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Laboratory diagnosismicrobiology

Streptococcus Pneumonia, Clinical Findings-Lab Diagnosis-Treatment.



pneumonia-examination
Streptococcus Pneumonia:

Morphology:
Shape:
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. 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 organism's ability to colonize mucosa of upper respiratory tract.
2. It produces a toxin called pneumolysin. It binds to cholesterol in host cell membrane and Inhibit antimicrobial properties of neutrophills 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 following lesions or diseases.
1. Pneumococcal Pneumonia or Lobar pneumonia
It is characterized by exudation of fibrinous edema fluid in to 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 development of type-specific development of antibodies.

2. Bacteremia and Its Complications.
Bacteremia means presence of bacteria in blood. From alveolar exudate organisms reach bloodstream via lymphatics and cause bacteremia, which have a triad of serious complications:
that is
a) Meningitis
b) Endocarditis
c) Septic arthritis.
Other complications include; Sinusitis, otitis media, pericarditis, Empyema adn 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 blood stream.
b) It may result from a skull fracture permitting pneumococci from nasopharynx to enter the meninges.

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

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

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

Laboratory Diagnosis Of Streptococcus Pneumoniae

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