Serratia

Serratia is a genus of Gram-negative, facultatively anaerobic, rod-shaped bacteria of the family Enterobacteriaceae. They are typically 1–5 μm in length and do not produce spores. The most common and pathogenic of the species in the genus, S. marcescens, is normally the only pathogen and usually causes nosocomial infections. However, rare strains of S. plymuthica, S. liquefaciens, S. rubidaea, and S. odoriferae have caused diseases through infection. S. marcescens is typically found in showers, toilet bowls, and around wetted tiles.Some members of this genus produce characteristic red pigment, prodigiosin, and can be distinguished from other members of the family Enterobacteriaceae by their unique production of three enzymes: DNase (nucA), lipase, and gelatinase (serralysin). The bacterium is an opportunistic human pathogen, capitalizing on its ability to form tight-knit surface communities called biofilms wherever it can. S. marcescens is thought to be transmitted through hand-to-hand transmission by hospital personnel. In the hospital, Serratia species tend to colonize the respiratory and urinary tracts, rather than the gastrointestinal tract, in adults. Serratia infection is responsible for about 2% of nosocomial infections of the bloodstream, lower respiratory tract, urinary tract, surgical wounds, and skin and soft tissues in adult patients. Outbreaks of S. marcescens meningitis, wound infections, and arthritis have occurred in pediatric wards. Cases of Serratia arthritis have been reported in outpatients receiving intra-articular injections. Species of Serratia have been isolated in a variety of environments, including soil, water, plants, animals and even air. Several methods can be used to study the epidemiology of S. marcescens. Usual enrichment strategies involve the use of media containing antibiotic and antifungal substances. A caprylate-thallous media seems to be highly preferred for the selective growth of genus Serratia, as it can use caprylic acid as a carbon source. Serological typing and different types of polymerase chain reaction can be used to identify the bacteria. Biotyping, bacteriocin typing, phage typing, plasmid analysis, and ribotyping can also be usedS. marcescens appears red on trypticase soy agar slants when grown at around 25 °C.S. marcescens and S. liquefaciens can be easily confused in the lab when using the analytical profile index system. They can both oxidise arabinose, but only S. liquefaciens can ferment arabinose in peptone water. S. marcescens was first documented as a red-coloured putrefaction of polenta by Bartolomeo Bizio in Padua. The bacterium was later named in honour of Italian physicist Serafino Serrati and marcescens because of the pigment's rapid discolouration and decay.:538