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  1. Gram positive, anaerobic, spore forming
  2. Pathogens normally found in intestinal tract
  3. Cl welchii, Cl tetani, Cl ramosum
A. Location of spores
  1. Cl. bifermentans-central
  2. Cl welchii ( perfringens) –subterminal;
  3. Cl tetani, Cl tetanomorphum, Cl sporogenes – spherical & terminal
  4. Cl tertium, Cl difficile, Cl cochlearum-oval and terminal
  5. Motility - ‘stately’; non motile: Cl welchi, Cl tetani Type VI
  6. Obligate anaerobe – Cl oedamatiens(novyi), Cl tetani, Cl botulinum;
  7. Aerotolerant – Cl histolyticum, Cl perfringens
  8. Culture media – RCM
  9. Pathogenic clostridia produced powerful exotoxins
B. Classification :
  1. Tetanus- Cl tetani
  2. Gas gangrene Cl perfringens (type A)
    a. Cl septicum, Cl novyi (Cl oedematiens)
    b. Cl histolyticum, Cl sordelii,
  3. Food poisoning-
    a.  Gastroenteritis-Cl perfringens (Type A)
    b.  Necrotizing enteritis-Cl perfringens (Type C)
    c.   Botulism- Cl botulinum
Regarding clostridium perfringens gas gangrene false is? (AIIMS Nov 2010)
A. Clostridium perfringens is the most common cause of gas gangrene             
B. Naegler reaction positive
C. Most important toxin is hyaluronidase
D. Food poisoning strain of clostridium perfringens produces heat resistant spores. 

Ans - C.

C.  perfringens (C. welchii)
  1. Most important cause of gas gangrene
  2. Spores rarely seen in culture or lesion
  3. Microaerophilic, thermophilic (450C)
  4. ‘Stormy fermentation’ in litmus milk test
  5. Five types (A-E) based on four major toxins (a, ß, e[epsilon], ?[iota])
  6. Minor toxins (?, d, ?, ?, ?[neta], ?[theta], ?[eta])
  7. Target hemolysis: narrow complete hemolysis (theta toxin) surrounded by wide zone of alpha hemolysis (alpha toxin)
  8. Selective medium : Neomycin blood agar
  9. Alpha toxin-Produced by all types; Most important biologically; Responsible for gas gangrene
  10. Phospholipase/Lecithinase (Nagler’s reaction for detection)
  11. Responsible for intravascular hemolysis
  12. Pathogenicity
  13. Gas gangrene: type A. Upto 60% gas gangrene cases (commonest).
  14. Food poisoning: Type A1 & A2, enterotoxin (similar to cholera and EPEC), formed in gut; cold or warmed up meat dish, self limited. Incubation period: 8-16 hours (infective-toxic type)
  15. Necrotizing enteritis (pig-bel): type C
D. Cl septicum
  1. ‘Citron bodies’: boat or leaf shaped pleomorphic bacilli with irregular staining
E.  Cl tetani-
normally present in soil and GIT of humans and animals
  1. Drumstick appearance
  2. Obligate anaerobe. 6 serotypes-I to VI
  3. Swarming-Filde’s technique to isolate
  4. Fir tree appearance
  5. Two exotoxins
    a. Tetanolysin: hemolysis, heat labile, oxygen labile, no role in tetanus
    b. Tetanospasmin: Neurotoxin, oxygen stable, antigenic, blocks presynaptic inhibition by selective cleavage of a protein component of synaptic vesicles, synaptobrevin II, and this prevents the release of neurotransmitters by the cells. Toxin binds to gangliosides.
  6. Horses most susceptible, birds and reptiles highly resistant.
  7. Tetanus is more common in developing countries where the climate is warm and in rural areas where soil is fertile and highly cultivated.
Not true about Clostridium tetani? AIIMS Nov 2010
A. It is dormant and present in soil and man and   animal intestine   
B. It is transmitted through infected wounds
C. It occurs more in winter and dry season                               
D.  Head immunity does not contribute

Ans- C.
F.  Cl botulinum-obligate anaerobe, subterminal spores, peritrichous flagella
  1. Widely distributed saprophyte, therefore demonstration of toxin essential
  2. Divided into 8 types (A to G) based on the antigenic differences in the toxins produced. Most strains produce more than one type of toxin
    Types A,B & E most frequently associated with human disease but all types can cause human disease
  3. Toxin-Not released during the life of bacterium
  4. Protoxin; proteolysed to the active form; all are neurotoxins except C2 which is enterotoxic
  5. Most potent toxin
  6. Heat stable
  7. Blocks release of Acetylcholine at neuromuscular junctions presynaptically and parasympathetic post ganglionic terminals
  8. Determined by bacteriophage-toxin C and D
  9. Botulism : food borne due to preformed toxin in preserved contaminated foods, infant (floppy child syndrome) due to ingestion of honey contaminated with spores, wound (esp in IVDU’s); diplopia, dysphagia,dysarthria, symmetric descending paralysis; no diarrhea
    Other spp. which can cause botulism-Cl baratii, Cl butyricum
G. Cl difficile motile, terminal oval spores
  1. Antibiotic associated colitis and Pseudomembranous enterocolitis
  2. Associated with oral antibiotics like Clindamycin
  3. Toxin A : enterotoxin – diarrhea
  4. Toxin B : Cytotoxin – CPE in Hep 2 and HDCC
  5. Diagnosis – Microscopy, culture, tissue culture, ELISA in stool for toxin detection A and B.
  6. Treatment: metronidazole, vancomycin

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