Fallon, J. T. | Search bioRxiv

bioRxiv2019

Staphylococcus pasteuri isolates (Spvs) from human atherosclerotic plaques mediate virulence, intracellular resistance and transendothelial invasion of macrophages: A mechanistic paradigm for microbial pathogenicity in atherosclerosis

Atherosclerotic cardiovascular disease, a chronic inflammatory condition of multifactorial etiology, is the leading cause of death worldwide. The concept of bacterial persistence has been proposed as one of several contributing factors to this disease. We hypothesized that the infectious agent(s) found at the site of the atheroma may be dormant but perpetuate virulence in response to host defense and other physiological triggers. In this study, we sought to identify the source of persistent infection in human atherosclerotic plaque and define how pathogen virulence and host defenses mediate plaque vulnerability. Whole genome sequencing (WGS) was used to identify bacteria from pure cultures obtained from atherosclerotic tissues of living subjects diagnosed with more than 70% occlusion of the carotid artery undergoing carotid endarterectomy (CE). WGS identified the predominant species as S. pasteuri (Spv) in all CE isolates grown in pure culture except one isolate which was identified as B. licheniformis. All S. pasteuri isolates (Spvs) were found to contain genes for widespread virulence, invasion, and intracellular resistance. As macrophages (M{varphi}s) play a decisive role at all stages of this disease we treated mouse M{varphi}s (RAW 264.7) with Spvs. While all Spvs tested demonstrated their ability to survive phagocytosis, the highly virulent Spvs also activated M{varphi}s and induced trans-endothelial cell migration of these cells which was mediated via the CC chemokine CCL1 and its receptor CCR8. In conclusion, we show that Spvs are found in CE plaques, have the capacity to survive phagocytosis and induce the transmigration of M{varphi}s across an endothelial barrier in a CCL1-CCR8 dependent process. These findings highlight the significance of carotid vessels as a reservoir for S. pasteuri, a pathogen found in products used routinely in human consumption; this may explain how microbial pathogenicity modulates plaque vulnerability in atherosclerosis.

pathology↗

bioRxiv2018

A novel core genome approach to enable prospective and dynamic monitoring of infectious outbreaks

Whole-genome sequencing is increasingly adopted in clinical settings to identify pathogen transmissions. Currently, such studies are performed largely retrospectively, but to be actionable they need to be carried out prospectively, in which samples are continuously added and compared to previous samples. To enable prospective pathogen comparison, genomic relatedness metrics based on single nucleotide differences must be consistent across time, efficient to compute and reliable for a large variety of samples. The choice of genomic regions to compare, i.e., the core genome, is critical to obtain a good metric.\n\nWe propose a novel core genome method that selects conserved sequences in the reference genome by comparing its k-mer content to that of publicly available genome assemblies. The conserved-sequence genome is sample set-independent, which enables prospective pathogen monitoring. Based on clinical data sets of 3436 S. aureus, 1362 K. pneumoniae and 348 E. faecium samples, we show that the conserved-sequence genome disambiguates same-patient samples better than a core genome consisting of conserved genes. The conserved-sequence genome confirms outbreak samples with high accuracy: in a set of 2335 S. aureus samples, it correctly identifies 44 out of 45 outbreak samples, whereas the conserved gene method confirms 38 out of 45 outbreak samples.

bioinformatics↗