In 1882, Gessard first discovered Pseudomonas, a strictly aerobic, gram-negative bacterium of relatively low virulence. The organism is ubiquitous, with a predilection to moist environments, primarily as waterborne and soilborne organisms. Pseudomonal species have been found in soil, water, plants, and animals; Pseudomonas aeruginosa colonization reportedly occurs in more than 50% of humans, and P aeruginosa is the most common pseudomonal species.
Pseudomonas is a clinically significant and opportunistic pathogen, often causing nosocomial infections. In addition to causing serious and often life-threatening diseases, these organisms exhibit innate resistance to many antibiotics and can develop new resistance after exposure to antimicrobial agents