CAP

Y Community Acquired Pneumonia (CAP)

–In a patient not hospitalized or less than 48 hours from hospital admission

–An acute infection of the lung parenchyma that  is associated with at least some symptoms of acute infection, accompanied by the presence of an acute infiltrate on a chest radiograph, or auscultatory findings consistent with pneumonia,

 HAP(nosocomial pneumonia) is a pneumonia that occurs ≥ 48 hrs. after hospital admission.

VAP is a pneumonia that occurs ≥ 48 -72hrs after tracheal intubation

Pathogenesis

Primary inhalation: when organisms bypass normal respiratory defense mechanisms or when the Pt inhales aerobic GN organisms that colonize the upper respiratory tract or respiratory support equipment

Aspiration pneumonia : occurs when the Pt aspirates colonized upper respiratory tract secretions . Stomach: reservoir of gram-negative bacilli that can ascend, colonizing the respiratory tract.

Hematogenous: originate from a distant source and reach the lungs via the blood stream.

CAP – Classification

• Anatomical (lobar, bronchopneumonia, interstitial).

• Etiological (infective, and non infective).

• Clinical (Typical and atypical CAP, and HAP, and Pneumonia in Immunocompromised

Infectious causes of CAP (Etiological)

• Pneumonia is due to infections caused primarily by Bacteria or Viruses and less commonly by Fungi and Parasites.

• Mixed infections with both viruses and bacteria may occur in up to 45% of infections in children and 15% of infections in adults.

Infectious causes of CAP (bacterial)

TYPICAL  - Streptococcus pneumonia 35%  - Staph aureus pneumonia  - Haemophilus influenzae  - Moraxella catarrhalis  - Klebsiella pneumoniae

ATYPICAL  - Mycoplasma pneumoniae  - Chlamydophila pneumoniae  - Legionella pneumophila

• Coxiella burnetii ***N.B: atypical pneumonia*** It does not respond to the usual antibiotics Causes a milder form of pneumonia (hence the term “walking pneumonia”) Typical pneumonia can come on more quickly + with more severe early symptoms

Other

• Anaerobic organisms
• TB pneumonia

Epidemiology:

•It is thought that the 3 main atypical pathogens might be implicated in up to 40% of  community acquired pneumonia(CAP)

•The precise incidence is not known. Not identified in clinical practice due to lack of readily available, reliable standardized tests to confirm  diagnosis.

Management of atypical pneumonia :

• •Macrolides, such as Erythromycin, Clarithromycin + Azithromycin have been shown to be effective in the Rx of all 3 organisms

• •Severe Legionella infections may require rifampicin + a macrolide

• •Tetracycline, Doxycycline + Fluoroquinolones are also effective

• •Recommened duration of therapy usually 2-3 weeks

Infectious causes of CAP (Non-bacterial)

A causative agent may not be isolated in approximately half of cases despite careful testing

Viral  - Influenza  - Parainfluenza pneumonia  - Measles

• Adenoviruses
• Corona viruses

Fungal

• Aspergillus
• Histoplasmosis
• Candidiasis

Others Parasitic Toxoplasma

Clinical Presentation of pneumonia

• Acute cough (>90%)
• Fevers/chills (80%)
• Sputum production (66%)
• Dyspnea (66%)
• Pleuritic chest pain (50%)
• Tachypnea (RR > 24)
• Bronchial breath sounds
• Percussion dullness
• Diminished breath soundnds

Laboratory Tests:

1. CBC with differential
2. BUN/Cr
3. glucose
4. liver enzymes
5. electrolytes
6. Gram stain/culture of sputum
7. pre-treatment blood cultures
8. oxygen saturation

Diagnostic Evaluation

CXR –usually needed to establish diagnosis –prognostic indicator –rule out other disorders –may help in etiological diagnosis

CT scan of Chest –Radiologic findings may not be present in the early stages of the disease, especially in the presence of dehydration, or may be difficult to be interpreted in the obese or those with a history of lung disease. A CT scan can give additional information in indeterminate cases