Color-enhanced Scanning Electron Micrograph (SEM) showing Serratia marcescens biofilm. S. marcescens is a species of rod-shaped Gram-negative bacteria in the family Enterobacteriaceae. A human pathogen, it is involved in hospital-acquired infections (HAIs), particularly catheter-associated bacteremia, urinary tract infections and wound infections. It is commonly found in bathrooms as a pink, pink-orange, or orange discoloration and slimy biofilm. It feeds on phosphorus-containing materials or fatty substances such as soap and shampoo residue. Image width: 51.3 micrometers. Magnification: 1950x if the image is printed 10 cm wide. Bar: 10 micrometers.