pneumonia Flashcards
PNEUMONIA definition
infection of the lung parenchyma
• Due to infection affecting distal airways and alveoli, with
the formation of an inflammatory exudate.
• Caused by a wide variety of infective pathogens
Bronchopneumonia
There is patchy
consolidation involving the
lung
Lobar pneumonia
Whole lobe of the lung is
affected
Bronchopneumonia PREDISPOSING CONDITIONS
• Extremes of age: infants and elderly
• Debilitating diseases: cardiac failure, chronic renal failure, CVA
• Pre-existing lung conditions: acute bronchitis, chronic obstructive
airway disease , cystic fibrosis.
• Failure to clear respiratory secretions: post-operative.
• Manifestation 2º to viral infection: influenza, measles
bronchopneumonia AETIOLOGICAL AGENTS
Streptococcus pneumoniae • Klebsiella pneumoniae • Staphylococcus aureus • Streptococcus pyogenes • Haemophilus influenzae • Pseudomonas aeruginosa • Legionella pneumophila
bronchopneumonia CLINICAL FEATURES
Fever
• Reduced consciousness
• Crackles (crepitations) on auscultation
• Septicaemia
bronchopneumonia PATHOGENESIS
Organisms colonise the bronchioles to cause bronchiolitis. • Inflammation spreads through the wall of a bronchiole into surrounding alveoli. • There may be significant damage to bronchiolar walls
bronchopneumonia GROSS MORPHOLOGY
Patchy consolidation • Basal and bilateral lesions • Initially focal, involving one or more lobes • Post mortem findings: • grey or grey-red lung • little resistance when gently pressing on affected area
bronchopneumonia MICROSCOPIC FEATURES
Neutrophil-rich exudate that fills the bronchi, bronchioles, and adjacent alveolar spaces. • Ciliated epithelium of bronchioles is damaged. • Capillaries are congested
LOBAR PNEUMONIA PREDISPOSING CONDITIONS
Adults ages 20-50
• Male predominance
• Elderly, diabetics, alcoholics
LOBAR PNEUMONIA AETIOLOGICAL AGENTS
Streptococcus pneumoniae infection common
• Klebsiella pnumoniae
LOBAR PNEUMONIA CLINICAL FEATURES
- -Acute onset
- -Fever, rigors
- -Dry cough
- -Rusty sputum
- -Pleuritic chest pain
LOBAR PNEUMONIA PATHOGENESIS
Organism inhaled into bronchial tree and reaches alveoli.
• Bacteria cause an inflammatory exudate which is initially watery.
Later, there is exudation of fibrin and neutrophils in the alveoli.
• Alveoli filled with exudate = consolidation.
• Exudate flows directly into the next alveolus via pores of Kohn,
carrying bacteria with it. Infection spread is through lumen rather
than through walls. This is important in that the damage to
bronchioles is much less than in bronchopneumonia
Four stages of lobar pneumonia
- Congestion
- Red hepatization
- Grey hepatization
- Resolution
COMPLICATIONS OF PNEUMONIA
- Healing with fibrosis leading to bronchiectasis
- Lung Abscess
- Empyema
- Spread of inflammation
Community-acquired Atypical
Pneumonias
characterized by patchy inflammatory
changes in the lungs, largely confined to the alveolar septa and
pulmonary interstitium
Community-acquired Atypical Pneumonias examples
Mycoplasma pneumoniae • Particularly common among children and young adults. • Occur sporadically or as local epidemics in closed communities (schools, military camps, prisons). Chlamydia pneumoniae • Milder pneumonia • Relatively common in asthmatics Legionella pneumophila • Causes severe pneumonia • Legionnaires’ disease
Viral pneumonia
- Influenza
- Human metapneumovirus
- Coronavirus
Influenza
Single-stranded RNA virus, bound by a
nucleoprotein that determines the virus type (A,
B, or C)
Human metapneumovirus
Paramyxovirus
• Common in young, elderly, immunocompromised
• Can develop severe infection
NOSOCOMIAL INFECTIONS
known as hospital-acquired, pneumonias are defined
as pulmonary infections acquired in the course of a hospital
stay.
ASPIRATION PNEUMONIA
Aspiration pneumonia occurs in debilitated patients or those who aspirate
gastric contents either while unconscious (e.g. after a stroke) or during
repeated vomiting.
Abscess formation is a common complication.
LUNG ABSCESS
A localized area of suppurative necrosis within the pulmonary parenchyma, resulting in the formation of one or more large cavities. • More common on right side following aspiration • More common basally and bilaterally in pneumonia
The causative organism may be introduced into the lung by any of the following
mechanism
- Aspiration of infective material
- Antecedent primary lung infection
- Septic embolism.
- Neoplasia.
- Miscellaneous.
CHRONIC PNEUMONIA
Histoplasmosis capsulatum
Warm, moist soil contaminated by droppings from bats and birds containing fungal spores • More common in immunocompromised • Cause granulomatous inflammation in lung • Yeast forms: round to oval, 2 to 4 μm in diameter.
Blastomyces dermatitidis
• Three clinical forms:
• Pulmonary blastomycosis • Disseminated blastomycosis • Rare primary cutaneous form (from direct inoculation of organisms into the skin)
Common bacterial
pathogens
S. pneumonia
H. influenza
S. aureus
M. tuberculosis
Fungi
- Pneumocystis jirovecii
- C. neoformans
- H. capsulatum
- C. immitis
- Aspergillus spp.
Protozoa
- T. gondii
- Cryptosporidium
- Strongyloides stercoralis
Viruses
Cytomegalovirus
Mucormycosis
Caused by Rhizopus and Mucor
fungi of the Zygomycetes class
