Pseudomonas aeruginosais an opportunistic bacterial pathogen responsible for 10% of all nosocomial (hospital-acquired) infections, a leading cause of nosocomial pneumonia in general patient populations, and the leading cause in intensive care patient populations. Since Pseudomonas is often resistant to antibiotics, an infection is life-threatening for compromised individuals such as burn victims, AIDS patients, and patients with cystic fibrosis. Respiratory failure, the leading cause of cystic fibrosis-associated death, results from chronic Pseudomonas infections that lead to lung damage as bacterial toxins attack lung epithelia. This damage then allows the infection to spread beyond the lungs. A secretion/intoxication system present on the bacterial surface transports toxins directly into epithelial cells, and a well-documented inhibition of this system through blockade of the bacterial toxin transport component PcrV provides demonstrable protection against lung injury and increased survival in animal models. Researchers at the University of California, San Francisco have shown that the PcrV protein is a highly effective vaccination agent against Pseudomonas, whether administered before or after infection.