Streptococcus Pneumonia:

Morphology:
Shape:
The individual organism is lancet-shaped.
Arrangement:


Mostly in Pairs or sometimes in short chains.
Capsule:
Present
Motility:
Non-motile
Spore:
Non-Spore Forming.

Growth Characteristics:
1. Aerobic or facultative anaerobes.
2. Ferments glucose and produce lactic acid but not gas, Lactic acid limits its growth.
3. The optimum temperature for growth is 37-degree centigrade.
4. Growth is promoted by 5-10 % CO2.

Enzymes and Toxins Produced by Pneumococci.
1. IgA protease enhances an organism's ability to colonize mucosa of the upper respiratory tract.
2. It produces a toxin called pneumolysin. It binds to cholesterol in the host cell membrane and Inhibits antimicrobial properties of neutrophils and opsonic activity of serum. Hence it enhances the virulence of organism and organism becomes more infectious.

Habitat and Transmission.
Its normal habitat is upper respiratory tract and it transmits via respiratory droplets.

Pathogenesis and Clinical Findings.
It causes the following lesions or diseases.
1. Pneumococcal Pneumonia or Lobar pneumonia
It is characterized by an exudation of fibrinous oedema fluid into alveoli, followed by Red blood cells and leukocytes, many pneumococci are also present in alveoli. This causes consolidation of portions of lungs which can be seen in X-rays.

Clinical Findings:
a) Sudden onset of high fever with violent shaking chills,
b) Sharp pleural pain and friction rub.
c) Cough, at first dry or productive of thin watery sputum, later sputum becomes bloody or rusty.
d) Spontaneous recovery occurs between 5th and 10th days, associated with the development of type-specific development of antibodies.

2. Bacteremia and Its Complications.
Bacteremia means the presence of bacteria in the blood. From alveolar exudate organisms reach bloodstream via lymphatics and cause bacteremia, which has a triad of serious complications:
that is
a) Meningitis
b) Endocarditis
c) Septic arthritis.
Other complications include; Sinusitis, otitis media, pericarditis, Empyema and septicemia.
3. Meningitis:
Pneumococcus is the second common bacterial pathogen that causes meningitis in adults.
Pathogenesis.
a) It may arise as a complication of pneumonia, in which pneumococci reach the meninges by way of the bloodstream.
b) It may result from a skull fracture permitting pneumococci from the nasopharynx to enter the meninges.

Otitis Media.
It is responsible for 50 % of cases of otitis media in children.

Immunity:
Type-specific immunity to re-infection with pneumococci develops. It is due to type specific anticapsular antibodies.

Treatment.
Augmentin (amoxicillin + clavulanic acid) is a drug of choice.
alternative drugs are.
1. Erythromycin
2. Cephalothin
3. Chloramphenicol (for pneumococcal meningitis.)

Laboratory Diagnosis Of Streptococcus Pneumoniae