pneumonia is an infection in the lungs caused by bacteria called
(also called pneumococcus ). Streptococcus pneumoniae is a Gram-positive
coccus that may be found in pairs or in short chains.
involves large portion of a lobe or an entire lobe of the lung .
pneumonia is of diminishing
significance because of prompt response to treatment, it is still a significant illness in industrialized nations.
non-industrialized world it is still a major cause of mortality.
It is commonly a disease of healthy young
to middle-aged adults, is rare in infants, and the elderly, and is
considerably more common in men than in women.
Alcoholics appear to be particularly
It can infect the
upper respiratory tracts of adults and children and can spread to the
blood, lungs, middle ear, or nervous system.
Pneumococcal pneumonia is commonly seen in
young adults after exposure to cold or after previous respiratory
It typically follows a viral infection, often
The onset of the
disease is sudden
with fever and chills
and ends in crisis after 9-10 days.
Chest pain due to pleural involvement is common, as is hemoptysis, which
is characteristically “rusty”, since it is derived from altered blood in
examination shows alveolar filling in large areas of lung, producing a
solid appearance that extend to entire lobes or segments.
Although the symptoms of pneumonia respond rapidly to antibiotic therapy, radiologically the lesion still takes several days to resolve.
antibiotic therapy the clinical course was characterized by severe fever, dyspnea, debility, and even loss of consciousness.
satisfactory resolution of a crisis was the result of a good immune
response to the infection.
However, often the outcome was not
favorable and the patient died.
Sequence of stages
is described in 4 phases:
All 4 phases may be
seen in different parts of the same lung.
Congestion (1-2 days)
2. Red hepatization
3. Gray hepatization
4. Resolution (8th-9th
In the earliest
stage of pneumococcal pneumonia, protein-rich edema fluid containing
numerous organisms (Streptococcus pneumoniae) fills the alveoli.
Marked congestion of the capillaries is typical.
Shortly after this
congestion occurs there is a massive outpouring of polymorphonuclear
leukocytes accompanied by intra-alveolar hemorrhage.
Many of the red blood
cells undergo lysis.
These cells, together with polymprphonuclear
leukocytes, produce the rusty sputum.
Because the firm consistency of the
affected lung is reminiscent of the liver, this stage has been named
The next phase,
occurring after 2 or more days, depending on the success of treatment,
involves the lysis of polymorphonuclear leukocytes and the appearance of
macrophages, which phagocytose the fragmented polymorphonuclear leukocytes
and other inflammatory debris.
The lung is now no longer congested but
still remains firm in this stage of “gray hepatization”.
The alveolar exudates is then removed and the lung gradually returns to normal.
A painful pleuritis is common because the
pneumonia often extends to the pleura.
There is usually a small pleural
effusion, which resolves.
However, this may occasionally be large and
and may heal with extensive fibrosis.
Rarely, the purulent exudates
persists and leads to a loculated collection of pus with fibrous walls (empyema).
Bacteremia is usually present in the early stage and may result in
endocarditis or meningitis.
Rarely, the alveolar lesion proceeds to
fibrosis, in which case the intra-alveolar exudates becomes organized as
fibroblasts leads to a shrunken and firm lobe, a rare complication known
outcome is a lung abscess.
Little is known about the precise pathogenesis of pneumococcal pneumonia.
The frequency of a previous respiratory
tract infection suggests that impairment of airway clearance mechanisms
may be important.
It has been suggested that the
organisms can multiply rapidly in the increased airway mucus and may then
be aspired into the periphery.
The remarkably severe acute inflammation
with spreading edema has led to speculation that immunologic mechanisms
may be involved
Cause of death:
Toxemia with peripheral circulatory failure.
Penicillin (penicillin G/amoxicillin) remains the drug of choice for
strains that are fully sensitive or have a moderately decreased
susceptibility to penicillin, whereas cefotaxime and ceftriaxone are the
first-line alternatives in cases with higher levels of resistance.
2. Abscess formation
4. Organization of
exudates with fibrosis.
5. Bacteremia &
septicemia with infection to other organs e.g. endocarditis, pericarditis,
meningitis, arthritis etc.