Antimicrobial susceptibility and microbiological and epidemiological characteristics of hypermucoviscous Klebsiella pneumoniae strains in a tertiary hospital in Hangzhou, China.

OBJECTIVES

Hypermucoviscous Klebsiella pneumoniae (HMKP) has been increasingly observed among clinical isolates. This study sought to examine the microbiological and epidemiological characteristics of HMKP strains in a tertiary hospital in Hangzhou, China.

METHODS

HMKP isolates were collected and were identified via matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). A string test was performed for the hypermucoviscous phenotype. Susceptibility to various antimicrobial agents was determined. Multilocus sequence typing (MLST), capsular serotypes and virulence-associated genes of HMKP isolates were assessed.

RESULTS

A total of 42 HMKP strains with a positive string test were collected, of which 32 (76.2%) were carbapenem-susceptible HMKP (CS-HMKP) and 10 (23.8%) were carbapenem-resistant HMKP (CR-HMKP). CS-HMKP strains were more susceptible to antimicrobial agents than CR-HMKP strains. Capsular serotypes K1 (38.1%; 16/42) and K2 (11.9%; 5/42) were the main capsular serotypes of all HMKP isolates. K57 was first reported in CR-HMKP strains. ST163 was the main sequence type (37.5%; 12/32) among CS-HMKP strains, whilst ST11 was unique to CR-HMKP strains. The regulator of the mucoid phenotype A gene (rmpA) and other virulence factors (allS, kfu, iutA, entB, iroN, fimH and wabG) were present in >80% of HMKP strains. Patients with CR-HMKP strains had a higher mortality rate than those with CS-HMKP strains.

CONCLUSION

Capsular serotypes K1 and K2 were the main capsular serotypes of the isolated HMKP strains. The emergence of CR-HMKP should be a concern as it was associated with an increased mortality rate, especially for ST11 CR-HMKP strains, demonstrating the global epidemic of carbapenem resistance.