SERRATIA MARCESCENS

'''Serratia marcescens''' is a species of Gram-negative bacterium in the family Enterobacteriaceae. A human pathogen, ''S. marcescens'' is involved in nosocomial infections, particularly urinary tract infections and wound infections. Serratia marcescens, Hejazi A, Falkiner FR, , , J Med Microbiol, 1997
''S. marcescens'' (bacillus), motile organism and can grow in temperatures ranging from 5–40°C and in pH levels ranging from 5 to 9. ''S. marcescens'' is differentiated from other Gram-negative bacteria, as it is able to perform casein hydrolysis. Performing casein hydrolysis allows for ''S. marcescens'' to produce extracellular metalloproteases which are believed to function in cell-to-extracellular matrix interactions. ''S. marcescens'' also exhibits tryptophan- and citrate-degradation. One of the end products of tryptophan degradation is pyruvic acid, which is then incorporated into different metabolic processes of ''S. marcescens''. A final product of citrate degradation is carbon. Thus, ''S. marcescens'' can rely on citrate as a carbon source. In identifying the organism one may also perform a ''methyl red test'', which determines if a microorganism performs mixed-acid fermentation. ''S. marcescens'' results in a negative test. Another determination of ''S. marcescens'' is its capability to produce lactic acid via oxidative and fermentative metabolism. Therefore, it is said that ''S. marcescens'' is lactose O/F+.^[1]
Due to its ubiquitous presence in the environment, and its preference for damp conditions, ''S. marcescens'' is commonly found growing in bathrooms (especially on tile grout), where it manifests as a pink discoloration. Once established, complete eradication of the organism is often difficult, but can be accomplished by application of a bleach-based disinfectant.''S. marcescens'' may also be found in environments such as dirt, supposedly "sterile" places, and the subgingival biofilm of teeth. Due to this, and the fact that S. marcescens produces a reddish-orange pigment called prodigiosin, S. marcescens may cause extrinsic staining of the teeth. The biochemical pathway illustrating the production of prodigiosin by S. marcescens is unknown except for the final two steps. In these steps, a monopyrrole (MAD) and a bipyrrole (MBC) undergo a condensation reaction by way of a condensing enzyme to ultimately form the tripyrrole pigment, prodigiosin.

Contents

Pathogenesis

Historical

References

External links

Pathogenesis

''S. marcescens'' can cause conjunctivitis, keratitis, endophthalmitis, and tear duct infections. It is common in the respiratory and urinary tracts of adults and the gastrointestinal system of children.^[2] Most ''S. marcescens'' strains are resistant to several antibiotics because of the presence of R-factors, which are a type of plasmid that carry one or more genes that encode resistance.
In coral, ''S. marcescens'' is the cause of the disease known as ''White pox''. In silkworms, it sometimes occurs as a secondary pathogen in viral flacherie disease.

Historical

In the 1950s ''S. marcescens'' was erroneously believed to be non-pathogenic and its reddish coloration was used in school experiments to track infections. It has also been used as a simulant in biological warfare tests by the United States Military.^[3][4] On September 26 and 27, 1950, the United States Navy conducted a secret experiment named "Operation Sea-Spray" in which some ''S. marcescens'' was released by bursting balloons of it over urban areas of the San Francisco Bay Area in California. Although the Navy later claimed the bacteria were harmless, beginning on September 29 eleven patients at a local hospital developed very rare, serious urinary tract infections and one of these individuals, Edward J. Nevin, died. Cases of pneumonia in San Francisco also increased after ''S. marcescens'' was released.^[5],[6]
Since 1950, ''S. marcescens'' has steadily increased as a cause of human infection, with many strains resistant to multiple antibiotics. The first indications of problems with the influenza vaccine produced by Chiron Corporation in 2004 involved ''S. marcescens'' contamination.
Because of its red pigmentation, caused by expression of the pigment prodigiosin,^[7] and its ability to grow on bread, ''S. marcescens'' has been evoked as a naturalistic explanation of Medieval accounts of the "miraculous" appearance of blood on the Eucharist that led to Pope Urban IV instituting the Feast of Corpus Christi in 1264. This followed celebration of a Mass at Bolsena in 1263, led by a Bohemian priest who had doubts concerning transubstantiation, or the turning of bread and wine into the body and blood of Christ during the Mass. During the Mass, the eucharist appeared to bleed and each time the priest wiped away the blood, more would appear. This event is celebrated in a fresco in the Pontifical Palace in the Vatican City, painted by Raphael. The Mass at Bolsena by Raphael
9. Brown, Alfred E (2007). Benson's Microbiological Applications.
10. http://jb.asm.org/cgi/reprint/114/3/999.pdf

References

1. [1]
2. ''Serratia Marcescens'' seton implant infection & orbital cellulitis
3. http://www.democracynow.org/article.pl?sid=05/07/13/1357237
4. http://archive.webactive.com/pacifica/demnow/dn980220.html
5. Clouds of Secrecy: The Army's Germ-Warfare Tests Over Populated Areas. (Foreword by Alan Cranston.), Cole, Leonard A., , , Rowman & Littlefield., 1988, ISBN 0-8476-7579-3
6. The Biology of Doom : America's Secret Germ Warfare Project., Regis, Ed, , , Diane Publishing Company., , ISBN 0-7567-5686-3
7.

External links

★