Background/Objectives: Lower respiratory tract infections (LRTIs) are frequent in the intensive care unit (ICU) and drive empiric broad-spectrum antibiotic use. Rapid multiplex PCR assays may improve pathogen detection and stewardship compared with conventional culture. We evaluated the real-world impact of the BioFire^® FilmArray^® Pneumonia Panel Plus (FA-PNEU^®) on antimicrobial management in suspected nosocomial LRTI. Methods: This was a single-centre, prospective observational cohort study conducted in a tertiary ICU (Madrid, Spain) between April 2021 and March 2025. Adult patients with suspected hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), or ventilator-associated tracheobronchitis (VAT) were included if paired respiratory samples underwent FA-PNEU^® and conventional culture (CC). Diagnostic accuracy and prescribing changes were analysed. Results: A total of 344 samples from 236 patients were included. FA-PNEU^® demonstrated high sensitivity (93.4%) and negative predictive value (97.9%) but moderate specificity (65.0%) and low positive predictive value (36.5%). False positives occurred in 85.8% of patients with prior antibiotic therapy targeting the detected organism. Antibiotic management was considered directly influenced by FA-PNEU^® when any prescribing decision (initiation, escalation, de-escalation, or discontinuation) explicitly followed the panel’s results rather than other clinical or microbiological information. Using this definition, FA-PNEU^® directly influenced antibiotic therapy in 57.6% of cases, while in 17.7%, prescribing was instead guided by a suspected alternative infection. In patients without prior antibiotics, treatment initiation or withholding was fully concordant with FA-PNEU^® results, while in those already receiving therapy, 60.8% underwent modification, two-thirds in agreement with the panel. Conclusions: In critically ill patients with suspected nosocomial LRTI, FA-PNEU^® provided rapid, high-sensitivity diagnostics that substantially influenced antimicrobial prescribing. Its greatest value lies in ruling out bacterial infection and guiding stewardship, though results must be interpreted within the full clinical and microbiological context.

Background/Objectives: Stenotrophomonas maltophilia is a common cause of lower respiratory tract infection (LRTI) in critically ill patients, but differences between ventilator-associated tracheobronchitis (VAT) and ventilator- or hospital-acquired pneumonia (VAP/HAP) remain unclear. We aimed to compare clinical outcomes between VAT and VAP/HAP and, secondarily, to explore antimicrobial treatment patterns and their association with treatment failure. Methods: We conducted a retrospective two-center cohort study of adults admitted to intensive care units (ICUs) in Madrid, Spain, between August 2021 and December 2025 with clinically significant S. maltophilia VAT, VAP, or HAP. The primary analysis included only the first (index) episode per patient. Results: Sixty-seven patients contributed 90 episodes. Among index episodes, therapeutic failure was more frequent in VAP/HAP than in VAT (40.6% vs. 14.3%; absolute risk difference, 26.3 percentage points; 95% confidence interval [CI], 5.0–45.2; p = 0.026). In a parsimonious Firth’s penalized logistic regression, VAP/HAP remained associated with therapeutic failure (adjusted odds ratio, 4.06; 95% CI, 1.32–14.25; p = 0.014). Results were consistent after adjustment for SOFA score at infection onset and when the analysis was restricted to VAP. ICU mortality was numerically higher in VAP/HAP (46.9% vs. 25.7%). In an exploratory Firth’s model, laboratory-reported in vitro active antimicrobial therapy was associated with lower odds of failure (adjusted odds ratio, 0.19; 95% CI, 0.05–0.72; p = 0.014); however, this exposure was susceptible to time-dependent bias, and empirical anti-S. maltophilia therapy, defined at treatment initiation, was not associated with failure (26.7% vs. 26.9%). Conclusions: The clinical and prognostic significance of respiratory S. maltophilia infection appears to differ by syndrome. VAP/HAP was associated with more therapeutic failure than VAT. The association between in vitro active therapy and lower failure was exploratory and requires confirmation, and no comparative effectiveness conclusions can be drawn for individual antimicrobial agents.