Viral-bacterial coinfection affects the presentation and alters the prognosis of severe community-acquired pneumonia.

Background: Multiplex polymerase chain reaction (mPCR) enables recovery of viruses from airways of patients with community-acquired pneumonia (CAP), although their clinical impact remains uncertain.

Methods: Among consecutive adult patients who had undergone a mPCR within 72 hours following their admission to one intensive care unit (ICU), we retrospectively included those with a final diagnosis of CAP. Four etiology groups were clustered: bacterial, viral, mixed (viral-bacterial) and no etiology. A composite criterion of complicated course (hospital death or mechanical ventilation > 7 days) was used. A subgroup analysis compared patients with bacterial and viral-bacterial CAP matched on the bacterial pathogens.

Results: Among 174 patients (132 men [76 %], age 63 [53-75] years, SAPSII 38 [27;55], median PSI score 106 [78;130]), bacterial, viral, mixed and no etiology groups gathered 46 (26 %), 53 (31 %), 45 (26 %) and 30 (17 %) patients, respectively. Virus-infected patients displayed a high creatine kinase serum level, a low platelet count, and a trend toward more frequent alveolar-interstitial infiltrates. A complicated course was more frequent in the mixed group (31/45, 69 %), as compared to bacterial (18/46, 39 %), viral (15/53, 28 %) and no etiology (12/30, 40 %) groups (p < 0.01). In multivariate analysis, the mixed (viral-bacterial) infection was independently associated with complicated course (reference: bacterial pneumonia; OR, 3.58; CI 95 %, 1.16-11; p = 0.03). The subgroup analysis of bacteria-matched patients confirmed these findings.

Conclusions: Viral-bacterial coinfection during severe CAP in adults is associated with an impaired presentation and a complicated course.