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Enterobacterales

Serratia liquefaciens

Motile Gram-negative bacilli

Identification & Growth

Identification

  • DNase, gelatinase and lipase positive; non-pigmented (unlike S. marcescens)
  • Ornithine-positive, ONPG-positive

Growth Conditions

  • MacConkey and blood agar, 30–37 °C, 18–24 h

Clinical Significance

  • Bacteremia related to contaminated solutions, urinary and wound infection

Intrinsic Resistance

  • Intrinsic resistance to ampicillin, first-generation cephalosporins, cefoxitin, colistin and nitrofurantoin

Bench Alerts

  • Inducible AmpC group: risk of emerging third-generation cephalosporin resistance during therapy
  • Outbreaks usually have a common source — notify infection control

Clinical Notes

Clinical presentations

  • Causes bacteremia associated with contaminated intravenous products and parenteral nutrition solutions.
  • Associated with urinary and respiratory tract infections in hospitalized patients.
  • Can cause hospital outbreaks related to contaminated medical devices and multidose solutions.

Specimens and collection

  • Serial blood cultures and culture of suspected intravenous bags/solutions are essential in outbreak investigation.
  • Environmental and hospital surface samples may be collected during epidemiologic outbreak investigation.
  • Urine and tracheal aspirate are indicated depending on the suspected clinical site.

Epidemiology and at-risk populations

  • Widely distributed in aquatic environments and capable of multiplying in contaminated intravenous solutions even under refrigeration.
  • Patients on total parenteral nutrition and long-term intravenous devices have increased risk.
  • Described hospital outbreaks are frequently linked to failures in pharmaceutical solution preparation or storage.

Resistance and therapeutic implications

  • Possesses an inducible chromosomal AmpC beta-lactamase, conferring intrinsic resistance to ampicillin and first-generation cephalosporins.
  • Can acquire additional resistance to fluoroquinolones and aminoglycosides, requiring individualized susceptibility testing.
  • Carbapenems or cefepime are often required for severe infections with suspected AmpC hyperproduction.

Bench and reporting notes

  • Isolation in multiple patients with the same antibiogram during the same time period should prompt investigation for a common-source outbreak.
  • Molecular typing (pulsed-field gel electrophoresis or sequencing) is useful to confirm clonality in outbreaks.
  • Notify the hospital infection control committee upon unusual isolation in blood cultures from multiple patients.

Sources

Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.

FAQ: Frequently Asked Questions

How to identify Serratia liquefaciens in the lab?

Serratia liquefaciens is identified through dnase, gelatinase and lipase positive; non-pigmented (unlike s. marcescens), ornithine-positive, onpg-positive.

What are the intrinsic resistances of Serratia liquefaciens?

This organism is naturally resistant to intrinsic resistance to ampicillin, first-generation cephalosporins, cefoxitin, colistin and nitrofurantoin. These drugs should not be reported as susceptible.

Where is Serratia liquefaciens commonly found?

It is typically associated with bacteremia related to contaminated solutions, urinary and wound infection.

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