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Pneumonia
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The MED
sharing Definition
❑Pneumonia: is a respiratory infection characterized by inflammation
of the alveolar space and/or the interstitial tissue of the lungs.
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sharing Pneumonia Terminology
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sharing Epidemiology
❑CAP is one of the most common and morbid condition.
❑Over 4.5 million outpatient and emergency room visits annually.
❑Nearly 9% of patients hospitalized with CAP will be rehospitalized
due to a new episode of CAP during the same year.
CAP incidence by age CAP incidence by comorbidity
 Etiology “Pathogens”
Pneumonia pathogens according to the source of infection
Type of pneumonia Common pathogens
Community-acquired pneumonia ❑ Typical pneumonia
▪ Streptococcus pneumonia (most common)
▪ Haemophilus influenzae
▪ Moraxella catarrhalis
The MED ▪ Klebsiella pneumoniae
▪ Staphylococcus aureus
sharing ❑ Atypical pneumonia
▪ Bacteria: Mycoplasma pneumoniae (most common), Chlamydophila pneumoniae,
Chlamydophila psittaci, Legionella pneumophila→legionellosis, Coxiella
burnetiid→ Q fever, Francisella tularensis→tularemia
▪ Viruses: (RSV, Influenza viruses, Parainfluenza viruses, CMV, Adenovirus,
Coronaviridae (e.g., SARS-CoV-2)

Hospital-acquired pneumonia ❑ Gram-negative pathogens

▪ Pneudomonas aeruginosa
▪ Enterobacteriaceae
❑ Staphylococci (Staphylococcus aureus)
❑ Streptococcus pneumoniae
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Pneumonia pathogens according to affected population The MED
Type of pneumonia Common pathogens sharing
Pneumonia in immunocompromised patients Encapsulated bacteria, Pneumocystis jirovecii→Pneumocystis jirovecii
pneumonia, Aspergillus fumigatus→Aspergillosis, Histoplasma capsulatum,
Coccidioids immitis, Candida species→candidiasis, Cytomegalovirus
(CMV)→CMV pneumonia, S. aureus, Gram-negative bacteria
Pneumonia in newborns Escherichia coli, Streptococcus agalactiae (Group B streptococcus),
Streptococcus pneumoniae, Haemophilus influenzae
Pneumonia in children (4weeks – 18years) C. Trachomatis (in infants), C. pneumoniae (in young children and adolescents),
S. pneumoniae, Respiratory syncytial virus (RSV), Mycoplasma

Pneumonia in young adults (18 – 40 years) Mycoplasma, Influenza virus, C. pneumoniae, S. pneumoniae
Pneumonia in adults (40 – 65 years) S. pneumoniae, H. influenzae, Mycoplasma, Anaerobes, Viruses
Pneumonia in elderly individuals S. pneumoniae, H. influenzae, Gram-negative bacteria, Anaerobes, Influenza
virus
Recurrent pneumonia Uncommon organisms (e.g., Nocardia, Coxiella burnetiid, Aspergillus,
Pseudomonas aeruginosa)

❖“Track my respiration: chlassic strep formation”: C. trachomatis, Mycoplasma,

Respiratory syncytial virus, Chlamydia pneumoniae, and Streptococcus
pneumoniae are the most common causative agents of pneumonia in children.
Pneumonia pathogens according to location
Type of pneumonia Common pathogens
Lobar pneumonia ❑ Most common: S. pneumoniae
❑ Less common The MED
▪ Legionella
▪ Klebsiella
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▪ H. influenzae
Bronchopneumonia ❑ S. pneumoniae
❑ S. aureus
❑ H. influenzae
❑ Klebsiella
Interstitial pneumonia ❑ Atypical pathogens
▪ Mycoplasma pneumoniae
▪ Chlamydophila pneumoniae
▪ Chlamydophila psittaci (primary transmitted by parrots)
▪ Legionella
▪ Viruses (e.g., RSV, CMV, Influenza, adenovirus)
▪ Coxiella burnetiid
Cryptogenic organizing pneumonia ❑ Noninfectious
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Classification
Pneumonia can be classified according to etiologies, location acquired, sharing
clinical features, and the area of the lung affected by the pathology.
❑Etiology
▪ Primary pneumonia
▪ Secondary pneumonia
❑Location acquired
▪ Community-acquired pneumonia (CAP)
▪ Hospital-acquired pneumonia (HAP)
▪ Healthcare-associated pneumonia (HCAP)
❑Clinical features
▪ Typical pneumonia
▪ Atypical pneumonia
❑Area of lung affected by the pathology
▪ Lobar pneumonia
▪ Bronchial pneumonia
▪ Interstitial pneumonia
▪ Cryptogenic organizing pneumonia
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Pathophysiology sharing
❑Routes of Infection
▪ Most common: microaspiration (droplet infection) of airborne pathogens or
oropharyngeal secretions.
▪ Aspiration of gastric acid (aspiration pneumonitis), food, or liquids
❑Pathogenesis
1. Failure of protective pulmonary mechanisms (e.g., cough reflex,
mucociliary clearance, alveolar macrophages).
2. Infiltration of the pulmonary parenchyma by the pathogen→ interstitial and
alveolar inflammation.
3. Impaired alveolar ventilation→ ventilation/perfusion (V/Q) mismatch with
intrapulmonary shunting (right to left)
4. Hypoxia due to increased alveolar-arterial oxygen gradient
▪ Hypoxia is worsened when the affected lung is in the dependent position, as perfusion to
the dependent lung is better compared to the nondependent lung.
▪ In the case of a large unilateral pulmonary abscess, it may be helpful to position the
patient so that the affected lung is in the dependent position in order to prevent the pus
from filling the unaffected lung.
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Pathophysiology sharing
❑Pattern of involvement
▪ Lobar pneumonia
▪ Classic (typical) pneumonia of an entire lobe; primary caused by pneumococci
▪ Characterized by inflammation intra-alveolar exudate, resulting in consolidation
▪ Can involve the entire lobe or the whole lung

Stages of lobar pneumonia

Stages of lobar pneumonia
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Pathophysiology sharing
❑Pattern of involvement
▪ Bronchopneumonia: mostly commonly a descending infection that affects the
bronchioles and adjacent alveoli
o Primary caused by pneumococci and/or other streptococci
o Characterized by acute inflammatory infiltrates that fill the bronchioles and the adjacent
alveoli (patchy distribution)
o Usually involves the lower lobes or right middle lobe and affects ≥ 1 lobe
o Manifests as typical pneumonia
o Necrotizing bronchopneumonia and pneumatocele are caused by Staphylococcus aureus and
are often preceded by an influenza infection.
▪ Interstitial pneumonia: interstitial inflammation, typically caused by Mycoplasma and
viral infections
o Characterized by a diffuse patchy inflammation that mainly involves the alveolar interstitial
cells
o Bilateral multifocal opacities are classically found on chest x-ray.
o Manifests as atypical pneumonia
o Often has an indolent course (walking pneumonia)
▪ Miliary pneumonia: multiple small infiltrations caused by hematogenous
dissemination (e.g., of tuberculosis)
▪ Cryptogenic organizing pneumonia: characterized by inflammation of the bronchioles
and surrounding structures.
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Pathogenesis
Pathogenesis
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Clinical Features
❑Typical pneumonia: is characterized by a sudden onset of symptoms
caused by lobar infiltration.
▪ Severe malaise
▪ High fever and chills
▪ Productive cough with purulent sputum (yellow-greenish)
o Crackles and bronchial breath sounds on auscultation
o Decreased breath sounds
o Enhanced bronchophony, egophony, and tactile fremitus
o Dullness on percussion
▪ Tachypnea and dyspnea (nasal flaring, thoracic retractions)
▪ Pleuritic chest pain when breathing, often accompanying pleural effusion
▪ Pain that radiates to the abdomen and epigastric region (particularly in
children)
❖Suspect bacterial pneumonia in immunocompromised patients with
acute high fever and pleural effusion.
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Clinical Features
❑Atypical pneumonia: typically has an indolent course (slow onset) and
commonly manifests with extrapulmonary symptoms.
▪ Nonproductive, dry mouth
▪ Dyspnea
▪ Auscultation often unremarkable
▪ Common extrapulmonary features include fatigue, headaches, sore throat,
myalgias, and malaise
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Diagnostic sharing
✓Pneumonia is a clinical diagnosis based on history, physical
examination, laboratory findings, and CXR findings.
✓Consider microbiological studies and advanced diagnostics based on
patient history, comorbidities, severity and entity of pneumonia.
❑Laboratory Studies:
▪ CBC, inflammatory markers: ↑CRP, ↑ESR, Leukocytosis
▪ ↑Serum procalcitonin (PCT): Procalcitonin is an acute phase reactant that can
help to diagnose bacterial lower respiratory tract infection.
▪ PCT cab be used to guide antibiotic treatment.
▪ PCT levels ≥0.25 mcg/L correlate with an increased probability of a bacterial infection.
▪ Low PCT level after 2-3 days of antibiotic therapy can help facilitate the decision to
discontinue antibiotics.
o Decrease of PCT to ≤80% of peak level
o Decrease of PCT to < 0.25 mcg/L
▪ ABG: ↓PaO2
▪ BMP, LFTs
Microbiological studies
Indication Microbiological studies to consider
Any admitted patient ▪ MRSA nares swab (PCR and/or culture)
Any patient being treated empirically ▪ Blood cultures (2 sets)
for MRSA or P. aeruginosa ▪ Sputum culture and Gram stain
Severe CAP, HAP, VAP ▪ Blood cultures (2 sets)
▪ Sputum culture and Gran stain
The MED ▪ Pneumococcal urinary antigen
sharing ▪ Legionella pneumophila urinary antigen
▪ Consider Chlamydia pneumoniae respiratory PCR
Influenza season ▪ Influenza nasal swab (NAAT)
▪ Consider respiratory virus panel nasal swab
(NAAT)
All patients in pandemic or epidemic ▪ Testing for specific pathogens: e.g., COVID-19
setting testing with SARS-CoV-2 PCR
 Diagnostic
❑Imaging Studies
▪ Chest x-ray (posteroanterior and lateral)
o Indications: all patients suspected of having pneumonia
o X-ray findings in pneumonia
• Lobar pneumonia
• Opacity of one or more pulmonary lobes
• Presence of air bronchograms: appearance of translucent bronchi inside opaque areas of
alveolar consolidation
The MED • Bronchopneumonia
• Poorly defined patchy infiltrates scattered throughout he lungs
sharing • Presence of air bronchograms
• Atypical or interstitial pneumonia
• Diffuse reticular opacity
• Absent (or minimal) consolidation
• Parapneumonic effusion
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Diagnostic sharing
❑Imaging Studies
▪ Chest CT (usually without contrast)
o Indications: Inconclusive CXR, Recurrent pneumonia, Poor response o treatment
o Advantages: more reliable evaluation of circumscribed opacities, pleural empyema, or
sites of consolidation
o Findings:
• Localized areas of consolidation (hyperdense)
• Air bronchograms
• Ground-glass opacities
• Pleural effusion/empyema
• Hyperdense fluid collection
• Split pleura sign
• Nodules
• Large (e.g., in tuberculosis or fungal pneumonia)
• Peribronchial (e.g., bronchopneumonia)
• Disseminated (e.g., septic emboli or varicella-zoster pneumonia)
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Diagnostic
❑Imaging Studies
▪ Lung ultrasound in pneumonia: Point-of-care ultrasound (POCUS) has high
sensitivity and specificity for the diagnosis of pneumonia.
o Indications:
• Evaluation of suspected pneumonia
• Assessment of undifferentiated dyspnea
o Characteristic findings
• Consolidation
• Irregular and serrated lung margins
• Air bronchograms
• Unilateral B-lines
• Pleural effusion

❖In the Emergency Department, consider POCUS to quickly confirm

pneumonia and assess for other causes of dyspnea.
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Diagnostic
❑Advanced diagnostics for pneumonia
▪ Bronchoscopy
o Indications
• Suspected mass (e.g., recurrent pneumonia)
• Need for pathohistological diagnosis (e.g., biopsy of a central mass discovered on CT
• Inconclusive results on CT
• Poor response to treatment

▪ Diagnostic thoracentesis
o Indications: consider if pleural effusion > 10mm is present to evaluate for pleural
empyema
o Consider therapeutic thoracentesis in large effusions (≥ half of the hemithorax) or if the
effusion is suspected of causing dyspnea.
o Consider tube thoracostomy if pleural empyema (e.g., echogenic debris on lung
ultrasound) or complicated effusion (e.g., pH < 7.20, glucose < 60 mg/dL, LDH above
three times the upper limit of serum LDH, positive culture) is suspected.
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sharing Management Checklist
❑Calculate the CURB-65 score and/or PSI/PORT score to identify patients who
would benefit from admission.
❑Assess severity of CAP with the IDSA/ATS criteria for severe CAP.
❑Order microbiological workup as indicated by patient severity and risk factors.
❑Community-acquired pneumonia: Start empiric antibiotics for CAP.
❑Hospital-acquired pneumonia: Start empiric antibiotics for HAP.
❑Ventilator-associated pneumonia: Start empiric antibiotics for VAP.
❑Evaluate and treat sepsis if present (see sepsis).
❑Administer supplemental O2 if patient is hypoxemic.
❑Consider advanced diagnostic evaluation.
❑Provide supportive care for pneumonia (e.g., antipyretics, , IV fluids).
❑Continuous pulse oximetry
❑Trend inflammatory markers, procalcitonin.
❑Narrow antibiotic therapy as soon as feasible.
 Community-acquired pneumonia: Initial evaluation and
site of care based on severity assessment in adults
Severity score Site of Care Microbiologic evaluation
Mild PSI: 1 or 2 Ambulatory care ▪ Covid-19 and influenza testing when incidence is high and
Or results wound change management
CURB-65: 0 ▪ Otherwise, testing is usually not needed
Moderate PSI: 3 or 4 General medical ward ▪ Blood cultures
Or ▪ Sputum Gram stain and culture
CURB-65: 1 to 2 ▪ Urine streptococcal antigen
▪ Legionella testing
▪ Testing for respiratory viruses during respiratory virus season
or when community incidence is high (PCR preferred)
▪ HIV screening
Severe PSI: 4 to 5 ICU ▪ Blood cultures
Or ▪ Sputum Gram stain and culture
CURB-64: ≥ 3 ▪ Urine streptococcal antigen test
And/or The MED ▪ Legionella testing
Fulfillment of ATS/IDSA ▪ Testing for respiratory viruses (PCR preferred)
criteria for ICU sharing ▪ Bronchoscopy specimens for Gram stain, fungal stain,
admission aerobic, fungal culture, and molecular testing (when feasible)
▪ HIV screening
CURB-65 score

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CAP outpatient antibiotics
CAP determining
appropriate site of care
(adults)
Community-acquired pneumonia: Empiric
antibiotic selection for adults admitted to
the general medical ward
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the general medical ward
antibiotic selection for adults admitted to
Community-acquired pneumonia: Empiric
Community-acquired pneumonia: Empiric
antibiotic selection for adults admitted to
the intensive care unit
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the intensive care unit
antibiotic selection for adults admitted to
Community-acquired pneumonia: Empiric
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Approach to the patient with a past
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penicillin reaction who requires antibiotics

 Transitioning inpatients with community-
acquired pneumonia from IV to oral antibiotics

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Procalcitonin-guided antibiotic discontinuation
in CAP patients Follow-up imaging for
immunocompetent adults
who have recovered from
community-acquired
pneumonia

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 Complication The MED
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❑Parapneumonic pleuritis
▪ Fibrinous pleuritis: inflammation → increased vessel permeability → fibrin-
rich exudate deposited on the serosal surface of the pleura → pleuritic chest
pain and friction rub
▪ Analgesics can be used for the relief of symptoms.
❑Parapneumonic pleural effusion (common)
❑Pleural empyema
❑Lung abscess
❑ARDS
❑Respiratory failure
❑Sepsis
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Prognosis
❑Mortality increases with age.
❑The mortality risk can be evaluated with the CURB-65 score.
▪ Score 0: ∼ 1%
▪ Score 1–2: ∼ 10%
▪ Score 3: ∼ 14%
▪ Score 4: ∼ 40%
❑HAP is associated with a mortality rate of > 20%.
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ICU criteria
❑The presence of three of these criteria warrants ICU admission:
▪ Altered mental status
▪ Hypotension requiring fluid support
▪ Temperature <36°C (96.8°F)
▪ Respiratory rate ≥30 breaths/minute
▪ Arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2) ratio ≤250
▪ Blood urea nitrogen (BUN) ≥20 mg/dL (7 mmol/L)
▪ Leukocyte count <4000 cells/microL
▪ Platelet count <100,000/microL
▪ Multilobar infiltrates