Core genome MLST reveals genetic and BafA-associated phenotypic diversities in Bartonella henselae strains

Bartonella henselae is a zoonotic pathogen responsible for cat-scratch disease. While multilocus sequence typing (MLST) has been utilized for strain classification, its ability to differentiate between B. henselae isolates is constrained. Researchers have now devised a B. henselae-specific core genome MLST (cgMLST) scheme, based on whole-genome sequencing data, to investigate the genetic and phenotypic variations among 80 strains originating from cats, humans, mongooses, and masked palm civets.

Utilizing the standard MLST scheme, the 80 strains were grouped into nine sequence types (STs). Conversely, the cgMLST method distinguished the strains into 72 cgSTs, significantly enhancing their discriminatory capacity. The cgMLST scheme incorporates 1,183 core genes and maintains applicability across all 80 strains. Through phylogenetic analysis, it was found that ST1, previously linked to cat-scratch disease, had further divided into three primary clusters and two singletons, highlighting substantial genetic heterogeneity within this ST.

Additionally, the bafA subtypes clustered predominantly according to the cgMLST-based phylogenetic structure, implying an intimate relationship between bafA variations and the genomic background of B. henselae strains. In an endothelial cell proliferation assay conducted on human umbilical vein endothelial cells, strains belonging to different cgSTs demonstrated strain-specific differences in proliferative capacity, which were correlated with the bafA subtype classification.

Certain strains induced focal cell fragmentation and reduced cell density at high multiplicity of infection, signifying strain-specific variations in endothelial cell injury.

In summary, this study establishes a high-resolution cgMLST framework for B. henselae, revealing that genetically distinct strains possess diverse endothelial cell phenotypes.