Gas-gangrene clostridia Flashcards

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1
Q

General features and habitat of Clostridium perfringens

A
Gram +
Rod shape (large)
Habitat- soil (can be even found in human normal intestinal flora)
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2
Q

Biochemical Properties of Clostridium perfringens

A

Obligate anaerobe (to distinguish from Bacillus species)

Spore forming (found in dirt and soil)- oval spores are centrally located

Lecithinase positive (+)

Gas producer- CO2, H2S, CH4

Capsule

Enzymes for invasion- collagenase, hyaluronidase, DNase, lipase, protease

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3
Q

Pathogenesis of Clostridium perfringens

A

Transmitted by food or trauma infections (associated with military and accidents)

Classified by Types A, B, C, D and E based on the toxins compositions

Spores germinate under anaerobic conditions in tissue (incubation of 1-3 days)

The vegetative cells produce alpha toxin (phospholipase C, which is lecithinase)

The toxin disrupts the phospholipid bilayer of the cell

This damage RBC, platelets, WBC and endothelial cells

Eventually leading to massive hemolysis, tissue destruction and hepatic toxicity

Beta toxin- necrotizing activity (when ingested, affects the intestine)

enterotoxin - produced in intestines, increase vascular permeability of GI

Iota toxin- increase vascular permeability of GI and necrotizing activity

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4
Q

Clinical Features of Clostridium perfringens

A

Gas gangrene (A.K.A clostridial myonecrosis)- contaminated wound with soil or feces.
Acute, increasing pain at wound site, tense tissue (by edema, from gas) and necrosis.
Systemic symptoms include: Fever, tachycardia, diaphoresis, pallor; rapid, high mortality if untreated

Food poisoning- reheated meat dishes, spores are ingested and grow to high number
Slow onset of 8-24 hour (incubation time for spore to germinate).
Enterotoxin production in gut causes self-limiting non-inflammatory, watery diarrhea
symptoms: watery diarrhea with abdominal cramps; self-limiting (after around 24 hours).

By sporulation, this organism can survive high temperatures during initial cooking; the spores germinate during cooling of the food, and vegetative forms of the organism multiply if the food is subsequently held at temperatures of 16-52C. If served without adequate reheating, live vegetative forms of C. perfringens may be ingested. The bacteria then elaborate the enterotoxin.

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5
Q

Diagnosis of Clostridium perfringens

A

Specimens- pus, necrotic tissue and blood

Double hemolysis zone alpha and beta on blood agar

Nagler’s medium- egg yolk plate with anti-alpha toxin, shows lecithinase activity

Enterotoxin detection- from fecal sample

Cultivation- greater than or equal to 105 organisms per gram of epidemiologically implicated food

An alternate criterion is that cultures of stool samples from persons affected yield greater than or equal to 106 colonies per gram

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6
Q

Treatment of Clostridium perfringens

A

Penicillin G- high dose is required

Amputation or hyperbaric chamber if gangrene; diarrhea is usually self-limiting

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7
Q

Prevention of Clostridium perfringens

A

Surgical management of wound to prevent anaerobic condition for bacteria

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8
Q

Other Gas Gangrene Clostridia

A

C.novyi
C.septicum
C.histolyticum
C.sordellii

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9
Q

C.novyi

A

General features: motile with peritrichous flagella

Three types based on the toxin produced: A, B (pathogenic) and C (non-pathogenic)

Virulence factors: α, β, δ, ε toxins with haemolytic (necrotic activity), phospholipases and lipases

Clinical feature: toxemia

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10
Q

C.septicum

A

General features: motile with peritrichous flagella

Associated with colon tumor

Virulence factors: α-toxin with necrotic and hemolytic activity

Diagnosis: from blood culture

Clinical feature: necrotizing fasciitis

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11
Q

C.histolyticum

A

Gas gangrene associated mostly with other bacteria

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12
Q

C.sordellii

A

Most often associated with gynecological infections

Can cause bacteremia, sepsis and even severe toxic shock syndrome

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