Aggressive or Moderate Fluid Resuscitation in Acute Pancreatitis.

BACKGROUND: Early aggressive hydration is widely recommended for the management of acute pancreatitis, but evidence for this practice is limited. METHODS: At 18 centers, we randomly assigned patients who presented with acute pancreatitis to receive goal-directed aggressive or moderate resuscitation with lactated Ringer's solution. Aggressive fluid resuscitation consisted of a bolus of 20 ml per kilogram of body weight, followed by 3 ml per kilogram per hour. Moderate fluid resuscitation consisted of a bolus of 10 ml per kilogram in patients with hypovolemia or no bolus in patients with normovolemia, followed by 1.5 ml per kilogram per hour in all patients in this group. Patients were assessed at 12, 24, 48, and 72 hours, and fluid resuscitation was adjusted according to the patient's clinical status. The primary outcome was the development of moderately severe or severe pancreatitis during the hospitalization. The main safety outcome was fluid overload. The planned sample size was 744, with a first planned interim analysis after the enrollment of 248 patients. RESULTS: A total of 249 patients were included in the interim analysis. The trial was halted owing to between-group differences in the safety outcomes without a significant difference in the incidence of moderately severe or severe pancreatitis (22.1% in the aggressive-resuscitation group and 17.3% in the moderate-resuscitation group; adjusted relative risk, 1.30; 95% confidence interval [CI], 0.78 to 2.18; P = 0.32). Fluid overload developed in 20.5% of the patients who received aggressive resuscitation and in 6.3% of those who received moderate resuscitation (adjusted relative risk, 2.85; 95% CI, 1.36 to 5.94, P = 0.004). The median duration of hospitalization was 6 days (interquartile range, 4 to 8) in the aggressive-resuscitation group and 5 days (interquartile range, 3 to 7) in the moderate-resuscitation group. CONCLUSIONS: In this randomized trial involving patients with acute pancreatitis, early aggressive fluid resuscitation resulted in a higher incidence of fluid overload without improvement in clinical outcomes. (Funded by Instituto de Salud Carlos III and others; WATERFALL ClinicalTrials.gov number, NCT04381169.).

Post-traumatic Bullous Pilomatrixoma Exploring the Pathogenesis.

ABSTRACT: This report demonstrates the rare variant of bullous pilomatrixoma in a 10-year-old boy who presented with a rapidly growing, red-colored, bullous nodule on his neck after trauma. The exact etiology of this subtype of pilomatrixoma is unclear, but previous studies have suggested that mechanical trauma may trigger its development.

Validation of an expanded, in-house library and an optimized preparation method for the identification of fungal isolates using MALDI-TOF mass spectrometry.

The goal of this study was to validate an optimized sample preparation method for filamentous fungal isolates coupled with the use of an in-house library for the identification of moulds using Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) in a multicenter context. For that purpose, three Spanish microbiology laboratories participated in the identification of 97 fungal isolates using MALDI-TOF MS coupled with the Filamentous Fungi library 3.0 (Bruker Daltonics) and an in-house library containing 314 unique fungal references. The isolates analyzed belonged to 25 species from the genus Aspergillus, Fusarium, Scedosporium/Lomentospora, the Mucorales order and the Dermatophytes group. MALDI-TOF MS identification was carried out from hyphae resuspended in water and ethanol. After a high-speed centrifugation step, the supernatant was discarded and the pellet submitted to a standard protein extraction step. The protein extract was analyzed with the MBT Smart MALDI Biotyper system (Bruker Daltonics). The rate of accurate, species-level identification obtained ranged between 84.5% and 94.8% and the score values were 1.8 for 72.2-94.9% of the cases. Two laboratories failed to identify only one isolate of Syncephalastrum sp. and Trichophyton rubrum, respectively and three isolates could not be identified in the third center (F. proliferatum, n = 1; T.interdigitale, n = 2). In conclusion, the availability of an effective sample preparation method and an extended database allowed high rates of correct identification of fungal species using MALDI-TOF MS. Some species, such as Trichophyton spp. are still difficult to identify. Although further improvements are still required, the developed methodology allowed the reliable identification of most fungal species.

MALDI-TOF mass spectrometry has been improved as a diagnostic method for the rapid and reliable identification of filamentous fungi by means of the creation of an expanded database containing reference protein spectra of the most clinically impacting fungal species.

Changes in the epidemiology of invasive fungal disease in a Pediatric Hematology and Oncology Unit: the relevance of breakthrough infections.

BACKGROUND: Invasive fungal disease (IFD) is a significant cause of morbimortality in children under chemotherapy or hematopoietic stem cell transplant (HSCT). The purpose of this study is to describe the changes in the IFD epidemiology that occurred in a Pediatric Hematology-Oncology Unit (PHOU) with an increasing activity over time. METHODS: Retrospective revision of the medical records of children (from 6 months to 18 years old) diagnosed with IFD in the PHOU of a tertiary hospital in Madrid (Spain), between 2006 and 2019. IFD definitions were performed according to the EORTC revised criteria. Prevalence, epidemiological, diagnostic and therapeutic parameters were described. Comparative analyses were conducted using Chi-square, Mann-Whitney and Kruskal-Wallis tests, according to three time periods, the type of infection (yeast vs mold infections) and the outcome. RESULTS: Twenty-eight episodes of IFD occurred in 27 out of 471 children at risk (50% males; median age of 9.8 years old, [IQR 4.9-15.1]), resulting in an overall global prevalence of 5.9%. Five episodes of candidemia and 23 bronchopulmonary mold diseases were registered. Six (21.4%), eight (28.6%) and 14 (50%) episodes met criteria for proven, probable and possible IFD, respectively. 71.4% of patients had a breakthrough infection, 28.6% required intensive care and 21.4% died during treatment. Over time, bronchopulmonary mold infections and breakthrough IFD increased (p=0.002 and p=0.012, respectively), occurring in children with more IFD host factors (p=0.028) and high-risk underlying disorders (p=0.012). A 64% increase in the number of admissions in the PHOU (p<0.001) and a 277% increase in the number of HSCT (p=0.008) were not followed by rising rates of mortality or IFD/1000 admissions (p=0.674). CONCLUSIONS: In this study, we found that yeast infections decreased, while mold infections increased over time, being most of them breakthrough infections. These changes are probably related to the rising activity in our PHOU and an increase in the complexity of the baseline pathologies of patients. Fortunately, these facts were not followed by an increase in IFD prevalence or mortality rates.

Oral Focal Mucinosis of the Tongue: A Rare Localization for a Rare Entity.

ABSTRACT: Oral focal mucinosis (OFM) is a rare connective tissue disorder that is characterized by the excessive production of hyaluronic acid due to myxoid degeneration of submucosal connective tissue. The disorder typically presents as an asymptomatic nodule or mass in the gingiva or hard palate, and OFM of the tongue is even more unusual. In this report, we present a case of OFM on the tongue in a 72-year-old female patient who presented with a symptomatic lump that had been growing for 6 months on the dorsum of her tongue. The patient reported discomfort and pain while speaking and swallowing, and the lump was visually apparent on examination. OFM is a benign condition that does not have any specific clinical or radiographical features that distinguish it from other more common oral lesions, such as lipoma or fibroma. Therefore, histopathological examination is essential for a definitive diagnosis. The management of OFM typically involves surgical excision of the lesion. In this case, complete surgical removal of the lesion under general anesthesia was performed, and the patient was followed up for 10 months postoperatively. During the follow-up period, there was no evidence of recurrence, and the patient reported significant improvement in her symptoms. In conclusion, OFM is a rare connective tissue disorder that can occur in the oral cavity. Although OFM of the tongue is even rarer, it should be considered in the differential diagnosis of oral lesions. Histopathological examination is essential for definitive diagnosis, and surgical excision is typically the preferred treatment modality.

Biosynthesis of the Inner Core of Bordetella pertussis Lipopolysaccharides: Effect of Mutations on LPS Structure, Cell Division, and Toll-like Receptor 4 Activation.

Previously developed whole-cell vaccines against Bordetella pertussis, the causative agent of whooping cough, appeared to be too reactogenic due to their endotoxin content. Reduction in endotoxicity can generally be achieved through structural modifications in the lipid A moiety of lipopolysaccharides (LPS). In this study, we found that dephosphorylation of lipid A in B. pertussis through the heterologous production of the phosphatase LpxE from Francisella novicida did, unexpectedly, not affect Toll-like receptor 4 (TLR4)-stimulating activity. We then focused on the inner core of LPS, whose synthesis has so far not been studied in B. pertussis. The kdtA and kdkA genes, responsible for the incorporation of a single 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) residue in the inner core and its phosphorylation, respectively, appeared to be essential. However, the Kdo-bound phosphate could be replaced by a second Kdo after the heterologous production of Escherichia coli kdtA. This structural change in the inner core affected outer-core and lipid A structures and also bacterial physiology, as reflected in cell filamentation and a switch in virulence phase. Furthermore, the eptB gene responsible for the non-stoichiometric substitution of Kdo-bound phosphate with phosphoethanolamine was identified and inactivated. Interestingly, the constructed inner-core modifications affected TLR4-stimulating activity. Whereas endotoxicity studies generally focus on the lipid A moiety, our data demonstrate that structural changes in the inner core can also affect TLR4-stimulating activity.

Granulocyte-colony stimulating factor in acute-on-chronic liver failure: Systematic review and meta-analysis of randomized controlled trials.

BACKGROUND AND AIMS: A dysfunctional immune response is key to the pathogenesis of acute-on-chronic liver failure (ACLF). It has been suggested that treatment with granulocyte colony-stimulating factor (G-CSF) increases survival in patients with ACLF by improving immune cell dysfunction and promoting liver regeneration. The aim of the study is to evaluate the survival benefit associated with G-CSF administration compared with standard medical therapy (SMT) in ACLF. METHODS: Systematic review and meta-analysis of randomized controlled trials. The primary outcome was survival at 60-90 days. We searched Ovid Medline, EMBASE, and Cochrane Central Register of Controlled Trials from inception to August 2021. Manual searches of reference lists in relevant articles and conference proceedings were also included. The revised Cochrane risk-of-bias tool was used for quality and risk of bias assessment. Two independent investigators extracted the data, and disagreements were solved by a third collaborator. RESULTS: The initial search identified 142 studies. Four randomized controlled trials were selected for quantitative analysis including 310 patients (154 G-CSF and 156 SMT). Significant heterogeneity was observed (I2=74%, Chi2=11.57, p=0.009). G-CSF administration did not improve survival in patients with ACLF (random-effects model, risk ratio=0.64 [95% CI 0.39, 1.07]). However, when considering only the results from the studies performed in Asia, a significant decrease on mortality was observed (risk ratio=0.53 [95% CI 0.35, 0.81]). Severity scores (MELD and Child) and CD34+ peripheral cells mobilization did not significantly improve with G-CSF. CONCLUSION: In a systematic review and meta-analysis, G-CSF administration did not significantly improve overall survival compared to SMT in patients with ACLF. The beneficial effects observed in Asian studies, as opposed to the European region, suggest that specific populations may benefit from further research aiming to identify certain subgroups with favourable outcomes when using G-CSF.

Rising from the Ashes: The Biogeographic Origins of Modern Coral Reef Fishes.

During the excavation of Mayan tombs, little did the archaeologists know that the fossils they discovered in the tomb stones would fundamentally alter our understanding of the earliest origins of coral reef fishes. Located just 500 kilometers from the point where an asteroid impact reconfigured the world's biological systems 66 million years ago, we find the earliest origins of three typical reef fish groups. Their presence in Mexico just 3 million years after this impact finally reconciles the conflict between the fossil and phylogenetic evidence for the earliest origins of reef fishes. The incorporation of these fossils into a global reconstruction of fish evolutionary history reveals a new picture of the early biogeography of reef fishes, with strong Atlantic links. From locations associated with biological destruction and societal collapse, we see evidence of the origins of one of the world's most diverse and spectacular marine ecosystems: coral reefs.

Tracking calcium dynamics from individual neurons in behaving animals.

Measuring the activity of neuronal populations with calcium imaging can capture emergent functional properties of neuronal circuits with single cell resolution. However, the motion of freely behaving animals, together with the intermittent detectability of calcium sensors, can hinder automatic monitoring of neuronal activity and their subsequent functional characterization. We report the development and open-source implementation of a multi-step cellular tracking algorithm (Elastic Motion Correction and Concatenation or EMC2) that compensates for the intermittent disappearance of moving neurons by integrating local deformation information from detectable neurons. We demonstrate the accuracy and versatility of our algorithm using calcium imaging data from two-photon volumetric microscopy in visual cortex of awake mice, and from confocal microscopy in behaving Hydra, which experiences major body deformation during its contractions. We quantify the performance of our algorithm using ground truth manual tracking of neurons, along with synthetic time-lapse sequences, covering a wide range of particle motions and detectability parameters. As a demonstration of the utility of the algorithm, we monitor for several days calcium activity of the same neurons in layer 2/3 of mouse visual cortex in vivo, finding significant turnover within the active neurons across days, with only few neurons that remained active across days. Also, combining automatic tracking of single neuron activity with statistical clustering, we characterize and map neuronal ensembles in behaving Hydra, finding three major non-overlapping ensembles of neurons (CB, RP1 and RP2) whose activity correlates with contractions and elongations. Our results show that the EMC2 algorithm can be used as a robust and versatile platform for neuronal tracking in behaving animals.

Regulated Expression of lpxC Allows for Reduction of Endotoxicity in Bordetella pertussis.

The Gram-negative bacterium Bordetella pertussis is the causative agent of a respiratory infection known as whooping cough. Previously developed whole-cell pertussis vaccines were effective, but appeared to be too reactogenic mainly due to the presence of lipopolysaccharide (LPS, also known as endotoxin) in the outer membrane (OM). Here, we investigated the possibility of reducing endotoxicity by modulating the LPS levels. The promoter of the lpxC gene, which encodes the first committed enzyme in LPS biosynthesis, was replaced by an isopropyl ß-D-1-thiogalactopyranoside (IPTG)-inducible promoter. The IPTG was essential for growth, even when the construct was moved into a strain that should allow for the replacement of LPS in the outer leaflet of the OM with phospholipids by defective phospholipid transporter Mla and OM phospholipase A. LpxC depletion in the absence of IPTG resulted in morphological changes of the cells and in overproduction of outer-membrane vesicles (OMVs). The reduced amounts of LPS in whole-cell preparations and in isolated OMVs of LpxC-depleted cells resulted in lower activation of Toll-like receptor 4 in HEK-Blue reporter cells. We suggest that, besides lipid A engineering, also a reduction in LPS synthesis is an attractive strategy for the production of either whole-cell- or OMV-based vaccines, with reduced reactogenicity for B. pertussis and other Gram-negative bacteria.

Configuration and dynamics of dominant inspiratory multineuronal activity patterns during eupnea and gasping generation in vitro.

The pre-Bötzinger complex (preBötC), located within the ventral respiratory column, produces inspiratory bursts in varying degrees of synchronization/amplitude. This wide range of population burst patterns reflects the flexibility of the preBötC neurons, which is expressed in variations in the onset/offset times of their activations and their activity during the population bursts, with respiratory neurons exhibiting a large cycle-to-cycle timing jitter both at the population activity onset and at the population activity peak, suggesting that respiratory neurons are stochastically activated before and during the inspiratory bursts. However, it is still unknown whether this stochasticity is maintained while evaluating the coactivity of respiratory neuronal ensembles. Moreover, the preBötC topology also remains unknown. In this study, by simultaneously recording tens of preBötC neurons and using coactivation analysis during the inspiratory periods, we found that the preBötC has a scale-free configuration (mixture of not many highly connected nodes, hubs, with abundant poorly connected elements) exhibiting the rich-club phenomenon (hubs more likely interconnected with each other). PreBötC neurons also produce multineuronal activity patterns (MAPs) that are highly stable and change during the hypoxia-induced reconfiguration. Moreover, preBötC contains a coactivating core network shared by all its MAPs. Finally, we found a distinctive pattern of sequential coactivation of core network neurons at the beginning of the inspiratory periods, indicating that, when evaluated at the multicellular level, the coactivation of respiratory neurons seems not to be stochastic.NEW & NOTEWORTHY By means of multielectrode recordings of preBötC neurons, we evaluated their configuration in normoxia and hypoxia, finding that the preBötC exhibits a scale-free configuration with a rich-club phenomenon. preBötC neurons produce multineuronal activity patterns that are highly stable but change during hypoxia. The preBötC contains a coactivating core network that exhibit a distinctive pattern of coactivation at the beginning of inspirations. These results reveal some network basis of inspiratory rhythm generation and its reconfiguration during hypoxia.

Disseminated lomentosporiosis in a heart transplant recipient: Case report and review of the literature.

BACKGROUND: Lomentospora prolificans (formerly S prolificans) is a saprophyte fungi that causes opportunistic infections in solid organ transplant (SOT) recipients. Resulting disseminated infections are difficult to treat and have a high mortality. Indications for antifungal prophylaxis after heart transplantation (HT) include CMV disease, reoperation, renal replacement therapy, extracorporeal membrane oxygenation (ECMO), and high environmental exposure to Aspergillus spores. However, the risk of breakthrough infections, such as Lomentosporiosis, remains a cause of concern. METHODS: We report the clinical findings, microbiology, treatment and outcome of a disseminated Lomentosporiosis in a heart transplant recipient with ECMO and antifungal prophylaxis. RESULTS: A 25-year-old male with complex grown-up congenital heart disease (GUCHD) was admitted for HT. He presented severe post-surgical complications including acute kidney injury and right heart and respiratory failure requiring venoarterial-ECMO, continuous renal replacement therapy (CCRT) and later on (+14) a ventricular assist device (VAD). Ganciclovir, cotrimoxazole, and antifungal prophylaxis with anidulafungin at standard doses had been started on day + 3 post HT. The patient presented seizures (+4), pancytopenia with mild neutropenia (days + 6 to + 11), influenza B (+7), and bacteremic Pseudomonas aeruginosa ventilator associated pneumonia (VAP) (+10). On days + 14 to + 16 Lomentospora prolificans was recovered from blood cultures, broncho aspirate, catheter tip, and skin biopsy. Despite treatment with L-AMB, voriconazole and terbinafine the patients died on day 17 after HT. Necropsy revealed disseminated infection with fungal invasion in central nervous system, heart, lung, cutaneous, and subcutaneous tissue. Broth microdilution tests demonstrated resistance to all antifungals. CONCLUSIONS: Lomentosporiosis is a rare complication that may emerge as a breakthrough invasive fungal infection in heart transplant recipients on ECMO despite antifungal prophylaxis.

Anti-Hu-mediated paraneoplastic chronic intestinal pseudo-obstruction associated with extraskeletal myxoid chondrosarcoma.

Chronic intestinal pseudo-obstruction (CIPO) is characterized by symptoms and signs of bowel obstruction in the absence of an anatomical cause. Almost 50 % of cases are secondary to systemic diseases of neurological, paraneoplastic, autoimmune, metabolic, or infectious origin.

Social work leadership in a medical school: A coordinated, compassionate COVID-19 response.

The COVID-19 pandemic has exposed the systemic inequities in our health care system and society has called for actions to meet the clinical, psychosocial and educational needs in health care settings and communities. In this paper we describe how an organized Department of Health Social Work in a medical school played a unique role in responding to the challenges of a pandemic with community, clinical, and educational initiatives that were integral to our community's health.

Responses to the Dix-Hallpike test in primary care: A comparison between subjective and objective benign paroxysmal positional vertigo.

Patients who experience both vertigo and nystagmus in the Dix-Hallpike test (DHT) are diagnosed with objective benign paroxysmal positional vertigo (BPPV). This test provokes only vertigo in between 11% and 48% of patients, who are diagnosed with subjective BPPV. Detection of nystagmus has important diagnostic and prognostic implications. To compare the characteristics of patients diagnosed with objective and subjective BPPV in primary care. Cross-sectional descriptive study. Two urban primary care centers. Adults (≥18 years) diagnosed with objective or subjective BPPV between November 2012 and January 2015. DHT results (vertigo or vertigo plus nystagmus; dependent variable: nistagmus as response to DHT), age, sex, time since onset, previous vertigo episodes, self-reported vertigo severity (Likert scale, 0-10), comorbidities (recent viral infection, traumatic brain injury, headache, anxiety/depression, hypertension, diabetes mellitus, dyslipidemia, cardiovascular disease, altered thyroid function, osteoporosis, cervical spondylosis, neck pain). In total, 134 patients (76.1% women) with a mean age of 52 years were included; 59.71% had subjective BPPV. Objective BPPV was significantly associated with hypertension, antihypertensive therapy, and cervical spondylosis in the bivariate analysis and with cervical spondylosis (OR=3.94, p=0.021) and antihypertensive therapy (OR 3.02, p=0.028) in the multivariate analysis. Patients with subjective BPPV were more likely to be taking benzodiazepines [OR 0.24, p=0.023]. The prevalence of subjective BPPV was higher than expected. Cervical spondylosis and hypertensive therapy were associated with objective BPPV, while benzodiazepines were associated with subjective BPPV.

A single Epley manoeuvre can improve self-perceptions of disability (quality of life) in patients with pc-BPPV: A randomised controlled trial in primary care.

Posterior canal benign paroxysmal positional vertigo (pc-BPPV) causes physical, functional, and emotional impairment. The treatment is the Epley manoeuvre (EM). OBJECTIVE: The purpose of the study was to compare the impact of the EM and a sham manoeuvre in primary care on self-perceived disability. DESIGN: Randomised, double-blind, sham-controlled clinical trial conducted in primary care with a follow-up of 1 year. PARTICIPANTS: Patients aged ≥18 years old diagnosed with pc-BPPV according to the Dix-Hallpike test (DHT) were randomised to: INTERVENTIONS: Intervention (EM) group or a control (sham manoeuvre) group. MAIN MEASUREMENTS: The main study covariates were age, sex, history of depression and anxiety, presence of nystagmus in the DHT, patient-perceived disability assessed with the Dizziness Handicap Inventory - screening version (DHI-S). Data were analyzed using bivariate and multivariate mixed Tobit analyses. RESULTS: Overall, 134 patients were studied: 66 in the intervention group and 68 in the control group. Median age was 52 years (interquartile range [IQR], 38.25-68.00 years. standard deviation, 16.98) and 76.12% of the patients were women. The DHT triggered nystagmus in 40.30% of patients. The median total DHI-S score for the overall sample at baseline was 16 (IQR, 8.00-22.00); 16 [IQR, 10.5-24.0] vs 10 [6.0-14.0] for women vs men (P<.001). Patients treated with the EM experienced a mean reduction of 2.03 points in DHI-S score over the follow-up period compared with patients in the sham group. CONCLUSIONS: Pc-BPPV affects the quality of life of primary care patients. A single EM can improve self-perceptions of disability by around 2 points on the DHI-S scale.

Substrate specificity of the pyrophosphohydrolase LpxH determines the asymmetry of Bordetella pertussis lipid A.

Lipopolysaccharides are anchored to the outer membrane of Gram-negative bacteria by a hydrophobic moiety known as lipid A, which potently activates the host innate immune response. Lipid A of Bordetella pertussis, the causative agent of whooping cough, displays unusual structural asymmetry with respect to the length of the acyl chains at the 3 and 3' positions, which are 3OH-C10 and 3OH-C14 chains, respectively. Both chains are attached by the acyltransferase LpxA, the first enzyme in the lipid A biosynthesis pathway, which, in B. pertussis, has limited chain length specificity. However, this only partially explains the strict asymmetry of lipid A. In attempts to modulate the endotoxicity of B. pertussis lipid A, here we expressed the gene encoding LpxA from Neisseria meningitidis, which specifically attaches 3OH-C12 chains, in B. pertussis This expression was lethal, suggesting that one of the downstream enzymes in the lipid A biosynthesis pathway in B. pertussis cannot handle precursors with a 3OH-C12 chain. We considered that the UDP-diacylglucosamine pyrophosphohydrolase LpxH could be responsible for this defect as well as for the asymmetry of B. pertussis lipid A. Expression of meningococcal LpxH in B. pertussis indeed resulted in new symmetric lipid A species with 3OH-C10 or 3OH-C14 chains at both the 3 and 3' positions, as revealed by MS analysis. Furthermore, co-expression of meningococcal lpxH and lpxA resulted in viable cells that incorporated 3OH-C12 chains in B. pertussis lipid A. We conclude that the asymmetry of B. pertussis lipid A is determined by the acyl chain length specificity of LpxH.

The inverse autotransporters of Yersinia ruckeri, YrInv and YrIlm, contribute to biofilm formation and virulence.

Yersinia ruckeri causes enteric redmouth disease (ERM) that mainly affects salmonid fishes and leads to significant economic losses in the aquaculture industry. An increasing number of outbreaks and the lack of effective vaccines against some serotypes necessitates novel measures to control ERM. Importantly, Y. ruckeri survives in the environment for long periods, presumably by forming biofilms. How the pathogen forms biofilms and which molecular factors are involved in this process, remains unclear. Yersinia ruckeri produces two surface-exposed adhesins, belonging to the inverse autotransporters (IATs), called Y. ruckeri invasin (YrInv) and Y. ruckeri invasin-like molecule (YrIlm). Here, we investigated whether YrInv and YrIlm play a role in biofilm formation and virulence. Functional assays revealed that YrInv and YrIlm promote biofilm formation on different abiotic substrates. Confocal microscopy revealed that they are involved in microcolony interaction and formation, respectively. The effect of both IATs on biofilm formation correlated with the presence of different biopolymers in the biofilm matrix, including extracellular DNA, RNA and proteins. Moreover, YrInv and YrIlm contributed to virulence in the Galleria mellonella infection model. Taken together, we propose that both IATs are possible targets for the development of novel diagnostic and preventative strategies to control ERM.

Genome-wide identification of genes directly regulated by ChvI and a consensus sequence for ChvI binding in Sinorhizobium meliloti.

ExoS/ChvI two-component signaling in the nitrogen-fixing α-proteobacterium Sinorhizobium meliloti is required for symbiosis and regulates exopolysaccharide production, motility, cell envelope integrity and nutrient utilization in free-living bacteria. However, identification of many ExoS/ChvI direct transcriptional target genes has remained elusive. Here, we performed chromatin immunoprecipitation followed by microarray analysis (chIP-chip) to globally identify DNA regions bound by ChvI protein in S. meliloti. We then performed qRT-PCR with chvI mutant strains to test ChvI-dependent expression of genes downstream of the ChvI-bound DNA regions. We identified 64 direct target genes of ChvI, including exoY, rem and chvI itself. We also identified ChvI direct target candidates, like exoR, that are likely controlled by additional regulators. Analysis of upstream sequences from the 64 ChvI direct target genes identified a 15 bp-long consensus sequence. Using electrophoretic mobility shift assays and transcriptional fusions with exoY, SMb21440, SMc00084, SMc01580, chvI, and ropB1, we demonstrated this consensus sequence is important for ChvI binding to DNA and transcription of ChvI direct target genes. Thus, we have comprehensively identified ChvI regulon genes and a 'ChvI box' bound by ChvI. Many ChvI direct target genes may influence the cell envelope, consistent with the critical role of ExoS/ChvI in growth and microbe-host interactions.