Clinical and Molecular Characteristics of Klebsiella pneumoniae Isolates Causing Bloodstream Infections in Japan: Occurrence of Hypervirulent Infections in Health Care

Although hypervirulent <i>Klebsiella pneumoniae</i> (hvKp) has been associated with severe community-acquired infections that occur among relatively healthy individuals, information about hvKp infections in health care settings remains limited. Here, we systematically analyzed the clinical and molecular characteristics of <i>K. pneumoniae</i> isolates causing bloodstream infections in a cross-sectional study. Clinical characteristics of <i>K. pneumoniae</i> bloodstream infections from hospitals across Japan were analyzed by a review of the medical records. Whole-genome sequencing of the causative isolates was performed. Bacterial species were confirmed and hvKp were identified using whole-genome sequencing data. Clinical characteristics of hvKp infections were compared with those of non-hvKp infections by bivariate analyses. Of 140 cases of <i>K. pneumoniae</i> bloodstream infections, 26 cases (18.6%) were caused by various clones of hvKp defined by the carriage of cardinal virulence genes. Molecular identification revealed that 24 (17.1%) and 14 (10%) cases were caused by <i>Klebsiella variicola</i> and <i>Klebsiella quasipneumoniae</i>, respectively. Patients with hvKp infections had higher proportions of diabetes mellitus (risk ratio [RR], 1.75; 95% confidence interval [CI], 1.05 to 2.94), and their infections had significantly higher propensity to involve pneumonia (RR, 5.85; 95% CI, 1.39 to 24.6), liver abscess (RR, 5.85; 95% CI, 1.39 to 24.6), and disseminated infections (RR, 6.58; 95% CI, 1.16 to 37.4) than infections by other isolates. More than one-half of hvKp infections were health care associated or hospital acquired, and a probable event of health care-associated transmission of hvKp was documented. hvKp isolates, which are significantly associated with severe and disseminated infections, are frequently involved in health care-associated and hospital-acquired infections in Japan.