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Clinical Edge Journal Scan Commentary: CAP December 2021


Although the majority of acute pneumonias are viral in etiology, standard practice dictates empiric administration of antimicrobial agents for the youngest, oldest, and patients with underlying comorbid conditions. The practitioner’s primary responsibility is to differentiate upper respiratory tract infections from pneumonia. The practitioner must also decide which patients with lower respiratory tract disease warrant more aggressive management.

The virtual elimination of Haemophilus influenzae type B as a respiratory pathogen, recognition of Mycoplasma pneumoniae as a common cause of pneumonia in older children and young adults, and atypical pathogens in elderly adults have recently changed our selection of initial empiric antimicrobial therapy for lower respiratory tract infections in some patients. It is increasingly important to use such information since narrow-spectrum antibiotics for empiric therapy of moderately severe community acquired pneumonia (CAP) should be standard therapy. 1 On the other hand, the addition of doxycycline to a beta-lactam antibiotic has recently been shown to improve outcomes of CAP in elderly adults. 2 Along with advanced age, male gender is also a risk factor for treatment failure of moderately severe CAP, 3 so should be taken into consideration in management decisions.

If a patient with mild CAP does not respond to initial antibacterial therapy, the most likely explanation is a viral cause. Other bacterial causes might also be considered, such as Staphylococcus aureus , multi-resistant pneumococcus, coliforms, ampicillin-resistant H. influenzae , fungi, or anaerobes depending on clinical and laboratory factors.

New, rapid diagnostic tests are also useful in making clinical decisions and are particularly important for children who are unable to produce sputum for examination and whose small airways limit use of bronchoscopy. Recent studies have shown that heparin-binding protein (HBP) predicts disease progression in children with severe CAP, directing the physician to do further testing of microbiologic etiology. 4

Treatment of pneumonia is usually empiric. If Chlamydia pneumoniae or M. pneumoniae is suspected as the responsible pathogen, azithromycin should be used as primary therapy. Quinolones or tetracycline-based antibiotics can be considered when macrolides are not tolerated. In children with community-acquired pneumonia (CAP) discharged from emergency departments or inpatient wards, findings from a trial including 814 children > 6 months old with CAP found that a lower dose and shorter course of amoxicillin was not inferior compared to higher doses and longer courses. The children were randomly assigned 1:1 after hospital discharge to receive one of the 4 possible combinations of amoxicillin dose (35-50 or 70-90 mg/kg) and duration (3 or 7 days). The results indicated that further outpatient treatment with amoxicillin at the lower dose was not inferior to a higher dose, and a 3-day treatment course was not inferior to a 7-day treatment course. 5

Pneumococcal urinary antigen testing (PUAT) has recently been shown to direct narrow spectrum antibiotic therapy when positive in children or allow earlier de-escalation from broad spectrum antibiotics. 6

When Staphylococcus aureus is suspected, methicillin resistance (MRSA) must be considered. Vancomycin has been standard therapy for this pathogen unless clindamycin susceptibility is documented. A recent study showed that the newer cephalosporin, ceftaroline, used as monotherapy or in combination with a macrolide or quinolone resulted in a lower hospital mortality rate than standard therapy with vancomycin or combination antibiotics. 7

Other data used to determine probable causes of CAP include associated clinical signs and symptoms, chest x-ray findings, and diagnostic laboratory tests. Sputum is rarely produced by children during episodes of pneumonia, so the usual common step in the management of adult severe pneumonias, Gram stain examination of sputum is eliminated.

Antibiotics are selected primarily on the basis of age and severity of illness. Duration of therapy is 7 to 10 days for uncomplicated CAP. Once the causative agent is identified by culture or with one of the rapid antigen detection assays, specific therapy may be readily selected.

Treatment of pneumonia is usually empiric but the preference for narrow spectrum antibiotics should be emphasized . 1 Amoxicillin for children and a quinolone for adults is the usual therapy.

If a patient with mild CAP does not respond to initial antibacterial therapy, the most likely explanation is a viral cause but for severely ill patients, other bacterial etiologies should also be considered, particularly MRSA where the addition of caftaroline would be considered. 7

References

  1. Schweitzer VA et al. Narrow-spectrum antibiotics for community-acquired pneumonia in Dutch adults (CAP-PACT): a cross-sectional, stepped-wedge, cluster-randomised, non-inferiority, antimicrobial stewardship intervention trial. Lancet Infect Dis. 2021(Oct 7).
  2. Uddin M et al. Effectiveness of Beta-Lactam plus Doxycycline for Patients Hospitalized with Community-Acquired Pneumonia Clin Infect Dis. 2021;ciab863 (Nov 9).
  3. Dinh A et al . Factors Associated With Treatment Failure in Moderately Severe Community-Acquired Pneumonia: A Secondary Analysis of a Randomized Clinical Trial. JAMA Netw Open. 2021;4(10):e2129566 (Oct 15).
  4. Huang C et al. Heparin-Binding Protein in Critically Ill Children With Severe Community-Acquired Pneumonia. Front Pediatr. 2021 (Oct 28).
  5. Bielicki JA et al. Effect of Amoxicillin Dose and Treatment Duration on the Need for Antibiotic Re-treatment in Children With Community-Acquired Pneumonia: The CAP-IT Randomized Clinical Trial. JAMA. 2021;326(17):1713-1724 (Nov 2).
  6. Greenfield A et al. Impact of Streptococcus pneumoniae Urinary Antigen Testing in Patients with Community-acquired Pneumonia Admitted within a Large Academic Health System. Open Forum Infect Dis. 2021;ofab522 (Oct 22).

Cilloniz C et al. Impact on in-hospital mortality of ceftaroline versus standard of care in community-acquired pneumonia: a propensity-matched analysis. Eur J Clin Microbiol Infect Dis. 2021 (Nov 12).



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