The Impact of Insertion Sequences on O-Serotype Phenotype and Its O-Locus-Based Prediction in Klebsiella pneumoniae O2 and O1

Abstract

Klebsiella pneumoniae is a nosocomial pathogen, pointed out by the World Helth Organisation (WHO) as “critical” regarding the highly limited options of treatment. Lipopolysaccharide (LPS, O-antigen) and capsular polysaccharide (K-antigen) are its virulence factors and surface antigens, determining O- and K-serotypes and encoded by O- or K-loci. They are promising targets for antibody-based therapies (vaccines and passive immunization) as an alternative to antibiotics. To make such immunotherapy effective, knowledge about O/K-antigen structures, drift, and distribution among clinical isolates is needed. At present, the structural analysis of O-antigens is efficiently supported by bioinformatics. O- and K-loci-based genotyping by polymerase chain reaction (PCR) or whole genome sequencing WGS has been proposed as a diagnostic tool, including the Kaptive tool available in the public domain. We analyzed discrepancies for O2 serotyping between Kaptive-based predictions (O2 variant 2 serotype) and the actual phenotype (O2 variant 1) for two K. pneumoniae clinical isolates. Identified length discrepancies from the reference O-locus resulted from insertion sequences (ISs) within rfb regions of the O-loci. In silico analysis of 8130 O1 and O2 genomes available in public databases indicated a broader distribution of ISs in rfbs that may influence the actual O-antigen structure. Our results show that current high-throughput genotyping algorithms need to be further refined to consider the effects of ISs on the LPS O-serotype.

Plasmid-encoded insertion sequences promote rapid adaptation in clinical enterobacteria

“…In patient JWC the gene mutated was wbbM in the rfb locus, which inactivation has been previously associated with O-serotype modification and LPS defects 60,61 . Interestingly, an analysis of K. pneumoniae genomes (n > 8000) found the rfb locus to be commonly disrupted by a variety of IS elements 60 . The other target found in this patient was an oatA -like (∼30% homology) acyltransferase.…”

The Mutation in wbaP cps Gene Cluster Selected by Phage-Borne Depolymerase Abolishes Capsule Production and Diminishes the Virulence of Klebsiella pneumoniae

“…Klebsiella strains can effectively be discriminated against based on the O- and K-typing. To date, 11 O-serotypes have been identified for K. pneumoniae (O1, O2a, O2ac, O2afg, O2aeh (called also O9), O3, O4, O5, O7, O8, and O12), with two sub-serotypes (O3a, O3b) [ 6 ]. O1 and O2 O-PS structures are composed of galactan-I (O1 and O2) and galactan-II (O1) that are characterized by at least two structural variants (v1 or v2), i.e., O1v1 or O1v2 and O2v1 or O2v2 [ 6 ].…”

“…To date, 11 O-serotypes have been identified for K. pneumoniae (O1, O2a, O2ac, O2afg, O2aeh (called also O9), O3, O4, O5, O7, O8, and O12), with two sub-serotypes (O3a, O3b) [ 6 ]. O1 and O2 O-PS structures are composed of galactan-I (O1 and O2) and galactan-II (O1) that are characterized by at least two structural variants (v1 or v2), i.e., O1v1 or O1v2 and O2v1 or O2v2 [ 6 ]. In turn, there are more than 140 genetically distinct capsular locus types, of which 77 well-characterized chemical structures are used in serotyping [ 7 ].…”

Omic insights into various ceftazidime-avibactam-resistant Klebsiella pneumoniae isolates from two southern Italian regions

“…Finally, the 16 isolates belonged to three different STs, namely ST101, ST307 and ST512, each associated with a specific capsular locus (17, 102 and 107) and an O-antigen. ST101, found only in Catania and in one strain from Catanzaro, was associated to the O1/O2v1 variant, while both ST307 and ST512 have somatic antigen variants, i.e., O1/O2v1 and O1/O2v2 ( Artyszuk et al., 2020 ). Of interest in these isolates is the co-presence of the rmp A2 regulator and the iut A aerobactin in 4 strains from Catania, indicating a hypermucoviscosity phenotype ( Paczosa and Mecsas, 2016 ; Wang et al., 2020 ).…”