Neisseria Gonorrhoeae Disease

Neisseria Gonorrhoeae Disease

Neisseria gonorrhoeae (Gonococci)

Neisseria gonorrhoeae
Neisseria gonorrhoeae

Neisseria gonorrhoeae is a venereal disease

1. Morphological characters

  • They are gram negative,non-sporeforming diplococci with concave adjacent side.
  • It appear like a shape of a kidney.
  • It contains pili that provide adhesion to mucosal surface and inhibit phagocytosis.

2. Cultural characters

  • These gonococci cells grow aerobically as well as anaerobically.
  • These organism can grow on selective media like Chocolate agar, Mueller-Hinton and Thayer Martin medium.
  • The optimum temperature for its growth is 36° C and it reguires a pH range of 7.2 to 7.6.
  • After incubation the colonies appear small, convex and translucent.

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Disease caused by Neisseria meningitidis

 Neisseria meningitidis.


  • It is a gram negative, non-motile cocci arranged in pairs called as diplococci.
  • Neisseria are aerobic, non-sporulating, oxidase positive cocci.
  • Neisseria meningitidis causes cerebrospinal fever that is Meningococcal meningitis.
Neisseria meningitidis
Neisseria meningitidis

1. Morphological characters

  • They are gram negative,spherical shape cocci with flattened adjacent side.
  • Its size ranges from 0.6-0.8 micrometer.
  • Its size,shape and staining properties changes as the incubation period increases.
  • Fresh culture cells are capsulated and as the culture becomes old its capsule disappears.

2. Cultural characters

  • Meningococci requires enriched media for its growth.
  • The growth media should be enriched with blood or serum.
  • Selective media like blood agar, chocolate agar, Mueller-Hinton starch casein agar are commonly used.
  • The optimum temperature required for its growth is 36°C and optimum pH is 7.5-7.6
  • The colonies are small in size bluish grey coloured and convex in elevation.

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Disease caused by Streptococcus pneumoniae

Disease caused by Streptococcus pneumoniae

The Streptococcus pneumoniae is gram-positive lancet shape bacteria. It may be diplococcus or streptococcus. Pneumococcus is non-motile, non-spore forming capsulated bacteria. They may be aerobic or facultative anaerobic in nature. They are a normal inhabitant of human respiratory tract Pneumococcus bacteria may be an important cause of pneumonia, otitis, sinusitis, bronchitis, meningitis and other infection like arthritis, conjunctivitis and suppurative lesions.

Streptococcus pneumoniae
Streptococcus pneumoniae

1. Morphology

  • Pneumococci are lancet shape with one end broad or rounded and other end pointed
  • If they occur in pair called as diplococci.
  • They are smaller than 1 micrometre in size.
  • The capsule enclose each pair of cells. These capsules can be made visible by using capsule staining method.
  • These cells are readily stained by gram staining procedure.

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Medical Microbiology

Medical Microbiology

Medical microbiology is a branch of science that deals with the study of of pathogenic micro-organisms and is concern with disease, diagnosis ,prevention, control and treatment.

Diseases caused by micro-organisms

  • Staphylococcus aureus
    Staphylococcus aureus
    Staphylococcus aureus

1. Morophology

  • Staphylococcus aureus are gram-positive spherical cocci approximately 1 micrometer in diameter.These cells may be arranged in singly,in pairs,shorts chains or in clusters.
  • They are non-spore forming, non-motile.They may be capsulated or non-capsulated.
  • Under influence of some chemicals the cocci form may change into L-forms.

2. Cultural characters

Staphylococcus aureus  colonies on blood agar showing zone of heamolysis.
Staphylococcus aureus colonies on blood agar showing zone of heamolysis.
  • Staphylococcus aureus may readily grow in ordinary media.It can grow on Nutrient agar, MacConkey’s agar.
  • It grow on temperature range of 10° C  to 42° C and optimum temperature for its growth is 37° C
  • Optimum pH is 7.3-7.6.
  • They may be aerobic or facultative anaerobic in nature.
  • The colonies are 2-4 mm in diameter,circular in shapes ,convex and shiny .
  • These organisms are golden yellow pigment producing organism.These pigment production occurs in aerobic cultures at optimum pH at 22°C.
  • Most of the strains of Staphylococcus  aureus show heamolytic activity on blood agar.
  • The Staphylococcus aureus show pink coloured colony due to lactose fermentation on MacConkey’s agar.

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Introduction to Microbiology

Taxonomic Differentiation of Microbes

Definition of Microbiology

It is a branch of science that deals with the study of microscopic forms of life these micro-organisms are less than 1 mm in size.

Characteristics of Micro-organisms 

  • These micro-organisms are very small in size generally less than 1 mm.
  • They are not visible through our naked eyes.
  • These organisms are either unicellular or multicellular.
  • Prokaryotic or eukaryotic in nature.
  • They may be motile or non motile.
  • Micro-organisms are present everywhere in our surrounding like air, water,soil, dust and bodies of plants, animals and human beings.

Taxonomic Differentiation of Micro-organisms


Taxonomic Differentiation of Microbes
Taxonomic Differentiation of Microbes


1. Protozoa

  •  Protozoa are unicellular, eukaryotic in nature.
  •  They are parasitic or saprophytic.
  •  The size range of protozoa is generally 10 – 50 micrometer.
  •  These organisms generally exist in aqueous environment and soil.
  •  They show motility by flagella, cilia, or pseudopodia.
  • Protozoa can absorbs their food material by cell membrane or by engulfing the food by phagocytosis.
  • Some parasites are pathogenic in nature .They can reproduce sexually or asexually.

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