A 10-year-old boy with cystic fibrosis presents with a chronic productive cough and recurrent pulmonary exacerbations. Sputum culture reveals a mucoid, Gram-negative rod. Which of the following organisms is the most likely causative agent?

Explanation

Pseudomonas aeruginosa is a predominant pathogen in patients with cystic fibrosis (CF), causing chronic lung infections and recurrent exacerbations. Its ability to produce alginate, a polysaccharide capsule, leads to the characteristic mucoid colony phenotype and facilitates biofilm formation, contributing to its persistence and resistance to host defenses and antibiotics. While S. aureus and H. influenzae can also infect CF patients, and Burkholderia cepacia complex is a significant CF pathogen, the description of a 'mucoid, Gram-negative rod' in a CF patient strongly points to P. aeruginosa.