Emergence of colistin-heteroresistant and carbapenem-resistant hypervirulent Klebsiella pneumoniae

Objectives: To investigate the clinical emergence of colistin-heteroresistant, hypervirulent, and multidrugresistant Klebsiella pneumoniae , and characterize the underlying molecular mechanisms.Methods: The population analysis profiles (PAPs) method was used to detect colistin heteroresistance. The time-killing assay was used to examine the effect of colistin on carbapenem-resistant Klebsiella pneumoniae (CRKP) in vitro. Galleria mellonella larvae infection model was used to test the potential virulence. qRT-PCR assay was conducted to compare the expression levels of efflux pump genes. Next and thirdgeneration sequencing were conducted to analyse the genomic features. Results: Two colistin-heteroresistant isolates were detected from a multi-center carbapenem-resistant Enterobacterales (CRE) surveillance study in China, which exhibited similar survival rates as the K2 hypervirulent reference strain ATCC 43816 in a G. mellonella larvae model. The two isolates belonged to ST11, harbouring the iucABCD, iutA, iroBCD , and rpmA 2 hypervirulent genes and pLVPK-like virulence plasmids. Colistin showed a weak effect on the heteroresistant strains in vitro. The efflux pump genes acrA, acrB, tolC, oqxA , and oqxB were upregulated in this subpopulation compared to the parental strains.Conclusions: This study showed the clinical emergence of colistin-heteroresistant, hypervirulent, and multidrug-resistant Klebsiella pneumoniae . AcrAB-TolC and OqxAB efflux overexpression were involved in mediating colistin heteroresistance.(c) 2023 The Authors. Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

This study investigated the clinical emergence of colistin-heteroresistant, hypervirulent, and multidrug-resistant Klebsiella pneumoniae, and characterized the underlying molecular mechanisms. The results showed the detection of two colistin-heteroresistant isolates, which exhibited similar survival rates as the hypervirulent reference strain. Additionally, overexpression of efflux pump genes was involved in mediating colistin heteroresistance.