Combined metagenomic- and culture-based approaches to investigate bacterial strain-level associations with medication-controlled mild-moderate atopic dermatitis.

Background: The skin microbiome is disrupted in atopic dermatitis (AD). Existing research focuses on moderate to severe, unmedicated disease. Objective: We sought to investigate metagenomic- and culture-based bacterial strain-level differences in mild, medicated AD and the effects these have on human keratinocytes (HKs). Methods: Skin swabs from anterior forearms were collected from 20 pediatric participants (11 participants with AD sampled at lesional and nonlesional sites and 9 age- and sex-matched controls). Participants had primarily mild to moderate AD and maintained medication use. Samples were processed for microbial metagenomic sequencing and bacterial isolation. Isolates identified as Staphylococcus aureus were tested for enterotoxin production. HK cultures were treated with cell-free conditioned media from representative Staphylococcus species to measure barrier effects. Results: Metagenomic sequencing identified significant differences in microbiome composition between AD and control groups. Differences were seen at the species and strain levels for Staphylococci, with S aureus found only in participants with AD and differences in Staphylococcus epidermidis strains between control and AD swabs. These strains showed differences in toxin gene presence, which was confirmed in vitro for S aureus enterotoxins. The strain from the participant with the most severe AD produced enterotoxin B levels more than 100-fold higher than the other strains (P < .001). Strains also displayed differential effects on HK metabolism and barrier function. Conclusions: Strain-level differences in toxin genes from Staphylococcus strains may explain varying effects on HK, with S aureus and non-aureus strains negatively affecting viability and barrier function. These differences are likely important in AD pathogenesis.

Pernio and early SARS-CoV-2 variants: natural history of a prospective cohort and the role of interferon.

Cases of new-onset pernio and recurrences in our cohort align tightly with trends in mean 7-day COVID-19 positivity in Wisconsin and mean temperature in Madison, Wisconsin by month.

Complete Genome Resources for Ralstonia Bacterial Wilt Strains UW763 (Phylotype I); Rs5 and UW700 (Phylotype II); and UW386, RUN2474, and RUN2279 (Phylotype III).

We share whole genome sequences of six strains from the Ralstonia solanacearum species complex, a diverse group of Betaproteobacteria that cause plant vascular wilt diseases. Using single-molecule real-time technology, we sequenced and assembled full genomes of Rs5 and UW700, two phylotype IA-sequevar 7 (IIA-7) strains from the southeastern United States that are closely related to the R. solanacearum species type strain, K60, but were isolated >50 years later. Four sequenced strains from Africa include a soil isolate from Nigeria (UW386, III-23), a tomato isolate from Senegal (UW763, I-14), and two potato isolates from the Madagascar highlands (RUN2474, III-19 and RUN2279, III-60). This resource will support studies of the genetic diversity, ecology, virulence, and microevolution of this globally distributed group of high-impact plant pathogens.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Ralstonia solanacearum Depends on Catabolism of Myo-Inositol, Sucrose, and Trehalose for Virulence in an Infection Stage-Dependent Manner.

The soilborne pathogen Ralstonia solanacearum causes a lethal bacterial wilt disease of tomato and many other crops by infecting host roots, then colonizing the water-transporting xylem vessels. Tomato xylem sap is nutritionally limiting but it does contain some carbon sources, including sucrose, trehalose, and myo-inositol. Transcriptomic analyses revealed that R. solanacearum expresses distinct catabolic pathways at low cell density (LCD) and high cell density (HCD). To investigate the links between bacterial catabolism, infection stage, and virulence, we measured in planta fitness of bacterial mutants lacking specific carbon catabolic pathways expressed at either LCD or HCD. We hypothesized that early in disease, during root infection, the bacterium depends on carbon sources catabolized at LCD, while HCD carbon sources are only required later in disease during stem colonization. A R. solanacearum ΔiolG mutant unable to use the LCD-catabolized nutrient myo-inositol was defective in tomato root colonization, but after it reached the stem this strain colonized and caused symptoms as well as wild type. In contrast, R. solanacearum mutants unable to use the HCD-catabolized nutrients sucrose (ΔscrA), trehalose (ΔtreA), or both (ΔscrA/treA), infected roots as well as wild-type R. solanacearum but were defective in colonization and competitive fitness in midstems and had reduced virulence. Further, xylem sap from tomato plants colonized by ΔscrA, ΔtreA, or ΔscrA/treA R. solanacearum mutants contained twice as much sucrose as sap from plants colonized by wild-type R. solanacearum. Together, these findings suggest that quorum sensing specifically adapts R. solanacearum metabolism for success in the different nutritional environments of plant roots and xylem sap.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

First Report of Bacterial Wilt Disease of Tomato, Pepper and Gboma Caused by the Ralstonia solanacearum Species Complex in Togo.

Tomato (Solanum lycopersicum), pepper (Capsicum annum), and gboma (Solanum macrocarpon) are major vegetables in Togo, with many people depending on these crops for their livelihood. In December 2018, during the dry season with temperatures between 21°C to 35°C, tomato ('Petomech'), pepper ('Gboyebesse') and gboma (local landrace) showing wilt symptoms without foliar yellowing were collected from two locations, Tchouloum and CECO-AGRO sites in the Sotouboua Prefecture of Togo, ~300 km from the capital city of Lome. Disease incidence ranged between 10% to 50% in multiple fields. Cut stems of most wilting tomato, pepper and gboma plants produced bacterial ooze in water and vascular discoloration was visible in longitudinal stem sections. Ground cut stem tissue tested positive with Rs ImmunoStrips specific to the Ralstonia solanacearum species complex (RSSC) (Agdia Inc., Elkhart, IN, USA). Collected samples were stored at ambient temperature and cultured within 36 hr. Culturing sap from cut stems plated on modified SMSA medium (Engelbrecht 1994) yielded colonies with typical RSSC morphology: slow-growing, irregular, mucoid, and white with red centers. Genomic DNA was extracted from thirteen isolates: two from gboma, five from tomato and six from pepper. The expected 280-bp band was amplified from all 13 genomic DNAs following polymerase chain reaction (PCR) using the 759/760 RSSC-specific primer pair (Opina et al. 1997). PCR with the 630/631 primers, which identify the Race 3 biovar 2 RSSC subgroup, did not yield a product from any Togo isolate (Opina et al. 1997). The phylotype multiplex PCR identified all Togo isolates as belonging to the phylotype I subgroup, also called R. pseudosolanacearum (Prior et al. 2016; Fegan and Prior 2005). Phylotype control DNAs were from strains GMI1000 (phylotype I, Asia), K60 (phylotype II, Americas), CMR15 (phylotype III, Africa), and PSI07 (phylotype IV, Indondesia). Comparative genomic analysis of the partial endoglucanase (egl) gene, amplified with the Endo primer pairs (Poussier et al. 2000), revealed all Togo strains belonged to sequevar 17, a group known to cause bacterial wilt of peanut in China. (Xu et al. 2009). The egl sequences are in NCBI GenBank accessions MT572393 to MT572405. Koch's postulates were completed by inoculating 28-day-old bacterial wilt-susceptible 'Bonny Best' tomato plants by soil soak (Khokhani et al. 2018). Briefly, soil around each unwounded plant was drenched with 50 ml of a 108 CFU/mL suspension of bacteria grown from a single colony. Five plants were inoculated with each of four randomly selected Togo strains. RSSC phylotype I strain GMI1000 served as a positive control and water treated plants as negative controls. Plants were kept in a 28°C growth chamber with a 12 hr photoperiod. All RSSC inoculated plants were fully wilted within a week; symptoms resembled to those observed in the field. Water treated control plants did not wilt. Culturing sap from all inoculated plants on SMSA medium yielded colonies with typical RSSC morphology that tested positive with the Rs ImmunoStrips. This is the first identification of RSSC in Togo. These results will guide development of disease management strategies and regionally appropriate breeding of vegetable lines with resistance to the phylotype I RSSC strains present in Togo.