Phase Separation Modulates the Thermodynamics and Kinetics of RNA Hybridization.

Biomolecular condensates can influence cellular function in a number of ways, including by changing the structural dynamics and conformational equilibria of the molecules partitioned within them. Here we use methyl transverse relaxation optimized spectroscopy (methyl-TROSY) NMR in conjunction with 2'-O-methyl labeling of RNA to characterize the thermodynamics and kinetics of RNA-RNA base pairing in condensates formed by the C-terminal intrinsically disordered region of CAPRIN1, an RNA-binding protein involved in RNA transport, translation, and stability. CAPRIN1 condensates destabilize RNA-RNA base pairing, resulting from a ∼270-fold decrease and a concomitant ∼15-fold increase in the on- and off-rates for duplex formation, respectively. The ∼30-fold slower diffusion of RNA single strands within the condensed phase partially accounts for the reduced on-rate, but the further ∼9-fold reduction likely reflects shedding of CAPRIN1 chains that are interacting with the RNA prior to hybridization. Our study emphasizes the important role of protein solvation in modulating nucleic acid recognition processes inside condensates.

The UK VIRTUS helmet: User feedback from Operation TORAL in Afghanistan.

In 2015, the VIRTUS helmet was introduced to UK Armed Forces and will ultimately replace the Mark 7 combat helmet. The VIRTUS helmet has a reduced trimline compared to the Mark 7 helmet and can incorporate attachments such as a visor, mandible guard and nape protection. An anonymous questionnaire was provided to 200 UK Armed Forces personnel deployed to four locations on Operation TORAL in Afghanistan between September and October 2019. This is the first User feedback survey assessing the VIRTUS helmet in an operational environment. Users were measured to ascertain the fit of their helmet and asked to rate perceived helmet mass and comfort using a 5-point Likert scale. Users were also asked whether the VIRTUS helmet was better than previous helmets and about their use of the nape protection. The VIRTUS helmet was perceived to be an improvement over previously issued UK combat helmets in terms of both comfort and mass.

AlphaFold2 as a replacement for solution NMR structure determination of small proteins: Not so fast!

The determination of a protein's structure is often a first step towards the development of a mechanistic understanding of its function. Considerable advances in computational protein structure prediction have been made in recent years, with AlphaFold2 (AF2) emerging as the primary tool used by researchers for this purpose. While AF2 generally predicts accurate structures of folded proteins, we present here a case where AF2 incorrectly predicts the structure of a small, folded and compact protein with high confidence. This protein, pro-interleukin-18 (pro-IL-18), is the precursor of the cytokine IL-18. Interestingly, the structure of pro-IL-18 predicted by AF2 matches that of the mature cytokine, and not the corresponding experimentally determined structure of the pro-form of the protein. Thus, while computational structure prediction holds immense promise for addressing problems in protein biophysics, there is still a need for experimental structure determination, even in the context of small well-folded, globular proteins.

Measuring the Social Impact of Burn injuries in Australia: An Adaptation of the Life Impact Burn Recovery Evaluation - The Aus-LIBRE Profile.

Burn survivors can experience social participation challenges throughout their recovery. The aim of this study was to develop a novel Australian English translation of the Life Impact Burn Recovery Evaluation (LIBRE) Profile, the Aus-LIBRE Profile. This study consisted of three stages: 1) translation of the LIBRE Profile from American to Australian English by Australian researchers/burns clinicians; 2) piloting and cognitive evaluation of the Aus-LIBRE Profile with burn survivors to assess the clarity and consistency of the interpretation of each individual item, and 3) review of the Aus-LIBRE Profile by colleagues who identify as Aboriginal Australians for cross-cultural validation. In stage 2, investigators administered the translated questionnaire to 20 Australian patients with burn injuries in the outpatient clinic (10 patients from xx and 10 patients from yy). Face validity of the Aus-LIBRE Profile was tested in 20 burns survivors (11 females) ranging from 21 to 74 years (median age 43 years). The total body surface area (TBSA) burned ranged from 1% to 50% (median 10%). Twelve language changes were made based on the feedback from the burn clinicians/researchers, study participants and colleagues who identify as Aboriginal Australians. Using a formal translation process, the Aus-LIBRE Profile was adapted for use in the Australian burn population. The Aus-LIBRE Profile will require psychometric validation and testing in the Australian burn patient population before broader application of the scale.

Predictors of Multidimensional Profiles of Participation After Traumatic Brain Injury: A TBI Model Systems Study.

OBJECTIVES: To identify personal, clinical, and environmental factors associated with 4 previously identified distinct multidimensional participation profiles of individuals following traumatic brain injury (TBI). SETTING: Community. PARTICIPANTS: Participants (n = 408) enrolled in the TBI Model Systems (TBIMS) Participation Module, all 1 year or more postinjury. DESIGN: Secondary data analysis of cross-sectional data from participants in a multicenter TBIMS module study on participation conducted between May 2006 and September 2007. Participants provided responses to questionnaires via a telephone interview at their study follow-up (1, 2, 5, 10, or 15 years postinjury). MAIN MEASURES: Participants provided responses to personal (eg, demographic), clinical (eg, function), environmental (eg, neighborhood type), and participation measures to create multidimensional participation profiles. Data from measures collected at the time of injury (preinjury questionnaire, injury characteristics) were also included. The primary outcome was assignment to one of 4 multidimensional participation profile groups based on participation frequency, importance, satisfaction, and enfranchisement. The measures used to develop the profiles were: Participation Assessment with Recombined Tools-Objective, Importance, and Satisfaction scores, each across 3 domains (Productivity, Social Relationships, Out and About in the Community) and the Enfranchisement Scale (contributing to one's community, feeling valued by the community, choice and control). RESULTS: Results of the multinomial regression analysis, with 4 distinct participation profile groups as the outcome, indicated that education, current employment, current illicit drug use, current driving status, community type, and Functional Independence Measure Cognitive at follow-up significantly distinguished participation profile groups. Findings suggest a trend toward differences in participation profile groups by race/Hispanic ethnicity. CONCLUSIONS: Understanding personal, clinical, and environmental factors associated with distinct participation outcome profiles following TBI may provide more personalized and nuanced guidance to inform rehabilitation intervention planning and/or ongoing clinical monitoring.

Structural transitions enable interleukin-18 maturation and signaling.

Several interleukin-1 (IL-1) family members, including IL-1ß and IL-18, require processing by inflammasome-associated caspases to unleash their activities. Here, we unveil, by cryoelectron microscopy (cryo-EM), two major conformations of the complex between caspase-1 and pro-IL-18. One conformation is similar to the complex of caspase-4 and pro-IL-18, with interactions at both the active site and an exosite (closed conformation), and the other only contains interactions at the active site (open conformation). Thus, pro-IL-18 recruitment and processing by caspase-1 is less dependent on the exosite than the active site, unlike caspase-4. Structure determination by nuclear magnetic resonance uncovers a compact fold of apo pro-IL-18, which is similar to caspase-1-bound pro-IL-18 but distinct from cleaved IL-18. Binding sites for IL-18 receptor and IL-18 binding protein are only formed upon conformational changes after pro-IL-18 cleavage. These studies show how pro-IL-18 is selected as a caspase-1 substrate, and why cleavage is necessary for its inflammatory activity.

Scanning the aged to minimize missed injury: An EAST multicenter study.

BACKGROUND: Despite the high incidence of blunt trauma in older adults, there is a lack of evidence-based guidance for computed tomography (CT) imaging in this population. We aimed to identify an algorithm to guide use of a Pan-Scan (Head/C-spine/Torso) or a Selective Scan (Head/C-spine ± Torso). We hypothesized that a patient's initial history and exam could be used to guide imaging. METHODS: We prospectively studied blunt trauma patients aged 65+ at 18 Level I/II trauma centers. Patients presenting >24 h after injury or who died upon arrival were excluded. We collected history and physical elements and final injury diagnoses. Injury diagnoses were categorized into CT body regions of Head/C-spine or Torso (chest, abdomen/pelvis, and T/L spine). Using machine learning and regression modeling as well as a priori clinical algorithms based, we tested various decision rules against our dataset. Our priority was to identify a simple rule which could be applied at the bedside, maximizing sensitivity (Sens) and negative predictive value (NPV) to minimize missed injuries. RESULTS: We enrolled 5,498 patients with 3,082 injuries. Nearly half (47.1%, n = 2,587) had an injury within the defined CT body regions. No rule to guide a Pan-Scan could be identified with suitable Sens/NPV for clinical use. A clinical algorithm to identify patients for Pan-Scan, using a combination of physical exam findings and specific high-risk criteria, was identified and had a Sens of 0.94 and NPV of 0.86 This rule would have identified injuries in all but 90 patients (1.6%) and would theoretically spare 11.9% (655) of blunt trauma patients a torso CT. CONCLUSIONS: Our findings advocate for Head/Cspine CT in all geriatric patients with the addition of torso CT in the setting of positive clinical findings and high-risk criteria. Prospective validation of this rule could lead to streamlined diagnostic care of this growing trauma population. LEVEL OF EVIDENCE: Level 2, Diagnostic Tests or Criteria.

Moderation Effects of Daily Behavior on Associations Between Symptoms and Social Participation Outcomes After Burn Injury: A 6-Month Digital Phenotyping Study.

OBJECTIVE: To examine the moderation effects of daily behavior on the associations between symptoms and social participation outcomes after burn injury. DESIGN: A 6-month prospective cohort study. SETTING: Community. PARTICIPANTS: Twenty-four adult burn survivors. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Symptoms and social participation outcomes were assessed weekly using smartphone surveys, including symptoms of pain (Patient-Reported Outcomes Measurement Information System [PROMIS] Pain Intensity and Pain Interference), anxiety (PROMIS Anxiety), and depression (Patient Health Questionnaire), as well as outcomes of social interactions and social activities (Life Impact Burn Recovery Evaluation [LIBRE] Social Interactions and Social Activities). Daily behaviors were automatically recorded by a smartphone application and smartphone logs, including physical activity (steps, travel miles, and activity minutes), sleep (sleep hours), and social contact (number of phone calls and message contacts). RESULTS: Multilevel models controlling for demographic and burn injury variables examined the associations between symptoms and social participation outcomes and the moderation effects of daily behaviors. Lower (worse) LIBRE Social Interactions and LIBRE Social Activities scores were significantly associated with higher (worse) PROMIS Pain Intensity, PROMIS Pain Interference, PROMIS Anxiety, and Patient Health Questionnaire-8 scores (P<.05). Additionally, daily steps and activity minutes were associated with LIBRE Social Interactions and LIBRE Social Activities (P<.05), and significantly moderated the association between PROMIS Anxiety and LIBRE Social Activities (P<.001). CONCLUSIONS: Social participation outcomes are associated with pain, anxiety, and depression symptoms after burn injury, and are buffered by daily physical activity. Future intervention studies should examine physical activity promotion to improve social recovery after burns.

Beyond surviving: A scoping review of collaborative care models to inform the future of post-discharge trauma care.

ABSTRACT: Trauma centers demonstrate an impressive ability to save lives, as reflected by inpatient survival rates of over 95% in the United States. Nevertheless, we fail to allocate sufficient effort and resources to ensure that survivors and their families receive the necessary care and support after leaving the trauma center. The objective of this scoping review is to systematically map the research on collaborative care models (CCM) that have been put forward to improve trauma survivorship. Of 833 articles screened, we included 16 studies evaluating eight collaborative care programs, predominantly in the U.S. The majority of the programs offered care coordination and averaged 9-months in duration. Three-fourths of the programs incorporated a mental health provider within their primary team. Observed outcomes were diverse: some models showed increased engagement (e.g., Center for Trauma Survivorship, trauma quality-of-life follow-up clinic), while others presented mixed mental health outcomes and varied results on pain and healthcare utilization. The findings of this study indicate that collaborative interventions may be effective in mental health screening, PTSD and depression management, effective referrals, and improving patient satisfaction with care. A consensus on core elements and cost-effectiveness of CCMs is necessary to set the standard for comprehensive care in post-trauma recovery.

Polyethylene terephthalate (PET) micro- and nanoplastic particles affect the mitochondrial efficiency of human brain vascular pericytes without inducing oxidative stress.

The objective of this investigation was to evaluate the influence of micro- and nanoplastic particles composed of polyethylene terephthalate (PET), a significant contributor to plastic pollution, on human brain vascular pericytes. Specifically, we delved into their impact on mitochondrial functionality, oxidative stress, and the expression of genes associated with oxidative stress, ferroptosis and mitochondrial functions. Our findings demonstrate that the exposure of a monoculture of human brain vascular pericytes to PET particles in vitro at a concentration of 50 µg/ml for a duration of 3, 6 and 10 days did not elicit oxidative stress. Notably, we observed a reduction in various aspects of mitochondrial respiration, including maximal respiration, spare respiratory capacity, and ATP production in pericytes subjected to PET particles for 3 days, with a mitochondrial function recovery at 6 and 10 days. Furthermore, there were no statistically significant alterations in mitochondrial DNA copy number, or in the expression of genes linked to oxidative stress and ferroptosis, but an increase of the expression of the gene mitochondrial transcription factor A (TFAM) was noted at 3 days exposure. These outcomes suggest that, at a concentration of 50 µg/ml, PET particles do not induce oxidative stress in human brain vascular pericytes. Instead, at 3 days exposure, PET exposure impairs mitochondrial functions, but this is recovered at 6-day exposure. This seems to indicate a potential mitochondrial hormesis response (mitohormesis) is incited, involving the gene TFAM. Further investigations are warranted to explore the stages of mitohormesis and the potential consequences of plastics on the integrity of the blood-brain barrier and intercellular interactions. This research contributes to our comprehension of the potential repercussions of nanoplastic pollution on human health and underscores the imperative need for ongoing examinations into the exposure to plastic particles.

Propensity weighted analysis of chemical venous thromboembolism prophylaxis agents in isolated severe traumatic brain injury: An EAST sponsored multicenter study.

BACKGROUND: In patients with severe traumatic brain injury (TBI), clinicians must balance preventing venous thromboembolism (VTE) with the risk of intracranial hemorrhagic expansion (ICHE). We hypothesized that low molecular weight heparin (LMWH) would not increase risk of ICHE or VTE as compared to unfractionated heparin (UH) in patients with severe TBI. METHODS: Patients ≥ 18 years of age with isolated severe TBI (AIS ≥ 3), admitted to 24 level I and II trauma centers between January 1, 2014 to December 31, 2020 and who received subcutaneous UH and LMWH injections for chemical venous thromboembolism prophylaxis (VTEP) were included. Primary outcomes were VTE and ICHE after VTEP initiation. Secondary outcomes were mortality and neurosurgical interventions. Entropy balancing (EBAL) weighted competing risk or logistic regression models were estimated for all outcomes with chemical VTEP agent as the predictor of interest. RESULTS: 984 patients received chemical VTEP, 482 UH and 502 LMWH. Patients on LMWH more often had pre-existing conditions such as liver disease (UH vs LMWH 1.7 % vs. 4.4 %, p = 0.01), and coagulopathy (UH vs LMWH 0.4 % vs. 4.2 %, p < 0.001). There were no differences in VTE or ICHE after VTEP initiation. There were no differences in neurosurgical interventions performed. There were a total of 29 VTE events (3 %) in the cohort who received VTEP. A Cox proportional hazards model with a random effect for facility demonstrated no statistically significant differences in time to VTE across the two agents (p = 0.44). The LMWH group had a 43 % lower risk of overall ICHE compared to the UH group (HR = 0.57: 95 % CI = 0.32-1.03, p = 0.062), however was not statistically significant. CONCLUSION: In this multi-center analysis, patients who received LMWH had a decreased risk of ICHE, with no differences in VTE, ICHE after VTEP initiation and neurosurgical interventions compared to those who received UH. There were no safety concerns when using LMWH compared to UH. LEVEL OF EVIDENCE: Level III, Therapeutic Care Management.

4-factor prothrombin complex concentrate is not inferior to andexanet alfa for the reversal or oral factor Xa inhibitors: An Eastern Association for the Surgery of Trauma multicenter study.

BACKGROUND: Andexanet Alfa (AA) is the only FDA approved reversal agent for apixaban and rivaroxaban (DOAC). There are no studies comparing its efficacy with 4-Factor Prothrombin Complex Concentrate (PCC). This study aimed to compare PCC to AA for DOAC reversal, hypothesizing non-inferiority of PCC. METHODS: We performed a retrospective, non-inferiority multicenter study of adult patients admitted from July 1, 2018 to December 31, 2019 who had taken a DOAC within 12 hours of injury, were transfused red blood cells (RBCs) or had traumatic brain injury, and received AA or PCC. Primary outcome was PRBC unit transfusion. Secondary outcome with ICU length of stay. MICE imputation was used to account for missing data and zero-inflated poisson regression was used to account for an excess of zero units of RBC transfused. 2 Units difference in RBC transfusion was selected as non-inferior. RESULTS: Results: From 263 patients at 10 centers, 77 (29%) received PCC and 186 (71%) AA. Patients had similar transfusion rates across reversal treatment groups (23.7% AA vs 19.5% PCC) with median transfusion in both groups of 0 RBC. According to the Poisson component, PCC increases the amount of RBC transfusion by 1.02 times (95% CI: 0.79-1.33) compared to AA after adjusting for other covariates. The averaged amount of RBC transfusion (non-zero group) is 6.13. Multiplying this number by the estimated rate ratio, PCC is estimated to have an increase RBC transfusion by 0.123 (95% CI: 0.53-2.02) units compared to AA. CONCLUSION: PCC appears non-inferior to AA for reversal of DOACs for RBC transfusion in traumatically injured patients. Additional prospective, randomized trials are necessary to compare PCC and AA for the treatment of hemorrhage in injured patients on DOACs. LEVEL OF EVIDENCE: Therapeutic/Care Management, Level III.

Quantifying redox transcription factor dynamics as a tool to investigate redox signalling.

A critical feature of the cellular antioxidant response is the induction of gene expression by redox-sensitive transcription factors. In many cells, activating these transcription factors is a dynamic process involving multiple redox steps, but it is unclear how these dynamics should be measured. Here, we show how the dynamic profile of the Schizosaccharomyces pombe Pap1 transcription factor is quantifiable by three parameters: signal amplitude, signal time and signal duration. In response to increasing hydrogen peroxide concentrations, the Pap1 amplitude decreased while the signal time and duration showed saturable increases. In co-response plots, these parameters showed a complex, non-linear relationship to the mRNA levels of four Pap1-regulated genes. We also demonstrate that hydrogen peroxide and tert-butyl hydroperoxide trigger quantifiably distinct Pap1 activation profiles and transcriptional responses. Based on these findings, we propose that different oxidants and oxidant concentrations modulate the Pap1 dynamic profile, leading to specific transcriptional responses. We further show how the effect of combination and pre-exposure stresses on Pap1 activation dynamics can be quantified using this approach. This method is therefore a valuable addition to the redox signalling toolbox that may illuminate the role of dynamics in determining appropriate responses to oxidative stress.

A delayed decoupling methyl-TROSY pulse sequence for atomic resolution studies of folded proteins and RNAs in condensates.

Solution NMR spectroscopy has tremendous potential for providing atomic resolution insights into the interactions between proteins and nucleic acids partitioned into condensed phases of phase-separated systems. However, the highly viscous nature of the condensed phase challenges applications, and in particular, the extraction of quantitative, site-specific information. Here, we present a delayed decoupling-based HMQC pulse sequence for methyl-TROSY studies of 'client' proteins and nucleic acids partitioned into 'scaffold' proteinaceous phase-separated solvents. High sensitivity and excellent quality spectra are recorded of a nascent form of superoxide dismutase and of a small RNA fragment partitioned into CAPRIN1 condensates.

Exploring Host-Guest Interactions within a 600 kDa DegP Protease Cage Complex Using Hydrodynamics Measurements and Methyl-TROSY NMR.

The DegP protease-chaperone operates within the periplasm of Gram-negative bacteria, where it assists in the regulation of protein homeostasis, promotes virulence, and is essential to survival under stress. To carry out these tasks, DegP forms a network of preorganized apo oligomers that facilitate the capture of substrates within distributions of cage-like complexes which expand to encapsulate clients of various sizes. Although the architectures of DegP cage complexes are well understood, little is known about the structures, dynamics, and interactions of client proteins within DegP cages and the relationship between client structural dynamics and function. Here, we probe host-guest interactions within a 600 kDa DegP cage complex throughout the DegP activation cycle using a model α-helical client protein through a combination of hydrodynamics measurements, methyl-transverse relaxation optimized spectroscopy-based solution nuclear magnetic resonance studies, and proteolytic activity assays. We find that in the presence of the client, DegP cages assemble cooperatively with few intermediates. Our data further show that the N-terminal half of the bound client, which projects into the interior of the cages, is predominantly unfolded and flexible, and exchanges between multiple conformational states over a wide range of time scales. Finally, we show that a concerted structural transition of the protease domains of DegP occurs upon client engagement, leading to activation. Together, our findings support a model of DegP as a highly cooperative and dynamic molecular machine that stabilizes unfolded states of clients, primarily via interactions with their C-termini, giving rise to efficient cleavage.

Optimization of TROSY- and anti-TROSY-based 15N CPMG relaxation dispersion experiments through phase cycling.

CPMG relaxation dispersion studies of biomolecular dynamics on the µs-ms timescale can provide detailed kinetic, thermodynamic, and structural insights into function. Frequently, the 15N spin serves as the probe of choice, as uniform incorporation of the 15N isotope is facile and cost-effective, and the interpretation of the resulting data is often relatively straightforward. In conventional CPMG relaxation dispersion experiments the application of CPMG pulses with constant radiofrequency (RF) phase can lead to artifactual dispersion profiles that result from off-resonance effects, RF field inhomogeneity, and pulse miscalibration. The development of CPMG experiments with the [0013]-phase cycle has significantly reduced the impact of pulse imperfections over a greater bandwidth of frequency offsets in comparison to constant phase experiments. Application of 15N-TROSY-based CPMG schemes to studies of the dynamics of large molecules is necessary for high sensitivity, yet the correct incorporation of the [0013]-phase cycle is non-trivial. Here we present TROSY- and anti-TROSY-based 15N CPMG experiments with the [0013]-phase cycling scheme and demonstrate, through comprehensive numerical simulations and experimental validation, enhanced resistance to pulse imperfections relative to traditional schemes utilizing constant phase CPMG pulses. Notably, exchange parameters derived from the new experiments are in good agreement with those obtained using other, more established, 15N-based CPMG approaches.

Design of amyloidogenic peptide traps.

Segments of proteins with high ß-strand propensity can self-associate to form amyloid fibrils implicated in many diseases. We describe a general approach to bind such segments in ß-strand and ß-hairpin conformations using de novo designed scaffolds that contain deep peptide-binding clefts. The designs bind their cognate peptides in vitro with nanomolar affinities. The crystal structure of a designed protein-peptide complex is close to the design model, and NMR characterization reveals how the peptide-binding cleft is protected in the apo state. We use the approach to design binders to the amyloid-forming proteins transthyretin, tau, serum amyloid A1 and amyloid ß1-42 (Aß42). The Aß binders block the assembly of Aß fibrils as effectively as the most potent of the clinically tested antibodies to date and protect cells from toxic Aß42 species.

Cryo-EM of the Nucleosome Core Particle Bound to Ran-RCC1 Reveals a Dynamic Complex.

Ras-related nuclear protein (Ran) is a member of the Ras superfamily of small guanosine triphosphatases (GTPases) and a regulator of multiple cellular processes. In healthy cells, the GTP-bound form of Ran is concentrated at chromatin, creating a Ran•GTP gradient that provides the driving force for nucleocytoplasmic transport, mitotic spindle assembly, and nuclear envelope formation. The Ran•GTP gradient is maintained by the regulator of chromatin condensation 1 (RCC1), a guanine nucleotide exchange factor that accelerates GDP/GTP exchange in Ran. RCC1 interacts with nucleosomes, which are the fundamental repeating units of eukaryotic chromatin. Here, we present a cryo-EM analysis of a trimeric complex composed of the nucleosome core particle (NCP), RCC1, and Ran. While the contacts between RCC1 and Ran in the complex are preserved compared with a previously determined structure of RCC1-Ran, our study reveals that RCC1 and Ran interact dynamically with the NCP and undergo rocking motions on the nucleosome surface. Furthermore, the switch 1 region of Ran, which plays an important role in mediating conformational changes associated with the substitution of GDP and GTP nucleotides in Ras family members, appears to undergo disorder-order transitions and forms transient contacts with the C-terminal helix of histone H2B. Nucleotide exchange assays performed in the presence and absence of NCPs are not consistent with an active role for nucleosomes in nucleotide exchange, at least in vitro. Instead, the nucleosome stabilizes RCC1 and serves as a hub that concentrates RCC1 and Ran to promote efficient Ran•GDP to Ran•GTP conversion.

Complete nucleotide sequence and comparative genomic analysis of microcin B17 plasmid pMccB17.

We present a comprehensive sequence and bioinformatic analysis of the prototypical microcin plasmid, pMccb17, which includes a definitive sequence for the microcin operon, mcb. Microcin B17 (MccB17) is a ribosomally synthesized and posttranslationally modified peptide produced by Escherichia coli. It inhibits bacterial DNA gyrase similarly to quinolone antibiotics. The mcb operon, which consists of seven genes encoding biosynthetic and immunity/export functions, was originally located on the low copy number IncFII plasmid pMccB17 in the Escherichia coli strain LP17. It was later transferred to E. coli K-12 through conjugation. In this study, the plasmid was extracted from the E. coli K-12 strain RYC1000 [pMccB17] and sequenced twice using an Illumina short-read method. The first sequencing was conducted with the host bacterial chromosome, and the plasmid DNA was then purified and sequenced separately. After assembly into a single contig, polymerase chain reaction primers were designed to close the single remaining gap via Sanger sequencing. The resulting complete circular DNA sequence is 69,190 bp long and includes 81 predicted genes. These genes were initially identified by Prokka and subsequently manually reannotated using BLAST. The plasmid was assigned to the F2:A-:B- replicon type with a MOBF12 group conjugation system. A comparison with other IncFII plasmids revealed a large proportion of shared genes, particularly in the conjugative plasmid backbone. However, unlike many contemporary IncFII plasmids, pMccB17 lacks transposable elements and antibiotic resistance genes. In addition to the mcb operon, this plasmid carries 25 genes of unknown function.

Failure rates of nonoperative management of low-grade splenic injuries with active extravasation: an Eastern Association for the Surgery of Trauma multicenter study.

Objectives: There is little evidence guiding the management of grade I-II traumatic splenic injuries with contrast blush (CB). We aimed to analyze the failure rate of nonoperative management (NOM) of grade I-II splenic injuries with CB in hemodynamically stable patients. Methods: A multicenter, retrospective cohort study examining all grade I-II splenic injuries with CB was performed at 21 institutions from January 1, 2014, to October 31, 2019. Patients >18 years old with grade I or II splenic injury due to blunt trauma with CB on CT were included. The primary outcome was the failure of NOM requiring angioembolization/operation. We determined the failure rate of NOM for grade I versus grade II splenic injuries. We then performed bivariate comparisons of patients who failed NOM with those who did not. Results: A total of 145 patients were included. Median Injury Severity Score was 17. The combined rate of failure for grade I-II injuries was 20.0%. There was no statistical difference in failure of NOM between grade I and II injuries with CB (18.2% vs 21.1%, p>0.05). Patients who failed NOM had an increased median hospital length of stay (p=0.024) and increased need for blood transfusion (p=0.004) and massive transfusion (p=0.030). Five patients (3.4%) died and 96 (66.2%) were discharged home, with no differences between those who failed and those who did not fail NOM (both p>0.05). Conclusion: NOM of grade I-II splenic injuries with CB fails in 20% of patients. Level of evidence: IV.