Pneumonia Flashcards
Classification Basis
- Setting of acquisition of infection
- Mechanism of acquisition
- Clinical presentation
- Infecting pathogen
- Radiographic pattern of infiltrate
- Immune status of patient
Healthcare-associated pneumonia
In non-hospitalized patients with extensive health care contact such as:
- Prior hospitalization for more than 2 days duration within the last 90 days
- Residing in a nursing home or long term care facility
- Outpatients Rx with IV antibiotics or chemotherapy, or wound care in the last 30 days
- Hemodialysis clinic within 30 days
Typical pneumonia
Associated with acute respiratory illness
* Characterized by productive cough, pleuritic chest pain, fever, Dyspnea
Atypical pneumonia
Has a less abrupt course with constitutional symptoms and mild upper respiratory tract symptoms preceding the onset of a non-productive cough.
Risk factors for CAP
- Alcoholism and smoking
- Age greater than 65 years
- Recent viral upper respiratory tract infection
- Underlying pulmonary diseases (e.g., COPD, bronchiectasis, lung cancer)
- Immunosuppression and other comorbid conditions (e.g., heart failure, chronic kidney disease, chronic liver disease, and diabetes mellitus)
- Proton pump inhibitor therapy in the last 30 days
- Stroke or sedating medications
Risk factors for Hospital Acquired Pneumonia
*Immunosuppression
* Severity of underlying illness (e.g., malnutrition, uremia, neutropenia)
* Prior surgery
* Prior and recent antibiotic administration
* Presence of invasive respiratory devices
* Enteral feeding with nasogastric or orogastric tubes
* Stress ulcer prophylaxis
* Blood transfusions
* Poor oral hygiene
* Altered mental status
CAP-related microorganisms - Strep, Staph and Klebsiella
- Streptococcus pneumoniae - most common cause, sometimes assoc. with bacteremia.
- Staphylococcus aureus - Uncommon cause in healthy adults but may follow influenza infection. Can cause severe necrotizing pneumonia often requiring ICU admission.
- Klebsiella Pneumoniae - Seen in alcoholics or excessive smokers and in association with aspiration. Can lead to aggressive necrotizing lobar pneumonia.
CAP - Related microorganisms: Hemophilus, Moraxella and Pseudomonas
- Hemophilus Influenza and Moraxella Catarrhalis - Cause pneumonia in elderly patients and those with COPD.
- Pseudomonas aeruginosa - Rare except in patients with structural lung disease such as cystic fibrosis and bronchiectasis.
Bacteriology for atypical pneumonia
- Mycoplasma pneumoniae - most common
- Other pathogens include Chlamydophila pneumoniae, Legionella spp, Coxiella burnetii (Q fever)
Bacteriology for Aspiration Pneumonia
- Anaerobic organisms causing pneumonia is typically the result of aspiration of oropharyngeal contents
- Aspiration pneumonia tends to be polymicrobial and may consist of the following anaerobic species;
Klebsiella, Peptostreptococcus, Bacteroides, Fusobacterium, and Prevotella
Viral pathogens in pneumonia
- Influenza A and B most common viral cause of pneumonia in patients at the extremes of age, with multiple comorbidities, and pregnant women
- Parainfluenza viruses, Respiratory syncytial virus (RSV), Adenovirus, Varicella-zoster virus, EBV, Coronaviruses are rare causes of viral pneumonia in adults
- Cytomegalovirus causes pneumonia only in immunosuppressed patients
Fungal pathogens
- Rare cause of acute CAP, usually in HIV patients
HAP, VAP, HCAP - Implicated organisms
Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Enterobacter spp, Serratia spp, Staphylococcus aureus especially MRSA, Acinetobacter baumannii - assoc. with prolonged mechanical ventilation and significant antimicrobial resistance
Risk factors for MRSA
Prolonged hospitalization, COPD, prior corticosteroid use, diabetes mellitus, hemodialysis, prior antimicrobial therapy etc.
Patients at high risk of HAP, VAP, HCAP
- Have been hospitalized for more than 5 days
- Had received antibiotics in the previous 90 days
- Are immunocompromised
- Have risk factors associated with HCAP
