The Evolving Etiology of Hospital-Acquired and Ventilator-Associated Pneumonia.

Nosocomial pneumonia (NP), including hospital-acquired and ventilator-associated pneumonia, remains a major threat to hospitalized patients. NP arises from aspiration of pathogens in the setting of alterations in the pulmonary microbiome and weakened host defenses. Pseudomonas aeruginosa and Staphylococcus aureus predominate, though there has been a rise in carbapenem-resistant gram negatives, complicating treatment and increasing mortality. Viral and fungal pathogens further contribute to the NP burden. Diagnostic challenges persist due to nonspecific clinical features, though multiplex polymerase chain reaction testing is improving pathogen identification. This article highlights emerging trends in NP epidemiology, antibiotic resistance, and novel diagnostics.