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Enterobacterales

Klebsiella oxytoca

Encapsulated Gram-negative bacilli

Identification & Growth

Identification

  • Indole-positive — this is what separates it from K. pneumoniae
  • Lactose-positive, non-motile, weakly urease-positive

Growth Conditions

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

Clinical Significance

  • Urinary tract infection, bacteremia, antibiotic-associated hemorrhagic colitis

Intrinsic Resistance

  • Chromosomal K1 beta-lactamase: intrinsic resistance to ampicillin, amoxicillin and ticarcillin

Bench Alerts

  • K1 hyperproduction gives piperacillin-tazobactam resistance with cefotaxime susceptible — this is not ESBL

Clinical Notes

Clinical presentations

  • Causes urinary tract infections, healthcare-associated pneumonia, and catheter-related bacteremia.
  • Recognized agent of antibiotic-associated hemorrhagic colitis, distinct from Clostridioides difficile.
  • Can cause neonatal infections and outbreaks in neonatal intensive care units.

Specimens and collection

  • Urine, blood, and tracheal aspirate are the most common specimens depending on the suspected infection site.
  • Stool should be collected in suspected antibiotic-associated hemorrhagic colitis, with concurrent negative C. difficile toxin testing.
  • Blood cultures before antimicrobials are essential for bacteremia workup.

Epidemiology and at-risk populations

  • Part of the normal human gut microbiota, similar to K. pneumoniae.
  • Recent antibiotic use, especially penicillins, is a risk factor for associated hemorrhagic colitis.
  • Hospitalized patients with invasive devices have increased risk of healthcare-associated infection.

Resistance and therapeutic implications

  • Produces a low-level chromosomal K1 beta-lactamase, conferring natural resistance to ampicillin.
  • Can acquire extended-spectrum beta-lactamases and carbapenemases, requiring phenotypic or molecular confirmatory testing.
  • Susceptibility profile should guide individualized therapy, without assuming uniform susceptibility within the Klebsiella genus.

Bench and reporting notes

  • Positive indole production phenotypically differentiates it from K. pneumoniae, which is indole-negative.
  • Routinely test for ESBL and carbapenemase in sterile-site isolates given the potential for acquired resistance.
  • Suspect this organism in post-antibiotic hemorrhagic colitis with negative C. difficile testing.

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 oxytoca in the lab?

Klebsiella oxytoca is identified through indole-positive — this is what separates it from k. pneumoniae, lactose-positive, non-motile, weakly urease-positive.

What are the intrinsic resistances of Klebsiella oxytoca?

This organism is naturally resistant to chromosomal k1 beta-lactamase: intrinsic resistance to ampicillin, amoxicillin and ticarcillin. These drugs should not be reported as susceptible.

Where is Klebsiella oxytoca commonly found?

It is typically associated with urinary tract infection, bacteremia, antibiotic-associated hemorrhagic colitis.

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