Purple urine bag syndrome

Purple urine bag syndrome is a medical syndrome where purple discoloration of urine occurs in people with urinary catheters and co-existent urinary tract infection. Bacteria in the urine produce the enzyme indoxyl phosphatase. This converts indoxyl sulfate in the urine into the red and blue colored compounds indirubin and indigo. The most commonly implicated bacteria are Providencia stuartii, Providencia rettgeri, Klebsiella pneumoniae, Proteus mirabilis, Escherichia coli, Morganella morganii, and Pseudomonas aeruginosa.