Serratia

Serratia is a genus of Gram-negative, facultatively anaerobic, rod-shaped bacteria of the Enterobacteriaceae family. The most common 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. Members of this genus produce characteristic red pigment, prodigiosin, and can be distinguished from other members of the family Enterobacteriaceae by its unique production of three enzymes: DNase, lipase, and gelatinase.

Etymology
The genus is named after Serafino Serrati, an Italian physicist.

Infection of humans
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.

Serratia infection has caused endocarditis and osteomyelitis in people addicted to heroin.

Cases of Serratia arthritis have been reported in outpatients receiving intra-articular injections.

Interesting History
S. marcescens was once thought to be a non-pathogenic bacteria. Because of the red pigment it produces, it was widely used to trace bacterial transmission and to study settling and drifting of bacteria in air currents. In 1950 the US Navy conducted a secret experiment called “Operation Sea-Spray” to study wind currents that might carry biological weapons. They filled balloons with S. marcescens and burst them over San Francisco. Shortly thereafter, doctors in the area noted a drastic increase in pneumonia and urinary tract infections.

The above statement is questionable and no legitimate sources are referenced. Operation Seaspray occurred in 1957 and pertains to a bilateral naval exercise to protect Blue Fleet’s vitally-important underway replenishment group (URG) from enemy submarine attacks (See Operation Strikeback).

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