Expanding the Bacterial Diversity of the Female Urinary Microbiome: Description of Eight New Corynebacterium Species

Update on novel validly published and included bacterial taxa derived from human clinical specimens and taxonomic revisions published in 2023

Taxonomy is a systematic practice in which microorganisms are granted names to facilitate and standardize multi-disciplinary communication. We summarize novel bacterial taxa derived from human clinical material that were published in peer-reviewed literature and/or included by the International Journal of Systematic and Evolutionary Microbiology during calendar year 2023, as well as taxonomic revisions that have been published/included by the same entity. While the majority of newly discovered facultative and anaerobic organisms were derived from microbiome surveillance, noteworthy novel taxa in the realm of pathogenicity potential include those related to Aerococcus spp., several Corynebacterium spp., Exercitatus varius gen. nov., sp. nov., and Mycoplasma phocimorsus sp. nov. With respect to nomenclature revision, the Bacillus and Clostridium genera continue to be visited annually. Creation of novel anaerobic Gram-negative bacillus genera Hallella, Hoylesella, Leyella, Segatella, and Xylanibacter impacted several Bacteroides spp. and Prevotella spp. Additional studies are necessary to ascertain the clinical significance of several of these microbes.

Description of two novel Corynebacterium species isolated from human nasal passages and skin

Strains of two novel Corynebacterium species were cultured from samples of human nostrils and skin collected in the United States and Botswana. These strains demonstrated growth on Columbia Colistin-Nalidixic Acid agar with 5% sheep blood and in liquid media (brain heart infusion and tryptic soy broth) supplemented with Tween 80, a source of the fatty acid oleic acid. Cells were Gram-positive, non-spore-forming, non-motile bacilli that showed catalase but not oxidase activity. Major fatty acids in both of these species were 18:1 ω9c (oleic acid), 16:0 (palmitic acid), and 18:0 (stearic acid). Analysis of the 16S ribosomal RNA gene sequences identified these strains as belonging to the genus Corynebacterium (family Corynebacteriaceae). Whole-genome sequencing revealed that these strains formed distinct branches on a phylogenomic tree, with C. tuberculostearicum being the closest relative but with average nucleotide identities of < 95% relative to all previously described species. These results indicate that these strains represent novel species of Corynebacterium, for which we propose the names Corynebacterium hallux sp. nov., with the type strain CTNIH22T (=ATCC TSD-435T=DSM 117774T), and Corynebacterium nasorum sp. nov., with the type strain KPL3804T (=ATCC TSD-439T=DSM 117767T). We also describe the characteristics of two strains isolated from human nasal passages that are members of the recently named species Corynebacterium yonathiae.

Infection by a multidrug-resistant Corynebacterium diphtheriae strain: prediction of virulence factors, CRISPR-Cas system analysis, and structural implications of mutations conferring rifampin resistance

Cases of diphtheria, even in immunized individuals, are still reported in several parts of the world, including in Brazil. New outbreaks occur in Europe and other continents. In this context, studies on Corynebacterium diphtheriae infections are highly relevant, both for a better understanding of the pathogenesis of the disease and for controlling the circulation of clones and antimicrobial resistance genes. Here we present a case of cutaneous infection by multidrug-resistant Corynebacterium diphtheriae and provide its whole-genome sequencing. Genomic analysis revealed resistance genes, including tet(W), sul1, cmx, rpoB2, rbpA and mutation in rpoB. We performed phylogenetic analyzes and used the BRIG to compare the predicted resistance genes with those found in genomes from other significant isolates, including those associated with some outbreaks. Virulence factors such as spaD, srtBC, spaH, srtDE, surface-anchored pilus proteins (sapD), nonfimbrial adhesins (DIP0733, DIP1281, and DIP1621), embC and mptC (putatively involved in CdiLAM), sigA, dtxR and MdbA (putatively involved) in post-translational modification, were detected. We identified the CRISPR-Cas system in our isolate, which was classified as Type II-U based on the database and contains 15 spacers. This system functions as an adaptive immune mechanism. The strain was attributed to a new sequence type ST-928, and phylogenetic analysis confirmed that it was related to ST-634 of C. diphtheriae strains isolated in French Guiana and Brazil. In addition, since infections are not always reported, studies with the sequence data might be a way to complement and inform C. diphtheriae surveillance.

Impact of coexisting type 2 diabetes mellitus on the urinary microbiota of kidney stone patients

Objectives

Type 2 diabetes mellitus (T2DM) commonly complicates kidney stone disease (KSD). Our objective is to investigate the variations in the urinary microbiota between individuals with KSD alone and those with KSD plus T2DM. This exploration could have implications for disease diagnosis and treatment strategies.

Methods

During lithotripsy, a ureterscope was employed, and 1 mL of urine was collected from the renal pelvis after bladder disinfection. Sequencing targeting the V3-V4 hypervariable region was performed using the 16S rRNA and Illumina Novaseq platform.

Results

The Shannon index showed a significant decrease in the KSD plus T2DM group compared to the KSD-only group (false discovery rate = 0.041). Principal Coordinate Analysis (PCoA) demonstrated a distinct bacterial community in the KSD plus T2DM group compared to the KSD-only group (false discovery rate = 0.027). The abundance of Sphingomonas, Corynebacterium, and Lactobacillus was significantly higher in the KSD plus T2DM group than in the KSD-only group (false discovery rate < 0.05). Furthermore, Enhydrobacter, Chryseobacterium, and Allobaculum were positively correlated with fasting blood glucose and HbA1c values (P < 0.05).

Conclusions

The urinary microbiota in the renal pelvis exhibits differences between patients with KSD plus T2DM and those with KSD alone. Further studies employing animal models are necessary to validate these distinctions, potentially paving the way for therapeutic developments based on the urinary microbiota.

Genomic characterization of the C. tuberculostearicum species complex, a prominent member of the human skin microbiome

IMPORTANCE

Amplicon sequencing data combined with isolate whole genome sequencing have expanded our understanding of Corynebacterium on the skin. Healthy human skin is colonized by a diverse collection of Corynebacterium species, but Corynebacterium tuberculostearicum predominates on many skin sites. Our work supports the emerging idea that C. tuberculostearicum is a species complex encompassing several distinct species. We produced a collection of genomes that help define this complex, including a potentially new species we term Corynebacterium hallux based on a preference for sites on the feet, whole-genome average nucleotide identity, pangenomic analysis, and growth in skin-like media. This isolate collection and high-quality genome resource set the stage for developing engineered strains for both basic and translational clinical studies.

Genomic characterization of the C. tuberculostearicum species complex, a ubiquitous member of the human skin microbiome

Corynebacterium is a predominant genus in the skin microbiome, yet its genetic diversity on skin is incompletely characterized and lacks a comprehensive set of reference genomes. Our work aims to investigate the distribution of Corynebacterium species on the skin, as well as to expand the existing genome reference catalog to enable more complete characterization of skin metagenomes. We used V1-V3 16S rRNA gene sequencing data from 14 body sites of 23 healthy volunteers to characterize Corynebacterium diversity and distribution across healthy human skin. Corynebacterium tuberculostearicum is the predominant species found on human skin and we identified two distinct C. tuberculostearicum ribotypes (A & B) that can be distinguished by variation in the 16S rRNA V1-V3 sequence. One is distributed across all body sites and the other found primarily on the feet. We performed whole genome sequencing of 40 C. tuberculostearicum isolates cultured from the skin of five healthy individuals across seven skin sites. We generated five closed genomes of diverse C. tuberculostearicum which revealed that C. tuberculostearicum isolates are largely syntenic and carry a diversity of methylation patterns, plasmids and CRISPR/Cas systems. The pangenome of C. tuberculostearicum is open with a core genome size of 1806 genes and a pangenome size of 5451 total genes. This expanded pangenome enabled the mapping of 24% more C. tuberculostearicum reads from shotgun metagenomic datasets derived from skin body sites. Finally, while the genomes from this study all fall within a C. tuberculostearicum species complex, the ribotype B isolates may constitute a new species.