Serratia marcescens is a bacteria that grows quickly in warm, wet environments. It is often seen in toilets and showers where it can be distinguished by its red color.
In children, Serratia generally infects the digestive tract. In adults, it is very opportunistic and rarely attacks healthy people. However, it can affect the urinary tract, respiratory tract and wounds, where it can spread quickly. It is a particular problem in people who use urinary catheters
Bleach should be used to disinfect areas where Serratia is suspected, even though most strains of the bacteria do not affect humans. However, the bacteria is very hardy and often can infect supposedly sterile medical items, such as syringes, if they are improperly manufactured.