Background: Although viruses are considered the most common detected cause of admitted cases of lower respiratory tract infections (LRΤΙs), data for patients with severe LRTI are missing. This study aimed to define the epidemiology of severe LRTI using the BIOFIRE® FILMARRAY® Pneumonia plus Panel (PNplus Panel) and the association of the results with the host inflammatory state.
Materials/methods: PROGRESS is a prospective randomized trial designed to evaluate a procalcitonin (PCT)-guided antibiotic stopping rule for the incidence of infection-associated adverse events in patients with sepsis (ClinicalTrials.gov NCT03333304). PNplus Panel was performed retrospectively using sputum of 90 patients with LRTI. Sepsis classification was done using the Sepsis-3 definitions. Primary endpoint was the comparison of the detection rate of pathogens between conventional microbiology (blood, sputum, pleural fluid cultures and urine antigen detection) and PNplus Panel. Secondary endpoints were the association of the PNplus Panel with the inflammatory host response and detection of antibiotic resistance.
Results: 56 patients with community-acquired pneumonia (CAP) and 34 with healthcare-associated pneumonia (HCAP) were studied; median pneumonia severity index was 113. PNplus detected at least one pathogen in 65 patients (72.2%) compared to 10% by conventional microbiology (p<0.0001); bacteria were the most common pathogens. Median PCT was 0.49 ng/ml for patients with ≥105 copies/ml of a bacterial pathogen as compared to 0.18 ng/ml in patients with a bacterial pathogen detected at <105 copies/ml (p=0.004). SOFA score, serum CRP and white blood cells did not differ between patients with undetected, bacterial, viral or bacterial-viral cause of infection. At least one resistance gene was detected in 14.4% of samples being more common in HCAP versus CAP (32.2% vs 5.1%; p=0.001).
Conclusions: PNplus detects severe pneumonia pathogens at significantly greater rate than conventional microbiology. The greater circulating PCT levels reflect the true virulence of the detected pathogens.