Genes involved in serum resistance in Klebsiella pneumoniae for the development of targeted therapy against this pathogen

A major causative pathogen of bloodstream infections (BSIs) is Klebsiella pneumoniae, and in particularly multidrug resistant (MDR) extended-spectrum β-lactamase (ESBLs)-producing strains. These infections have limited treatment options leading to fatal outcomes, which emphasizes the need to identify new treatment targets. A major virulence trait of these strains resides in their ability to survive and proliferate in human blood. Several bacterial components were shown to be associated with serum resistance in Kpn, including the capsule and the lipopolysaccharide (LPS), but the specific genes conferring serum resistance in this pathogen are still unknown.

We focused on two isogenic MDR ESBL-producing clinical blood isolates, KpnB10 and KpnB199, which possessed an opposite serum resistance phenotype, with KpnB199 being serum-resistant and KpnB10 serum-sensitive. We used comparative genomics and proteomics analyses to identify serum-resistant related genes. We identified 299 mutated genes and 61 differentially regulated proteins classified into 15 KEGG pathways. The most enriched pathways identified were amino acid/carbohydrate transport and metabolism, and cell wall/membrane/envelope biogenesis. The most highly expressed proteins in KpnB199 compared to KpnB10 are related to biofilm-formation and LPS-biosynthesis, which we supported by experimental phenotypic data. Based on the differential proteomics data we chose a panel of candidate proteins and using complementation and knockout experiments we identified a set of proteins that contribute to Kpn serum resistance.

This study describes for the first time specific genes involved in the survival of Kpn in human sera and may be used for the design of novel diagnosis and therapeutics against this dangerous pathogen.