Comparative study of the etiology of nosocomial bacteremic pneumonia in ventilated and non-ventilated patients: a 10-year experience in an institution.

The etiology of nosocomial pneumonia (NP) in non-mechanically ventilated patients [hospital-acquired pneumonia (HAP)] is poorly understood because of difficulties in obtaining reliable respiratory samples. While it is thought to resemble that of mechanically ventilated patients [ventilator-associated pneumonia (VAP)], few studies compare etiology in both groups. We compared the etiology of bacteremic NP (bNP) episodes in HAP and VAP over 10 years in our institution. We defined NP in adults according to the American Thoracic Society criteria. bNP episodes were defined as significant isolates in ≥1 blood culture concordant with ≥1 respiratory pathogen isolated with <7 days of difference. During 2010-2019, 188 patients were included. The comparison between HAP ( n = 104) and VAP ( n = 84) revealed the following factors: male sex (80.8%/63.1%; P < 0.01); median age (69.3/67.8 y-o; P = 0.602); etiology [ Staphylococcus aureus (40.49%/21.4%; P < 0.01), Enterobacterales (35.6%/39.3%; P = 0.601), and Pseudomonas aeruginosa (14.4%/34.5%; P < 0.01)]. Microorganisms were considered multidrug-resistant in 29.8%/21.4% of cases, respectively ( P = 0.193). Median hospital stay in HAP/VAP was 45.0/53.5 days ( P = 0.255), mortality was 55.8%/53.6% ( P = 0.770), and related mortality was 45.2%/35.7% ( P = 0.233). The etiology of bNP in hospitalized patients is similar but not identical in HAP and VAP. The differences included a higher prevalence of S. aureus in HAP and Pseudomonas aeruginosa in VAP. bNP is a serious disease, with mortality >40%. IMPORTANCE This study on bacteremic nosocomial pneumonia (bNP) demonstrates the importance of this condition both in patients undergoing and not undergoing mechanical ventilation. Staphylococcus aureus , Enterobacterales, and non-fermenting Gram-negative bacilli are all causative agents in ventilator-associated pneumonia (VAP) and hospital-acquired pneumonia (HAP), with a predominance of S. aureus in HAP and of Pseudomonas aeruginosa in VAP. Mortality in this condition is very high. Therefore, new therapeutic and preventive approaches should be sought.