NAME: Serratia spp.
SYNONYM OR CROSS REFERENCE: Serratia, S. marcescens (Serratia pattern 1, Serratia biotype 1, phenon A), S. liquefaciens, S. entomophila, S. ficaria, S. fonticola, S. glossinae, S. grimesii ,S. marcescens (S. marcescens ss marcescens and S. marcescens ss sakuensis) S. nematodiphila , S. odorifera, S. plymuthica, S. proteamaculans (S. proteamaculans ss proteamaculans, S. proteamaculans ss quinovora), S. rubidaea, S. ureilytica Footnote 1, Footnote 2.
CHARACTERISTICS: Serratia spp. are chemoorganotrophic, facultative anaerobic bacteria with low nutritional requirements, and belong to the Enterobacteriaceae family Footnote 3. They are gram negative rods, 0.9-2 µm long and 0.5-0.8 μm in diameter Footnote 2. They possess peritrichous flagella that allow them to swim and swarm (with differentiation), and are ubiquitous in soil, water, and plant surfaces.
Many species produce a red to pink pigment, named prodigiosin, which is easier to observe in phosphate-free medium incubated at 30°C rather than 37°C Footnote 3. This pigment is suspected to have antibiotic, potent immunosuppressive, proapoptotic, and anticancer properties, while its role for Serratia spp. is still unknown Footnote 2. S. marcescens produces a biofilm, with unique cellular and structural differentiation characteristics to those of the standard biofilms produced by Pseudomonas aeruginosa and Escherichia coli. The latter bacteria produce biofilms, which only consist of microcolonies of undifferentiated cells. Serratia spp. also produces β-lactamases. All of the former metabolic processes are controlled by quorum sensing. S. marcescens ssp. sakuensis is able to produce endospores, but other members of the genus are not Footnote 4.
PATHOGENICITY/TOXICITY: Serratia spp. are opportunistic pathogens and are one of the ten most common causes of bacteremia in North America Footnote 5. They are responsible for a variety of infections, including bacteremia, pneumonia, intravenous catheter-associated infections, osteomyelitis, endocarditis, and, rarely, endogenous and exogenous endophthalmitis Footnote 2, Footnote 6. Symptom of endophthalmitis appears rapidly after infection, and may include fever, erythema, ocular pain, periorbital swelling, and hypopyon (pus in the eyes). The mortality rate from bacteremia due to Serratia spp. 6 months after infection is 37% Footnote 7.
Serratia infections in neonates are frequent (11-15% in neonatal intensive care unit) and may include bloodstream infection (42%), conjunctivitis (26%), pneumonia (13%), urinary tract infection (8%), meningitis (7%), and surgical site infections Footnote 8. Other infections in infants are documented (otitis externa, enterocolitis and omphalitis, gastroenteritis, septic arthritis, and intraperitoneal infection/abcess), but are rare. Risk factors include birth weight, use of mechanical ventilation, and gestational age (under 37 weeks are at greater risk). The mortality rate in neonates is 44%.
EPIDEMIOLOGY: Worldwide distribution Footnote 3. Biotypes, serotypes and biogroups may be region-specific. Sporadic infections are considered endemic. Epidemics may be caused by contact with a common source by multiple patients, or by patient-to-patient contact. The intestinal tract of newborns may also be infected. S. marcescens non-pigmented strains are more likely to cause an infection than pigmented strains Footnote 9.
Until recently, Serratia was considered to be a mostly nosocomial pathogen Footnote 7, Footnote 10. In 2007, a study in the Calgary health care region (Canada) demonstrated that 65% of infections with Serratia species were actually of community origin. According to the same study, 10.8 per 100,000 inhabitants are carrying the pathogen and 0.9 per 100,000/year develop bacteremia. The rate of Serratia isolation is higher in those over 60 years of age. In the under 60 population, the rate of isolation in men and woman are slightly different (65.9 per 100,000 in men and 36.5 per 100,000 in women). The difference in isolation is mostly observed for hospital-acquired infection. There is no seasonal or yearly variation in incidence. 92% of isolates were Serratia marcescens, 4% S. liquefaciens, 1% S. odorifera and 1% S. rubidaea. Other isolates included S. fonticola, S. plymuthica, and nonspeciated Serratia (2%). Bacteremia was usually caused by S. marcescens (88%) and S. liquefaciens (7%). S. odorifera (2%) and nonspeciated Serratia also have caused bacteremias. Men over 60 years of ages were most susceptible to developing bacteremia.
HOST RANGE: Plants and animals (including human) have been found to be hosts to the different Serratia spp. Footnote 3.
INFECTIOUS DOSE: Unknown.
MODE OF TRANSMISSION: Ingestion of contaminated foods and direct contact Footnote 3. Nosocomial transmission may occur by hand contact from hospital personnel and other patients. Fomites may also spread Serratia.
INCUBATION PERIOD: Unknown.
COMMUNICABILITY: Serratia may be directly transmitted from person-to-person, but rates are unknown Footnote 3.
RESERVOIR: Soil and animal (including human) are considered reservoirs Footnote 3.
ZOONOSIS: None Footnote 3.
VECTORS: None Footnote 3.
DRUG SUSCEPTIBILITY: Serratia spp. are usually susceptible to aminoglycosides, fluoroquinolones, and co-trimazole Footnote 7.
DRUG RESISTANCE: Many Serratia spp. isolates (39-73%) are resistant to gentamicin Footnote 7. They are all resistant to penicillins and cephalosporin.
SUSCEPTIBILITY TO DISINFECTANTS: Phenolic disinfectants, 1% sodium hypochlorite, 70% ethanol, formaldehyde, glutaraldehyde, iodophore, and peracetic acid are effective against Serratia spp. Footnote 11.
SURVIVAL OUTSIDE HOST: S. marcescens may survive from 3 days to 2 month on dry, inanimate surfaces, and 5 weeks on dry floor Footnote 16. The organism may survive less than 4 days in a blood bag under aerobic conditions and 20 days in semi-anaerobic/anaerobic conditions Footnote 17. It has been also reported to survive in contact lens disinfectant (with chlorheximide), double-distilled water, non-medicated hand soap, but no duration has been reported for those cases Footnote 18-Footnote 20.
SURVEILLANCE: Monitor for symptoms and perform bacteriological isolation and serotyping/biotyping Footnote 3.
FIRST AID/TREATMENT: Give appropriate antibiotherapy Footnote 3.
IMMUNIZATION: None currently available.
PROPHYLAXIS: None currently available.
LABORATORY-ACQUIRED INFECTIONS: 5 laboratory acquired infection with S. marcescens have been reported as of 1999 Footnote 11.
SOURCES/SPECIMENS: Serratia spp. are found in feces, wound exudates, respiratory specimen, blood, eye culture, and urine Footnote 10.
PRIMARY HAZARDS: Accidental parenteral inoculation, droplets exposure of mucous membrane, infectious aerosols, and ingestion Footnote 11.
SPECIAL HAZARDS: None.
RISK GROUP CLASSIFICATION: Risk Group 2. This risk group applies to the genus as a whole, and may not apply to every species within the genus.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes Footnote 21.
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities Footnote 21.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up.
DISPOSAL: All material should be decontaminated before disposal with steam sterilization, incineration or chemical disinfection.
STORAGE: Samples and biological material should be store in appropriately labelled sealed containers.
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2011