Compositions and methods are provided related to Pseudomonas bacteria. The compositions and methods may be used for diagnosis and therapy of medical conditions involving infection with Pseudomonas bacteria. Such infections include Pseudomonas aeruginosa in the lungs of patients with cystic fibrosis. A compound useful in the present methods may be used in combination with a therapeutic agent or may be linked to a therapeutic agent. Pseudomonas bacteria may be inhibited by blocking colonization, inhibiting virulence factors, arresting growth or killing the bacteria.