MORPHOLOGY OF NEISSERIA GONORRHOEAE (GONOCOCCUS)
Shape – Neisseria gonorrhoeae is an oval or spherical (coccus) shape bacterium with the adjacent side Concave.
Size – The size of Neisseria gonorrhoeae is about 0.6 – 1.0 µm (micrometer) in diameter.
Arrangement Of Cells – Neisseria gonorrhoeae is arranged in singly or in pairs (diplococci), with the adjacent side Concave and they are usually present intracellularly when direct microscopic examination of the specimen from the lesions is carried out.
Motility – Neisseria gonorrhoeae is a Non-motile bacterium.
Flagella – Neisseria gonorrhoeae is a Non-flagellated bacterium, fimbriae may present.
Spores – Neisseria gonorrhoeae is a Non-sporing Bacterium
Capsule – N. gonorrhoeae is a capsulated bacterium and is present in such a way that a capsule encloses each pair of cocci. The capsule can easily be demonstrated using India ink preparation, which appear as a clear halo in a dark background. Moreover, the presence of capsule depends on the origin of the specimen as the specimen taken from the carrier may or may not contains encapsulated N. gonorrhoeae whereas the sample isolated from Urethral or Vaginal discharge or from blood usually contains encapsulated N. gonorrhoeae.
Gram Staining Reaction – Neisseria gonorrhoeae is a Gram –ve (Negative) bacterium.
CULTURE REQUIREMENTS OF NEISSERIA GONORRHOEAE (GONOCOCCUS)
⇒ Special requirements – It is quite difficult to grow it in the laboratory as compared to N. meningitidis however, Gonococci or Neisseria gonorrhoeae have complex nutritional requirements and readily grow in a media containing Blood or Serum, commonly Blood Agar medium, Chocolate Agar medium & Mueller Hinton Agar medium is used for the cultivation of Neisseria gonorrhoeae in Laboratory.
⇒ Optimum temperature – Neisseria gonorrhoeae grows best at 35 –36°C
⇒ Optimum pH – The pH requirement of N. gonorrhoeae ranges from 5.8 – 8.0 but the maximum growth in the laboratory is observed at 7.0 – 7.2.
⇒ Oxygen requirements – N. gonorrhoeae is an Aerobic bacterium i.e. can grow in the presence of oxygen as well as anaerobic organism i.e. can grow in the absence of oxygen.
⇒ It requires a moist environment with a 5 – 10% CO2 for the growth in the laboratory.
⇒ There are various culture media used for the cultivation of N. gonorrhoeae (Gonococcus) in the laboratory and most commonly the Blood Agar and MHA medium is used, the other media are as follows –
- Sheep Blood Agar medium
- Columbia Horse Blood Agar medium
- Chocolate agar medium
- Thayer Martin medium with Antibiotics Vancomycin, Colistin, and Nystatin (selective medium)
- Modified Thayer Martin medium with Antibiotics Vancomycin, Colistin, Nystatin & Trimethoprim (selective medium)
- Martin – Lewis medium (selective medium)
- New York city medium (selective medium)
- The liquid medium (Glucose Broth medium, TSB medium, Peptone water, etc.)
⇒ The Thayer Martin medium which is a Selective medium for Neisseria gonorrhoeae can be prepared by incorporating Antibiotics and Nutrients in Thayer Martin Agar base or in GC Agar base medium for the growth of Neisseria gonorrhoeae (Gonococcus).
⇒ Similarly, the New York City medium which is also a selective medium for Neisseria gonorrhoeae can be prepared by incorporating Antibiotics and Supplementary nutrients in the NYC Agar Base medium for the Growth of Neisseria gonorrhoeae (Meningococcus)
CULTURE CHARACTERISTICS OF NEISSERIA GONORRHOEAE (GONOCOCCUS)
|Culture Characters||Blood Agar Medium (BAM)||Thayer Martin Medium||New York City Medium||Chocolate Agar Medium (CAM)
|Shape||Circular or Round||Circular or Round||Circular or Round||Circular or Round|
|Size||1-2 mm||1-3 mm||1 -2 mm||1 -2 mm|
|Elevation||Convex or slightly Umbonate||Convex or slightly Umbonate||Convex or slightly Umbonate||Convex or slightly Umbonate|
|Surface||Finely granular or smooth (s per the strain)||Finely granular or smooth (s per the strain)||Finely granular or smooth (s per the strain)||Finely granular or smooth (s per the strain)|
|Color||Grey||Colorless to Grey||Colorless to Grey||Colorless to Grey|
|Structure||Opaque||Transparent or Opaque||Transparent or Opaque||Opaque|
|Hemolysis||γ – Hemolysis (No hemolysis)||γ – Hemolysis (No hemolysis)||γ – Hemolysis (No hemolysis)||γ – Hemolysis (No hemolysis)|
There is much variation in the colony morphology of Neisseria gonorrhoeae which are divided into 4 types as T1 to T4 which are described as follows:
|Size||Small (1-2 mm)||Small (1-2 mm)||Large (2-4 mm)||Large (2-4 mm)|
|Color||Brown||Brown||Usually Colorless||Usually Colorless|
|Auto agglutination||Auto agglutinable||Auto agglutinable||Non- Auto agglutinable||Non- Auto agglutinable|
|Virulence||Highly virulent||Highly virulent||Avirulent||Avirulent|
|Pigmentation||Present||Present||Non – Pigmented||Non – Pigmented|
|Commonly known as||P+||P++||P-||P-|
In liquid culture media like peptone water and TS broth, the growth of the bacterium occurs as Granular turbidity in the broth medium which is further analyzed for the morphology (under the microscope), gram reaction, biochemical tests, and Neisseria gonorrhoeae specific tests.
In Blood Agar medium, the colonies of the Neisseria gonorrhoeae are small, grayish in color and show γ – Hemolysis i.e. N. gonorrhoeae produce Non-Hemolytic colonies.
Similarly, on chocolate agar medium, N. gonorrhoeae grows well, producing small translucent colonies.
In Modified Thayer Martin medium, the colonies of Neisseria gonorrhoeae are small, grayish and Granular with slight umbonation.
In New York City medium, Neisseria gonorrhoeae grow well and produce circular, convex, grayish or colorless colonies usually.
That’s all about the Morphology & Culture characteristics of Neisseria gonorrhoeae