Morphology & Culture Characteristics of Clostridium tetani
   

MORPHOLOGY AND CULTURE CHARACTERISTICS OF CLOSTRIDIUM TETANI

MORPHOLOGY OF CLOSTRIDIUM TETANI

ShapeClostridium tetani is a slender, rod shape (bacillus) bacterium with a characteristic drumstick appearance due to the presence of spores.

Size – The size of Clostridium tetani is about 4–8 µm × 0.5 µm (micrometer).

Arrangement Of CellsClostridium tetani is arranged singly, in pairs or in short chains. They are pleomorphic organisms.



MotilityClostridium tetani is a motile bacterium.

FlagellaClostridium tetani is a flagellated bacterium with Peritrichate flagella arrangement.

Spores – The Round, terminal & Bulging spores are present in C. tetani giving the bacterium a characteristic drumstick shape appearance when examined under the microscope.

CapsuleC. tetani is a capsulated bacterium. The capsule can easily be demonstrated using India ink preparation, appear as a clear halo in a dark background.

Gram Staining Reaction – Clostridium tetani is a Gram +ve (Positive) bacterium.

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CULTURE REQUIREMENTS OF CLOSTRIDIUM TETANI

Special requirements – Unlike C. perfringens, Clostridium tetani have no complex nutritional requirements and readily grow in an ordinary medium like NAM. Also, it grows well in the media containing Blood or Serum, commonly Blood Agar medium & Robertson Cooked meat broth medium is used for the cultivation of Clostridium tetani in Laboratory.

 Optimum temperatureClostridium tetani range from 14 –43°C as per the strain, usually grown at 33–37°C in laboratories.

⇒ Optimum pH – 7.4 – 7.6

clostridium tetani on blood agar - morphology of clostridium tetani - culture characteristics of clostridium tetani - morphology & culture characters of clostridium tetani

⇒ Oxygen requirementsClostridium tetani is an obligate anaerobic bacterium i.e. can only grow in the absence of oxygen (Strict anaerobe).

⇒ There are various culture media used for the cultivation of C. tetani in the laboratory and most commonly the Sheep Blood Agar medium and CMB medium is used, the other media are as follows:-

  • Nutrient Agar medium
  • Columbia Horse Blood Agar medium
  • MacConkey Agar medium
  • The liquid medium (Nutrient Broth medium, TSB medium, etc.).

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CULTURE CHARACTERISTICS OF CLOSTRIDIUM TETANI



Cultural CharacteristicsStiff Sheep Blood Agar Medium (3% Agar)Nutrient Agar medium (NAM)MacConkey Agar medium (MAC)
ShapeIrregularIrregularIrregular
Size0.5-1 mmSwarming growth0.5-1 mm
ElevationSlightly raisedFlatSlightly raised
ColorGreyColorless – whiteGreenish fluorescence
SurfaceRoughSwarming growth spread throughout the plate with rough surfaceRough
StructureTranslucent –OpaqueTransparent - TranslucentTranslucent –Opaque
HemolysisAlpha hemolysis initially, followed by beta - hemolysis----------

In Sheep’s Blood Agar medium with normal agar content (1.5%), the growth of Clostridium tetani appears as swarming layer over the surface of the medium. By increasing the content of agar in the medium to 3%, prevents the swarming and individual colonies of the bacterium appear on the Medium. Initially, it shows the alpha hemolytic colonies followed by the beta hemolysis which is due to the action of tetanolysin (a hemolysin toxin produced by C. tetani)

clostridium tetani on stiff blood agar medium - clostridium tetani on 3% blood agar medium
CLOSTRIDIUM TETANI CULTURE ON SHEEP’S BLOOD AGAR MEDIUM CONTAINING 3% AGAR

Similarly, in Nutrient agar medium the growth of Clostridium tetani appears as a swarming layer throughout the medium, the layer is so thin and transparent that it is difficult to observe via naked eyes unless you are an experienced microbiologist.

CLOSTRIDIUM TETANI ON BLOOD AGAR MEDIUM - CLOSTRIDIUM TETANI ON REGULAR BLOOD AGAR MEDIUM 1.5% AGAR
CLOSTRIDIUM TETANI CULTURE ON SHEEP BLOOD AGAR MEDIUM CONTAINING 1.5% AGAR (SWARMING)

In Roberson’s cooked meat broth medium, C. tetani grow well, produce turbidity and the meat is not digested but may turn Black especially on prolonged incubation. It also produces gas and turns pH of the medium Acidic.

In liquid culture media like Trypticase soy broth or Nutrient broth, the growth of the bacterium occurs as a turbidity in the broth medium, which is further analyzed for the morphology (under the microscope), gram reaction, biochemical tests, and Clostridium tetani specific tests.

Moreover, a different technique which is specific for the cultivation of anaerobic microorganisms is employed for the isolation of Clostridium tetani, known as the Deep agar Shake Culture in which the specimen is inoculated by shaking in freshly prepared agar medium before it solidifies. The Clostridium tetani colonies appear as spherical fluffy balls, 1-3 mm (diameter), filamentous with the radial arrangement in the medium.

THAT’S ALL ABOUT THE MORPHOLOGY AND CULTURE CHARACTERISTICS OF CLOSTRIDIUM TETANI



Further Reading:

Clostridium tetani – Antimicrobe

C. tetani – Textbook of microbiology

Clostridium tetani – Wikipedia

C. tetani – Microbewiki

Clostridium tetani – Veterian key

SAHIL BATRA

Hi, I'm the Founder and Developer of Paramedics World, a blog truly devoted to Paramedics. I am a Medical Lab Tech, a Web Developer and Bibliophiliac. My greatest hobby is to teach and motivate other peoples to do whatever they wanna do in life.

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