From the Guidelines
Community-acquired pneumonia (CAP) is characterized by signs and symptoms of respiratory infection, including cough, sputum production, and fever, as well as radiographic evidence of lung involvement, as noted in a 2020 study published in the Annals of Internal Medicine 1. The presentation of CAP can vary based on the causative pathogen and the severity of the disease. Common respiratory signs and symptoms include:
- Cough, which may be productive with purulent sputum
- Dyspnea
- Tachypnea
- Chest pain that worsens with breathing
- Abnormal breath sounds on examination, such as crackles, wheezing, or decreased breath sounds Systemic manifestations typically include:
- Fever
- Chills
- Fatigue
- Malaise
- Headache
- Sometimes confusion, particularly in elderly patients Some patients may exhibit cyanosis due to hypoxemia. The severity can range from mild to severe, with severe cases potentially presenting with respiratory distress, hypotension, or altered mental status. Elderly patients often present atypically with fewer respiratory symptoms but more pronounced confusion, dehydration, or exacerbation of underlying conditions, as highlighted in a 2021 study published in the Annals of Internal Medicine 1. The presentation varies based on the causative pathogen, with atypical pneumonia (caused by organisms like Mycoplasma or Legionella) sometimes featuring more prominent systemic symptoms and less severe respiratory findings. Physical examination may reveal dullness to percussion over affected lung areas, increased tactile fremitus, and occasionally signs of pleural effusion. These symptoms develop when pathogens invade the lower respiratory tract, triggering an inflammatory response that causes alveolar filling with exudate, impairing gas exchange and producing the characteristic clinical picture. The diagnosis of CAP is based on a combination of clinical presentation, radiographic findings, and laboratory tests, as noted in a study published in the Clinical Infectious Diseases journal in 2000 1. The most recent and highest quality study, published in 2021, provides the best guidance on the signs and symptoms of CAP, and should be prioritized in clinical decision-making 1.
From the Research
Signs and Symptoms of Community-Acquired Pneumonia (CAP)
Community-acquired pneumonia (CAP) can be diagnosed in a patient with 2 or more signs or symptoms of pneumonia in conjunction with consistent radiographic findings without an alternative explanation 2. The signs and symptoms of CAP may include:
- Temperature >38 °C or ≤36 °C
- Leukocyte count <4000/μL or >10 000/μL
- New or increased cough
- Dyspnea
Diagnosis of CAP
Diagnosis of acute community-acquired pneumonia is based on the history, physical examination, and chest x-ray 3. Appropriate diagnostic studies for patients with moderately-severe to severe pneumonia include:
- Sputum Gram's stain and culture
- Blood cultures
- Acute serum sample
- Urinary antigen test for Legionella pneumophila
Treatment of CAP
First-line therapy for CAP varies by disease severity and etiology 2, 3, 4, 5, 6. Hospitalized patients without risk factors for resistant bacteria can be treated with β-lactam/macrolide combination therapy, such as ceftriaxone combined with azithromycin, for a minimum of 3 days 2. Monotherapy with oral Levofloxacin was as effective as treatment with Ceftriaxone plus Azithromycin combination in patients with CAP who required hospitalization 4. Azithromycin combination therapy significantly reduced the mortality of patients with severe CAP who met the IDSA/ATS criteria 5.
Empiric Antibiotics for CAP
A network meta-analysis identified the empiric antibiotic with the highest probability of being the best in terms of cure rate and mortality rate in hospitalized patients with CAP 6. The results showed that:
- Ceftaroline and piperaciline have the highest probability of being the best for cure rate
- Ceftriaxone plus levofloxacin, ertapenem, and amikacin plus clarithromycin have the highest probability of being the best for mortality rate