Differences in Severity of Bacteraemia Caused by Hypermucoviscous and Non-hypermucoviscous Klebsiella Pneumoniae

Background: Klebsiella pneumoniae strains pose a significant threat to public health. Currently, it is inconclusive whether hypermucoviscous K. pneumoniae (hmKp; semi-quantitatively defined by a positive 'string test') bacteraemia is clinically more severe than non-hmKp bacteraemia. Hence, this systematic review and meta-analysis was conducted with the aim of drawing some conclusions on hypermucoviscosity and bacteraemia.

Methods: PubMed and Web of Science databases were searched for all relevant publications from January 2000 to March 2022. The outcome measures were mortality rate and abscess formation.

Results: Fourteen observational studies were included in this systematic review, comprising a total of 3092 patients with K. pneumoniae bacteraemia, including 746 (24.1%) patients with hmKp strains. The meta-analysis showed that hmKp bacteraemia did not account for a significant increase in the incidence of all-cause mortality compared with non-hmKp bacteraemia [pooled hazard ratio 1.30, 95% confidence interval (CI) 0.79-2.12; P=0.30]. However, hmKp bacteraemia was associated with a significant increase in the incidence of abscess formation compared with non-hmKp bacteraemia (pooled odds ratio 7.74, 95% CI 4.96-12.06; P<0.00001).

Conclusions: Although mortality may not be dependent on the causative agent, this review reaffirms the importance of the string test to detect hmKp. There is a need for prudent management, especially for patients with hmKp, that should include investigations for liver abscess and/or metastatic spread, and measures for early and proper source control as this can improve the prognosis.