3 John F. Prescott A brief description of the main characteristics of the major clostridial pathogens of animals is given in Table 3.1. More details of these pathogens, the diseases they cause, details of their pathogenic mechanisms, details of the epidemiology of infection, and details of diagnosis of the diseases they cause are given in relevant chapters later in this book. Table 3.1 Summary of the main characteristics of the major clostridial pathogens of animals
Brief Description of Animal Pathogenic Clostridia
Species
Morphology, cultural and other characteristics
Types
Major toxin(s)
Main disease(s)
Main source(s)
Main hosts affected
C. botulinum
0.6–1.6 x 3–20 µm; spores oval, STa; colonies 2–6- mm, β-hemolytic; motile;
Geographic variation in distribution of the different types; C. botulinum is defined by production of antigenically different botulinum neurotoxins (BoNTs) encoded by mobile genetic elements, but consists of four distinct species. BoNT sequencing is identifying numerous toxin subtypes, variants; other BoNT-producing species (C. baratii, C. butyricum) can also cause botulism in humans
A
Botulinum toxin (BoNT) A
Botulism in many mammalian and avian species
Vegetables, fruit (meat, fish)
Humans, mink, chickens
B
BoNT-B
Meat, pork products. vegetables, fish
Humans, horses, cattle
Cα
BoNT-C!
Vegetation, invertebrates, carrion
Waterfowl
Cβ
BoNT-C1, D
Spoiled feed, carrion
Horses, cattle, mink humans
D
BoNT-D
Carrion, chicken manure
Cattle, sheep, chickens, horses, humans
E
BoNT-E
Raw fish, marine mammals
Humans, fish, fish-eating birds
F
BoNT-F
Meat, fish
Humans
G
BoNT-G
Soil
Humans
C. chauvoei
0.5–1.7 x 1.6–10 µm; spores oval, C to STa; colonies 0.5–3 mm, β-hemolytic; motile
–
CctA (toxin A)
Blackleg in cattle and rarely sheep
Soil, intestine, latent in muscle of healthy animals (endogenous)
Numerous animal species, especially domesticated ruminants; dogs, rabbits (not humans)
C. colinum
1 x 3–4 µm, single or pairs; spores (if any) oval, STa; colonies pinpoint–0.5 mm; most α-hemolytic; motile
–
Unknown
Ulcerative enteritis of avian species
Intestinal tract quail, chickens, grouse, partridge, pheasants, turkey
Captive bobwhite quail most susceptible; other avian species (grouse, partridge, pheasants, turkeys, other birds including pigeons) less so
C. difficile
0.5–2 x 3–17 µm; sometimes short chains; spores oval, STa; colonies 2–5 mm, circular or rhizoid, flat; motile; chartreuse green under UV light if grown on Brucella blood agar with vitamin K-hemin; para-cresol smell (of horse manure) is characteristic; CCFAb selective media effective for isolation from feces
–
TcdA, TcdB, large clostridial toxins (LCTs)
Necrotizing enterocolitis (often antibiotic-associated) in several mammalian species; pseudomembranous colitis in humans
Soil, large intestine and feces of animals, including herbivores and swine, manured soil; human and animal hospital environments; possibly fecally contaminated meats; rising rates of human and possibly animal infections associated with the epidemic strain (PFGE type NAP1, ribotype 027)
Numerous species, especially humans, animals with expanded large bowels (horses, swine, guinea-pigs, rabbits, gerbils, hamsters), but also calves, dogs, elephants, ratites, etc., especially if treated orally with broad-spectrum antibiotics
C. haemolyticum
0.6–1.6 x 2–18 µm, singly or in pairs; spores oval, STa; colonies 1–3 mm, raised to convex, gray, scalloped margin; β-hemolytic; motile
–
PLPC (beta toxin), identical to C. novyi beta toxin but produced in larger amounts
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