Which of the following organisms is a common cause of pneumonia in patients recovering from surgery?

Pseudomonas aeruginosa is a common cause of pneumonia in patients recovering from surgery due to its opportunistic nature and ability to thrive in hospital environments. This organism is particularly known for causing infections in patients with weakened immune systems or those with underlying health conditions, such as those recovering from surgeries. After surgical procedures, patients may have compromised respiratory systems, especially if they were intubated or had prolonged ventilation support, which makes them susceptible to infections from this bacterium.

Pseudomonas aeruginosa has several virulence factors that allow it to adhere to surfaces, evade the host's immune response, and resist antibiotics, making it a formidable pathogen in healthcare settings. Additionally, its ability to form biofilms can complicate treatment and lead to chronic infections, further solidifying its role as a leading cause of pneumonia in such patients.

In contrast, while the other organisms listed can cause pneumonia, they are generally not as prevalent in postoperative patients as Pseudomonas aeruginosa. Escherichia coli and Klebsiella pneumoniae may be more associated with urinary tract infections or intra-abdominal infections. Streptococcus pneumoniae is more typically associated with community-acquired pneumonia rather than opportunistic infections in immunocompromised surgical patients