A 55-year-old diabetic man presents with fever, right upper quadrant pain, and a multiloculated liver abscess on imaging. Blood and aspirate cultures grow a highly mucoid, lactose-fermenting gram-negative rod. On culture plate, an inoculation loop drawn through the colony produces a viscous string longer than 5 mm. This phenotype identifies:

• A Classical Klebsiella pneumoniae producing carbapenemase
• B Klebsiella oxytoca producing cytotoxin
• C Hypervirulent Klebsiella pneumoniae of K1 or K2 capsular serotype ✓
• D ESBL-producing Klebsiella pneumoniae of classical biotype

Explanation

The positive string test defines the hypermucoviscous phenotype of hypervirulent K. pneumoniae (hvKP), classically capsular serotypes K1 and K2. hvKP occurs predominantly in Southeast Asia, affects diabetic and apparently healthy hosts, and characteristically causes metastatic infections including liver abscess, endophthalmitis and meningitis. Classical K. pneumoniae, whether ESBL or carbapenemase producing, causes hospital-acquired pneumonia, UTI and bacteremia but rarely metastatic liver abscess, and gives a negative string test.

Reference: Harrison Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.