In situ control of root–bacteria interactions using optical trapping in transparent soil

Bacterial attachment on root surfaces is an important step preceding the colonisation or internalisation and subsequent infection of plants by pathogens. Unfortunately, bacterial attachment is not well understood because the phenomenon is difficult to observe. Here we assessed whether this limitation could be overcome using optical trapping approaches. We have developed a system based on counter-propagating beams and studied its ability to guide Pectobacterium atrosepticum (Pba) cells to different root cell types within the interstices of transparent soils. Bacterial cells were successfully trapped and guided to root hair cells, epidermis cells, border cells and tissues damaged by laser ablation. Finally, we used the system to quantify the bacterial cell detachment rate of Pba cells on root surfaces following reversible attachment. Optical trapping techniques could greatly enhance our ability to deterministically characterise mechanisms linked to attachment and formation of biofilms in the rhizosphere.

Improving Transungual Permeation Study Design by Increased Bovine Hoof Membrane Thickness and Subsequent Infection

Ungual formulations are regularly tested using human nails or animal surrogates in Franz diffusion cell experiments. Membranes sometimes less than 100 µm thick are used, disregarding the higher physiological thickness of human nails and possible fungal infection. In this study, bovine hoof membranes, healthy or infected with Trichophyton rubrum, underwent different imaging techniques highlighting that continuous pores traversed the entire membrane and infection resulted in fungal growth, both superficial, as well as in the membrane’s matrix. These membrane characteristics resulted in substantial differences in the permeation of the antifungal model substance bifonazole, depending on the dosage forms. Increasing the thickness of healthy membranes from 100 µm to 400 µm disproportionally reduced the permeated amount of bifonazole from the liquid and semisolid forms and allowed for a more pronounced assessment of the effects by excipients, such as urea as the permeation enhancer. Similarly, an infection of 400-µm membranes drastically increased the permeated amount. Therefore, the thickness and infection statuses of the membranes in the permeation experiments were essential for a differential readout, and standardized formulation-dependent experimental setups would be highly beneficial.

Hydro-responsive wound dressings for treating hard-to-heal wounds: a narrative review of the clinical evidence

A break in skin integrity must be repaired as quickly as possible to avoid excess blood and fluid loss, and to minimise the onset of infection. Hard-to-heal wounds, in which the progression of the wound healing response is compromised, present several challenges to healing (for example, the presence of devitalised tissue acting as a physical barrier to healing and as a focus for bacterial contamination with the potential for subsequent infection). The objective of this article is to present, as a narrative review, the clinical evidence supporting the use of a unique hydro-responsive wound dressing (HydroClean, HRWD1, PAUL HARTMANN AG, Germany). The dressing provides a simple treatment option to address a number of clinical challenges clinicians must overcome in order to facilitate wound healing progression. These studies demonstrated that this product supported successful debridement/cleansing of a wide variety of wounds, including hard-to-heal wounds, enabled wound bed preparation, and lead to positive healing outcomes, including in wounds that previously had failed to heal. The simplicity of using HRWD1 as a single dressing can help clinicians overcome a variety of challenges when treating both acute and hard-to-heal wounds, which, with the benefit of proven patient outcomes, could make it an ideal choice for a first-line treatment.

Expression of the Type III Secretion System Genes in Epiphytic Erwinia amylovora Cells on Apple Stigmas Benefits Endophytic Infection at the Hypanthium

Erwinia amylovora causes fire blight on rosaceous plants. One of the major entry points of E. amylovora into hosts is flowers, where E. amylovora proliferates epiphytically on stigmatic and hypanthium surfaces and, subsequently, causes endophytic infection at the hypanthium. The type III secretion system (T3SS) is an important virulence factor in E. amylovora. Although the role of T3SS during endophytic infection is well characterized, its expression during epiphytic colonization and role in the subsequent infection is less understood. Here, we investigated T3SS gene expression in epiphytic E. amylovora on stigma and hypanthium of apple flowers under different relative humidities (RH). On stigma surfaces, T3SS was expressed in a high percentage of E. amylovora cells, and its expression promoted epiphytic growth. On hypanthium surfaces, however, T3SS was expressed in fewer E. amylovora cells than on the stigma, and displayed no correlation with epiphytic growth, even though T3SS expression is essential for infection. E. amylovora cells grown on stigmatic surfaces and then flushed down to the hypanthium displayed a higher level of T3SS expression than cells grown on the hypanthium surface alone. Furthermore, E. amylovora cells precultured on stigma had a higher potential to infect flowers than E. amylovora cells precultured in a T3SS-repressive medium. This suggests that T3SS induction during the stigmatic epiphytic colonization may be beneficial for subsequent infection. Finally, epiphytic expression of T3SS was influenced by RH. Higher percentage of stigmatic E. amylovora cells expressed T3SS under high RH than under low RH. [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 .

Covid Reinfection versus Asymptomatic Carrier State: A Case Report

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), first discovered in China in December 2019, has been implicated in the current coronavirus disease 2019 (COVID-19) pandemic. Although much has been learned about the virus which peaked with the development of the vaccine, there is still a lot of unanswered questions. Maximum duration of positive SARS-CoV-2 real-time reverse transcriptase polymerase chain reaction (RT-PCR) from symptom onset may be up to 3 months [1], however it is not known if the continued detection of the viral genome implies prolonged infectivity or presence of a non-viable virus [2]. Most people with COVID-19 develop antibodies after resolution of acute infection [2]. The exact duration of these antibodies in the body is unknown, but some studies have shown that both memory T-cells and B-cells can persist up to 6 to 8 months after acute SARS-CoV-2 infection [3]. These SARS-CoV-2 antibodies may confer some immunity to the person after the acute infection and have been associated with protection against subsequent infection in nonhuman primates by the same viral strain during the early recovery phase [4]. In humans, however, it is unknown to what extent this immune response indicates a protective immunity to subsequent infection with SARS-CoV-2 [5]. Few cases of reinfection have been documented worldwide with varying symptom severity; the first case in the US was published in January 2021 (reinfection occurred in June 2020) [5]. None of the initial cases reported the presence of SARS-CoV-2 antibodies at the time of reinfection. We present a patient who tested positive to SARS-CoV-2 RT-PCR twice in 10 months (Table 1). At both times, she was asymptomatic and the second time, she had coexisting SARS-CoV-2 antibodies.

RSV immunizes bystander cells to IAV infection using interferons β and λ

We observed the interference between two prevalent respiratory viruses, respiratory syncytial virus (RSV) and influenza A virus (IAV, H1N1), and characterized its molecular underpinnings in alveolar epithelial cells (A549). We found that RSV induces higher interferon (IFN) β production than IAV and that IFNβ priming confers higher protection against infection with IAV than with RSV. Consequently, we focused on the sequential infection scheme: RSV-then-IAV. Using the A549 WT, IFNAR1 KO, IFNLR1 KO, and IFNAR1–IFNLR1 double KO cell lines we found that both IFNβ and IFNλ are necessary for maximum protection against subsequent infection. Immunostaining revealed that preinfection with RSV partitions the cell population into a subpopulation susceptible to subsequent infection with IAV and an IAV-proof subpopulation. Strikingly, the susceptible cells turned out to be those already compromised and efficiently expressing RSV, whereas the bystander, interferon-primed cells are resistant to IAV infection. Thus, the virus–virus exclusion at the cell population level is not realized through a direct competition for a shared ecological niche (single cell) but rather achieved with the involvement of specific cytokines induced within the host innate immune response.

Superficial mycosis, at the site or distant to the surgical site, appears to predispose patients to bacterial periprosthetic joint infections

Background: It is traditionally believed that presence of fungal infection in the nail or skin of patients is a risk factor for subsequent infection. The literature is devoid of any evidence to confirm or refute this belief. This study examined a possible relationship between the presence of superficial skin or nail mycoses and subsequent periprosthetic joint infection (PJI) in patients undergoing total joint arthroplasty (TJA). Methods: This is a single-centre, retrospective study of patients who underwent primary TJA between 2000 and 2018. 55 patients with superficial mycoses of skin or nail, at the time of arthroplasty were identified and a variable number matching with up to a 1:5 ratio was performed with 182 patients undergoing TJA who had no superficial mycosis. The groups were further divided into knee and hip TJA. The outcome of TJA in the cohorts was compared. Results: Preoperative demographics were similar between the 2 groups. The incidence of PJI in patients undergoing TKA within a year was significantly higher in patients with superficial mycosis at 8.6% (3/35) compared to 0% (0/120) in patients without mycosis. However, all infections were caused by bacterial species and none were fungal. Multiple regression analysis demonstrated that the presence of superficial mycosis had a strong correlation with development of PJI postoperatively in our TKA cohort. Conclusions: Identification of fungal infection (mycosis) of skin and nail in patients awaiting TJA is important. These patients appear to have a higher risk for developing bacterial PJI than those without fungal infections. Further study is needed to determine if treatment of these patients prior to arthroplasty stands to reverse the high risk for PJI that these patients carry.

A Novel Risk Predictive Scoring Model For Predicting Subsequent Infection After Carbapenem-Resistant Gram-Negative Bacteria Colonization In Hematological Malignancies Patients

PurposeTo investigate the high-risk factors associated with the increased vulnerability for subsequent clinical infection in Carbapenem-resistant Gram-negative bacteria (CR-GNB) colonized hematological malignancies (HMs) patients, and build a statistical model to predict subsequent infection.MethodAll adult HMs patients with positive anal swab culture for CR-GNB between January 2018 and June 2020 were prospectively followed to assess for any subsequent CR-GNB infections and to investigate the risk factors and clinical features of subsequent infection.ResultsA total of 392 HMs patients were enrolled. Of them, 46.7% developed a subsequent clinical infection, and 42 (10.7%) were confirmed infection and 141 (36%) were clinically diagnosed infection. Klebsiella pneumoniae was the dominant species. The overall mortality rate of patients colonized and infected with CR-GNB was 8.6% and 43.7%. A multivariate analysis showed that remission induction chemotherapy, the duration of agranulocytosis, mucositis, and hypoalbuminemia were significant predictors of subsequent infection after CR-GNB colonization. According to our novel risk predictive scoring model, the high-risk group were > 3 times more likely to develop a subsequent infection in comparison with the low-risk group.ConclusionOur risk predictive scoring model can early and accurately predict subsequent infection in HMs patients with CR-GNB colonization. Early administration of CR-GNB-targeted empirical therapy in the high-risk group is strongly recommended to decrease their mortality.

WHY DO INSECTS EVOLVE IMMUNE PRIMING? A SEARCH FOR CROSSROADS

Until recently, it was assumed that insects lack immune memory since they do not have vertebrate-like specialized memory cells. Therefore, their most well studied evolutionary response against pathogens was increased basal immunity. However, growing evidence suggests that many insects also exhibit a form of immune memory (immune priming), where prior exposure to a low dose of infection confers protection against subsequent infection by the same pathogen that acts both within and across generations. Most strikingly, they can rapidly evolve as a highly parallel and mutually exclusive strategy from basal immunity, under different selective conditions and with divergent evolutionary trade-offs. However, the relative importance of priming as an optimal immune strategy also has contradictions, primarily because supporting mechanisms are still unclear. In this review, we adopt a comparative approach to highlight several emerging evolutionary, ecological and mechanistic features of priming vs basal immune responses that warrant immediate attention for future research.