Colonization Density Research Articles

Effects of direct and conventional planting systems on mycorrhizal activity in wheat grown in the Cerrado

Direct planting systems offer several benefits to the soil and plants, as reflected in soil organisms. The Arbuscular mycorrhizal fungi are extremely sensitive to environmental changes and can be used as indicators of soil quality. This study focused on the native diversity of mycorrhizae in the region. Thus, the objective of this work was to evaluate mycorrhizal colonization, spore density, soil glomalin content and species diversity in five wheat genotypes under direct and conventional planting systems. This work was carried out in the experimental area of Embrapa Cerrados, Planaltina, DF, Brazil. The rates of mycorrhizal colonization, spore density and easily extractable glomalin were evaluated, and species of arbuscular mycorrhizal fungi were identified in five wheat genotypes under direct and conventional planting. For all the genotypes under conventional planting, there was a decrease in mycorrhizal colonization, the number of spores in the rhizosphere and the amount of easily extractable glomalin. The composition of the arbuscular mycorrhizal fungal community differed among the wheat genotypes and management systems. The richness of morphospecies of AMF in the direct planting system was similar to that in the conventional system, with twelve species each, but the conventional system reduced root colonization and spore density. The most common species were A. scrobiculata, Si. tortuosum and G. macrocarpum, which were found in all the genotypes in both cultivation systems.

Study on the synergistic effects of siderophore bacteria and arbuscular mycorrhizal fungi on the improvement of iron nutrition in Cinnamomum camphor

Iron, an essential micronutrient for plant growth, is often found in insoluble forms in alkaline soils, leading to inadequate absorption, poor plant growth, and iron deficiency chlorosis. This study explores the effects of co-inoculation with the siderophore bacteria Lysinibacillus fusiformis (S5) and Arbuscular mycorrhizal fungi (AMF) on the iron uptake and growth of Cinnamomum camphora seedlings. The experiment included four treatment groups: a control with plain water, AMF only, S5 only, and a combined AMF+S5 group, over a three-month pot experiment. Compared to the control, the combined AMF+S5 treatment significantly enhanced root mycorrhizal colonization and spore density by 15.6% and 31.8%, respectively. Additionally, there were increases in stem thickness, plant height, and root length by 34.7%, 15.6%, and 80.3%, respectively. In terms of photosynthetic physiology, the combined treatment improved the net photosynthetic rate and stomatal conductance by 37.5% and 46.7%, respectively, while reducing intercellular CO2 concentration by 8.7%. Furthermore, total iron content in Cinnamomum camphora increased by 11%, and root-available iron content (FCR) by 26.6%. These results demonstrate that co-inoculation with AMF and siderophore bacteria significantly promotes growth and iron absorption in seedlings, effectively mitigating symptoms of iron deficiency chlorosis, providing a scientific basis for developing efficient microbial co-inoculation techniques.

The ecology of giant kelp colonization and its implications for kelp forest restoration.

The success and cost-effectiveness of kelp forest restoration hinges on understanding the colonization ecology of kelps, particularly with respect to dispersal potential, recruitment success, and subsequent establishment. To gain needed insight into these processes we examined spatial patterns and temporal trajectories of the colonization of a large artificial reef by the giant kelp Macrocystis pyrifera. The 151 ha artificial reef complex was constructed in three phases over 21 years, enabling dispersal, recruitment, and subsequent establishment to be examined for a wide range of environmental conditions, dispersal distances, and source population sizes. Natural colonization of all phases of the artificial reef by giant kelp was rapid (within 1 year) and extended across the entire 7-km-long reef complex. Colonization density declined with distance from the nearest source population, but only during the first phase when the distance from the nearest source population was ≤3.5 km. Despite this decline, recruitment on artificial reef modules farthest from the source population was sufficient to produce dense stands of kelp within a couple of years. Experimental outplanting of the artificial reef with laboratory-reared kelp embryos was largely successful but proved unnecessary, as the standing biomass of kelp resulting from natural recruitment exceeded that observed on nearby natural reefs within 2-3 years of artificial reef construction for all three phases. Such high potential for natural colonization following disturbance has important implications for kelp forest restoration efforts that employ costly and logistically difficult methods to mimic this process by active seeding and transplanting.

RSV and rhinovirus increase pneumococcal carriage acquisition and density, whereas nasal inflammation is associated with bacterial shedding

Epidemiological studies report the impact of co-infection with pneumococcus and respiratory viruses upon disease rates and outcomes, but their effect on pneumococcal carriage acquisition and bacterial load is scarcely described. Here, we assess this by combining natural viral infection with controlled human pneumococcal infection in 581 healthy adults screened for upper respiratory tract viral infection before intranasal pneumococcal challenge. Across all adults, respiratory syncytial virus (RSV) and rhinovirus asymptomatic infection confer a substantial increase in secondary infection with pneumococcus. RSV also has a major impact on pneumococcal density up to 9days post challenge. We also study rates and kinetics of bacterial shedding through the nose and oral route in a subset. High levels of pneumococcal colonization density and nasal inflammation are strongly correlated with increased odds of nasal shedding as opposed to cough shedding. Protection against respiratory viral infections and control of pneumococcal density may contribute to preventing pneumococcal disease and reducing bacterial spread.

Effects of grassland degradation on diversity of arbuscular mycorrhizal fungi of a pioneer plant.

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts that engage in crucial interactions with plants, playing a vital role in grassland ecology. Our study focuses on the pioneer plant Agropyron cristatum, and we collected soil samples from four degraded grasslands in Yudaokou to investigate the response of community composition to the succession of degraded grasslands. We measured the vegetation status, soil physical and chemical properties, AMF colonization, and spore density in different degraded grasslands. High-throughput sequencing was employed to analyze AMF in soil samples. Correlations among community composition, soil characteristics, and plant factors were studied using principal component and regression analyses. The distribution of AMF in grasslands exhibited variation with different degrees of degradation, with Glomus, Scutellospora, and Diversispora being the dominant genera. The abundance of dominant genera in AMF also varied, showing a gradual increase in the relative abundance of the genus Diversispora with higher degradation levels. AMF diversity decreased from 27.7% to 12.4% throughout the degradation process. Among 180 samples of Agropyron cristatum plants, AMF hyphae and vesicles displayed the highest infection status in non-degraded grasslands and the lowest in severely degraded ones. Peak AMF spore production occurred in August, with maximum values in the 0-10-cm soil layer, and the highest spore densities were found in lightly degraded grasslands. Apart from pH, soil factors exhibited a positive correlation with AMF infection during grassland degradation. Furthermore, changes in AMF community composition were jointly driven by vegetation and soil characteristics, with vegetation coverage and soil organic carbon significantly impacting AMF distribution. Significant differences in AMF variables (spore number and diversity index) were also observed at different soil depths. Grassland successional degradation significantly influences AMF community structure and composition. Our future focus will be on understanding response mechanisms and implementing improvement methods for AMF during grassland degradation and subsequent restoration efforts.

Variability in Maize Seed Bacterization and Survival Correlating with Root Colonization by Pseudomonas Isolates with Plant-Probiotic Traits.

Seed treatment with plant growth-promoting bacteria represents the primary strategy to incorporate them into agricultural ecosystems, particularly for crops under extensive management, such as maize. In this study, we evaluated the seed bacterization levels, root colonization patterns, and root competitiveness of a collection of autochthonous Pseudomonas isolates that have demonstrated several plant-probiotic abilities in vitro. Our findings indicate that the seed bacterization level, both with and without the addition of various protectants, is specific to each Pseudomonas strain, including their response to seed pre-hydration. Bacterization kinetics revealed that while certain isolates persisted on seed surfaces for up to 4 days post-inoculation (dpi), others experienced a rapid decline in viability after 1 or 2 dpi. The observed differences in seed bacterization levels were consistent with the root colonization densities observed through confocal microscopy analysis, and with root competitiveness quantified via selective plate counts. Notably, isolates P. protegens RBAN4 and P. chlororaphis subsp. aurantiaca SMMP3 demonstrated effective competition with the natural microflora for colonizing the maize rhizosphere and both promoted shoot and root biomass production in maize assessed at the V3 grown stage. Conversely, P. donghuensis SVBP6 was detected at very low levels in the maize rhizosphere, but still exhibited a positive effect on plant parameters, suggesting a growth-stimulatory effect during the early stages of plant development. In conclusion, there is a considerable strain-specific variability in the maize seed bacterization and survival capacities of Pseudomonas isolates with plant-probiotic traits, with a correlation in their root competitiveness under natural conditions. This variability must be understood to optimize their adoption as inputs for the agricultural system. Our experimental approach emphasizes the critical importance of tailoring seed bacterization treatments for each inoculant candidate, including the selection and incorporation of protective substances. It should not be assumed that all bacterial cells exhibit a similar performance.

Effect of AMF Inoculation on Reducing Excessive Fertilizer Use.

Excessive use of chemical fertilizer is a global concern. Arbuscular mycorrhizal fungi (AMF) are considered a potential solution due to their symbiotic association with crops. This study assessed AMF's effects on maize yield, fertilizer efficiency, plant traits, and soil nutrients under different reduced-fertilizer regimes in medium-low fertility fields. We found that phosphorus supplementation after a 30% fertilizer reduction enhanced AMF's positive impact on grain yield, increasing it by 3.47% with pure chemical fertilizers and 6.65% with mixed fertilizers. The AMF inoculation did not significantly affect the nitrogen and phosphorus fertilizer use efficiency, but significantly increased root colonization and soil mycelium density. Mixed fertilizer treatments with phosphorus supplementation after fertilizer reduction showed greater mycorrhizal effects on plant traits and soil nutrient contents compared to chemical fertilizer treatments. This study highlights that AMF inoculation, closely linked to fertilization regimes, can effectively reduce fertilizer use while sustaining or enhancing maize yields.

Effect of single-patient room design on the incidence of nosocomial infection in the intensive care unit: a systematic review and meta-analysis.

Previous studies have yielded varying conclusions regarding the impact of single-patient room design on nosocomial infection in the intensive care unit (ICU). We aimed to examine the impact of ICU single-patient room design on infection control. We conducted a comprehensive search of PubMed, Embase, the Cochrane Library, Web of Science, CNKI, WanFang Data, and CBM databases from inception to October 2023, without language restrictions. We included observational cohort and quasi-experimental studies assessing the effect of single- versus multi-patient rooms on infection control in the ICU. Outcomes measured included the nosocomial infection rate, incidence density of nosocomial infection, nosocomial colonization and infection rate, acquisition rate of multidrug-resistant organisms (MDROs), and nosocomial bacteremia rate. The choice of effect model was determined by heterogeneity. Our final analysis incorporated 12 studies involving 12,719 patients. Compared with multi-patient rooms in the ICU, single-patient rooms demonstrated a significant benefit in reducing the nosocomial infection rate (odds ratio [OR]: 0.68; 95% confidence interval [CI]: 0.59, 0.79; p < 0.00001). Analysis based on nosocomial infection incidence density revealed a statistically significant reduction in single-patient rooms (OR: 0.64; 95% CI: 0.44, 0.92; p = 0.02). Single-patient rooms were associated with a marked decrease in nosocomial colonization and infection rate (OR: 0.44; 95% CI: 0.32, 0.62; p < 0.00001). Furthermore, patients in single-patient rooms experienced lower nosocomial bacteremia rate (OR: 0.73; 95% CI: 0.59, 0.89; p = 0.002) and lower acquisition rate of MDROs (OR: 0.41; 95% CI: 0.23, 0.73; p = 0.002) than those in multi-patient rooms. Implementation of single-patient rooms represents an effective strategy for reducing nosocomial infections in the ICU. https://www.crd.york.ac.uk/PROSPERO/).

The Relationships between the Population Density of Fir Bark Beetles and Niche Breadth.

Bark beetles are a significant link in the chain of diseases that lead to the accelerated dying of firs (Abies alba Mill.), a key species in the cultivation of stable mixed-tree stands. The aim of this work was to evaluate biotic interactions in populations of bark beetles that colonised natural traps made from firs. The tested hypothesis was that the niche breadth of the species increases with the increasing density of the population. The research was carried out in near-natural forests containing fir, growing in the Suchedniów-Oblęgorek Landscape Park in central Poland. Data were collected from 30 traps trees and 30 windfalls in the years 2010-2023. Cryphalus piceae Ratz. prefers heavily weakened trees, as shown by the fact that it colonised all of the natural traps, which lack any defensive reactions. The sampling method used in the study proved effective, as confirmed by the segregation of the niches of all of the bark beetles. Using nonlinear regression (linearisable model and piecewise linear regression), models were constructed that describe the niche breadths of the bark beetles. The niche parameter is correlated with the density of colonisation. The derived models explain around 77-84% of the variation in the niche breadth of bark beetles on natural traps. The mean relative errors of estimation do not exceed 20%. The niche breadth parameter obtained from the derived regression equations may be used in models that describe-for example-the impact of observed climate change on the population dynamics of bark beetles.

Three-Dimensional Imaging of the Enteric Nervous System in Human Pediatric Colon Reveals New Features of Hirschsprung’s Disease

Hirschsprung's disease is defined by the absence of the enteric nervous system (ENS) from the distal bowel. Primary treatment is "pull-through" surgery to remove bowel that lacks ENS, with reanastomosis of "normal" bowel near the anal verge. Problems after pull-through are common, and some may be due to retained hypoganglionic bowel (ie, low ENS density). Testing this hypothesis has been difficult because counting enteric neurons in tissue sections is unreliable, even for experts. Tissue clearing and 3-dimensional imaging provide better data about ENS structure than sectioning. Regions from 11 human colons and 1 ileal specimen resected during Hirschsprung's disease pull-through surgery were cleared, stained with antibodies to visualize the ENS, and imaged by confocal microscopy. Control distal colon from people with no known bowel problems were similarly cleared, stained, and imaged. Quantitative analyses of human colon, ranging from 3 days to 60 years old, suggest age-dependent changes in the myenteric plexus area, ENS ganglion area, percentage of myenteric plexus occupied by ganglia, neurons/mm2, and neuron Feret's diameter. Neuron counting using 3-dimensional images was highly reproducible. High ENS density in neonatal colon allowed reliable neuron counts using 500-μm2× 500-μm2 regions (36-fold smaller than in adults). Hirschsprung's samples varied 8-fold in proximal margin enteric neuron density and had diverse ENS architecture in resected bowel. Tissue clearing and 3-dimensional imaging provide more reliable information about ENS structure than tissue sections. ENS structure changes during childhood. Three-dimensional ENS anatomy may provide new insight into human bowel motility disorders, including Hirschsprung's disease.

Nasal Delivery of Haemophilus haemolyticus Is Safe, Reduces Influenza Severity, and Prevents Development of Otitis Media in Mice.

Despite vaccination, influenza and otitis media (OM) remain leading causes of illness. We previously found that the human respiratory commensal Haemophilus haemolyticus prevents bacterial infection in vitro and that the related murine commensal Muribacter muris delays OM development in mice. The observation that M muris pretreatment reduced lung influenza titer and inflammation suggests that these bacteria could be exploited for protection against influenza/OM. Safety and efficacy of intranasal H haemolyticus at 5 × 107 colony-forming units (CFU) was tested in female BALB/cARC mice using an influenza model and influenza-driven nontypeable Haemophilus influenzae (NTHi) OM model. Weight, symptoms, viral/bacterial levels, and immune responses were measured. Intranasal delivery of H haemolyticus was safe and reduced severity of influenza, with quicker recovery, reduced inflammation, and lower lung influenza virus titers (up to 8-fold decrease vs placebo; P ≤ .01). Haemophilus haemolyticus reduced NTHi colonization density (day 5 median NTHi CFU/mL = 1.79 × 103 in treatment group vs 4.04 × 104 in placebo, P = .041; day 7 median NTHi CFU/mL = 28.18 vs 1.03 × 104; P = .028) and prevented OM (17% OM in treatment group, 83% in placebo group; P = .015). Haemophilus haemolyticus has potential as a live biotherapeutic for prevention or early treatment of influenza and influenza-driven NTHi OM. Additional studies will deem whether these findings translate to humans and other respiratory infections.

Safety and efficacy of whole-body chlorhexidine gluconate cleansing with or without emollient in hospitalised neonates (NeoCHG): a multicentre, randomised, open-label, factorial pilot trial

Healthcare-associated infections account for substantial neonatal in-hospital mortality. Chlorhexidine gluconate (CHG) whole body skin application could reduce sepsis by lowering bacterial colonisation density, although safety and optimal application regimen is unclear. Emollients, including sunflower oil, may independently improve skin condition, thereby reducing sepsis. We aimed to inform which concentration and frequency of CHG, with or without emollient, would best balance safety and the surrogate marker of efficacy of reduction in bacterial colonisation, to be taken forward in a future pragmatic trial evaluating clinical outcomes of sepsis and mortality. In this multicentre, randomised, open-label, factorial pilot trial, neonates in two hospital sites (South Africa, Bangladesh) aged 1-6 days with gestational age ≥ 28 weeks and birthweight 1000-1999 g were randomly assigned in a factorial design stratified by site to three different concentrations of CHG (0.5%, 1%, and 2%), with or without emollient (sunflower oil) applied on working days vs alternate working days. A control arm received neither product. Caregivers were unblinded although laboratory staff were blinded to randomisation Co-primary outcomes were safety (change in neonatal skin condition score incorporating dryness, erythema, and skin breakdown) and efficacy in reducing bacterial colonisation density (change in total skin bacterial log10CFU from randomisation to day-3 and day-8). The trial is registered at the ISRCTN registry, ISRCTN69836999. Between Apr 12 2021 and Jan 18 2022, 208 infants were randomised and 198 were included in the final analysis. Skin condition scores were low with mean 0.1 (sd=0.3; N=208) at baseline, 0.1 (sd=0.3; N=199) at day 3 and 0.1 (sd=0.3; N=189) at day 8, with no evidence of differences between concentration (1% CHG vs 0.5% estimate=-0.3, 95% CI= (-1.2, 0.6), p=0.55. 2% CHG vs 0.5% CHG estimate=0.5 (-0.4, 1.4), p=0.30), increasing frequency (estimate=-0.4; 95% CI= (-1.1, 0.4), p=0.33), emollient (estimate=-0.5, (-1.2, 0.3), p=0.23) or with control (estimate=-0.9, (-2.3, 0.4), p=0.18). Mean log10CFU was 4.9 (sd=3.0; N=208) at baseline, 6.3 (sd=3.1; N=198) at day 3 and 8.4 (sd=2.6; N=183) with no evidence of differences between concentration (1% CHG vs 0.5% estimate=-0.4; 95% CI= (-1.1, 0.23); p=0.23. 2% CHG vs 0.5% CHG estimate=0.0 (-0.6, 0.6), p=0.96), with increasing frequency (estimate=-0.4; 95% CI= (-0.9, 0.2); p=0.17), with emollient (estimate=0.4, 95% CI= (-0.2, 0.9); p=0.18) or with control (estimate=-0.2, 95% CI= (-1.3, 0.9); p=0.73). By day-8, overall 158/183 (86%) of neonates were colonised with Enterobacterales, and 72/183 (39%) and 69/183 (9%) with Klebsiella spp resistant to third-generation cephalosporin and carbapenems, respectively. There were no CHG-related SAEs, emollient-related SAEs, grade 3 or 4 skin scores or grade 3 or 4 hypothermias. In this pilot trial of CHG with or without sunflower oil, no safety issues were identified, and further trials examining clinical outcomes are warranted. The relatively late start application of emollient, at a mean of 3.8 days of life, may have reduced the impact of the intervention although no subgroup effects were detected. There was no clear evidence in favour of a specific concentration of chlorhexidine, and there was rapid colonisation with Enterobacterales with frequent antimicrobial resistance, regardless of skin application regimen. The MRC Joint Applied Global Health award, the Global Antibiotic Research and Development Partnership (GARDP), MRC Clinical Trials Unit core funding (UKRI) and St. George's, University of London.

Host plants directly determine the α diversity of rhizosphere arbuscular mycorrhizal fungal communities in the National Tropical Fruit Tree Field Genebank

Arbuscular mycorrhizal fungi (AMF) typically exhibit reduced diversity in nutrient-rich soils. However, whether the influence of host plants on AMF within the rhizosphere is direct or indirect through the alteration of soil nutrient levels has yet to be determined. This study explored the diversity and colonization of AMF in the National Tropical Fruit Tree Genebank, where chemical fertilizers are used to preserve minor tropical fruit germplasms. We aimed to understand the direct and indirect effects of host plants on AMF community dynamics, sporulation, and colonization. By analyzing fine roots and rhizosphere soil from 12 tropical fruit trees, we assessed mycorrhizal colonization indices, soil nutrients, AMF spore density, and community structure. Despite their low colonization density and arbuscular abundance, all the tree roots harbored AMF, with spore densities ranging from 24.00 to 204.80 spores/100 g of dry soil. High-throughput sequencing identified 207 AMF virtual taxa (VTs) from 60 soil samples, with dominant taxa, including early-evolved Paraglomus fungi and ruderal AMF, being minimally affected by soil nutrient levels. Interestingly, there was no correlation between α diversity and spore density. Structural equation modeling (SEM) indicated that host plant evolutionary divergence time (ET) directly influenced AMF α diversity indices and indirectly impacted spore density via soil nutrients. However, neither ETs nor soil nutrients significantly affected the AMF community structure, with only arbuscular abundance showing a negative correlation with ET. This research underscores the intricate relationship between host plants and AMF in genebanks, offering insights for effective AMF resource management and informed conservation practices.Graphical

P052 Mucosal IgG-like naive B-cell expansion and maturation contribute to ulcerative colitis pathogenesis

Abstract Background A higher abundance of colonic naive B-cells and IgG plasma cells is implicated in the pathogenesis of ulcerative colitis (UC) during active inflammatory episodes. However, B-cell inhibition by targeting CD20 was found to be ineffective in achieving remission in UC patients indicating that the causal role of the B-cell expansion in UC is not well understood. In this study, we performed single cell RNA-sequencing (scRNA-seq) on mucosal tissue where we interrogated the B-cells in inflamed and non-inflamed UC colon biopsies. We subsequently explored the pathogenic role of B-cells in colitis mouse models. Methods We collected biopsies from the colon of 5 UC patients with active inflammation and 5 UC patients showing no inflamed mucosa. Three mucosal biopsies were collected from the same colon location for each patient and processed for scRNA-seq. We acquired usable transcriptomes of 21.475 cells. In a T-cell transfer colitis mice model, we evaluated the effects of the co-transfer of naive B-cells. Both CD4+ T and naive B-cells were transferred into SCID mice through intraperitoneal injection in ratios of 2:1, 1:1 and 1:2 (T:B ratio). The colitis course was followed for 35 days. Results Differential abundance analysis relative to all immune cells confirmed a higher abundance of naive B-cells (p= 0.03) and IgG plasma B-cells (p= 0.002) in inflamed relative to non-inflamed UC patient tissue, whereas no differences in abundance of transitional B-cells and memory B-cells were found. Pseudo-time analysis indicated a higher rate of maturation in the naive B-cells in inflamed tissue. This was evidenced by higher expression of IGHG1 (p= 0.025) and IGHG3 (p&amp;lt; 0.001) in naive B-cells in inflamed tissue. In a T-cell transfer model, we co-transferred naive B-cells to the CD4+ T-cell pool into SCID mice in various ratios (2:1, 1:1 and 1:2 T to B-cells respectively) and T-cell only control. Significant increase in disease severity was observed in a 1:2 T:B ratio based on body weight loss, increase of colon density, mouse colitis histology index and histological changes by disrupted mucosa. This observation was associated to significant elevated IgG concentration in serum and colon and B-cell presence in colon through immunohistochemistry. Conclusion We observed significantly higher abundance of naive B-cells and IgG plasma cells in inflamed relative to non-inflamed UC colon tissue, where naive B-cells were shown to be more mature and IgG-like in inflamed condition. Notably, transferring increased ratio of naive B-cells resulted in elevated disease severity in a colitis model, demonstrating its pathogenic role. Our findings suggest that specific targeting of the IgG-like naive B-cell may be beneficial for UC patients.

Impact of Helicobacter pylori colonization density and depth on gastritis severity

Background and objectivesHelicobacter pylori (H. pylori) infection is the most common etiology of chronic gastric. H. pylori gastritis would gradually evolve into gastric atrophy, intestinal metaplasia, dysplasia and malignant lesions. Herein, this study aimed to investigate the potential impact of H. pylori colonization density and depth on the severity of histological parameters of gastritis.MethodsA prospective monocentric study was conducted from December 2019 to July 2022, enrolling patients with confirmed chronic H. pylori infection via histopathological evaluation. H. pylori colonization status was detected by immunohistochemical staining, pathological changes of gastric specimens were detected by hematoxylin eosin staining. Epidemiological, endoscopic and histopathological data were collected.ResultsA total of 1120 patients with a mean age of 45.8 years were included. Regardless of the previous history of H. pylori eradication treatment, significant correlations were observed between the density and depth of H. pylori colonization and the intensity of gastritis activity (all P < 0.05). Patients with the lowest level of H. pylori colonization density and depth exhibited the highest level of mild activity. In whole participants and anti-H. pylori treatment-naive participants, H. pylori colonization density and depth were markedly correlated with the severity of chronic gastritis and gastric atrophy (all P < 0.05). H. pylori colonization density (P = 0.001) and depth (P = 0.047) were significantly associated with ulcer formation in patients naive to any anti-H. pylori treatment. No significant associations were observed between the density and depth of H. pylori colonization and other histopathological findings including lymphadenia, lymphoid follicle formation and dysplasia.ConclusionsAs the density and depth of H. pylori colonization increased, so did the activity and severity of gastritis, along with an elevated risk of ulcer formation.

Serotype 3 Experimental Human Pneumococcal Challenge (EHPC) study protocol: dose ranging and reproducibility in a healthy volunteer population (challenge 3)

IntroductionSince the introduction of pneumococcal conjugate vaccines, pneumococcal disease rates have declined for many vaccine-type serotypes. However, serotype 3 (SPN3) continues to cause significant disease and is identified in colonisation...

Investigation of an outbreak of metallo-β-lactamase producing Pseudomonas aeruginosa linked to the water distribution system in a Hematopoietic Stem Cell Transplantation Unit.

Pseudomonas aeruginosa (PA) is an opportunistic pathogen. Metallo-β-lactamase producing PA (MBL-PA) poses a problematic issue given limited available treatments. In Argentina, it accounts for less than one percent of healthcare-associated infections. To describe an outbreak of verona integron-encoded metallo-β-lactamase (VIM) Pseudomonas aeruginosa in a Hematopoietic Stem Cell Transplantation Unit (HSCTU), and the strategies implemented to control it. Investigation of an outbreak by MBL-PA in an HSCTU in May 2023. Active case search, environmental sampling, identification and susceptibility pattern of strains, mitigation strategies. Case: patient admitted to the HSCTU with positive sample for MBL-PA after 48hours of admission. Mitigation strategies: biweekly rectal swabbing, contact precautions, dedicated nursing staff, waterless patient care, and disinfection of bacterial reservoirs. In May 2023 two cases were identified. A retrospective search determined an additional case. One (10%) of the environmental samples was positive for VIM type MBL-PA in the drain of the hand hygiene station in the nurse's office. Strains were susceptible to colistin and fosfomycin and intermediate to aztreonam. Incidence density (ID) of colonization and infection by MBL-PA in the HSCTU were .68/1,000 patient-days (pd) and 0, respectively, in the second semester of 2022. In the first semester of 2023, ID rose to 2.93/1,000 pd for colonization and .73/1,000 pd for infection.Mitigation strategies aimed at reducing exposure of immunocompromised hosts to water. No new cases have been identified since. We report an MBL-PA outbreak probably linked to the water distribution system in an HSCTU, and mitigation strategies put in place.

Spider silk enhanced tissue engineering of cartilage tissue: Approach of a novel bioreactor model using adipose derived stromal cells.

Human cartilage tissue remains a challenge for the development of therapeutic options due to its poor vascularization and reduced regenerative capacities. There are a variety of research approaches dealing with cartilage tissue engineering. In addition to different biomaterials, numerous cell populations have been investigated in bioreactor-supported experimental setups to improve cartilage tissue engineering. The concept of the present study was to investigate spider silk cocoons as scaffold seeded with adipose-derived stromal cells (ASC) in a custom-made bioreactor model using cyclic axial compression to engineer cartilage-like tissue. For chemical induction of differentiation, BMP-7 and TGF-β2 were added and changes in cell morphology and de-novo tissue formation were investigated using histological staining to verify chondrogenic differentiation. By seeding spider silk cocoons with ASC, a high colonization density and cell proliferation could be achieved. Mechanical induction of differentiation using a newly established bioreactor model led to a more roundish cell phenotype and new extracellular matrix formation, indicating a chondrogenic differentiation. The addition of BMP-7 and TGF-β2 enhanced the expression of cartilage specific markers in immunohistochemical staining. Overall, the present study can be seen as pilot study and valuable complementation to the published literature.

Bacterial nasopharyngeal colonisation in children in South Africa before and during the COVID-19 pandemic: an observational study

Deployment of non-pharmaceutical interventions such as face masking and physical distancing during the COVID-19 pandemic could have altered the transmission dynamics and carriage of respiratory organisms. We evaluated colonisation with Streptococcus pneumoniae and other upper respiratory tract bacterial colonisers before and during the COVID-19 pandemic. We did two cross-sectional surveys in Soweto, South Africa from July 3 to Dec 13, 2018 (pre-COVID-19 period) and from Aug 4, 2021, to March 31, 2022 (COVID-19 period) in healthy children (aged ≤60 months) who had recorded HIV status and had not received antibiotics in the 21 days before enrolment. At enrolment, we collected nasopharyngeal swab samples from child participants. Following nucleic acid extraction, nanofluidic quantitative PCR was used to screen all samples for 92 S pneumoniae serotypes and 14 other bacteria. The primary objective was to compare the prevalence and density of pneumococcal nasopharyngeal colonisation, overall and stratified by 13-valent pneumococcal conjugate vaccine (PCV13) serotypes and non-vaccine serotypes. Secondary study objectives included a comparison of serotype-specific pneumococcal colonisation and density, as well as colonisation by the 14 other bacteria in the COVID-19 versus pre-COVID-19 period. We used an adjusted multiple logistic and linear regression model to compare the colonisation prevalence and density between study periods. We analysed nasopharyngeal swabs from 1107 children (n=571 in the pre-COVID-19 period; n=536 in the COVID-19 period). We observed no change in overall pneumococcal colonisation between periods (274 [51%] of 536 in the COVID-19 period vs 282 [49%] of 571 in the pre-COVID-19 period; adjusted odds ratio [aOR] 1·03 [95% CI 0·95-1·12]). The prevalence of PCV13 serotypes was lower in the COVID-19 than in the pre-COVID-19 period (72 [13%] vs 106 [19%]; 0·87 [0·78-0·97]), whereas the prevalence of non-typeable S pneumoniae was higher (34 [6%] vs 63 [12%]; 1·30 [1·12-1·50]). The mean log10 density for overall pneumococcal colonisation was lower in the COVID-19 period than in the pre-COVID-19 period (3·96 [95% CI 3·85-4·07] vs 4·72 [4·63-4·80] log10 genome equivalents per mL; p<0·0001). A lower density of non-vaccine serotypes (3·63 [3·51-3·74] vs 4·08 [3·95-4·22] log10 genome equivalents per mL; p<0·0001) and non-typeable S pneumoniae (3·11 [2·94-3·29] vs 4·41 [4·06-4·75] log10 genome equivalents per mL; p<0·00001) was also observed in the COVID-19 period. There was no difference in the density of PCV13 serotypes between the periods. The prevalence of colonisation during the COVID-19 versus pre-COVID-19 period was lower for non-typeable Haemophilus influenzae (280 [49%] vs 165 [31%]; aOR 0·77 [95% CI 0·71-0·84]), Moraxella catarrhalis (328 [57%] vs 242 [45%]; 0·85 [0·79-0·92]), and Neisseria lactamica (51 [9%] vs 13 [2%]; 0·64 [0·52-0·78]), but higher for Acinetobacter baumannii (34 [6%] vs 102 [19%]; 1·55 [1·35-1·77]) and Staphylococcus aureus (29 [5%] vs 52 [10%]; 1·28 [1·10-1·50]). There were variable effects on the colonisation prevalence and density of bacterial organisms during the COVID-19 compared with the pre-COVID-19 period. The lower prevalence of PCV13 serotype together with other respiratory organisms including non-typeable H influenzae and M catarrhalis could have in part contributed to a decrease in all-cause lower respiratory tract infections observed in South Africa during the initial stage of the COVID-19 pandemic. The pathophysiological mechanism for the increase in A baumannii and S aureus colonisation warrants further investigation, as does the clinical relevance of these findings. The Bill & Melinda Gates Foundation.

Unveiling Candida albicans intestinal carriage in healthy volunteers: the role of micro- and mycobiota, diet, host genetics and immune response

ABSTRACT Candida albicans is a commensal yeast present in the gut of most healthy individuals but with highly variable concentrations. However, little is known about the host factors that influence colonization densities. We investigated how microbiota, host lifestyle factors, and genetics could shape C. albicans intestinal carriage in 695 healthy individuals from the Milieu Intérieur cohort. C. albicans intestinal carriage was detected in 82.9% of the subjects using quantitative PCR. Using linear mixed models and multiway-ANOVA, we explored C. albicans intestinal levels with regard to gut microbiota composition and lifestyle factors including diet. By analyzing shotgun metagenomics data and C. albicans qPCR data, we showed that Intestinimonas butyriciproducens was the only gut microbiota species whose relative abundance was negatively correlated with C. albicans concentration. Diet is also linked to C. albicans growth, with eating between meals and a low-sodium diet being associated with higher C. albicans levels. Furthermore, by Genome-Wide Association Study, we identified 26 single nucleotide polymorphisms suggestively associated with C. albicans colonization. In addition, we found that the intestinal levels of C. albicans might influence the host immune response, specifically in response to fungal challenge. We analyzed the transcriptional levels of 546 immune genes and the concentration of 13 cytokines after whole blood stimulation with C. albicans cells and showed positive associations between the extent of C. albicans intestinal levels and NLRP3 expression, as well as secreted IL-2 and CXCL5 concentrations. Taken together, these findings open the way for potential new interventional strategies to curb C. albicans intestinal overgrowth.