Staphylococcus aureus
invasion of the osteocyte lacuno-canalicular network (OLCN) is a novel mechanism of bacterial persistence and immune evasion in chronic osteomyelitis. Previous work highlighted
...S. aureus
cell wall transpeptidase, penicillin binding protein 4 (PBP4), and surface adhesin,
S. aureus
surface protein C (SasC), as critical factors for bacterial deformation and propagation through nanopores
in vitro
, representative of the confined canaliculi
in vivo
. Given these findings, we hypothesized that cell wall synthesis machinery and surface adhesins enable durotaxis- and haptotaxis-guided invasion of the OLCN, respectively. Here, we investigated select
S. aureus
cell wall synthesis mutants (Δpbp3, Δatl, and ΔmreC) and surface adhesin mutants (ΔclfA and ΔsasC) for nanopore propagation
in vitro
and osteomyelitis pathogenesis
in vivo
.
In vitro
evaluation in the microfluidic silicon membrane-canalicular array (μSiM-CA) showed
pbp3
,
atl
,
clfA
, and
sasC
deletion reduced nanopore propagation. Using a murine model for implant-associated osteomyelitis,
S. aureus
cell wall synthesis proteins were found to be key modulators of
S. aureus
osteomyelitis pathogenesis, while surface adhesins had minimal effects. Specifically, deletion of
pbp3
and
atl
decreased septic implant loosening and
S. aureus
abscess formation in the medullary cavity, while deletion of surface adhesins showed no significant differences. Further, peri-implant osteolysis, osteoclast activity, and receptor activator of nuclear factor kappa-B ligand (RANKL) production were decreased following
pbp3
deletion. Most notably, transmission electron microscopy (TEM) imaging of infected bone showed that
pbp3
was the only gene herein associated with decreased submicron invasion of canaliculi
in vivo
. Together, these results demonstrate that
S. aureus
cell wall synthesis enzymes are critical for OLCN invasion and osteomyelitis pathogenesis
in vivo
.
Lower respiratory tract infection (LRTI) commonly causes hospitalization in adults. Because bacterial diagnostic tests are not accurate, antibiotics are frequently prescribed. Peripheral blood gene ...expression to identify subjects with bacterial infection is a promising strategy. We evaluated whole blood profiling using RNASeq to discriminate infectious agents in adults with microbiologically defined LRTI. Hospitalized adults with LRTI symptoms were recruited. Clinical data and blood was collected, and comprehensive microbiologic testing performed. Gene expression was measured using RNASeq and qPCR. Genes discriminatory for bacterial infection were identified using the Bonferroni-corrected Wilcoxon test. Constrained logistic models to predict bacterial infection were fit using screened LASSO. We enrolled 94 subjects who were microbiologically classified; 53 as "non-bacterial" and 41 as "bacterial". RNAseq and qPCR confirmed significant differences in mean expression for 10 genes previously identified as discriminatory for bacterial LRTI. A novel dimension reduction strategy selected three pathways (lymphocyte, α-linoleic acid metabolism, IGF regulation) including eleven genes as optimal markers for discriminating bacterial infection (naïve AUC = 0.94; nested CV-AUC = 0.86). Using these genes, we constructed a classifier for bacterial LRTI with 90% (79% CV) sensitivity and 83% (76% CV) specificity. This novel, pathway-based gene set displays promise as a method to distinguish bacterial from nonbacterial LRTI.
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Atopic dermatitis (AD) is an inflammatory disorder characterized by dominant type 2 inflammation leading to chronic pruritic skin lesions, allergic comorbidities, and Staphylococcus ...aureus skin colonization and infections. S aureus is thought to play a role in AD severity.
This study characterized the changes in the host-microbial interface in subjects with AD following type 2 blockade with dupilumab.
Participants (n = 71) with moderate-severe AD were enrolled in a randomized (dupilumab vs placebo; 2:1), double-blind study at Atopic Dermatitis Research Network centers. Bioassays were performed at multiple time points: S aureus and virulence factor quantification, 16s ribosomal RNA microbiome, serum biomarkers, skin transcriptomic analyses, and peripheral blood T-cell phenotyping.
At baseline, 100% of participants were S aureus colonized on the skin surface. Dupilumab treatment resulted in significant reductions in S aureus after only 3 days (compared to placebo), which was 11 days before clinical improvement. Participants with the greatest S aureus reductions had the best clinical outcomes, and these reductions correlated with reductions in serum CCL17 and disease severity. Reductions (10-fold) in S aureus cytotoxins (day 7), perturbations in TH17-cell subsets (day 14), and increased expression of genes relevant for IL-17, neutrophil, and complement pathways (day 7) were also observed.
Blockade of IL-4 and IL-13 signaling, very rapidly (day 3) reduces S aureus abundance in subjects with AD, and this reduction correlates with reductions in the type 2 biomarker, CCL17, and measures of AD severity (excluding itch). Immunoprofiling and/or transcriptomics suggest a role for TH17 cells, neutrophils, and complement activation as potential mechanisms to explain these findings.
Obesity is a risk factor for osteoarthritis (OA), the greatest cause of disability in the US. The impact of obesity on OA is driven by systemic inflammation, and increased systemic inflammation is ...now understood to be caused by gut microbiome dysbiosis. Oligofructose, a nondigestible prebiotic fiber, can restore a lean gut microbial community profile in the context of obesity, suggesting a potentially novel approach to treat the OA of obesity. Here, we report that - compared with the lean murine gut - obesity is associated with loss of beneficial Bifidobacteria, while key proinflammatory species gain in abundance. A downstream systemic inflammatory signature culminates with macrophage migration to the synovium and accelerated knee OA. Oligofructose supplementation restores the lean gut microbiome in obese mice, in part, by supporting key commensal microflora, particularly Bifidobacterium pseudolongum. This is associated with reduced inflammation in the colon, circulation, and knee and protection from OA. This observation of a gut microbiome-OA connection sets the stage for discovery of potentially new OA therapeutics involving strategic manipulation of specific microbial species inhabiting the intestinal space.
The evidence linking chronic kidney disease (CKD) to spontaneous intracerebral hemorrhage (ICH) is inconclusive owing to possible confounding by comorbidities that frequently coexist in patients with ...these 2 diseases.
To determine whether there is an association between CKD and ICH risk.
A 3-stage study that combined observational and genetic analyses was conducted. First, the association between CKD and ICH risk was tested in the Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) study, a multicenter case-control study in the US. All participants with available data on CKD from ERICH were included. Second, this analysis was replicated in the UK Biobank (UKB), an ongoing population study in the UK. All participants in the UKB were included in this study. Third, mendelian randomization analyses were implemented in the UKB using 27 CKD-related genetic variants to test for genetic associations. ERICH was conducted from August 1, 2010, to August 1, 2017, and observed participants for 1 year. The UKB enrolled participants between 2006 and 2010 and will continue to observe them for 30 years. Data analysis was performed from November 11, 2019, to May 10, 2022.
CKD stages 1 to 5.
The outcome of interest was ICH, ascertained in ERICH via expert review of neuroimages and in the UKB via a combination of self-reported data and International Statistical Classification of Diseases, Tenth Revision, codes.
In the ERICH study, a total of 2914 participants with ICH and 2954 controls who had available data on CKD were evaluated (mean SD age, 61.6 14.0 years; 2433 female participants 41.5%; 3435 male participants 58.5%); CKD was found to be independently associated with higher risk of ICH (odds ratio OR, 1.95; 95% CI, 1.35-2.89; P < .001). This association was not modified by race and ethnicity. Replication in the UKB with 1341 participants with ICH and 501 195 controls (mean SD age, 56.5 8.1 years; 273 402 female participants 54.4%; 229 134 male participants 45.6%) confirmed this association (OR, 1.28; 95% CI, 1.01-1.62; P = .04). Mendelian randomization analyses indicated that genetically determined CKD was associated with ICH risk (OR, 1.56; 95% CI, 1.13-2.16; P = .007).
In this 3-stage study that combined observational and genetic analyses among study participants enrolled in 2 large observational studies with different characteristics and study designs, CKD was consistently associated with higher risk of ICH. Mendelian randomization analyses suggest that this association was causal. Further studies are needed to identify the specific biological pathways that mediate this association.
Abstract
Background
Respiratory syncytial virus (RSV) is a leading cause of infant respiratory disease. Infant airway microbiota has been associated with respiratory disease risk and severity. The ...extent to which interactions between RSV and microbiota occur in the airway, and their impact on respiratory disease susceptibility and severity, are unknown.
Methods
We carried out 16S rRNA microbiota profiling of infants in the first year of life from (1) a cross-sectional cohort of 89 RSV-infected infants sampled during illness and 102 matched healthy controls, and (2) a matched longitudinal cohort of 12 infants who developed RSV infection and 12 who did not, sampled before, during, and after infection.
Results
We identified 12 taxa significantly associated with RSV infection. All 12 taxa were differentially abundant during infection, with 8 associated with disease severity. Nasal microbiota composition was more discriminative of healthy vs infected than of disease severity.
Conclusions
Our findings elucidate the chronology of nasal microbiota dysbiosis and suggest an altered developmental trajectory associated with RSV infection. Microbial temporal dynamics reveal indicators of disease risk, correlates of illness and severity, and impact of RSV infection on microbiota composition.
The findings of our study provide novel insights into the developmental dynamics of the nasal microbiome in the first year of life as they relate to susceptibility, acute illness, severity, and convalescence associated with first-time RSV infection.
Pathogen evolution and subsequent phenotypic heterogeneity during chronic infection are proposed to enhance Staphylococcus aureus survival during human infection. We tested this theory by genetically ...and phenotypically characterizing strains with mutations constructed in the mismatch repair (MMR) and oxidized guanine (GO) system, termed mutators, which exhibit increased spontaneous-mutation frequencies. Analysis of these mutators revealed not only strain-dependent increases in the spontaneous-mutation frequency but also shifts in mutational type and hot spots consistent with loss of GO or MMR functions. Although the GO and MMR systems are relied upon in some bacterial species to prevent reactive oxygen species-induced DNA damage, no deficit in hydrogen peroxide sensitivity was found when either of these DNA repair pathways was lost in S. aureus. To gain insight into the contribution of increased mutation supply to S. aureus pathoadaptation, we measured the rate of α-hemolysin and staphyloxanthin inactivation during serial passage. Detection of increased rates of α-hemolysin and staphyloxanthin inactivation in GO and MMR mutants suggests that these strains are capable of modifying virulence phenotypes implicated in mediating infection. Accelerated derivation of altered virulence phenotypes, combined with the absence of increased ROS sensitivity, highlights the potential of mutators to drive pathoadaptation in the host and serve as catalysts for persistent infections.
Evidence from in vitro and animal models has identified the pulmonary toxicity of flavors in electronic cigarettes (ECIGs); however, less is known from epidemiological studies about the effects of ...flavors in the respiratory health. This study examined the longitudinal association between exposure to ECIGs flavors and nocturnal dry cough among ECIGs users. A secondary analysis of data from the Population Assessment of Tobacco and Health Study (2014–2019) was conducted. The study population included adults who provided information (n = 18,925) for a total of 38,638 observations. Weighted-incidence estimates and weighted- generalized estimating equation models were performed to assess unadjusted and adjusted associations. The weighted incidence proportion (WIP) of nocturnal dry cough was significantly higher among current (WIP:16.6%; 95%CI 10.5, 21.2) and former fruit flavored ECIGs users (WIP:16.6%; 95%CI 11.3, 21.9) as compared to non-ECIGs users (WIP:11.1%; 95%CI 10.6, 11.6). Current ECIGs users of fruit flavors showed 40% higher risk of reporting cough than non-ECIGs users (aRR:1.40, 95%CI 1.01, 1.94). Former ECIGs users of multiple flavors and other flavors had 300% and 66% higher risk to develop cough, respectively (aRR:3.33, 95%CI 1.51, 7.34 and aRR:1.66, 95%CI 1.0.9, 2.51), relative to non-ECIGs users. We observed a significantly higher risk of developing nocturnal dry cough in the past 12 months in current and former ECIGs users of fruit flavors and in former ECIGs users of multiple flavors. To the extent that cough may serve as an early indicator of respiratory inflammation and potential disease risk, the association between ECIGs use and cough raises potential concerns.
During sepsis, acute lung injury (ALI) results from activation of innate immune cells and endothelial cells by endotoxins, leading to systemic inflammation through proinflammatory cytokine ...overproduction, oxidative stress, and intracellular Ca2+ overload. Despite considerable investigation, the underlying molecular mechanism(s) leading to LPS-induced ALI remain elusive. To determine whether stromal interaction molecule 1-dependent (STIM1-dependent) signaling drives endothelial dysfunction in response to LPS, we investigated oxidative and STIM1 signaling of EC-specific Stim1-knockout mice. Here we report that LPS-mediated Ca2+ oscillations are ablated in ECs deficient in Nox2, Stim1, and type II inositol triphosphate receptor (Itpr2). LPS-induced nuclear factor of activated T cells (NFAT) nuclear accumulation was abrogated by either antioxidant supplementation or Ca2+ chelation. Moreover, ECs lacking either Nox2 or Stim1 failed to trigger store-operated Ca2+ entry (SOCe) and NFAT nuclear accumulation. LPS-induced vascular permeability changes were reduced in EC-specific Stim1-/- mice, despite elevation of systemic cytokine levels. Additionally, inhibition of STIM1 signaling prevented receptor-interacting protein 3-dependent (RIP3-dependent) EC death. Remarkably, BTP2, a small-molecule calcium release-activated calcium (CRAC) channel blocker administered after insult, halted LPS-induced vascular leakage and pulmonary edema. These results indicate that ROS-driven Ca2+ signaling promotes vascular barrier dysfunction and that the SOCe machinery may provide crucial therapeutic targets to limit sepsis-induced ALI.
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