Klebsiella pneumoniae
Encapsulated, non-motile Gram-negative rod of the Enterobacteriaceae family that is a major cause of nosocomial pneumonia, urinary tract infections, and bacteremia, particularly in immunocompromised and hospitalized patients.
Organism Card
| Domain | Must know |
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| Identity |
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| Lab discriminator |
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| Reservoir / transmission |
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| Key virulence |
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| Clinical syndromes |
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| Diagnosis |
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| Treatment |
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| Prevention |
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| Classic traps |
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Exam Intelligence
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GC 105 explicitly lists Klebsiella under Enterobacterales with disease associations: UTI, abdominal infections, diarrhoeal syndromes, and many others. It emphasises ESBL producers are "resistant to β-lactams except carbapenems" and CPE as an emerging resistance threat. [1] — This is the single highest-yield antibiotic resistance teaching point for Klebsiella in the exam.
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GC 105 Expert Practice Tip 5: "If you have a patient with documented severe infection due to ESBL +ve Enterobacteriaceae, carbapenems are the antibiotic of choice." [1] — Expect an MCQ where you must pick meropenem/imipenem over ceftriaxone when ESBL is stated.
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GC 101 Handouts mention Klebsiella granulomatis (causes granuloma inguinale / donovanosis) as a separate species diagnosed by Giemsa staining for Donovan bodies [10] — do NOT confuse with K. pneumoniae; this is a classic trap in STD questions.
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AOS Microbiology material and Gen Clerk Microbiology Summary reinforce MALDI-TOF MS as the modern identification method for Enterobacterales species-level identification. [11]
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Endogenous endophthalmitis: Ryan Ho Ophthalmology notes state Klebsiella pneumoniae accounts for 60% of endogenous bacterial endophthalmitis in East Asia, classically associated with liver abscess in uncontrolled DM. [7] — This is a classic minicase/SAQ vignette: DM patient → liver abscess → new eye pain/visual loss → emergency ophthalmology consult.
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Encapsulated organism list for asplenic patients (from Maksim Surgery Notes): "Some Nasty Killers Have Some Capsule Protection" — S. pneumoniae, N. meningitidis, Klebsiella pneumoniae, H. influenzae, Salmonella typhi, Cryptococcus neoformans, P. aeruginosa. [4] — Examiners may ask which organisms pose risk post-splenectomy; Klebsiella is included.
- Klebsiella vs E. coli in UTI: Both are G−ve lactose-fermenting Enterobacterales. Klebsiella is non-motile, indole −ve, urease +ve; E. coli is motile, indole +ve, urease −ve. In uncomplicated UTI, E. coli dominates (~75–85%); Klebsiella ~6%. In complicated/nosocomial UTI, Klebsiella proportion rises.
- Klebsiella vs S. pneumoniae pneumonia: Both cause lobar consolidation with bulging fissure, but Klebsiella classically affects alcoholics/DM patients with "currant-jelly" (thick, blood-tinged, mucoid) sputum, typically upper lobe; S. pneumoniae is the commonest CAP organism overall with rusty sputum. Both are encapsulated.
- ESBL trap: If a vignette states the isolate is "ESBL-producing" or "resistant to 3rd-gen cephalosporins", the answer is carbapenem (meropenem/imipenem), NOT piperacillin-tazobactam (controversial, not reliable for severe infections).
- K. pneumoniae vs K. granulomatis: Completely different diseases. K. granulomatis causes donovanosis (genital ulcer with beefy-red granulation tissue, Donovan bodies on Giemsa stain) — an STD, not pneumonia/UTI.
- SBP organisms: G−ve (E. coli > Klebsiella) more common than G+ve. Monomicrobial growth expected; polymicrobial → think secondary bacterial peritonitis from surgical cause [8].
No specific past paper questions directly naming or centring on Klebsiella pneumoniae were identified in the indexed past paper stems from 2016–2025 Fourth Summative MCQ, SAQ, or Minicase papers. Klebsiella-relevant knowledge is most likely tested indirectly through:
- UTI microbiology stems (asking the 2nd commonest uropathogen)
- Antibiotic resistance questions (ESBL, carbapenem resistance)
- SBP management questions (empirical 3rd-gen cephalosporin)
- Liver abscess / endophthalmitis clinical vignettes
Students should be prepared to identify Klebsiella as the answer in any stem featuring: DM + liver abscess, mucoid G−ve rod, ESBL resistance pattern, or endogenous endophthalmitis in East Asia.
[1] Lecture slides: GC 105. Medically important microbes what every doctor should know.pdf [2] Senior notes: Adrian Lui Pediatrics Notes.pdf (p.341) [3] Senior notes: Ryan Ho GI.pdf (p.237 — Pyogenic Liver Abscess) [4] Senior notes: Maksim Surgery Notes.pdf (p.153 — Splenectomy / OPSI / encapsulated organisms) [5] Senior notes: Ryan Ho Urogenital.pdf (p.123–127) [6] Senior notes: Maksim Medicine Notes.pdf (p.187 — Pneumonia) [7] Senior notes: Ryan Ho Opthalmology.pdf (p.32 — Endophthalmitis) [8] Senior notes: Ryan Ho GI.pdf (p.319 — SBP); MBBS Final MB (Medicine) (Felix PY Lai).pdf (p.796) [9] Senior notes: Ryan Ho Urogenital.pdf (p.114 — PD peritonitis) [10] Lecture slides: GC 101. Diagnosis of infections [Handouts].pdf (p.8) [11] Senior notes: Gen Clerk Anaes + Microbiology Summary.pdf (p.28)
Escherichia coli
Gram-negative, facultatively anaerobic, rod-shaped bacterium of the family Enterobacteriaceae that is a normal gut commensal but includes pathogenic strains causing urinary tract infections, gastroenteritis, neonatal meningitis, and septicemia.
Proteus mirabilis
A Gram-negative, motile, urease-producing rod of the family Enterobacteriaceae, commonly causing urinary tract infections with characteristic alkaline urine and struvite staghorn calculi.