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ANAEROBES AND PSEUDOMONAS OPPORTUNISTIC INFECTIONS

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Many species in human flora. Many grow simultaneously ... cultures have fruity smell. Slime layer is anti-phagocytic. Toxin A - ADP ribosylates EF2 ... – PowerPoint PPT presentation

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Title: ANAEROBES AND PSEUDOMONAS OPPORTUNISTIC INFECTIONS


1
ANAEROBES AND PSEUDOMONAS - OPPORTUNISTIC
INFECTIONS
Faculty Dr. Alvin Fox
2
MAJOR POINTS
Overview of anaerobic bacteriology
Anaerobic non-spore-formers
Anaerobic spore-formers (clostridia)
Pseudomonas (a strict aerobe)
3
KEY WORDS
  • Obligate anaerobes
  • Strict anaerobes
  • Polymicrobic (mixed) infection
  • Spore formers
  • Non-spore formers
  • Bacteroides
  • B. fragilis
  • Clostridium tetani
  • Tetanospasmin
  • C. perfringens
  • Lecithinase (phospholipase, ? toxin)
  • C. perfringens enterotoxin
  • C. botulinum
  • Botulinum toxin
  • C. difficile
  • C. difficile enterotoxin
  • Pseudomonas aeruginosa
  • Pyocyanin
  • Fluorescein
  • Toxin A

4
Obligate (strict) anaerobes
  • no oxidative phosphorylation
  • fermentation
  • killed by oxygen
  • lack certain enzymes
  • superoxide dismutase
  • O2-2H to H2O2
  • catalase
  • H2O2 to H20 O2
  • peroxidase
  • H2O2 to H20 /NAD to NADH)

5
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

6
Polymicrobic anaerobic infection
  • Simultaneous infection with facultative
    anaerobe
  • diminishes O2 supply further
  • aids growth of obligate anaerobes

7
Endogenous versus exogenous infection
  • Two sources
  • normal human flora
  • endogenous
  • environment (e.g. soil)
  • exogenous

8
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

9
Sites of anaerobes in normal flora
  • intestine
  • major site
  • 95-99, total bacterial mass
  • mouth
  • genitourinary tract

10
Bacteroides fragilis
  • minor component of gut flora
  • most common (strict) anaerobic infection after
    abdominal surgery

11
  • Enterobacteriaceae (facultative anaerobes)
  • commonly cause disease
  • low numbers gut flora
  • Strict anaerobes
  • much less commonly cause disease
  • high numbers gut flora
  • .

12
Strict anaerobe infectious disease
  • Sites throughout body
  • Muscle, cutaneous/sub-cutaneous necrosis
  • abscesses

13
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

14
LABORATORY IDENTIFICATION
  • BIOCHEMICAL KITS
  • e.g. API SYSTEM
  • GAS CHROMATOGRAPHY
  • volatile fermentation products

15
ANAEROBIC NON-SPORE-FORMERS OF CLINICAL
IMPORTANCE
Bacteroides e.g. B. fragilis Fusobacterium,
Porphyromonas, Prevotella
Gram-negative rods
Gram-positive rods Actinomyces,
Bifidobacterium, Eubacterium Lactobacillus,
Mobiluncus, Propionibacterium
Gram-positive cocci
Peptostreptococcus and Peptococcus
Gram-negative cocci Veillonella
16
Bacteroides fragilis
  • Major disease causing strict anaerobic
  • non-spore-former
  • Prominent capsule
  • anti-phagocytic
  • abscess formation
  • Endotoxin
  • low toxicity
  • structure different than other
    lipolysaccharide

17
ANAEROBIC SPORE-FORMERS (CLOSTRIDIA)
  • Gram-positive rods
  • human intestine
  • soil

18
A severe case of tetanus. muscles, back and
legs are rigid muscle spasms can break bones
can be fatal (e.g respiratory falure)
19
Clostridium tetani
  • Non-invasive

20
Tetanospasmin
  • disseminates systemically
  • binds to ganglioside receptors
  • inhibitory neurones in CNS
  • glycine
  • neurotransmitter
  • stops nerve impulse to muscles
  • spastic paralysis
  • severe muscle contractions and spasms
  • can be fatal

21
Vaccination

  • infant
  • DPT (diptheria, pertussis, tetanus)
  • tetanus extremely uncommon in US.
  • tetanus toxoid
  • antigenic
  • no exotoxic activity

22
C. perfringens
  • soil, fecal contamination
  • war
  • gas gangrene
  • swelling of tissues
  • gas release
  • fermentation products
  • wound contamination

23
Pathogenesis
  • tissue degrading enzymes
  • lecithinase ? toxin
  • proteolytic enzymes
  • saccharolytic enzymes
  • destruction of blood vessels
  • tissue necrosis
  • anaerobic environment created
  • organism spreads

24
Without treatment death occurs within 2 days
  • effective
  • antibiotic therapy
  • debridement
  • anti-toxin
  • amputation death is rare

25
Laboratory identification
  • lecithinase production

26
Food poisoning
  • enterotoxin producing strains

27
C. botulinum
28
Botulism
  • food poisoning
  • rare
  • fatal
  • germination of spore
  • inadequately sterilized canned food
  • home
  • not an infection

29
Botulinum toxin
  • binds peripheral nerve receptors
  • acetylcholine neurotransmitter
  • inhibits nerve impulses
  • flaccid paralysis
  • death
  • respiratory
  • cardiac failure

30
Infection with C. botulinum
  • Neonatal botulism
  • uncommon
  • the predominant form of botulism
  • colonization occurs
  • no normal flora to compete
  • unlike adult

31
Wounds
  • extremely rare
  • an infection

32
Botulinum toxin
  • Bioterrorism
  • not an infection
  • resembles a chemical attack

33
Treatment
  • anti-toxin
  • antibiotic therapy (if infection)

34
C. difficile
  • After antibiotic use
  • intestinal normal flora
  • greatly decreased
  • colonization occurs
  • enterotoxin secreted
  • pseudomembanous colitis

35
Therapy
  • discontinuation of initial antibiotic (e.g.
    ampicillin)
  • specific antibiotic therapy (e.g. vancomycin)

36
PSEUDOMONAS AERUGINOSA
37
Pseudomonas
  • Aerobic
  • Gram-negative rod
  • majority of human infections
  • P. aeruginosa

38
Common in the environment
  • water
  • air
  • soil

39
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
  • .

40
Identification
  • Pigments
  • pyocyanin (blue-green)
  • fluorescein (green-yellow, fluorescent)
  • biochemical reactions
  • cultures have fruity smell

41
Pathogenesis
  • Slime layer is anti-phagocytic
  • Toxin A - ADP ribosylates EF2
  • similar to diphtheria toxin
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