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1
NON-CLOSTRIDIAL ANAEROBIC INFECTION
Judit Szabó
Medical Microbiology
Endogenous and exogenous anaerobic
infections
Two sources:
normal human flora • endogenous
–environment (e.g. soil) • exogenous
Source of spore-formingand non-spore forming
• Spore-forming (Clostridia) – exotoxins– common in the environment (e.g. soil)
• Non spore-forming– no exotoxins – mostly members of the normal flora
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
Sites of anaerobes in normal flora
• intestine (Bacteroides fragilis)– major site– 95-99% total bacterial mass
• mouth (Prevotella, Porphyromonas)• genitourinary tract (Lactobacilli)• skin (Propinonibacterium)
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Non spore-forming anaerobic bacteria
Gram-negative rods: BacteroidesFusobacterium, Porphyromonas, PrevotellaGram-positive rods: Actinomyces,
Bifidobacterium, Eubacterium, Lactobacillus, Mobiluncus, Propionibacterium
Gram-negative cocci:Veillonella
Gram-positive cocci: Peptostreptococcus,Peptococcus
Bacteroides fragilis
Prominent capsule– anti-phagocytic– abscess formation
Endotoxin – low toxicity– structure different than other LPS
Non spore-forming anaerobic infection
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Parodontitis
Aspiration abscess Liver abscess
Peritonsillar abscess Mastoiditis
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Diabetic foot Actinomycosis
• chronic infection• commonly of the face and neck• produces abscesses and open
draining sinuses • by trauma, surgery, or infection
(dental abscess or oral surgery). • breaks through the skin surface to
produce a draining sinus tract.
Symptomes of actinomycosis
• a swelling or hard, red-to-reddish-purple lump on the face or upper neck
• fever • weight loss • pain is minimal to absent • draining sores in the skin, particularly
those on the chest wall resulting from lung infection with Actinomyces
Actinomycosis on the chest Oral actinomycosis
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Facial actinomycosis Lung actinomycosis
Diagnosis of actinomycosis
• "sulfur granules" in the fluid (histological diagnosis)
• microscope: Gram-positive rods• culture (slow, difficult)
Microscopical picture of actinomyces spp.
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Actinomyces israelii on anaerobic blood agar
Differential diagnosis
Treatment of actinomycosis
The treatment is long-term, with 1- 2months of penicillin iv., followedpenicillin per os.
Surgical drainage of the lesion may berequired.
Bacterial vaginosis
•
Lactobacilli Clue cells
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Treatment of bacterial vaginosis
• Metronidazol
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
• Culture (5-7 days) in anaerobic chamber or GasPak system
• Biochemical kits– e.g. API system
• Gas chromatography– volatile fermentation products
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Determination of antibiotic sensitivity
• Detection of MIC by E-test or microdilution
• Disk diffusion test (Kirby-Bauer) is not correct
The principles of therapy
• To improve vascular perfusion by correcting fluid and electrolyte deficits
• To combat the effects of bacteria and their toxic metabolites
• To eliminate the primary source of infection by means of excision, closure or isolation
• To aspirate infected exudate and to drain the site of the primary lesion
• To treat local or distant complications as necessary
Primary resistance
Anaerobes are resistant to cephalosporins and aminoglycosides!
Treatment of the anaerobic infections
Empirical therapy:• Gram-negative: metronidazole• Gram-positive: clindamycin
Other anti-anaerobical drugs:-imipenem, piperacillin+tazobactam,
amoxicillin+clavulanic acid, moxifloxacin