Differences in severity of bacteraemia caused by hypermucoviscous and non-hypermucoviscous Klebsiella pneumoniae

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.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.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).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.