Pseudomonas aeruginosa bacteria inside biofilm, computer illustration. This is a Gram-negative, aerobic, enteric, rod prokaryote. P. aeruginosa causes skin infections, urinary tract infections and septicaemia. It produces a blue-green pigment, pyocyanin, which characterizes the bluish pus produced by the infection. It is found in soil, water, skin flora, and most man-made environments throughout the world. Many strains are antibiotic-resistant and produce biofilms. A biofilm is a colony of bacteria that forms a coating on a surface. Common places for biofilms of P. aeruginosa to develop are on contact lenses, where they can cause eye infections, on catheters, where they cause catheter-associated infections, and on wound surfaces, where they cause wound infections.