Escherichia coli vs Klebsiella and Enterobacter
How to tell Escherichia coli and Klebsiella and Enterobacter apart when a board question makes them look alike.
E coli is indole-positive UTI; Klebsiella is capsule mucoid pneumonia; Enterobacter is hospital AmpC resistance.
Side by side
Most common uncomplicated UTI organism; lactose-fermenting gram-negative rod that is classically indole positive.
Klebsiella is heavily encapsulated and mucoid; Enterobacter is healthcare-associated with inducible AmpC resistance concern.
Uropathogenic E coli uses adhesins to ascend the urinary tract; other pathotypes use distinct toxins or invasion mechanisms.
Klebsiella capsule resists phagocytosis; Enterobacter resistance mechanisms complicate hospital infections.
Indole-positive lactose fermenter in cystitis points E coli.
Mucoid encapsulated pneumonia points Klebsiella; inducible AmpC in nosocomial pneumonia/UTI points Enterobacter.
The trap
All three can ferment lactose, so lactose positivity alone does not distinguish them.
The repair move
For lactose-fermenting rods, attach one lab clue and one syndrome to each genus.
Try a free question
CoreA young woman with cystitis has a gram-negative rod that ferments lactose and is indole positive. Which organism is the most common cause of uncomplicated UTI?
Show answer and explanation
Answer: A. Escherichia coli. E coli is the most common uncomplicated UTI cause, ferments lactose, and is classically indole positive.
Why the other choices are tempting
- B. Klebsiella is lactose-fermenting, encapsulated, urease-positive, and indole-negative in classic K pneumoniae teaching.
- C. Enterobacter is lactose-fermenting and healthcare/device associated with AmpC resistance concerns.
- D. Proteus is urease-positive, swarming, and non-lactose fermenting.
- E. Pseudomonas is a non-lactose-fermenting oxidase-positive rod.
Flashcards
Tap a card to flip it.
What is the fastest separator for Escherichia coli vs Klebsiella and Enterobacter?
E coli is indole-positive UTI; Klebsiella is capsule mucoid pneumonia; Enterobacter is hospital AmpC resistance.
What clue should make you choose Escherichia coli?
Most common uncomplicated UTI organism; lactose-fermenting gram-negative rod that is classically indole positive.
Quick answers
What is the fastest way to tell Escherichia coli from Klebsiella and Enterobacter?
E coli is indole-positive UTI; Klebsiella is capsule mucoid pneumonia; Enterobacter is hospital AmpC resistance.
What is the key clue for Escherichia coli?
Most common uncomplicated UTI organism; lactose-fermenting gram-negative rod that is classically indole positive.
What is the key clue for Klebsiella and Enterobacter?
Klebsiella is heavily encapsulated and mucoid; Enterobacter is healthcare-associated with inducible AmpC resistance concern.
What is the common trap with Escherichia coli vs Klebsiella and Enterobacter?
All three can ferment lactose, so lactose positivity alone does not distinguish them.