Comparison of Clinical and microbiologic characteristics between K1/K2 and non-K1/K2 serotype of hypervirulent Klebsiella pneumoniae infections in Korea

Background: Hypermucoviscous K. pneumoniae is emerging pathogen associated with K1/K2 serotypes. The purpose of study is to compare clinical and microbiologic characteristics between K1/K2 and non-K1/K2 serotype of hypervirulent K. Pneumoniae.

Methods: This study was performed on 155 hypervirulent K. pneumoniaeisolates, from December 2013 through November 2015 in Dongsan Medical Center. Asymptomatic colonizers were excluded. The capsular serotypes were identified using specific primers by polymerase chain reaction. The hypermucoviscous phenotype was confirmed with string test.

Results: K1/K2 was 105 isolates (67.7%) of hypervirulent K. pneumoniae. Community-acquired infection was more associated with K1/K2 (68.6% vs 44.0%, p=0.031). Male were 78 (74.3%) of K1/K2 and 29 (58.0%) of non-K1/K2 (p=0.040). K1/K2 was less associated with antimicrobial resistance and comorbid conditions. rmpA gene and magA gene were more detected in K1/K2 than non-K1/K2 (rmpA: 95.2% vs 42.0%, p=0.001; magA: 58.1% vs 2.0%, p=0.001). Infection sources were distributed as follows: intraabdominal infection (IAI, 41.0%), pneumonia (34.3%), urinary tract infection (UTI, 8.6%) in K1/K2 and pneumonia (54.5%), IAI (28 .0%), and UTI (14.0%) in non-K1/K2. Percutaneous catheter drainage (p=0.048) was more needed for treatment in K1/K2. Infection related 30-day mortality was higher (10.7% vs 25.0%, p=0.044) in non-K1/K2 than K1/K2. Risk factors of 30-day mortality was solid tumor (95% CI, 1.412 to 14.397; p=0.011) and pneumonia (95% CI, 1.192 to 13.423; p=0.025).

Conclusion: IAI was most common cause of hypervirulent K. pneumoniae infection with K1/K2 serotype and pneumonia was the most common cause in non-K1/K2 serotype. Present study result showed 30-day mortality in hypervirulent K. pneumoniae infection is more related comorbidity and infection focus rather than serotype.