Enterobacterales

Klebsiella pneumoniae

Encapsulated Gram-negative bacilli

Identification & Growth

Identification

Oxidase-negative, non-motile, indole-negative, weakly urease-positive, VP-positive
TSI A/A with abundant gas

Growth Conditions

MacConkey agar: large, mucoid, pink colonies
Hypervirulent strain: positive string test (> 5 mm)
35–37 °C, 18–24 h

Clinical Significance

Hospital-acquired pneumonia, UTI, bacteremia, surgical-site infection, liver abscess

Intrinsic Resistance

Ampicillin and amoxicillin (chromosomal SHV beta-lactamase)
Penicillin G, macrolides, clindamycin, glycopeptides, linezolid, daptomycin

Bench Alerts

Never report ampicillin as susceptible
The leading KPC producer in Brazil — a reduced meropenem zone is an outbreak warning
ESBL production is frequent in the hospital setting

Clinical Notes

Clinical presentations

Causes community- and hospital-acquired pneumonia, including necrotizing forms with "currant jelly" sputum production.
An important cause of complicated urinary tract infection and device-related bacteremia in hospitalized patients.
Hypervirulent strains cause primary pyogenic liver abscess, metastatic endophthalmitis, and meningitis in previously healthy patients, especially in Asia.

Specimens and collection

Sputum, urine, and blood cultures should be collected before antibiotic therapy, following proper aseptic technique for each site.
Liver abscess material should be obtained by image-guided aspiration, sent for aerobic and anaerobic culture.
Rectal swabs are used for active surveillance of carbapenem-resistant Enterobacterales colonization in the hospital setting.

Epidemiology and at-risk populations

Diabetic patients, chronic alcohol users, and immunosuppressed patients have increased risk of invasive disease, including hypervirulent liver abscess.
One of the main species associated with hospital outbreaks of carbapenem-resistant Enterobacterales (CRE).
ICU patients with prolonged mechanical ventilation and extensive antimicrobial use have elevated colonization/infection risk.

Resistance and therapeutic implications

It is intrinsically resistant to ampicillin due to chromosomal beta-lactamase production, a trait that should be reflected in the report.
Carbapenemase production (mainly KPC, also NDM and OXA-48-like) is a global therapeutic threat and requires laboratory confirmation.
ESBL-producing strains require carbapenem use or newer beta-lactam/beta-lactamase inhibitor agents according to susceptibility profile.

Bench and reporting notes

Gram-negative rod, lactose-fermenting, with characteristically mucoid colonies on MacConkey agar due to a prominent polysaccharide capsule.
Modified Hodge test or molecular/immunochromatographic methods are used to confirm carbapenemase production.
The report should highlight intrinsic ampicillin resistance and clearly flag carbapenemase-producing isolates for infection control.

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 pneumoniae in the lab?

Klebsiella pneumoniae is identified through oxidase-negative, non-motile, indole-negative, weakly urease-positive, vp-positive, tsi a/a with abundant gas.

What are the intrinsic resistances of Klebsiella pneumoniae?

This organism is naturally resistant to ampicillin and amoxicillin (chromosomal shv beta-lactamase), penicillin g, macrolides, clindamycin, glycopeptides, linezolid, daptomycin. These drugs should not be reported as susceptible.

Where is Klebsiella pneumoniae commonly found?

It is typically associated with hospital-acquired pneumonia, uti, bacteremia, surgical-site infection, liver abscess.

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