Improving antibiotic stewardship in pneumonia: Is more aggressive viral testing a key to success?

EJRC Article Review

Pneumonia has a substantial impact in the ICU, as a leading reason of acute respiratory failure and for mechanical ventilation. Since appropriate antibiotic use is crucial to limiting morbidity and mortality in pneumonia, intensivists normally prescribe broad-spectrum antimicrobial agents when suspected. Discovering a viral pathogen as the sole responsible of a case of pneumonia may reassure the clinician to safely discontinue antibiotics, thus improving antibiotic stewardship.

To explore the epidemiology and outcomes of viral pneumonia in the ICU, Shorr and colleagues performed a secondary analysis of a prospective cohort of adult patients with suspected cases of community-acquired, hospital-acquired and ventilator-associated pneumonia, requiring mechanical ventilation for >24 hours, in a single centre, during a 1-year period.

The cohort included 364 patients. Viral testing was performed in >95% of cases, revealing viruses as the sole cause of pneumonia in almost 22% of cases. Bacterial organisms were identified in almost 46% of cases. No organism was recovered on the remainder. There were no differences between the groups of viral pneumonia and non-viral pneumonia with respect to demographics, comorbidities, severity of illness and immune status (including corticoid administration, use of immunosuppressant drugs, solid organ transplantation and HIV). However, viral pneumonia was more frequent in patients who had undergone stem cell transplantation (SCT) (OR 2.51; 95% CI 1.20-5.27). In this cohort, 67% of viral pneumonias were complicated by shock, with no differences with pneumonias caused by other pathogens. Outcomes with respect to mortality, length of stay, duration of mechanical ventilation and readmission rates were also similar between those with a viral pathogen and those with other causes of pneumonia. Multivariate analysis showed that APACHE-II <26 and SCT were associated with viral pneumonia.

Study Strengths & Limitations

Strengths of the study were the high rate of viral testing performance, use of a cohort of mechanically ventilated patients and the potential to generate new hypothesis.

Limitations include the single-centre design secondary analysis (thus, retrospective and not generalisable), that the diagnostic protocol including viral testing was not standardised (i.e. possible bias, including underestimation of certain pathogens), the intrinsic limitations of microbiologic tests (sensitivity and specificity) and the possibility of confounding by indication in the multivariate analysis.

Take Home Messages

• Viruses are a common cause of pneumonia associated with acute respiratory failure requiring mechanical ventilation.
• Viral pneumonia may result in severe critical illness associated with shock, with the same outcomes as non-viral pneumonia, regardless patient characteristics.
• More aggressive diagnostic strategies, with wider use of viral diagnostic tests, may allow to formally identify a virus as the only pathogen in pneumonia, enabling the discontinuation of antimicrobial agents and improving antibiotic stewardship.

This article review was prepared and submitted by ESICM NEXT member David Pérez Torres, Department of Intensive Care, Río Hortega University Hospital, Valladolid, Spain, on behalf of the ESICM Journal Review Club.

References

Shorr AF, Fisher K, Micek ST and Kollef MH. The Burden of Viruses in Pneumonia Associated With Acute Respiratory Failure: An Underappreciated Issue. Chest. 2017 Dec 21. pii: S0012-3692(17)33236-1 [Epub ahead of print]. DOI: 10.1016/j.chest.2017.12.005