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Enterobacterales

Klebsiella variicola

Encapsulated Gram-negative bacilli

Identification & Growth

Identification

  • Phenotypically identical to K. pneumoniae; separated by updated MALDI-TOF databases or sequencing

Growth Conditions

  • MacConkey, mucoid colonies; 35–37 °C, 18–24 h

Clinical Significance

  • Bacteremia and urinary tract infection, with reported mortality comparable to K. pneumoniae

Intrinsic Resistance

  • Ampicillin and amoxicillin have no activity (genus chromosomal beta-lactamase)

Bench Alerts

  • Frequently reported as K. pneumoniae — check the MALDI-TOF database version

Clinical Notes

Clinical presentations

  • Causes bacteremia, neonatal sepsis, and respiratory tract infections clinically indistinguishable from K. pneumoniae.
  • Frequently misidentified as K. pneumoniae by conventional automated biochemical systems.
  • Associated with higher bacteremia mortality in some case series compared to K. pneumoniae.

Specimens and collection

  • Blood and respiratory aspirate are the primary specimens depending on clinical presentation.
  • Correlation with epidemiologic data is important, as there are reports of plant and agricultural environmental origin.
  • Serial blood cultures in neonates with late-onset sepsis should be processed with precise species identification.

Epidemiology and at-risk populations

  • Member of the Klebsiella pneumoniae complex, also found in plant environments and associated with plant nitrogen fixation.
  • Neonates in intensive care units are a relevant at-risk population for bacteremia due to this organism.
  • Hospitalized immunocompromised patients have a risk of invasive infection similar to K. pneumoniae.

Resistance and therapeutic implications

  • Can acquire extended-spectrum beta-lactam and carbapenemase resistance genes, similar to K. pneumoniae.
  • Susceptibility testing should follow the same protocols used for the K. pneumoniae complex.
  • Species distinction does not alter empiric therapeutic approach but is relevant for epidemiology and surveillance.

Bench and reporting notes

  • Definitive identification requires MALDI-TOF with an updated library or sequencing, as traditional biochemical methods do not distinguish it from the K. pneumoniae complex.
  • Reference laboratories should consider re-identification of atypical isolates labeled as K. pneumoniae with unusual phenotype.
  • Report as a member of the K. pneumoniae complex when exact species identification is unavailable.

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 Klebsiella variicola in the lab?

Klebsiella variicola is identified through phenotypically identical to k. pneumoniae; separated by updated maldi-tof databases or sequencing.

What are the intrinsic resistances of Klebsiella variicola?

This organism is naturally resistant to ampicillin and amoxicillin have no activity (genus chromosomal beta-lactamase). These drugs should not be reported as susceptible.

Where is Klebsiella variicola commonly found?

It is typically associated with bacteremia and urinary tract infection, with reported mortality comparable to k. pneumoniae.

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