Pseudomonas infection refers to a disease caused by one of the species of the genus Pseudomonas. P. aeruginosa is an opportunistic human pathogen, most commonly affecting immunocompromised patients, such as those with cystic fibrosis or AIDS. Infection can affect many different parts of the body, but infections typically target the respiratory tract (e.g. patients with CF or those on mechanical ventilation), causing bacterial pneumonia. In a surveillance study between 1986 and 1989, P. aeruginosa was the third leading cause of all nosocomial infections, and specifically the number one leading cause of hospital-acquired pneumonia and third leading cause of hospital-acquired UTI. Treatment of such infections can be difficult due to multiple antibiotic resistance, and in the United States, there was an increase in MDRPA (Multidrug-resistant Pseudomonas aeruginosa) resistant to ceftazidime, ciprofloxacin, and aminoglycosides, from 0.9% in 1994 to 5.6% in 2002.