Clinical spectrum and molecular characteristics of Klebsiella pneumoniae causing community-acquired extrahepatic abscess

Background and Purpose: Klebsiella pneumoniae causes a wide spectrum of infections, including abscess and non-abscess formation. This study investigated the clinical spectrum and molecular characteristics of community-acquired Klebsiella infection with primary extrahepatic abscess. Methods: From April 2004 through March 2007, a total of 18 strains of K. pneumoniae, 11 from blood and 7 from focal purulent specimens, were recovered from a medical center in southern Taiwan. The clinical data were collected from medical records. Hypermucoviscosity phenotype was defined as positive string test. The virulence genes, including rmpA (regulator of mucoid phenotype), magA (specific to K1 capsule serotype), K₂A (specific to K2 capsule serotype), and kfu (an iron uptake system) were amplified by polymerase chain reaction using specific primers. Results: Twelve men and 6 women with ages ranging from 37 to 74 years were enrolled. Fifteen patients had underlying diabetes mellitus. The duration of hospitalization ranged from 1 to 96 days. Three patients died by the end of treatment. All of the K. pneumoniae strains carried rmpA and 16 strains showed the hypermucoviscosity phenotype. Of the 18 strains, 7 strains were positive for k₂A and 4 strains carried magA. kfu was identified in 4 magA-positive strains and 2 magA-negative/k₂A-negative strains. Conclusion: Diabetes mellitus was the most frequent underlying disease among our patients. The rmpA and/ or hypermucoviscosity phenotype were the most common virulence factors in K. pneumoniae isolates causing extrahepatic abscesses, among which K2 capsule serotype (k₂A⁺) was more prevalent than K1 capsule serotype (magA⁺).