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Schenectady County Community College

Serratia marcescens

Gram stain:  negative
Cell shape:  bacillus
Oxygen requirements:  facultative anaerobe
Motility:  motile
Other:  Produces red pigment at room temperature.

Habitat:  Occurs naturally in soil and water as well as the intestines.

Pathogenicity:  Important as a nocosomial infection; associated with urinary and respiratory tract infections, endocarditis, osteomyelitis, septicemia, wound infections, eye infections, meningitis.

Transmission:  direct contact, droplets; has been found growing on catheters, in saline irrigation solutions, and in other supposedly sterile solutions.

Treatment:  Includes cephalosporins, gentamicin, amikacin, but most strains are resistant to several antibiotics because of the presence or R-factors on plasmids.

We used to think that this bacteria was non-pathogenic, and because of the pigment it produces, it was used widely to trace bacterial transmission. In 1951 and 1952 the US Army conducted a study 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 noted a drastic increase in pneumonia and urinary tract infections.


A good example of a streak plate
Nosocomial Outbreak Due to Serratia marcescens in a Maternity Hospital
Serratia marcescens cellulitis