A case of invasive infection caused by a highly virulent strain of Klebsiella pneumoniae displaying hypermucoviscosity in a patient with hepatic involvement without liver abscess.

Klebsiella pneumoniae is an opportunistic nosocomial pathogen belonging to the Enterobacteriaceae family that is associated with a wide range of infections. In the 1980s a new hypervirulent (hypermucoviscous) variant of Klebsiella pneumoniae (hvKP) emerged in southeast Asia and is now increasingly spreading to Western countries due to an invasive syndrome. hvKP isolates can cause serious, life-threatening community-acquired infections in younger healthy hosts, including liver abscess, pneumonia, meningitis and endophthalmitis. We present a case of an 83-year-old man who was examined in the Medicine Department of San Camillo Hospital in Treviso for dehydration in gastroenteritis. Since he presented fever on admission, microbiological investigations were performed and empiric antibiotic therapy with cefotaxime was started. Blood analysis showed a high level of cholestasis indexes and transaminases. Blood cultures were found positive for K. pneumoniae that showed hypermucoviscosity. The hypermucoviscous phenotype of this K. pneumoniae isolate was easily identified by the "string test". Abdominal computed tomography and ultrasonography did not show presence of liver abscesses. After a few days of antibiotic therapy the patient's clinical condition improved. Correct microbiology identification of this kind of strain was essential for appropriate clinical management.