S. aquatilis[3] S. entomophila S. ficaria S. fonticola S. glossinae[3] S. grimesii S. liquefaciens S. marcescens S. myotis[3] S. nematodiphila S. odorifera S. plymuthica S. proteamaculans S. quinivorans S. rubidaea S. symbiotica S. ureilytica[3] S. vespertilionis[3] Serratia is a genus of Gram-negative, facultatively anaerobic, rod-shaped bacteria of the family Enterobacteriaceae.
[5] They are typically 1–5 μm in length, do not produce spores,[6] and can be found in water, soil, plants, and animals.
[5] Serratia was thought to be a harmless environmental bacteria until it was discovered that the most common species in the genus, S. marcescens, is an opportunistic pathogen of many animals, including humans.
[8] S. marcescens is frequently found in showers, toilet bowls, and around wet tiles as a pinkish to red biofilm but only causes disease in immunocompromised individuals.
Aside from S. marcescens, some rare strains of the Serratia species – S. plymuthica, S. liquefaciens, S. rubidaea, and S. odoriferae – have been shown to cause infection such as osteomyelitis and endocarditis.
[9] Various strains of Serratia occupy an eclectic range of habitats: soil, water, plants, insects, and others.
Only one species of Serratia, S. marinorubra, has been identified on coconuts from various regions of the world, including California, France, and Brazil.
For example, in aphids, strains of S. symbiotica play a key nutritional role by providing the host with vitamins and amino acids.
During the summer in Padura, Italy, the town people discovered that their polenta dish turned red.
Species of Serratia have been isolated in a variety of environments, including soil, water, plants, animals and even air.
A caprylate-thallous medium seems to be highly preferred for the selective growth of genus Serratia, as it can use caprylic acid as a carbon source.
Most strains of S. marcescens appear red on trypticase soy agar slants when grown at around 25 °C.
The virulence of Serratia strains can also be identifiable by type 4 fimbriae, small hair-like projections.
[21] Serratia secretes a host of virulence factors, including prodigiosin, biosurfactants, DNAse, lipase, protease, gelatinase, hemolysin, chitinase, chloroperoxidase, and alkaline phosphatase.
Prodigiosin, a growth pigment, is often used as a phenotypic identification marker of Serratia species due to its red colorization.
[23][24] Endonucleases, such as DNAse, may aid in scavenging activity, allowing them to exploit the environment and maximize the availability of nutrients.
Due to its short half-life and tendency to remain bound to cells upon secretion, hemolysin has scarcely been identified in Serratia.
However, some studies employing more accurate detection techniques have evidenced hemolytic activity in almost all strains of Serratia.
[29][30] Chloroperoxidase allows the hydrolysis of phosphodiester bonds[31] while alkaline phosphatases are involved in cell signaling processes.
Serratia uses a metabolic enzyme, ADP glucose pyrophosphorylase, with distinct kinetic properties from those found in Enterobacteriaceae in that it is not greatly activated by fructose bisphosphate.
ADP glucose pyrophosphorylase from strains of S. marcescens demonstrated optimal activity in buffer at pH 7.5 and 8.0, respectively.
S. marcescens is thought to be transmitted through hand-to-hand transmission; in one hospital half of all tested personnels' hands were found to be positive for the pathogen.