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)
3KEY 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
4Obligate (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)
-
5Polymicrobic 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
6Polymicrobic anaerobic infection
- Simultaneous infection with facultative
anaerobe - diminishes O2 supply further
- aids growth of obligate anaerobes
7Endogenous versus exogenous infection
- Two sources
- normal human flora
- endogenous
- environment (e.g. soil)
- exogenous
8Source 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
9Sites of anaerobes in normal flora
- intestine
- major site
- 95-99, total bacterial mass
- mouth
- genitourinary tract
10Bacteroides 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
-
- .
12Strict anaerobe infectious disease
- Sites throughout body
- Muscle, cutaneous/sub-cutaneous necrosis
- abscesses
13Problems 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
14LABORATORY IDENTIFICATION
- BIOCHEMICAL KITS
- e.g. API SYSTEM
- GAS CHROMATOGRAPHY
- volatile fermentation products
15ANAEROBIC 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
16Bacteroides fragilis
- Major disease causing strict anaerobic
- non-spore-former
- Prominent capsule
- anti-phagocytic
- abscess formation
- Endotoxin
- low toxicity
- structure different than other
lipolysaccharide
17ANAEROBIC SPORE-FORMERS (CLOSTRIDIA)
- Gram-positive rods
- human intestine
- soil
18A severe case of tetanus. muscles, back and
legs are rigid muscle spasms can break bones
can be fatal (e.g respiratory falure)
19Clostridium tetani
20Tetanospasmin
- 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
21Vaccination
- infant
- DPT (diptheria, pertussis, tetanus)
- tetanus extremely uncommon in US.
- tetanus toxoid
- antigenic
- no exotoxic activity
22C. perfringens
- soil, fecal contamination
- war
- gas gangrene
- swelling of tissues
- gas release
- fermentation products
- wound contamination
-
23Pathogenesis
- tissue degrading enzymes
- lecithinase ? toxin
- proteolytic enzymes
- saccharolytic enzymes
- destruction of blood vessels
- tissue necrosis
- anaerobic environment created
- organism spreads
24Without treatment death occurs within 2 days
- effective
- antibiotic therapy
- debridement
- anti-toxin
- amputation death is rare
25Laboratory identification
26Food poisoning
- enterotoxin producing strains
27C. botulinum
28Botulism
- food poisoning
- rare
- fatal
- germination of spore
- inadequately sterilized canned food
- home
- not an infection
29Botulinum toxin
- binds peripheral nerve receptors
- acetylcholine neurotransmitter
- inhibits nerve impulses
- flaccid paralysis
- death
- respiratory
- cardiac failure
30Infection with C. botulinum
- Neonatal botulism
- uncommon
- the predominant form of botulism
- colonization occurs
- no normal flora to compete
- unlike adult
31Wounds
- extremely rare
- an infection
32Botulinum toxin
- Bioterrorism
- not an infection
- resembles a chemical attack
33Treatment
- anti-toxin
- antibiotic therapy (if infection)
34C. difficile
- After antibiotic use
- intestinal normal flora
- greatly decreased
- colonization occurs
- enterotoxin secreted
- pseudomembanous colitis
35Therapy
- discontinuation of initial antibiotic (e.g.
ampicillin) - specific antibiotic therapy (e.g. vancomycin)
36 PSEUDOMONAS AERUGINOSA
37Pseudomonas
- Aerobic
- Gram-negative rod
- majority of human infections
- P. aeruginosa
38Common in the environment
39P. 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
- .
40Identification
- Pigments
- pyocyanin (blue-green)
- fluorescein (green-yellow, fluorescent)
- biochemical reactions
- cultures have fruity smell
41Pathogenesis
- Slime layer is anti-phagocytic
- Toxin A - ADP ribosylates EF2
- similar to diphtheria toxin