Borrelia nietonii sp. nov.: Relapsing Fever Spirochetes Transmitted By the Tick Ornithodoros hermsi Designated Previously as Borrelia hermsii Genomic Group II.

Background: The taxonomic status of the relapsing fever spirochete Borrelia hermsii in western North America was established in 1942 and based solely on its specific association with the soft tick vector Ornithodoros hermsi. Multilocus sequence typing (MLST) of the 16S rRNA, flaB, gyrB, glpQ, and 16S-23S rRNA intergenic spacer of B. hermsii isolates collected over many years from various geographic locations and biological sources identified two distinct clades designated previously as B. hermsii Genomic Group I (GGI) and Genomic Group II (GGII). To better assess the taxonomic relationship of these two genomic groups to each other and other species of Borrelia, DNA sequences of the entire linear chromosome were determined. Materials and Methods: Genomic DNA samples were prepared from 11 spirochete isolates grown in Barbour-Stoenner-Kelly-H medium. From these preparations, DNA sequences of the entire linear chromosome of two isolates of B. hermsii belonging to each genomic group and seven additional species were determined. Results: Chromosomal sequences of four isolates of B. hermsii contained 919,212 to 922,307 base pairs. DNA sequence identities between the two genomic groups of B. hermsii were 95.86-95.99%, which were more divergent than chromosomal sequences comparing Borrelia parkeri and Borrelia turicatae (97.13%), Borrelia recurrentis and Borrelia duttonii (97.07%), and Borrelia crocidurae and B. duttonii (97.09%). The 3' end of the chromosome of the two GGII isolates also contained a unique intact oppA gene absent from all other species examined. Conclusion: Previous MLST and the chromosomal sequences presented herein support the division of the B. hermsii species complex into two species, B. hermsii sensu stricto ( = GGI) and Borrelia nietonii sp. nov. ( = GGII). We name this unique relapsing fever spirochete in honor of our late friend and colleague Dr. Nathan Nieto for his outstanding contributions to our understanding of tick-borne relapsing fever.

Insights into the molecular basis of reduced vancomycin susceptibility among three prominent Staphylococcus aureus clonal complexes.

Staphylococcus aureus is a leading cause of healthcare-associated infections globally. Vancomycin-resistant S. aureus (VRSA), those with high-level resistance [minimum inhibitory concentration (MIC) of 16-32 µg/mL vancomycin], are uncommon, whereas vancomycin-intermediate S. aureus (VISA; MIC of 4-8 µg/mL), are isolated more frequently and develop during long-term and/or repeated use of the antibiotic. VISA can be difficult to eradicate and infections may persist. Our knowledge of mechanisms that underlie the development of VISA is incomplete. We used a genomics approach to investigate the VISA phenotype in three prominent S. aureus lineages. All VISA clinical isolates tested had increased cell wall thickness compared with vancomycin-susceptible S. aureus strains. Growth rates of clonal complex (CC) 5, CC8, and CC45 clinical isolates were reduced in 2 µg/mL vancomycin compared to media alone. Culture in 2 and 4 µg/mL vancomycin sequentially for two weeks reduced susceptibility to daptomycin, televancin, tigecycline, and vancomycin in a majority of CC5, CC8, and CC45 isolates tested. We identified alleles reported previously to contribute to the VISA phenotype, but unexpectedly, these alleles were unique to each CC. A subtherapeutic concentration of vancomycin elicited changes in the VISA transcriptome-common and unique-among the three CCs tested. Multiple genes, including those encoding a glycerate kinase, an M50 family metallopeptidase, and an uncharacterized membrane protein, were upregulated among all three lineages and not reported previously as associated with VISA. Although there are lineage-specific changes in DNA sequence, our findings suggest changes in the VISA transcriptome constitute a general response to stress that confers reduced susceptibility to multiple antibiotics. IMPORTANCE: Our understanding of the mechanisms that underlie the development of vancomycin-intermediate Staphylococcus aureus (VISA) is incomplete. To provide a more comprehensive view of this process, we compared genome sequences of clonal complex (CC) 5, CC8, and CC45 VISA clinical isolates and measured changes in the transcriptomes of these isolates during culture with a subtherapeutic concentration of vancomycin. Notably, we identified differentially expressed genes that were lineage-specific or common to the lineages tested, including genes that have not been previously reported to contribute to a VISA phenotype. Changes in gene expression were accompanied by reduced growth rate, increased cell wall thickness, and reduced susceptibility to daptomycin, televancin, tigecycline, and vancomycin. Our results provide support to the idea that changes in gene expression contribute to the development of VISA among three CCs that are a prominent cause of human infections.

Topical Steroid Withdrawal is a Targetable Excess of Mitochondrial NAD.

Background: Topical corticosteroids (TCS) are first-line therapies for numerous skin conditions. Topical Steroid Withdrawal (TSW) is a controversial diagnosis advocated by patients with prolonged TCS exposure who report severe systemic reactions upon treatment cessation. However, to date there have been no systematic clinical or mechanistic studies to distinguish TSW from other eczematous disorders. Methods: A re-analysis of a previous survey with eczematous skin disease was performed to evaluate potential TSW distinguishing symptoms. We subsequently conducted a pilot study of 16 patients fitting the proposed diagnostic criteria. We then performed: tissue metabolomics, transcriptomics, and immunostaining on skin biopsies; serum metabolomics and cytokine assessments; shotgun metagenomics on microbiome skin swabs; genome sequencing; followed by functional, mechanistic studies using human skin cell lines and mice. Results: Clinically distinct TSW symptoms included burning, flushing, and thermodysregulation. Metabolomics and transcriptomics both implicated elevated NAD+ oxidation stemming from increased expression of mitochondrial complex I and conversion of tryptophan into kynurenine metabolites. These abnormalities were induced by glucocorticoid exposure both in vitro and in a cohort of healthy controls (N=19) exposed to TCS. Targeting complex I via either metformin or the herbal compound berberine improved outcomes in both cell culture and in an open-label case series for patients with TSW. Conclusion: Taken together, our results suggest that TSW has a distinct dermatopathology. While future studies are needed to validate these results in larger cohorts, this work provides the first mechanistic evaluation into TSW pathology, and offers insights into clinical identification, pharmacogenomic candidates, and directed therapeutic strategies.