Testing the effects of Bdellovibrio on wheat (Triticum aestivum) and as a food security agent in mushrooms (Agaricus bisporus)

Bdellovibrio bacteriovorus is a naturally soil-dwelling, Gram-negative predatory bacterium that attaches to, invades, and replicates within a wide range of other Gram-negative bacterial species, killing such prey in the process. A small number of previous studies testing the effect of B. bacteriovorus against known Gram-negative plant pathogens have suggested that B. bacteriovorus has potential as a ‘food security agent’ against Gram-negative bacterial infections in crop plants. My project built on this knowledge by screening a range of known Gram-negative bacterial plant pathogens and Plant Growth-Promoting Rhizobacteria (PGPRs) for susceptibility to Bdellovibrio predation in vitro; testing predation-susceptible strains in a simple, semi-sterile in vivo system on the surface of Agaricus bisporus mushrooms; and finally testing the effect of Bdellovibrio addition in a more complex, natural Triticum aestivum (wheat) soil rhizosphere mesocosm. An in vitro prey strain growth assay showed that susceptibility to B. bacteriovorus predation varied between a range of 20 Gram-negative (mostly Pseudomonas) bacterial pathogen/PGPR species, isolated from a range of different host crops or soil environments. Four of these species (Pseudomonas avellanae 48, P. syringae pv. phaseolicola, P. tolaasii 2192T and P. agarici 2289) were highly susceptible to predation, and three species (B. vietnamiensis G4, P. marginalis 667, and Pectobacterium atrosepticum SCRI1143) showed apparent resistance to predation. P. tolaasii 2192T, causes dark, pathogenic lesions on post-harvest mushroom host crops; In vivo co-inoculation tests on the surface of A. bisporus mushrooms showed that lesions were significantly reduced with B. bacteriovorus treatment, which was due to B. bacteriovorus predatory killing and reduction of prey cell numbers, preventing symptoms. B. bacteriovorus also preyed upon and killed a putative pathogenic Pseudomonas species isolated from a grey lesion on an organic, garden mushroom, but some likely commensal species isolated from mushroom tissue showed resistance to predation. These data together suggest that B. bacteriovorus could be used commercially to prolong the shelf life of mushrooms, reducing crop losses through spoilage, with minimal negative effects on mushroom PGPR species. Finally, inoculating B. bacteriovorus into the soil around young winter wheat plants in a natural pot soil mesocosm was found to increase plant growth and grain yield at harvest; this was contrary to my initial hypothesis that B. bacteriovorus would reduce wheat plant growth, by preying upon and killing PGPR species such as P. fluorescens that reduce wheat plant infection with Gaeumannomyces graminis var. tritici, the yield-reducing take-all fungal pathogen of wheat. The soil was found to be low in nitrogen; thus B. bacteriovorus inoculation could have increased wheat growth due to B. bacteriovorus death in the soil and subsequent release of nutrients including nitrogen. However, some B. bacteriovorus cells survived in the soil where they could prey upon some Gram-negative bacterial species, reducing their numbers. Some of the wheat growth and yield-producing effects of B. bacteriovorus may be due to the predation of species that are associated with late flowering, and therefore grain development, in wheat, allowing time for more grain to develop. Alternatively, it could be due to processes performed by B. bacteriovorus in the soil that are not related to predation, such as production of the plant hormone IAA, or B. bacteriovorus colonisation of the roots and predation of root-associated pathogenic bacterial species. Further studies are required to identify the mechanisms behind these unexpected crop yield-promoting effects, and the extent of any nutrient ‘boost’ effect due to death of B. bacteriovorus in the wheat soil, to determine whether B. bacteriovorus could be used as a pre-harvest growth and yield-promoting agent. Although most studies of B. bacteriovorus so far have focussed on its predatory activity, it likely performs other functions in its natural soil habitat, which may underlie some of the growth and yield-promoting effects shown here. However, these data show that B. bacteriovorus could be used commercially as a ‘food security agent’ when used as a post-harvest treatment to prevent crop spoilage and loss (as for A. bisporus mushrooms)

Bdellovibrio bacteriovorus HD100 guards against Pseudomonas tolaasii brown-blotch lesions on the surface of post-harvest Agaricus bisporus supermarket mushrooms

BACKGROUND: Pseudomonas tolaasii is a problematic pathogen of cultured mushrooms, forming dark brown 'blotches' on mushroom surfaces and causing spoilage during crop growth and post-harvest . Treating P. tolaasii infection is difficult, as other, commensal bacterial species such as Pseudomonas putida are necessary for mushroom growth, so treatments must be relatively specific. RESULTS: We have found that P. tolaasii is susceptible to predation in vitro by the δ-proteobacterium Bdellovibrio bacteriovorus. This effect also occurred in funga, where B. bacteriovorus was administered to post-harvest mushroom caps before and after administration of the P. tolaasii pathogen. A significant, visible improvement in blotch appearance, after incubation, was observed on administration of Bdellovibrio. A significant reduction in viable P. tolaasii cell numbers, recovered from the mushroom tissue, was detected. This was accompanied by a more marked reduction in blotch severity on Bdellovibrio administration. We found that there was in some cases an accompanying overgrowth of presumed-commensal, non-Pseudomonas bacteria on post-harvest mushroom caps after Bdellovibrio-treatment. These bacteria were identified (by 16SrRNA gene sequencing) as Enterobacter species, which were seemingly resistant to predation. We visualised predatory interactions occuring between B. bacteriovorus and P. tolaasii on the post-harvest mushroom cap surface by Scanning Electron Microscopy, seeing predatory invasion of P. tolaasii by B. bacteriovorus in funga. This anti-P. tolaasii effect worked well in post-harvest supermarket mushrooms, thus Bdellovibrio was not affected by any pre-treatment of mushrooms for commercial/consumer purposes. CONCLUSIONS: The soil-dwelling B. bacteriovorus HD100 preys upon and kills P. tolaasii, on mushroom surfaces, and could therefore be applied to prevent spoilage in post-harvest situations where mushrooms are stored and packaged for sale

A mixed-method investigation of patient monitoring and enhanced feedback in routine practice: Barriers and facilitators

Objective: To investigate the barriers and facilitators of an effective implementation of an outcome monitoring and feedback system in a UK National Health Service psychological therapy service. Method: An outcome monitoring system was introduced in two services. Enhanced feedback was given to therapists after session 4. Qualitative and quantitative methods were used, including questionnaires for therapists and patients. Thematic analysis was carried out on written and verbal feedback from therapists. Analysis of patient outcomes for 202 episodes of therapy was compared with benchmark data of 136 episodes of therapy for which feedback was not given to therapists. Results: Themes influencing the feasibility and acceptability of the feedback system were the extent to which therapists integrated the measures and feedback into the therapy, availability of administrative support, information technology, and complexity of the service. There were low levels of therapist actions resulting from the feedback, including discussing the feedback in supervision and with patients. Conclusions: The findings support the feasibility and acceptability of setting up a routine system in a complex service, but a number of challenges and barriers have to be overcome and therapist differences are apparent. More research on implementation and effectiveness is needed in diverse clinical settings

30-day mortality after systemic anticancer treatment for breast and lung cancer in England: a population-based, observational study

Background: 30-day mortality might be a useful indicator of avoidable harm to patients from systemic anticancer treatments, but data for this indicator are limited. The Systemic Anti-Cancer Therapy (SACT) dataset collated by Public Health England allows the assessment of factors affecting 30-day mortality in a national patient population. The aim of this first study based on the SACT dataset was to establish national 30-day mortality benchmarks for breast and lung cancer patients receiving SACT in England, and to start to identify where patient care could be improved. Methods: In this population-based study, we included all women with breast cancer and all men and women with lung cancer residing in England, who were 24 years or older and who started a cycle of SACT in 2014 irrespective of the number of previous treatment cycles or programmes, and irrespective of their position within the disease trajectory. We calculated 30-day mortality after the most recent cycle of SACT for those patients. We did logistic regression analyses, adjusting for relevant factors, to examine whether patient, tumour, or treatment-related factors were associated with the risk of 30-day mortality. For each cancer type and intent, we calculated 30-day mortality rates and patient volume at the hospital trust level, and contrasted these in a funnel plot. Findings: Between Jan 1, and Dec, 31, 2014, we included 23 228 patients with breast cancer and 9634 patients with non-small cell lung cancer (NSCLC) in our regression and trust-level analyses. 30-day mortality increased with age for both patients with breast cancer and patients with NSCLC treated with curative intent, and decreased with age for patients receiving palliative SACT (breast curative: odds ratio [OR] 1·085, 99% CI 1·040–1·132; p<0·0001; NSCLC curative: 1·045, 1·013–1·079; p=0·00033; breast palliative: 0·987, 0·977–0·996; p=0·00034; NSCLC palliative: 0·987, 0·976–0·998; p=0·0015). 30-day mortality was also significantly higher for patients receiving their first reported curative or palliative SACT versus those who received SACT previously (breast palliative: OR 2·326 99% CI 1·634–3·312; p<0·0001; NSCLC curative: 3·371, 1·554–7·316; p<0·0001; NSCLC palliative: 2·667, 2·109–3·373; p<0·0001), and for patients with worse general wellbeing (performance status 2–4) versus those who were generally well (breast curative: 6·057, 1·333–27·513; p=0·0021; breast palliative: 6·241, 4·180–9·319; p<0·0001; NSCLC palliative: 3·384, 2·276–5·032; p<0·0001). We identified trusts with mortality rates in excess of the 95% control limits; this included seven for curative breast cancer, four for palliative breast cancer, five for curative NSCLC, and seven for palliative NSCLC. Interpretation: Our findings show that several factors affect the risk of early mortality of breast and lung cancer patients in England and that some groups are at a substantially increased risk of 30-day mortality. The identification of hospitals with significantly higher 30-day mortality rates should promote review of clinical decision making in these hospitals. Furthermore, our results highlight the importance of collecting routine data beyond clinical trials to better understand the factors placing patients at higher risk of 30-day mortality, and ultimately improve clinical decision making. Our insights into the factors affecting risk of 30-day mortality will help treating clinicians and their patients predict the balance of harms and benefits associated with SACT. Funding: Public Health England

Ras GTPase-like protein MglA, a controller of bacterial social-motility in Myxobacteria, has evolved to control bacterial predation by Bdellovibrio

Bdellovibrio bacteriovorus invade Gram-negative bacteria in a predatory process requiring Type IV pili (T4P) at a single invasive pole, and also glide on surfaces to locate prey. Ras-like G-protein MglA, working with MglB and RomR in the deltaproteobacterium Myxococcus xanthus, regulates adventurous gliding and T4P-mediated social motility at both M. xanthus cell poles. Our bioinformatic analyses suggested that the GTPase activating protein (GAP)-encoding gene mglB was lost in Bdellovibrio, but critical residues for MglABd GTP-binding are conserved. Deletion of mglABd abolished prey-invasion, but not gliding, and reduced T4P formation. MglABd interacted with a previously uncharacterised tetratricopeptide repeat (TPR) domain protein Bd2492, which we show localises at the single invasive pole and is required for predation. Bd2492 and RomR also interacted with cyclic-di-GMP-binding receptor CdgA, required for rapid prey-invasion. Bd2492, RomRBd and CdgA localize to the invasive pole and may facilitate MglA-docking. Bd2492 was encoded from an operon encoding a TamAB-like secretion system. The TamA protein and RomR were found, by gene deletion tests, to be essential for viability in both predatory and non-predatory modes. Control proteins, which regulate bipolar T4P-mediated social motility in swarming groups of deltaproteobacteria, have adapted in evolution to regulate the anti-social process of unipolar prey-invasion in the “lone-hunter” Bdellovibrio. Thus GTP-binding proteins and cyclic-di-GMP inputs combine at a regulatory hub, turning on prey-invasion and allowing invasion and killing of bacterial pathogens and consequent predatory growth of Bdellovibrio

Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

Introduction: The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures. Methods: In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025. Findings: Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2–6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p&lt;0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5–5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p&lt;0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4–10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p&lt;0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32–4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP &gt;5mg/L, OR 3·55 [1·23–11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation. Interpretation: After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification