pneumonia, acute inflammation and consolidation (solidification) of
the lung are due to a bacterial agent. Clinical signs and symptoms include
fever and chills; productive cough with yellow-green (pus) or rusty (bloody)
sputum; tachypnea; pleuritic chest pain; and decreased breath sounds, rales,
and dullness to percussion.
typically show elevated white blood cell count with a left shift (an increase
in immature leukocytes). Chest x-ray for lobar pneumonia typically shows lobar
or segmental consolidation (opacification), and for bronchopneumonia typically
shows patchy opacification. Pleural effusion may also be picked up on chest
general, the keys to effective therapy are identification of the organism and
early treatment with antibiotics.
pneumonia is characterized by consolidation of an entire lobe. The
infect-ing organism is typically Streptococcus
pneumoniae (95%) or Klebsiella .
The lancet-shaped diplococcus Streptococcus
pneumoniae is alpha-hemolytic, bile soluble, and optochin sensitive.
4 classic phases of lobar pneumonia
are congestion (active hyperemia and
edema); red hepatization
(neutrophils and hemorrhage); grey
hepatization (degra-dation of red blood cells); and resolution (healing). In today’s antibiotic era, these changes are
not generally observed in practice.
is characterized by scattered patchy consolidation centered
onbronchioles; the inflammation tends to be bilateral, multilobar, and basilar,
and particularly susceptible populations include the young, old, and terminally
ill. Infecting organisms exhibit more variation than in lobar pneumonia, and
include Staphylococci, Streptococci,
Haemophilus influenzae, Pseudomonas aeruginosa, etc.Microscopic examination
of tissue shows acute inflammation of bronchioles and surrounding alveoli. The
diagnosis can often be established with sputum gram stain and sputum culture,
but will sometimes require blood cultures.
of pneumonia include fibrous scarring and pleural adhesions, lung abscess,
empyema (pus in a body cavity), and sepsis.
of pneumonia is generally initial empiric antibiotic treatment, modified by the
results of cultures and organism sensitivities.
abscess is a localized collection of neutrophils (pus) and necrotic
pulmonaryparenchyma. The etiology varies with the clinical setting. Aspiration is the most common cause. It
tends to involve right lower lobe and typically has mixed oral flora (often
both anaerobic and aerobic) for infecting organisms.
abscess may also occur following a pneumonia, especially one due to S. aureus or Klebsiella . Lung abscesses may also occur following airway
obstruction (postob-structive) or deposition of septic emboli in the lung.
of lung abscess include empyema, pulmonary hemorrhage, and sec-ondary
Atypical pneumonia is
the term used for interstitial pneumonitis without consolida-tion. It is more
common in children and young adults.
Infecting organisms that can
cause atypical pneumonia includeMycoplasmapneumoniae,
influenza virus, parainfluenza virus, respiratory syncytial virus (RSV)(which
is especially important in young children), adenovirus,
cytomegalovirus (CMV) (which is especially important in the
immunocompromised), varicella virus,
and many others.
x-ray typically shows diffuse interstitial infiltrates. An elevatedcold
agglutinin titer specifically suggests Mycoplasma
as a cause, which is important to identify since antibiotic therapy for Mycoplasma exists. Lung biopsy, if
performed, typically shows lymphoplasmacytic inflammation within the alveolar
include superimposed bacterial infections and Reye syndrome (potentially
triggered by viral illness [influenza/varicella] treated with aspirin).
(TB).The number of cases of TB is declining in the United States,
butthe proportion of cases in people born outside the country is rising. In
this clinical setting, a positive PPD skin test may demonstrate that the person
has been exposed to the mycobacterial antigens. Individuals who have received
the BCG vaccine in some foreign countries may have a positive PPD test without
being infected. In such cases chest x-ray and sputum smears and cultures are
is usually acquired by inhalation of aerosolized bacilli.
clinical presentation of Mycobacterium tuberculosis includes
fevers and night sweats, weight loss, cough, and hemoptysis.
Primary pulmonary TB develops
on initial exposure to the disease. The Ghonfocus of primary TB is
characterized by subpleural caseous granuloma formation, either above or below
the interlobar fissure. The term Ghon
complex refers to the combination of the Ghon focus and
secondarily-involved hilar lymph nodes with granulomas. Most primary pulmonary
tuberculosis lesions (95%) will undergo fibro-sis and calcification.
Progressive pulmonary TB can
take several forms, including cavitary tuberculosis,miliary pulmonary
tuberculosis, and tuberculous bronchopneumonia.
Secondary pulmonary TB (also
known as postprimary or reactivation TB) occurseither with reactivation of an
old, previously quiescent infection or with reinfection secondary to a second
exposure to the mycobacteria. In secondary pulmonary TB, the infection often
produces a friable nodule at the lung apex (Simon focus) second-ary to the high
oxygen concentration present at that site, since the upper parts of the lung
typically ventilate more efficiently than the lower parts. Biopsy of affected
tissues will typically show AFB-positive caseating granulomas.
dissemination to other organ systems
can occur in advanced TB via a hematogenous route that often results in a
miliary pattern within each affected organ. Sites that may become involved
include meninges; cervical lymph nodes (scrofula) and larynx; liver/spleen,
kidneys, adrenals, and ileum; lumbar vertebrae bone marrow (Pott disease); and
fallopian tubes and epididymis.
mycobacteria.M. avium complex (MAC) typically occurs in AIDSpatients
with CD4 counts <50 cells/mm3 and presents as disseminated
diagnosis of TB requires identification of the bacilli. Positive sputum smear
necessitates culture for species identification. Adequate treatment requires
drug susceptibility testing.