Frontiers in immunology
Closely related ST11 Klebsiella pneumoniae isolates with transient attenuation and re-emergence of carbapenem resistance during prolonged hospitalization: a case report
By Zeng M, Jiang Y, Yan F and 3 others.
Abstract
Background
Apparent transitions in carbapenem susceptibility among sequential Klebsiella pneumoniae isolates are often interpreted as strain replacement. However, phenotypic variation among closely related isolates may also produce similar phenotypic shifts, particularly in heavily treated patients.
Case presentation
We report a 91-year-old long-term hospitalized patient from whom three sequential ST11 Klebsiella pneumoniae isolates were recovered from blood and urine over a 3-month period. The initial bloodstream isolate (KPB1) exhibited a hypermucoviscous phenotype, KPC production, and carbapenem resistance. A subsequent urinary isolate (KPU2) lost the hypermucoviscous phenotype and showed attenuation of carbapenem resistance, becoming susceptible to imipenem, meropenem, and doripenem while remaining resistant to ertapenem. A later urinary isolate (KPU3) reverted to carbapenem resistance while remaining non-hypermucoviscous. Repeat antimicrobial testing confirmed these findings. Core-genome SNP analysis identified 16-20 pairwise differences among the three isolates, supporting close genomic relatedness despite their phenotypic discordance.