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Clostridium species
Dr.Batool
General characters of Clostridium
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Their natural habitat is the soil or intestinal tract as saprophytes.
Obligate Anaerobes.
Gram positive rod shaped.
Arranged in pairs or short chains with rounded pointed ends.
Most clostridia are motile by peri-trichous flagella.
All species form endospores and have a fermentative type
of metabolism.
7- Have three important qualities:
 Multiply only in the absence of oxygen
 Have the ability to survive adverse conditions
 Release potent toxins during process of multiplying
Growth characteristics of anaerobic microorganisms are:
1- Lack of superoxide dismutase (Unable to utilize O as the final
oxygen acceptor).
2- Lack of cytochrome and cytochrome oxidase.
3- lack catalase and peroxidase
Clostridium species:
1- C. perfringens (invasive infection): cause gas gangrene; food
poisoning, bacteremia, myonecrosis.
2- C. tetani (non-invasive infection): cause tetanus.
3- C. botulinum : cause botulism (especially in canned food).
4- C. difficile : cause pseudomembranous colitis, Clostridium
difficile associated diarrhea(CDAD), Antibiotic- associated
diarrhea(ASD).
The Clostridium species can be classified in to :
1- Saccharolytic include (C. perfringens, C. septicum).
2- Proteolytic include (C. tetani ).
3- Mixed Saccharolytic and proteolytic include (C. botulinum).
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Clostridium species
Dr.Batool
Media:
o Robertson's medium (Cooked meat broth) is a special media for all
types of Clostridia.
o Nutrient agar
o Blood agar (many types of Clostridia produce a hemolysis).
o Lactose egg yolk milk agar ( undergoes stormy fermentation with
clot form by gas) with C. perfringens.
o Thioglycolate broth (transport media) necessary used for all types
of Clostridia.
C. perfringens(c.welchii)
1- Gram positive, rod-shaped and capsulated.
2- Non-motile.
3- Anaerobic.
4- Found in many environmental sources as well as in the
intestines of humans and animals. C. perfringens is commonly
found on raw meat and poultry.
5- Five types of strains ( A – E ).
6- Four lethal toxins ( Alpha, Beta, Epsilon and Iota).
7- Enterotoxin.
8- Positive Nagler‟s reaction
The Lethal Toxins:
1- Alpha-toxin (lecithinase) and Beta-toxins
 Gas gangrene -necrotizing cell membranes
 Food-borne illness
2- Epsilon-toxin
 Increases intestinal permeability causing vascular damage and
oedema in major organs
 Liver damage
 Higher blood pressure
3- Iota-toxin
 Food-borne illness
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Clostridium species
Dr.Batool
Enzymes:
Clostridium perfringens produce enzymes that digest subcutaneous
tissue and muscles.
a. DNAase
b. Hyaluronidase
c. Collagenase
Pathogenesis of C. perfringens:
1- Pathogenesis of gas gangrene :
With Invasive of vegetative cells of C. perfringens and multiple , C.
perfringens ferment of saccharide in tissue and produce gas, or ((spores
reach tissue either by contaminated of traumatized area (with soil, feces)
The distention of tissue and interference with blood supply, together with
secretion of necrotizing toxin and hyaluronidase lead to spread of
infection. Providing an opportunity for increased bacterial growth,
hemolytic anemia with severe toxemia and death.
Symptoms:
1- Gas gangrene causes very painful swelling.
2- Blisters filled with brown-red fluid
3- Drainage from the tissues, foul-smelling brown-red or bloody fluid.
4- Moderate to high fever with sweating
5- Moderate to severe pain around a skin injury
6- Pale skin color, later changing to dark red or purple.
7- Progressive swelling around a skin injury
8- Vesicle formation, combining into large blisters
Diagnosis :
A Gram stain of the wound discharge reveals gram-positive rods and
an absence of polymorphonuclear cells. Other organisms are also
present in up to 75% of cases. This test is essential for rapid diagnosis.
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Clostridium species
Dr.Batool
Treatment:
1- Surgery is needed quickly to remove dead, damaged, and infected
tissue. Or surgical removal of an arm or leg may be needed to control the
spread of infection.
2- Antibiotics (intravenously). A combination of clindamycin and
metronidazole is a good choice for patients allergic to penicillin.
Because other non-Clostridia bacteria are frequently found in gas
gangrene tissue cultures, additional antimicrobial coverage is indicated.
3- Hyperbaric oxygen for this condition, with varying degrees of success.
Prevention:
Clean any skin injury thoroughly. Watch for signs of infection (such as
redness, pain, drainage, or swelling around a wound).
2- Pathogenesis of food poisoning :
Some strain of C. perfringens produce a powerful enterotoxin, especially
when grown in meat dishes. when vegetative cells are ingested and
sporulated in the gut ,enterotoxin is formed lead to marked hyper
secretion in the jejunum and ileum, with loss of fluid and electrolytes in
diarrhea. Much less frequent symptoms include nausea, vomiting and
fever.
 Although C. perfringens may live normally in the human intestine,
illness is caused by eating food contaminated with large numbers
of C. perfringens bacteria that produce enough toxin in the
intestines to cause illness.
 What are the symptoms of clostridium perfringens?
The hallmark of Clostridium 1 ♣ food poisoning is sudden, 2 ♣ watery
diarrhea accompanied by 3 ♣ abdominal pain that may range from mild
to severe. Usually there is no fever (distinguishing it from Salmonella and
others) and no vomiting (distinguishing it from Staph and others).
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Clostridium species
Dr.Batool
 How long does clostridium perfringens last?
Symptoms usually begin 8 to 12 hours after consuming contaminated
food (sometimes 6 to 24 hours).
Diagnosis:
1- Stool culture.
2- Testing contaminated food.
Prevention:
To prevent infection, leftover cooked meat should be refrigerated
promptly and reheated thoroughly before serving.
Treatment
1- Fluids and rest
2- Antibiotics are not given.
Note : {{{ C. perfringens spores can survive high temperatures. During
cooling and holding of food at temperatures from (12°C–60°C), the
spores germinate and then the bacteria grow. The bacteria grow very
rapidly between (43°C–47°C). If the food is served without reheating to
kill the bacteria, live bacteria may be eaten. The bacteria produce a toxin
inside the intestine that causes illness.
Note : How can C. perfringens food poisoning be prevented?
To prevent the growth of C. perfringens spores that might be in food after
cooking beef, poultry, gravies, and other foods commonly associated with
C. perfringens infections should be cooked thoroughly to recommended
temperatures, and then kept at a temperature that is either warmer than
(60°C) or cooler (5°C); these temperatures prevent the growth of C.
perfringens spores that might have survived the initial cooking process.
Meat dishes should be served hot right after cooking.
Leftover foods should be refrigerated at (5°C) or below as soon as
possible and within two hours of preparation. It is okay to put hot foods
directly into the refrigerator. Large pots of food like soup or stew or large
cuts of meats like roasts or whole poultry should be divided into small
quantities for refrigeration. Foods should be covered. Leftovers should be
reheated to at least (74°C) before serving.
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Clostridium species
Dr.Batool
Foods that have dangerous bacteria in them may not taste, smell, or look
different. Any food that has been left out too long may be dangerous to
eat, even if it looks okay. }}}
Clostridium tetani
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Causative agent often tetanus (Lockjaw).
Found in soil, intestinal tracts, and feces of animals.
Small, motile.
Spore-forming (drum stick appearance);
Extremely sensitive to oxygen toxicity.
Portal of entry (by skin wound).
Virulence factors (exotoxin, neurotoxin):
1- Tetanospasmin ( is neurotoxin).
2- Tetanolysin (which causes lysis of RBCs).
Pathogenesis of Clostridium tetani:
Cl. Tetani enter  through contamination of devitalized tissue (wound, burn,
injury, umbilical stump, surgical suture, contaminated nail), Cl. Tetani is
not invasive organism, the infection remains localized in the area of entry
where the dead tissue,  the spores which germinated at the site of
entry and produce (♣ necrotic tissue, ♣ calcium salt, and ♣ associated
with pyogenic infections) all these aid establishment of low oxidationreduction potential and release of neurotoxin (Tetanospasmin )
migrates along neural paths from local wound  Tetanolysin 
Tetanospasmin (responsible for clinical manifestations of tetanus.
 An A-B toxin, released when the bacteria lyse.
Subunit A is a zinc endopeptidase that acts on CNS:  Inhibits release of an
inhibitory mediator (GABA or glycine)  which acts on postsynaptic
spinal neurons  causing spastic paralysis.
Clinical Disease :
1- Incubation period: 4-5 days.
2- convulsive tonic contraction of voluntary muscles
3- Spasms involve first the area of injury, then the muscles of the
lockjaw.
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Clostridium species
Dr.Batool
4- Other voluntary muscles become involved gradually, resulting in
generalized tonic spasms.
5- Death usually results from interference with respiration.
6- The mortality rate of generalized tetanus ~50%.
7- In more severe cases, the autonomic nervous systems are
also involved.
 Localized tetanus (confined to the musculature of primary
site of infection.
 Cephalic tetanus (site of infection: head).
 Generalized tetanus (80% prevalence in Lockjaw).
 Neonatal tetanus (infection of the umbilical wound) which lead to
mortality > 90%, and developmental defects are present in
survivors.
Diagnosis :
1- depends on the clinical picture and a history of injury.
2- Proof of isolation of C. tetani from contaminated wounds depends on
production of toxin and its neutralization by specific antitoxin.
Prevention and Treatment:
1- Prevention is much more important than treatment
a - Active immunization with toxoid.
b- (Booster shot) for previously immunized individuals.
c- This may be accompanied by antitoxin (intramuscular) injected into
a different area of the body.
d- Proper care of wounds.
e- Surgical debridement to remove the necrotic tissue.
f- Prophylactic use of antitoxin.
2- Antibiotic treatment (penicillin, clindamycin, vancomycin).
 Antibiotic may also control on pyogenic infection.
3- Patients with symptoms of tetanus should receive muscle
relaxants, sedation and assisted ventilation.
References:
1- Jawetz, Melnick, & Adelberg’s.( 2013). Medical Microbiology (Twenty-Sixth Edition).
2- Ray, C.G., ed. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill.
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