Carefully consider each patient’s risk factors.
Introduction:
It’s that time of the year again! Emergency Departments all over the country are brimming with long lines of patients with signs and symptoms of respiratory illnesses. Community acquired pneumonia (CAP) is one of the most common diagnoses encountered in any ED, but clinical practice guideline recommendations have stagnated for years, while increasingly complex patients and multi-drug resistant community pathogens abound. After several years of patient waiting, new CAP guidelines were published this month.
These guidelines are supported by the American Thoracic Society and Infectious Diseases Society of America, and are endorsed by the Society of Infectious Disease Pharmacists. The author panel addresses 16 unique areas for recommendations covering: diagnostic testing, appropriate level of care, selection and duration of empiric and ongoing antibiotic therapy, and subsequent recommendations for care.
These guideline cover the time spectrum from the point of clinical diagnosis to the completion of antimicrobial therapy, but does not address diagnostic criteria or pneumonia prevention. It addresses adult patients living in the US, and excludes specific recommendations for pediatric patients, immunocompromised, or patients who have recently completed international travel.
The Bugs: Antibiotic selections in the guidelines are based upon the most common treatable bacterial causes of CAP in the US, which include: Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Staphylococcus aureus, Legionella species, Chlamydia pneumoniae, and Moraxella catarrhalis. Viral pathogens and MDROs rising in prevalence throughout the US, such as MRSA and Pseudomonas aeruginosa are also of concern.
The Tests: Controversy and comfort over which diagnostic tests to order when has been a long-standing issue facing ED physicians. The new guidelines make standard recommendations for diagnostic testing relatively clear. Sputum gram stain and culture and blood cultures should be obtained for patients at highest risk for MRSA or P. aeruginosa. This includes patients with severe CAP, patients with history of prior MRSA or P. aeruginosa infection, and patients who have been hospitalized on parenteral antibiotics within the preceding 90 days.
Testing of urine for pneumococcal and Legionella antigens is recommended for patients with the most severe CAP. Rapid influenza nucleic acid amplification tests (NAAT) are recommended at the time of diagnosis when influenza is circulating in the surrounding community. Serum procalcitonin levels, if obtained, should not have any bearing on initial empiric antibiotic therapy. The Pneumonia Severity Index (PSI) score is the guideline- preferred method to determine need for hospitalization, but appropriate level of care should be determined by clinical judgement.
The Drugs: Here’s where the new guidelines get interesting. Key recommendations for both outpatient and inpatient CAP therapy are summarized in the charts below.
| Outpatient Therapy | |
| Healthy adult, no comorbidities or risk factors for MRSA, P. aeruginosa
|
Amoxicillin (high dose) or |
| Doxycycline or | |
| Macrolide (azithromycin, clarithromycin) in areas with < 25% resistance(1) | |
| Adult with comorbidities(2)
|
Combo therapy with amoxicillin/clavulanate or cephalosporin and |
| doxycycline or a macrolide (in areas with resistance < 25%)(1) or | |
| Respiratory fluoroquinolone monotherapy | |
- Macrolides currently have resistance rates > 25% in the majority of the US. Macrolide monotherapy should only be used in areas of low resistance where contraindications to alternatives are present.
- Comorbidities include: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; and malignancy.
| Inpatient Therapy | Nonsevere inpatient pneumonia | Severe inpatient pneumonia |
| Standard treatment | Beta-lactam + macrolide or respiratory FQ | Beta-lactam + macrolide or beta-lactam + FQ |
| Prior respiratory MRSA isolate | Add vancomycin OR linezolid; obtain cultures/ nasal PCR | Add vancomycin or linezolid; obtain cultures/ nasal PCR |
| Prior respiratory P. aeruginosa isolate | Add coverage (pip/tazo, cefepime, ceftazidime, imipenem, meropenem, aztreonam); obtain cultures | Add coverage (pip/tazo, cefepime, ceftazidime, imipenem, meropenem, aztreonam); obtain cultures |
| Recent Hospitalization, IV Abx, Local RF for MRSA | Obtain cultures; no MRSA coverage unless positive | Add vancomycin or linezolid; obtain cultures/ nasal PCR |
| Recent Hospitalization, IV Abx, Local RF for P. aeruginosa | Obtain cultures; no P. aeruginosa coverage unless positive | Add coverage (pip/tazo, cefepime, ceftazidime, imipenem, meropenem, aztreonam); obtain cultures |
All CAP patients should receive a minimum five-day duration of antibiotic therapy. Patients with comorbidities should receive broader spectrum treatment due to higher likelihood of poor outcomes and pre-existing risk factors for antibiotic resistance. The guidelines do not give an order of preference for antibiotic therapy in both the outpatient and inpatient settings, so careful consideration of each patient’s history regarding drug allergies, drug-drug interactions, and risks for adverse effects from each individual agent is important. Routine empiric anaerobic coverage for aspiration is no longer recommended.
Remember the lectures you heard that categorized CAP, HAP, and HCAP? Well, those categories no longer exist. Instead, the new guidelines place strong emphasis on local epidemiology patterns, validated risk factors for MDRO’s, and rapid de-escalation of treatment pending culture results.
Patients being treated empirically for MRSA or P. aeruginosa should have evidence of either of those organisms being present, or rapid de-escalation of antibiotic therapy is recommended. MRSA by PCR and/or sputum cultures are recommended to allow de-escalation or confirmation of need for continued therapy.
Summary
In summary, think carefully about each patient’s risk factors and prior pulmonary infections. Obtain blood and sputum cultures in the highest risk patients. For outpatient management, macrolide resistance is over 25% in many areas, so macrolides should no longer be used as monotherapy in those areas. Ratchet up the antibiotic coverage based on how sick the patient is, but then rapidly de-escalate once culture data is available.
