There was a fairly recent update to the community-acquired pneumonia guidelines. Let's review the 2019 IDSA/ATA CAP Guidelines antimicrobial recommendations -
We recently had an update to the Community-Acquired Pneumonia (CAP) guidelines in 2019 by Infectious Disease Society of America (IDSA) and ATS (American Thoracic Society). Noteworthy changes include antibiotic recommendations and rationale behind changes to diagnostics. There has been more recent literature to support additional options to be considered for empiric CAP outpatient treatment.
As with any other infection, our empiric therapies are targeted towards most likely causative organism. Additionally, comorbidities determine our antibiotic regimen since there is an increased risk of more resistant strains. Let's go through the 2019 IDSA/ATS CAP Guidelines antimicrobial recommendations.
Common Organisms Associated with CAP
Respiratory Pathogens
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Atypical Organisms - not easily detected on common assays
Legionella pneumophila
Mycoplasma pneumoniae
Chlamydia pneumoniae
Empiric Outpatient Regimens in Low Risk Patients (w/o Comorbidities)
Empiric treatments should be based on comorbidities and risk factors for more broad resistant organisms
Risk factors for MRSA and PsA: prior respiratory isolation of either pathogen
Recent hospitalization AND receipt of IV antibiotics within the past 90 days
Comorbidities: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; asplenia
No comorbidities or risk factors for MRSA or PsA | |
|---|---|
Monotherapy | Amoxicillin 1000 mg po TID |
Select one agent | Doxycycline 100 mg po bid |
| Azithromycin 500 mg, then 250 qday |
"The recommendation for amoxicillin was based on several studies that showed efficacy of this regimen for inpatient CAP despite presumed lack of coverage of this antibiotic for atypical organisms." – ATS/IDSA 2019 CAP Guidelines
Empiric Outpatient Regimens in High Risk Patients (w/ Comorbidities)
Empiric treatments should be based on comorbidities and risk factors for more broad resistant organisms
Risk factors for MRSA and PsA: prior respiratory isolation of either pathogen
Recent hospitalization AND receipt of IV antibiotics within the past 90 days
Comorbidities: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; asplenia
Patients with comorbidities are at higher risk of more resistant bacterial strains
Comorbidities WITHOUT MRSA/PsA risk factors | |
|---|---|
Combination therapy with beta-lactam AND azithromycin OR doxycycline (preferred) | Amoxicillin-clavulanate 875 mg po BID OR cephalosporins (cefuroxime 500 mg po BID or cefpodoxime 200 mg po BID) AND azithromycin OR doxycycline |
OR | |
Respiratory fluoroquinolone monotherapy | Levofloxacin 750 mg po qday Moxifloxacin 400 mg po qday Gemifloxacin 320 mg po qday |
Treatment Duration and Guideline Updates
Treatment is a minimum of 5 days; duration dependent on clinical improvement
Obtain sputum/blood cultures with PsA or MRSA suspicion (including MRSA PCR nares). Not recommended for mild to moderate disease.
Preference of beta-lactam/macrolide combination over monotherapy fluoroquinolones for admitted patients.
Selecting the Right Antibiotic for CAP
The recent update to the 2019 IDSA/ATA CAP Guidelines provide more clear direction on low vs high risk patients. We also have new agents that can be considered for empiric regimens, specifically amoxicillin and doxycycline. Common organisms include S. pneumoniae, H. influenzae, M. catarrhalis, L. pneumophila, and C. pneumoiae. Antibiotics are dependent on the presence of comorbidities, warranting more expansive antibiotics to account for more resistant bacterial strains. Treatment is a minimum of five days and clinical improvement determines total duration. Get the empiric antibiotics for the right patients; we'll need to look at their specific characteristics first.
Mark Nguyen, PharmD, BCEMP
References
Metlay et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-e67.
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