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

Although hypervirulent Klebsiella pneumoniae (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 K. pneumoniae isolates causing bloodstream infections in a cross-sectional study. Clinical characteristics of K. pneumoniae 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 K. pneumoniae 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 Klebsiella variicola and Klebsiella quasipneumoniae, respectively. Patients with hvKp infections had higher proportions of diabetes mellitus (risk ratio [RR], 1.75; 95% confidence interval [Cl], 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.