Page 503 - Robbins Basic Pathology by Vinay Kumar, Abul K. Abbas, Jon C. Aster

Pulmonary Infections 489
A • Along with S. pneumoniae and H. influenzae, M. catarrhalis
B •
C
Figure 12–32 A, Acute pneumonia. The congested septal capillaries
and extensive neutrophil exudation into alveoli correspond to early red
hepatization. Fibrin nets have not yet formed. B, Early organization of
intra-alveolar exudates, seen in areas to be streaming through the pores
of Kohn (arrow). C, Advanced organizing pneumonia, featuring transfor-
mation of exudates to fibromyxoid masses richly infiltrated by macro-
phages and fibroblasts.
Haemophilus influenzae
• Both encapsulated and unencapsulated forms are impor-
tant causes of community-acquired pneumonias. The
former can cause a particularly life-threatening form of
pneumonia in children, often after a respiratory viral
infection.
• Adults at risk for developing infections include those
with chronic pulmonary diseases such as chronic
bronchitis, cystic fibrosis, and bronchiectasis. H. influen-
zae is the most common bacterial cause of acute exacerbation
of COPD.
• Encapsulated H. influenzae type b was formerly an
important cause of epiglottitis and suppurative menin-
gitis in children, but vaccination against this organism
in infancy has significantly reduced the risk.
Moraxella catarrhalis
• M. catarrhalis is being increasingly recognized as a cause
of bacterial pneumonia, especially in elderly persons.
• It is the second most common bacterial cause of acute
exacerbation of COPD in adults.
constitutes one of the three most common causes of otitis
media (infection of the middle ear) in children.
Staphylococcus aureus
• S. aureus is an important cause of secondary bacterial
pneumonia in children and healthy adults after viral
respiratory illnesses (e.g., measles in children and influ-
enza in both children and adults).
• Staphylococcal pneumonia is associated with a high
incidence of complications, such as lung abscess and
empyema.
• Staphylococcal pneumonia occurring in association with
right-sided staphylococcal endocarditis is a serious com-
plication of intravenous drug abuse.
It is also an important cause of nosocomial pneumonia
(discussed later).
Klebsiella pneumoniae
• K. pneumoniae is the most frequent cause of gram-
negative bacterial pneumonia.
Figure 12–33 Gross view of lobar pneumonia with gray hepatization.
The lower lobe is uniformly consolidated.