxin A
Obligate (strict) anaerobes
   •   no oxidative phosphorylation
   •   fermentation
   •   killed by oxygen
   •   lack certain enzymes
       – superoxide dismutase
           * O2-+2H+ H2O2
       – catalase
           * H2O2 H20 + O2
       – peroxidase
           * H2O2 H20 /NAD to NADH
Polymicrobic anaerobic infection
• Many species in human flora
• Many grow simultaneously - opportunistic
  conditions
     • opportunistic growth
        –injured tissue
          *limited blood/O2

     • no growth
        – healthy tissues
          *high O2 content
 Polymicrobic anaerobic infection

• Simultaneous infection with facultative anaerobe
  –diminishes O2 supply further
  – aids growth of obligate anaerobes
 Endogenous versus exogenous
         infection
• Two sources
  – normal human flora
     • endogenous
  – environment (e.g. soil)
     • exogenous
  Source of spore-formers and
      non-spore formers
• Spore-formers (clostridia)
  – exotoxins
  – common in the environment (e.g. soil)
  – found in normal flora
• Non - spore-formers
  – no exotoxins
  – mostly normal flora
      Sites of anaerobes in
          normal flora

• intestine
   – major site
   – 95-99% total bacterial mass
• mouth
• genitourinary tract
    Bacteroides fragilis
• minor component of gut flora
• most common (strict) anaerobic
  infection after abdominal
  surgery
• Enterobacteriaceae (facultative anaerobes)
   – commonly cause disease
   – low numbers gut flora

• Strict anaerobes
   – much less commonly cause disease
   – high numbers gut flora


  .
   Strict anaerobe infectious
             disease
• Sites throughout body
• Muscle, cutaneous/sub-cutaneous
  necrosis
• abscesses
      Problems in identification of
          anaerobic infections
• air in sample (sampling, transportation)
  – no growth

• identification takes several days or longer
  – limiting usefulness

• often derived from normal flora
  – sample contamination can confuse
        LABORATORY
       IDENTIFICATION
• BIOCHEMICAL KITS
 - e.g. substrate utilization


• GAS CHROMATOGRAPHY
 – volatile fermentation products
ANAEROBIC NON-SPORE-FORMERS
   OF CLINICAL IMPORTANCE
Gram-negative rods: Bacteroides e.g. B. fragilis
                      Fusobacterium,
                      Porphyromonas, Prevotella
 Gram-positive rods:
 Actinomyces, Bifidobacterium, Eubacterium
 Lactobacillus, Mobiluncus, Propionibacterium
Gram-positive cocci: Peptostreptococcus and Peptococcus

Gram-negative cocci: Veillonella
     Bacteroides fragilis
• Major disease causing strict anaerobic
  non-spore-former
• Prominent capsule
  – anti-phagocytic
  – abscess formation

• Endotoxin
  – low toxicity
  – structure different than other
     lipolysaccharide
ANAEROBIC SPORE-FORMERS
      (CLOSTRIDIA)

• Gram-positive rods
  – human intestine
  – soil
A severe case of tetanus.
muscles, back and legs are rigid
muscle spasms can break bones
can be fatal (e.g respiratory falure)
        Clostridium tetani




spore

                         vegetative
         Clostridium tetani
• Non-invasive
         Tetanospasmin
• disseminates systemically
• binds to ganglioside receptors
   – inhibitory neurones in CNS
• glycine
   – neurotransmitter
• stops nerve impulse to muscles
• spastic (rigid) paralysis
• severe muscle contractions and spasms
• can be fatal
             Vaccination


• infant
• DPT (diptheria, pertussis, tetanus)
• tetanus extremely uncommon in US
• tetanus toxoid
       – antigenic
       – no exotoxic activity
         C. perfringens
• soil, fecal contamination
• war
• gas gangrene
  – swelling of tissues
  – gas release
     * fermentation products
• wound contamination
            Pathogenesis
• tissue degrading enzymes
    – lecithinase [ toxin]
    – proteolytic enzymes
    – saccharolytic enzymes

• destruction of blood vessels
• tissue necrosis
• anaerobic environment created
• organism spreads
Without treatment death
occurs within 2 days

     effective antibiotic therapy
     debridement
     anti-toxin
     amputation & death is rare
          Laboratory identification

• lecithinase production
       Food poisoning
• enterotoxin producing strains
C. botulinum
               Botulism
• food poisoning
  – rare
  – fatal

• germination of spore
• inadequately sterilized canned food
  – home

• not an infection
           Botulinum toxin
• binds peripheral nerve receptors
   – acetylcholine neurotransmitter
• inhibits nerve impulses
• flaccid paralysis
• death
   – respiratory
   – cardiac failure
  Infection with C. botulinum
• Neonatal botulism
  – uncommon
  – the predominant form of botulism
  – colonization occurs
     • no normal flora to compete
     • unlike adult
             Wounds

– extremely rare
– an infection
          Botulinum toxin
• Bioterrorism
  – not an infection
  – resembles a chemical attack
                Treatment
• anti-toxin
• antibiotic therapy (if infection)
       C. difficile
• After antibiotic use
• intestinal normal flora
  – greatly decreased
• colonization occurs
• enterotoxin secreted
• pseudomembanous colitis
              Therapy

• discontinuation of initial
  antibiotic (e.g. ampicillin)

• specific antibiotic therapy (e.g.
  vancomycin)
PSEUDOMONAS AERUGINOSA




  Gram negative rod
          Pseudomonas

• Aerobic
• Gram-negative rod
• majority of human infections
  – P. aeruginosa
 Common in the environment

• water
• air
• soil
P. aeruginosa and compromised host
    • Burns and wounds
       – destruction of blood vessels
       – phagocyte access limited
    •cancer
       – cytotoxic drugs
          *destroy the immune system
    •cystic fibrosis
       – altered respiratory epithelium
       – pneumonia

    .
           Identification
• Pigments
   – pyocyanin (blue-green)
   – fluorescein (green-yellow, fluorescent)

• biochemical reactions

• cultures have fruity smell
     Pathogenesis
• Slime layer is anti-phagocytic

• Toxin A - ADP ribosylates EF2
   – similar to diphtheria toxin

				
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posted:1/26/2011
language:English
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