Gas-gangrene clostridia Flashcards
General features and habitat of Clostridium perfringens
Gram + Rod shape (large) Habitat- soil (can be even found in human normal intestinal flora)
Biochemical Properties of Clostridium perfringens
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
Pathogenesis of Clostridium perfringens
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
Clinical Features of Clostridium perfringens
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.
Diagnosis of Clostridium perfringens
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
Treatment of Clostridium perfringens
Penicillin G- high dose is required
Amputation or hyperbaric chamber if gangrene; diarrhea is usually self-limiting
Prevention of Clostridium perfringens
Surgical management of wound to prevent anaerobic condition for bacteria
Other Gas Gangrene Clostridia
C.novyi
C.septicum
C.histolyticum
C.sordellii
C.novyi
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
C.septicum
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
C.histolyticum
Gas gangrene associated mostly with other bacteria
C.sordellii
Most often associated with gynecological infections
Can cause bacteremia, sepsis and even severe toxic shock syndrome
