A 55-year-old diabetic man presents with fever, right upper quadrant pain, and vision loss in the right eye. CT reveals a liver abscess. Klebsiella pneumoniae is isolated from blood and abscess. Which bedside test is used to identify the hypervirulent phenotype?

• A Urease test
• B Optochin susceptibility
• C Bile solubility test
• D String test ✓

Explanation

The string test (mucoviscosity test) is a bedside test for hypervirulent Klebsiella pneumoniae (hvKP). D colony is touched with a loop; if a viscous string >5 mm forms, the test is positive. hvKP is associated with liver abscess and metastatic infections like endophthalmitis. Urease is positive in Klebsiella but not specific for hypervirulence. Optochin and bile solubility tests are for Streptococcus pneumoniae. The most tempting distractor is urease, but the string test is specific for the hypervirulent phenotype.

Reference: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 9th ed.

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