What is the diagnosis and treatment for atypical pneumonia?

From the Guidelines

Atypical pneumonia should be treated with azithromycin (500mg on day 1, then 250mg daily for 4 more days) or doxycycline (100mg twice daily for 7-14 days) as first-line therapy, considering the increasing resistance to macrolides in some areas, as reported in a study from 2019 1.

Treatment Considerations

When considering treatment for atypical pneumonia, it's essential to take into account the potential for macrolide resistance, particularly in regions with high resistance rates.

• Macrolides, such as azithromycin, are effective against Mycoplasma pneumoniae, but resistance rates are increasing, especially in Asia, with up to 95% of isolates resistant to macrolides in one study 1.
• Doxycycline is an alternative option, with good efficacy against M. pneumoniae, and is recommended as a cost-effective alternative 1.
• Respiratory fluoroquinolones, such as levofloxacin or moxifloxacin, are also effective, but their use is generally reserved for more severe cases or patients with comorbidities, due to concerns about resistance development 1.

Patient Management

In addition to antibiotic therapy, patients with atypical pneumonia should:

• Rest and maintain adequate hydration
• Use antipyretics for fever management
• Be monitored for signs of severity, such as respiratory distress or significant comorbidities, which may require hospitalization

Diagnosis and Presentation

Atypical pneumonia often presents with:

• Gradual onset
• Prominent headache
• Low-grade fever
• Minimal sputum production
• Patchy, diffuse infiltrates on chest X-rays, rather than lobar consolidation Most patients can be treated as outpatients, but those with severe symptoms or significant comorbidities may require hospitalization. Symptoms usually improve within 48-72 hours of starting appropriate antibiotics, though complete resolution may take several weeks.

From the FDA Drug Label

Azithromycin Tablets, USP are indicated for the treatment of patients with mild to moderate infections (pneumonia: see WARNINGS) caused by susceptible strains of the designated microorganisms in the specific conditions listed below Community-acquired pneumonia due to Chlamydophila pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae or Streptococcus pneumoniae in patients appropriate for oral therapy Treatment of pneumonia In the treatment of pneumonia, azithromycin has only been shown to be safe and effective in the treatment of community-acquired pneumonia due to Chlamydia pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae or Streptococcus pneumoniae in patients appropriate for oral therapy

Atypical pneumonia is caused by Chlamydophila pneumoniae or Mycoplasma pneumoniae.

• Azithromycin is indicated for the treatment of community-acquired pneumonia due to these organisms in patients appropriate for oral therapy 2.
• Azithromycin should not be used in patients with pneumonia who are judged to be inappropriate for oral therapy because of moderate to severe illness or risk factors such as any of the following: patients with cystic fibrosis, patients with nosocomially acquired infections, patients with known or suspected bacteremia, patients requiring hospitalization, elderly or debilitated patients, or patients with significant underlying health problems that may compromise their ability to respond to their illness (including immunodeficiency or functional asplenia) 2.

From the Research

Definition and Causes of Atypical Pneumonia

• Atypical pneumonia is caused by atypical pathogens that are not detectable with Gram stain and cannot be cultured using standard methods 3.
• The most common causative organisms of atypical pneumonia are Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella species 3.

Diagnosis of Atypical Pneumonia

• The diagnosis of atypical pneumonia is based on clinical symptoms, physical signs, and laboratory data 3.
• The Japanese pneumonia guidelines have proposed a differential diagnosis for typical bacterial pneumonia and atypical pneumonia to select an appropriate antibiotic for the management of mild-to-moderate pneumonia 3.

Treatment of Atypical Pneumonia

• Azithromycin is effective in the treatment of atypical pneumonia, with a 1.5 g total dose being equally effective when administered as a three- or five-day regimen 4, 5.
• A single 1.5 g dose of azithromycin may be an alternative to the standard 3-day azithromycin regimen in the treatment of outpatients with atypical pneumonia syndrome 6.
• Doxycycline, a fluoroquinolone with enhanced activity against Streptococcus pneumoniae, or a macrolide is appropriate for outpatient treatment of immunocompetent adult patients 7.
• Hospitalized adults should be treated with cefotaxime or ceftriaxone plus a macrolide, or with a fluoroquinolone alone 7.

Special Considerations

• In elderly individuals and patients with underlying diseases, the differential diagnosis may be difficult or a mixed infection may be latent, and the administration of a β-lactam drug plus a macrolide or tetracycline, or only fluoroquinolone should be considered from the beginning to cover bacterial and atypical pneumonia 3.
• Outpatient treatment of children two months to five years of age consists of high-dose amoxicillin given for seven to 10 days, while older children can be treated with a macrolide 7.