Which organism is most often responsible for hospital-acquired pneumonia?

Pseudomonas aeruginosa is frequently identified as the leading cause of hospital-acquired pneumonia (HAP). This organism is a gram-negative bacterium known for its ability to survive in a wide range of environments and its resistance to many antibiotics. Its relevance in HAP is particularly significant in patients who are immunocompromised, those with chronic lung diseases, or individuals who have been on mechanical ventilation.

Pseudomonas aeruginosa is capable of forming biofilms and producing various virulence factors, which contribute to its pathogenicity in a healthcare setting. This includes its ability to adhere to surfaces, evade the immune response, and resist multiple antibiotic therapies, making infections difficult to treat. As a result, the presence of Pseudomonas in respiratory cultures from patients with pneumonia acquired in a hospital setting often points to its role as a primary pathogen in such cases.

Other organisms like Klebsiella pneumoniae can also be implicated in HAP, but Pseudomonas aeruginosa remains more prevalent and is recognized for its specific association with the healthcare environment. Streptococcus pneumoniae and Mycoplasma pneumoniae are more commonly associated with community-acquired pneumonia rather than hospital-acquired cases, further emphasizing why Pseudomonas