LoRaD: Marginal likelihood estimation with haste (but no waste).

The Lowest Radial Distance (LoRaD) method is a modification of the recently introduced Partition-Weighted Kernel method for estimating the marginal likelihood of a model, a quantity important for Bayesian model selection. For analyses involving a fixed tree topology, LoRaD improves upon the Steppingstone or Thermodynamic Integration (Path Sampling) approaches now in common use in phylogenetics because it requires sampling only from the posterior distribution, avoiding the need to sample from a series of ad hoc power posterior distributions, and yet is more accurate than other fast methods such as the Generalized Harmonic Mean (GHM) method. We show that the method performs well in comparison to the Generalized Steppingstone method on an empirical fixed-topology example from molecular phylogenetics involving 180 parameters. The LoRaD method can also be used to obtain the marginal likelihood in the variable-topology case if at least one tree topology occurs with sufficient frequency in the posterior sample to allow accurate estimation of the marginal likelihood conditional on that topology. [Bayesian; marginal likelihood; phylogenetics.].

An experimental test of Lanchester's models of combat in the neotropical termite Nasutitermes corniger (Blattodea: Termitidae).

Lanchester's models of combat have been invoked to explain the mechanics of group fighting in social animals. Specifically, Lanchester's square law posits that the fighting ability of the group is proportional to the square of the number of combatants. Although used to explain a variety of ecological phenomena, the models have not been thoroughly tested. We tested the Lanchester models using group battles between colonies of the termite Nasutitermes corniger. Our main goals were to determine if mortality rates fit the Lanchester models, and if so, whether the behavioural mechanisms underlying a group's success match those used in deriving the model. We initiated battles between pairs of colonies with different ratios of fighters and recorded deaths over time. We found that the numerically larger army has an advantage, but that the advantage is not as pronounced as predicted by Lanchester's square law. We also video-recorded battles to analyse individual behaviour, which did not support the mechanisms invoked by Lanchester. Instead, the killing power of an individual is increased by the presence of nest-mates, giving the larger group a disproportionate advantage. Although the behavioural mechanisms leading to the advantage may differ, our results still support some of the proposed ecological phenomena.

An Unusual Case of COVID-19 Presenting as Acute Psychosis.

PURPOSE: To report a case of COVID-19 presenting with acute psychosis, without the hallmark respiratory symptoms of fever, cough, and shortness of breath associated with the novel virus. CASE SUMMARY: A 58 year-old male presented with acute psychosis and no symptoms associated with COVID-19. He denied fever, chills, chest pain, shortness of breath, or gastrointestinal symptoms. The patient had a medical history of coronary artery disease, chronic hepatitis C, polysubstance abuse (including cocaine and alcohol), liver disease, anxiety, and panic disorder. Patient was confused, disruptive, unable to communicate, and admitted to hallucinations. Prior to transfer to a psychiatric facility, the patient developed a cough, triggering COVID-19 testing and a positive result. He was initially treated with hydroxychloroquine before this was discontinued. The patient was treated with haloperidol and lorazepam before returning to baseline. He was discharged home with continued isolation. CONCLUSION: Acute psychosis, with or without other symptoms, appears to be a potential presentation of COVID-19 and should be considered by clinicians as a possible presenting manifestation. Other coronaviruses appear to have also been linked to neurological manifestations, including psychosis. Neurological manifestations of the virus vary widely, but have been reported multiple times. Treatment, as shown in this case report, appears to be supportive and symptom based for the associated psychotic symptoms. Optimal antiviral treatment is still yet to be clearly defined, as research continues on how to best treat the virus itself.

Dysphagia after Stroke: An Unmet Antibiotic Stewardship Opportunity.

The goal of antibiotic stewardship is to improve antibiotic use, often by reducing unnecessary treatment. Bedside dysphagia screening tools help identify patients at high risk of aspiration following stroke. Presence of dysphagia does not indicate a need for antibiotic treatment. Therefore, this retrospective, cohort study was developed to evaluate the association of dysphagia and antibiotic prescribing following stroke. There were 117 patients included. Patients were placed into 2 cohorts based on the results of the dysphagia screening, with 55 patients positive for dysphagia and 62 patients negative for dysphagia. Patients with dysphagia tended to be older, had higher National Institutes of Health stroke scores, and lower renal function. Patients with dysphagia were prescribed more empiric antibiotics than those without dysphagia (18.2% vs. 3.2%, p = 0.01). This resulted in 53 antibiotic days of therapy in the dysphagia cohort compared to 19 antibiotic days of therapy in the no dysphagia cohort (p = 0.1). No patients later developed pneumonia and only one patient was started antibiotics after 48 h. Two cases of Clostridioides difficile were reported. Both patients were in the dysphagia cohort and received antibiotics. Multivariable logistic regression demonstrated that positive chest x-ray findings and failed dysphagia screen were independent conditions associated with initiating antibiotics. These findings indicate that antibiotic use was higher in patients following stroke with a positive dysphagia screen. Close monitoring of stroke patients, particularly when positive for dysphagia, might be an under-recognized antibiotic stewardship opportunity.

Risk Factor Evaluation for Methicillin-Resistant Staphylococcus aureus and Pseudomonas aeruginosa in Community-Acquired Pneumonia.

BACKGROUND: The 2019 community-acquired pneumonia guidelines recommend using recent respiratory cultures and locally validated epidemiology plus risk factor assessment to determine empirical coverage of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. OBJECTIVE: To develop a methodology for evaluating local epidemiology and validating local risk factors for P aeruginosa and MRSA. METHODS: This multicenter, retrospective cohort evaluated adult patients admitted for pneumonia. Risk factors for MRSA and P aeruginosa were evaluated using multivariable logistic regression and reported as adjusted odds ratios (aORs). RESULTS: There were 10 723 cases evaluated. Lung abscess/empyema had the highest odds associated with MRSA (aOR = 4.24; P < 0.0001), followed by influenza (aOR = 2.34; P = 0.01), end-stage renal disease (ESRD; aOR = 2.09; P = 0.006), illicit substance use (aOR = 1.7; P = 0.007), and chronic obstructive pulmonary disease (COPD; aOR = 1.26; P = 0.04). For P aeruginosa, the highest odds were in bronchiectasis (aOR = 6.13; P < 0.0001), lung abscess/empyema (aOR = 3.36; P = 0.005), and COPD (aOR = 1.84; P < 0.0001). Isolated COPD without other risk factors did not pose an increased risk of either organism. CONCLUSION AND RELEVANCE: Influenza, ESRD, lung abscess/empyema, and illicit substance use were local risk factors for MRSA. Bronchiectasis and lung abscess/empyema were risk factors for Pseudomonas. COPD was associated with MRSA and Pseudomonas. However, isolated COPD had similar rates of MRSA and Pseudomonas pneumonia compared with the total population. This study established a feasible methodology for evaluating local risk factors.

Utility of the respiratory viral panel as an antimicrobial stewardship tool.

WHAT IS KNOWN AND OBJECTIVE: The development of rapid diagnostics has revolutionized antimicrobial stewardship with efforts targeting earlier de-escalation or discontinuation of antibiotics. The respiratory viral panel (RVP) is one tool quickly able to detect common viral and bacterial pathogens using polymerase chain reaction technology. Utility may be further enhanced in conjunction with procalcitonin (PCT). However, the optimal use of the RVP to the clinical pharmacist in the treatment of community-acquired respiratory infections remains unclear. METHODS: The purpose of this guide is to review the available literature regarding the impact of the RVP with and without procalcitonin on antimicrobial stewardship efforts and to provide guidance on how to use each of these tools. RESULTS AND DISCUSSION: In total, 13 studies were included, 5 of which utilized PCT in conjunction with RVP and 8 of which did not use PCT. The majority of studies were retrospective in nature, and the most common outcomes evaluated were antibiotic days of therapy (DOT) and time to antibiotic discontinuation. WHAT IS NEW AND CONCLUSION: After review, RVP alone has limited value to antimicrobial stewardship; however, when used in conjunction with procalcitonin, RVP has the potential to reduce antibiotic use and duration.

Engaging student pharmacists to improve Hospital Consumer Assessment of Health Care Providers and Systems scores.

INTRODUCTION: Student pharmacists have historically served in shadowing roles for their experiential training at our institution. However, engaging students through active learning assignments has the potential to benefit both the student and the institution. The purpose of this project was to evaluate the impact of student pharmacists on Hospital Consumer Assessment of Health Care Providers and Systems (HCAHPS) scores, a direct reflection of patient satisfaction within the hospital. METHODS: In a four-month quality-improvement pilot project, student pharmacists were given active learning assignments directed at helping patients understand the purpose and side effects of their medications. Patients with hospital-initiated medications were provided with medication cards via student pharmacist-run counseling programs. The primary outcome was top response ("always") in medication-related HCAHPS scores. Secondary outcomes included scores on individual questions, number of medication education encounters, number of interventions, cost savings, and student feedback. RESULTS: There were 482 medication education encounters. The top response for all medication-related HCAHPS scores improved by 14% (49% to 63%). Top response regarding medication indication increased 23% (63% to 86%). There were 552 interventions accepted, projecting a savings of $135,658. The top score on student evaluations of the practice site increased 20% (69% to 89%). CONCLUSIONS: Student pharmacists can have a meaningful impact on medication-related HCAHPS scores. Additionally, student pharmacists benefit from active learning opportunities by providing and improving patient care leading to a more meaningful experience.

Non-occlusive ST-segment elevated myocardial infarction following the administration of liposomal amphotericin B in the treatment of cryptococcal meningitis.

WHAT IS KNOWN AND OBJECTIVE: Liposomal amphotericin B (L-AmB) is the cornerstone of many serious invasive fungal infections. Despite lower frequencies of commonly reported adverse events in clinical trials compared to conventional formulations, post-marketing complications continue to mount. CASE DESCRIPTION: We present a case of chest pain following the initial dose of L-AmB for cryptococcal meningitis. Electrocardiogram demonstrated no acute electrocardiogram findings. Upon rechallenge, the chest pain worsened was subsequently accompanied by ST-segment elevation. Emergent coronary angiography found no acute findings. WHAT IS NEW AND CONCLUSION: Providers should be aware of cardiac complications with L-AmB, including non-occlusive ST-segment elevation.

Peripheral neuropathy in non-Hodgkin's lymphoma patients receiving vincristine with and without aprepitant/fosaprepitant.

BACKGROUND: Peripheral neuropathy is a common treatment-related adverse effect associated with vincristine. Vincristine is a major CYP3A4 substrate and is often administered alongside the neurokinin-1 (NK-1) receptor antagonists, aprepitant or fosaprepitant, which are moderate CYP3A4 inhibitors. This inhibition may result in increased concentrations of vincristine and an increased incidence of toxicity. OBJECTIVE: The primary objective of this study was to investigate if there is a clinically significant drug interaction between vincristine and aprepitant or fosaprepitant resulting in early-onset peripheral neuropathy. The secondary objective of this study was to investigate the cumulative rate of chemotherapy-induced peripheral neuropathy (CIPN). METHODOLOGY: This was a single-centered, retrospective, cohort chart review. Patients receiving vincristine-based chemotherapy between 1 July 2010 through 30 June 2018 were identified and reviewed for concomitant use of aprepitant or fosaprepitant and incidence of neuropathy. Early-onset CIPN was defined as neuropathy onset during the first cycle of chemotherapy. RESULTS: A total of 115 subjects were retrospectively reviewed over the study period, of whom 71 were included in the aprepitant/fosaprepitant group and 44 were included in the group without a NK-1 receptor antagonist. Of the subjects who received aprepitant/fosaprepitant, 26.7% experienced early-onset peripheral neuropathy as compared to 22.7% in the group without a NK-1 receptor antagonist (P = 0.627). Overall, CIPN was higher in the group who received aprepitant/fosaprepitant compared to the group without (56% vs. 36%, P = 0.036). CONCLUSION: There appears to be an increased risk of CIPN with the concomitant use of vincristine and aprepitant or fosaprepitant.

False negative diagnostic errors with polymerase chain reaction for the detection of cryptococcal meningoencephalitis.

The accuracy of the BioFire FilmArray Meningitis/Encephalitis (ME) panel for the identification of Cryptococcus has recently been called into question. The primary objective of this study was to assess the agreement between the BioFire ME polymerase chain reaction (PCR) and other markers of cryptococcal infection. This retrospective review identified five patients with cryptococcal meningoencephalitis, 4 of whom had a negative ME panel for Cryptococcus. All five cases had positive serum cryptococcal antigens, and three of five had a positive cerebrospinal fluid (CSF) culture for Cryptococcus. The BioFire ME panel does not appear to be reliable for ruling out Cryptococcus meningoencephalitis; multiple testing methods are recommended.

Continuous Infusion Ampicillin for the Outpatient Management of Enterococcal Endocarditis: A Case Report and Literature Review.

Treatment of enterococcal endocarditis requires up to 6 weeks of intravenous (IV) antimicrobial therapy. When susceptible, an ampicillin-based regimen is preferred. Studies evaluating ampicillin stability utilizing high-pressure liquid chromatography have indicated enhanced stability (greater than 24 hours at room temperature), supporting outpatient administration. Thus, we report the successful treatment of a 30-year-old male with tricuspid valve enterococcal endocarditis in an outpatient setting using continuous infusion ampicillin via an ambulatory infusion pump. The patient received daily gentamicin at an outpatient infusion center with the ampicillin dose to be infused over the next 24 hours. Outpatient ambulatory infusion pumps allow for delivery of ampicillin via continuous infusion or pump-programmed pulse dosing. Preparation and administration in an outpatient infusion center may be a viable option to circumvent stability and delivery issues. Furthermore, 81% (34/42) of treatment days were completed outpatient, supporting that this approach may increase access to treatment and help reduce the economic burden to health care.

Partition Weighted Approach for Estimating the Marginal Posterior Density with Applications.

The computation of marginal posterior density in Bayesian analysis is essential in that it can provide complete information about parameters of interest. Furthermore, the marginal posterior density can be used for computing Bayes factors, posterior model probabilities, and diagnostic measures. The conditional marginal density estimator (CMDE) is theoretically the best for marginal density estimation but requires the closed-form expression of the conditional posterior density, which is often not available in many applications. We develop the partition weighted marginal density estimator (PWMDE) to realize the CMDE. This unbiased estimator requires only a single MCMC output from the joint posterior distribution and the known unnormalized posterior density. The theoretical properties and various applications of the We carry out simulation studies to investigate the empirical performance of the PWMDE and further demonstrate the desirable features of the proposed method with two real data sets from a study of dissociative identity disorder patients and a prostate cancer study, respectively.

Order, please! Uncertainty in the ordinal-level classification of Chlorophyceae.

BACKGROUND: Chlorophyceae is one of three most species-rich green algal classes and also the only class in core Chlorophyta whose monophyly remains uncontested as gene and taxon sampling improves. However, some key relationships within Chlorophyceae are less clear-cut and warrant further investigation. The present study combined genome-scale chloroplast data and rich sampling in an attempt to resolve the ordinal classification in Chlorophyceae. The traditional division into Sphaeropleales and Volvocales (SV), and a clade containing Oedogoniales, Chaetopeltidales, and Chaetophorales (OCC) was of particular interest with the addition of deeply branching members of these groups, as well as the placement of several incertae sedis taxa. METHODS: We sequenced 18 chloroplast genomes across Chlorophyceae to compile a data set of 58 protein-coding genes of a total of 68 chlorophycean taxa. We analyzed the concatenated nucleotide and amino acid datasets in the Bayesian and Maximum Likelihood frameworks, supplemented by analyses to examine potential discordant signal among genes. We also examined gene presence and absence data across Chlorophyceae. RESULTS: Concatenated analyses yielded at least two well-supported phylogenies: nucleotide data supported the traditional classification with the inclusion of the enigmatic Treubarinia into Sphaeropleales sensu lato. However, amino acid data yielded equally strong support for Sphaeropleaceae as sister to Volvocales, with the rest of the taxa traditionally classified in Sphaeropleales in a separate clade, and Treubarinia as sister to all of the above. Single-gene and other supplementary analyses indicated that the data have low phylogenetic signal at these critical nodes. Major clades were supported by genomic structural features such as gene losses and trans-spliced intron insertions in the plastome. DISCUSSION: While the sequence and gene order data support the deep split between the SV and OCC lineages, multiple phylogenetic hypotheses are possible for Sphaeropleales s.l. Given this uncertainty as well as the higher-taxonomic disorder seen in other algal groups, dwelling on well-defined, strongly supported Linnaean orders is not currently practical in Chlorophyceae and a less formal clade system may be more useful in the foreseeable future. For example, we identify two strongly and unequivocally supported clades: Treubarinia and Scenedesminia, as well as other smaller groups that could serve a practical purpose as named clades. This system does not preclude future establishment of new orders, or emendment of the current ordinal classification if new data support such conclusions.

BEAGLE 3: Improved Performance, Scaling, and Usability for a High-Performance Computing Library for Statistical Phylogenetics.

BEAGLE is a high-performance likelihood-calculation library for phylogenetic inference. The BEAGLE library defines a simple, but flexible, application programming interface (API), and includes a collection of efficient implementations for calculation under a variety of evolutionary models on different hardware devices. The library has been integrated into recent versions of popular phylogenetics software packages including BEAST and MrBayes and has been widely used across a diverse range of evolutionary studies. Here, we present BEAGLE 3 with new parallel implementations, increased performance for challenging data sets, improved scalability, and better usability. We have added new OpenCL and central processing unit-threaded implementations to the library, allowing the effective utilization of a wider range of modern hardware. Further, we have extended the API and library to support concurrent computation of independent partial likelihood arrays, for increased performance of nucleotide-model analyses with greater flexibility of data partitioning. For better scalability and usability, we have improved how phylogenetic software packages use BEAGLE in multi-GPU (graphics processing unit) and cluster environments, and introduced an automated method to select the fastest device given the data set, evolutionary model, and hardware. For application developers who wish to integrate the library, we also have developed an online tutorial. To evaluate the effect of the improvements, we ran a variety of benchmarks on state-of-the-art hardware. For a partitioned exemplar analysis, we observe run-time performance improvements as high as 5.9-fold over our previous GPU implementation. BEAGLE 3 is free, open-source software licensed under the Lesser GPL and available at https://beagle-dev.github.io.

Vancomycin plus nafcillin salvage for the treatment of persistent methicillin-resistant Staphylococcus aureus bacteremia following daptomycin failure: a case report and literature review.

BACKGROUND: Evidence supporting beta-lactam plus vancomycin synergy for methicillin-resistant Staphylococcus aureus (MRSA) continues to grow. Current in vivo evidence demonstrates that combination therapy is associated with shorter time to blood sterilization than vancomycin monotherapy. However, this combination has not been reported as salvage therapy for persistent MRSA bacteremia. CASE REPORT: We report a case of an 81-year-old male who was successfully treated with vancomycin plus nafcillin after failing vancomycin monotherapy, daptomycin monotherapy, and daptomycin plus gentamicin combination therapy. The patient originally presented with sepsis from a suspected urinary tract infection. Blood cultures drawn on days 1, 3, 5, 15, 19, 23, and 28 remained positive for MRSA despite multiple antimicrobial therapy changes. On day 29, therapy was changed to vancomycin plus nafcillin. Blood cultures drawn on day 32 remained negative. After 11 days, nafcillin was changed to piperacillin-tazobactam due to an infected decubitus ulcer. The combination was continued for 42 days after achieving blood sterility, 71 days after the patient originally presented. Evidence regarding salvage therapy for persistent bacteremia is sparse and is limited to case reports and case series. CONCLUSION: This case report supports that vancomycin plus an anti-staphylococcal beta-lactam combination should be further studied as salvage therapy for persistent MRSA bacteremia.

Assessing Combinability of Phylogenomic Data Using Bayes Factors.

With the rapid reduction in sequencing costs of high-throughput genomic data, it has become commonplace to use hundreds of genes to infer phylogeny of any study system. While sampling a large number of genes has given us a tremendous opportunity to uncover previously unknown relationships and improve phylogenetic resolution, it also presents us with new challenges when the phylogenetic signal is confused by differences in the evolutionary histories of sampled genes. Given the incorporation of accurate marginal likelihood estimation methods into popular Bayesian software programs, it is natural to consider using the Bayes Factor (BF) to compare different partition models in which genes within any given partition subset share both tree topology and edge lengths. We explore using marginal likelihood to assess data subset combinability when data subsets have varying levels of phylogenetic discordance due to deep coalescence events among genes (simulated within a species tree), and compare the results with our recently described phylogenetic informational dissonance index (D) estimated for each data set. BF effectively detects phylogenetic incongruence and provides a way to assess the statistical significance of D values. We use BFs to assess data combinability using an empirical data set comprising 56 plastid genes from the green algal order Volvocales. We also discuss the potential need for calibrating BFs and demonstrate that BFs used in this study are correctly calibrated.

Failure of ceftolozane-tazobactam salvage therapy in complicated pneumonia with lung abscess.

Treatment of Pseudomonas aeruginosa remains challenging, despite the availability ceftolozane-tazobactam. We report a treatment failure with ceftolozane-tazobactam salvage therapy for pneumonia complicated by lung abscess. Drug resistance, dose selection, and source control are possible contributing factors. Ceftolozane-tazobactam susceptibility testing should precede therapy and consideration should be given to dosing selection.

Treatment strategies for persistent methicillin-resistant Staphylococcus aureus bacteraemia.

WHAT IS KNOWN AND OBJECTIVE: Treatment of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia is a long-standing challenge to health care, often complicated by metastatic infections, treatment failure and mortality. When MRSA bacteraemia persists despite adequate initial treatment, current Infectious Diseases Society of America guidelines recommend evaluation and removal of possible sources of infection. In addition, a change in therapy may be considered. The objective of this review was to explore the therapeutic options for the treatment of persistent MRSA bacteraemia. METHODS: A literature search of PubMed, MEDLINE and Google Scholar was performed using the following search terms: [methicillin-resistant Staphylococcus aureus OR MRSA] AND [bacteraemia OR bloodstream infection] AND [persistent OR persistence OR refractory OR treatment failure OR salvage] AND treatment. We evaluated relevant, adult, English-language, peer-reviewed studies published between 1985 and May 2018. In vitro and animal studies were considered as supportive of in vivo data. RESULTS AND DISCUSSION: Randomized, controlled trials are lacking. However, case series and case reports support multiple treatment options including high-dose daptomycin in combination with an antistaphylococcal ß-lactam, ceftaroline, trimethoprim-sulfamethoxazole (TMP-SMX) or fosfomycin; ceftaroline alone or in combination with vancomycin or TMP-SMX; linezolid alone or in combination with a carbapenem, or telavancin. WHAT IS NEW AND CONCLUSION: Given the heterogeneity of the data, a preferred regimen has not emerged. Prescribers must take into consideration recent exposure, source control, and available synergy and clinical data. Further comparative trials are needed to establish a preferred regimen and the creation of a universal treatment algorithm.

A New Monte Carlo Method for Estimating Marginal Likelihoods.

Evaluating the marginal likelihood in Bayesian analysis is essential for model selection. Estimators based on a single Markov chain Monte Carlo sample from the posterior distribution include the harmonic mean estimator and the inflated density ratio estimator. We propose a new class of Monte Carlo estimators based on this single Markov chain Monte Carlo sample. This class can be thought of as a generalization of the harmonic mean and inflated density ratio estimators using a partition weighted kernel (likelihood times prior). We show that our estimator is consistent and has better theoretical properties than the harmonic mean and inflated density ratio estimators. In addition, we provide guidelines on choosing optimal weights. Simulation studies were conducted to examine the empirical performance of the proposed estimator. We further demonstrate the desirable features of the proposed estimator with two real data sets: one is from a prostate cancer study using an ordinal probit regression model with latent variables; the other is for the power prior construction from two Eastern Cooperative Oncology Group phase III clinical trials using the cure rate survival model with similar objectives.

Organellar phylogenomics inform systematics in the green algal family Hydrodictyaceae (Chlorophyceae) and provide clues to the complex evolutionary history of plastid genomes in the green algal tree of life.

PREMISE OF THE STUDY: Phylogenomic analyses across the green algae are resolving relationships at the class, order, and family levels and highlighting dynamic patterns of evolution in organellar genomes. Here we present a within-family phylogenomic study to resolve genera and species relationships in the family Hydrodictyaceae (Chlorophyceae), for which poor resolution in previous phylogenetic studies, along with divergent morphological traits, have precluded taxonomic revisions. METHODS: Complete plastome sequences and mitochondrial protein-coding gene sequences were acquired from representatives of the Hydrodictyaceae using next-generation sequencing methods. Plastomes were characterized, and gene order and content were compared with plastomes spanning the Sphaeropleales. Single-gene and concatenated-gene phylogenetic analyses of plastid and mitochondrial genes were performed. KEY RESULTS: The Hydrodictyaceae contain the largest sphaeroplealean plastomes thus far fully sequenced. Conservation of plastome gene order within Hydrodictyaceae is striking compared with more dynamic patterns revealed across Sphaeropleales. Phylogenetic analyses resolve Hydrodictyon sister to a monophyletic Pediastrum, though the morphologically distinct P. angulosum and P. duplex continue to be polyphyletic. Analyses of plastid data supported the neochloridacean genus Chlorotetraëdron as sister to Hydrodictyaceae, while conflicting signal was found in the mitochondrial data. CONCLUSIONS: A phylogenomic approach resolved within-family relationships not obtainable with previous phylogenetic analyses. Denser taxon sampling across Sphaeropleales is necessary to capture patterns in plastome evolution, and further taxa and studies are needed to fully resolve the sister lineage to Hydrodictyaceae and polyphyly of Pediastrum angulosum and P. duplex.