Serratia marcescens (/səˈreɪʃiə mɑːrˈsɛsɪnz/) is a species of rod-shaped, Gram-negative bacteria, that is also a facultative anaerobic organism, classified as an opportunistic pathogen in the family Enterobacteriaceae. It was discovered in 1819 by
Bartolomeo Bizio in Padua, Italy.