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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

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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