An update of the American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) clinical guideline for management and prevention of community-acquired pneumonia (CAP) was published in print form (also available at http://www.idsociety.org). These guidelines are an update of the guidelines published by ATS/IDSA in 2019.1
The following are selected recommendations from this new guideline regarding diagnosis and treatment of CAP. Comments by the authors of this review are in italics.
- Obtaining a blood culture, sputum culture, or sputum Gram stain routinely in adults treated in outpatient settings is not recommended.
- Pretreatment blood culture, sputum culture and Gram stain of respiratory secretion are recommended in adults with the following:
- –Classified as having severe CAP
- –Receiving empiric therapy for methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa
- –Previous documented infection of MRSA or P. aeruginosa
- –Hospitalized and received parenteral antibiotics in the last 90 days
Diagnosis is assessed based on patient's clinical presentation of signs and symptoms, as well as diagnostic imaging. Typical signs and symptoms of pneumonia include couth with or without sputum production, shortness of breath, chest pain, tachypnea, and increased work of breathing. Systemic signs can include fever, chills, malaise, fatigue, and elevated white blood cell counts. A diagnosis is confirmed when the chest x-ray shows infiltrates and clinical presentation matches.
The decision to obtain cultures should be determined on the basis of clinical presentation, local etiological considerations, and local antimicrobial stewardship processes. Historically, sputum cultures and Gram stains had poor positive predictive values. Routinely obtaining cultures have led to false-positive results from contaminants leading to inappropriate antibiotic use and increased hospital length of stay. In severe CAP, however, delay in covering multidrug resistant organisms may lead to worse patient outcomes. Therefore, the benefit of obtaining early cultures is crucial for deescalation in this patient population.
- The routine uses of urinary antigens Streptococcus pneumoniae or Legionella are not recommended. Exceptions to this recommendation include adults with severe CAP, patients who may have been exposed to an area of recent outbreak, or CAP associated with recent travel.
- If a patient presents with flu-like symptoms or illness, clinical judgments should warrant testing for influenza.
- Procalcitonin should not be used alone as a clinical predictor of initiation antibiotics.
- The Pneumonia Severity Index (PSI) is not recommended over the tool based on confusion, urea level, respiratory rate, blood pressure, and age greater or equal to 65 to determine if patients warrant hospitalization.
The rationale behind the use of urinary antigens comes from randomized trials that have demonstrated poor negative predictive value of urinary antigen testing2; however, a handful of large observational studies have shown that urinary antigen testing has been associated with a reduction in mortality.3 Overall, the basis behind the recommendation to avoid unnecessary testing is appropriate given the current landscape of available literature.
In the past, some investigators have previously suggested that certain levels of procalcitonin indicate presence of bacterial infections.4 The guidelines now recommend that procalcitonin should not be used alone as a clinical predictor of initiation antibiotics based on recent literature that failed to identify a procalcitonin threshold to distinguish between bacterial and viral pathogens.5
The PSI and CURB-65 were developed as validated clinical prediction rules for prognosis of CAP in immunocompetent patients. The PSI is now recommended over the CURB-65 to determine if patients warrant hospitalization.6 Consistent with previous guidelines, clinical prediction tools should be used in combination with clinical judgments.
- The term health care–associated pneumonia (HCAP) should be eliminated.
The 2005 ATS/IDSA guidelines for the management of hospital-acquired and ventilator associated pneumonia defined a subset of pneumonia, which was termed HCAP.7 It attempted to stratify patients with potential risk factors for multidrug-resistant infections. These previous risk factors included patients who reside in a nursing home or long-term care facility, hospitalization for at least 2 days in the last 90 days, receiving home infusion therapy, chronic dialysis, home wound care, or a caregiver who is known to have an antibiotic-resistant pathogen. Many studies have recently demonstrated that risk factors used to define HCAP do not correlate with higher rates of antimicrobial-resistant pathogens.8 The two consistently proven and strongest risk factors associated with MRSA and P. aeruginosa infections are a previous hospitalization (within the last 90 days) in which the patient received treatment with parenteral antibiotics and previous confirmed infection with either MRSA or P. aeruginosa. Recent literature has outlined deficiencies in the positive predictive value of the current HCAP criteria.9 Patients should be stratified based on their individual risk for MRSA or P. aeruginosa and treated accordingly.
- Outpatient empiric treatment
- –Macrolide monotherapy should only be used in geographical areas with proven pneumococcal resistance of less than 25%.
- –Amoxicillin or doxycycline should be used in patients without comorbidities.
- –Macrolide in combination with Augmentin or a cephalosporin or respiratory fluoroquinolone monotherapy should be used in patients with comorbidities.
- Inpatient empiric treatment without MRSA and P. aeruginosa risk factors
- –Combination therapy with a β-lactam and a macrolide is recommended.
- –Monotherapy with a respiratory fluoroquinolone is recommended.
- –Patients who have a contraindication to both macrolides and fluoroquinolones should receive combination therapy with a β-lactam and doxycycline.
- Inpatient treatment with MRSA and P. aeruginosa risk factors
- –Empiric therapy for MRSA includes vancomycin or linezolid.
- –Empiric therapy for P. aeruginosa includes piperacillin-tazobactam, cefepime, ceftazidime, aztreonam, meropenem, and imipenem.
- –Oseltamivir is recommended for adults with CAP to test positive for influenza in both the inpatient and outpatient setting.
- –Treatment within 2 days of symptom onset or hospitalization may result in the best outcomes.10
- –In patients with a positive influenza test, no evidence of a bacterial pathogen (including a low procalcitonin level), and early clinical stability, early discontinuation of antibiotics should be considered.
In the 2007 guidelines, nonsevere CAP patients without comorbidities qualified for macrolide monotherapy as first line treatment.11 Since then, the prevalence of resistant strains of S. pneumoniae has increased. It is currently estimated that macrolide resistance is greater than 25% in most areas of the United States.12
Treatment within 2 days of symptom onset or hospitalization may result in the best outcomes.10 The use of anti-influenza agents in the outpatient setting reduces duration of symptoms and likelihood of complications in patients with influenza. Anti-influenza agents have shown to reduce mortality risk in the inpatient setting. Although it is most beneficial to start therapy within 2 days of symptom onset, studies also support starting at a later time to prevent the risk of viral shedding and potential transmission to other patients.13
In adults with CAP who test positive for influenza, standard antibacterial treatment should be initiated. Bacterial infections can occur concomitantly with an influenza infection. Staphylococcus aureus is the most common superimposed bacterial infection associated with influenza pneumonia. In patients with a positive influenza test, no evidence of a bacterial pathogen, and early clinical stability, early discontinuation of antibiotics should be considered.
DURATION OF THERAPY
- Duration of therapy should be based on clinical improvement with a minimum of at least 5 days treatment.
- Longer courses of antibiotic therapy are recommended for the following:
- –Pneumonia complicated by meningitis, endocarditis, and other deep-seated infection.
- –Infection with other, less-common pathogens (eg, Burkholderia pseudomallei, Mycobacterium tuberculosis, or endemic fungi)
- –MRSA or P. aeruginosa infections (total antibiotic duration of 7 days)
Validated measures such as heart rate, respiratory rate, blood pressure, oxygen saturation, temperature, appetite, and normal mentation should be used to determine clinical improvement. Antibiotic therapy should be continued until the patient achieves stability for at least 5 days. Most patients will achieve clinical stability within the first 2 to 3 days; therefore, a total duration of 5 days is appropriate. Procalcitonin levels are useful in settings where the hospital length of stay exceeds 5 to 7 days. Failure to achieve clinical stability within 5 days is associated with higher mortality and worse clinical outcomes.14 This should prompt the assessment for a pathogen resistant to the current therapy, a complication of pneumonia, or another source of infection.
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