ABSTRACT
Viruses are obligate intracellular parasites that rely on host cell metabolism for successful replication. Thus, viruses rewire host cell pathways involved in central carbon metabolism to increase the availability of building blocks for successful propagation. However, the underlying mechanisms of virus-induced alterations to host metabolism are largely unknown. Noroviruses (NoVs) are highly prevalent pathogens that cause sporadic and epidemic viral gastroenteritis. In the present study, we uncovered several strain-specific and shared host cell metabolic requirements of three murine norovirus (MNV) strains, MNV-1, CR3, and CR6. While all three strains required glycolysis, glutaminolysis, and the pentose phosphate pathway for optimal infection of macrophages, only MNV-1 relied on host oxidative phosphorylation. Furthermore, the first metabolic flux analysis of NoV-infected cells revealed that both glycolysis and glutaminolysis are upregulated during MNV-1 infection of macrophages. Glutamine deprivation affected the viral lifecycle at the stage of genome replication, resulting in decreased non-structural and structural protein synthesis, viral assembly, and egress. Mechanistic studies further showed that MNV infection and overexpression of the non-structural protein NS1/2 increased the enzymatic activity of the rate-limiting enzyme glutaminase. In conclusion, the inaugural investigation of NoV-induced alterations to host glutaminolysis identified NS1/2 as the first viral molecule for RNA viruses that regulates glutaminolysis either directly or indirectly. This increases our fundamental understanding of virus-induced metabolic alterations and may lead to improvements in the cultivation of human NoVs.
Subject(s)
Caliciviridae Infections , Glutamine , Norovirus , Viral Nonstructural Proteins , Virus Replication , Norovirus/physiology , Virus Replication/physiology , Mice , Animals , Viral Nonstructural Proteins/metabolism , Viral Nonstructural Proteins/genetics , Glutamine/metabolism , Caliciviridae Infections/virology , Caliciviridae Infections/metabolism , Macrophages/virology , Macrophages/metabolism , Humans , Glutaminase/metabolism , Glycolysis/physiology , RAW 264.7 CellsABSTRACT
Akt (protein kinase B) is a key signaling protein in eukaryotic cells that controls many cellular processes, such as glucose metabolism and cell proliferation, for survival. As obligate intracellular pathogens, viruses modulate host cellular processes, including Akt signaling, for optimal replication. The mechanisms by which viruses modulate Akt and the resulting effects on the infectious cycle differ widely depending on the virus. In this study, we explored the effect of Akt serine 473 phosphorylation (p-Akt) during murine norovirus (MNV) infection. p-Akt increased during infection of murine macrophages with acute MNV-1 and persistent CR3 and CR6 strains. Inhibition of Akt with MK2206, an inhibitor of all three isoforms of Akt (Akt1/2/3), reduced infectious virus progeny of all three virus strains. This reduction was due to decreased viral genome replication (CR3), defective virus assembly (MNV-1), or altered cellular egress (CR3 and CR6) in a virus strain-dependent manner. Collectively, our data demonstrate that Akt activation increases in macrophages during the later stages of the MNV infectious cycle, which may enhance viral infection in unique ways for different virus strains. The data, for the first time, indicate a role for Akt signaling in viral assembly and highlight additional phenotypic differences between closely related MNV strains. IMPORTANCE Human noroviruses (HNoV) are a leading cause of viral gastroenteritis, resulting in high annual economic burden and morbidity, yet there are no small-animal models supporting productive HNoV infection or robust culture systems producing cell culture-derived virus stocks. As a result, research on drug discovery and vaccine development against norovirus infection has been challenging, and no targeted antivirals or vaccines against HNoV are approved. On the other hand, murine norovirus (MNV) replicates to high titers in cell culture and is a convenient and widespread model in norovirus research. Our data demonstrate the importance of Akt signaling during the late stage of the MNV life cycle. Notably, the effect of Akt signaling on genome replication, virus assembly, and cellular egress is virus strain specific, highlighting the diversity of biological phenotypes despite small genetic variability among norovirus strains. This study is the first to demonstrate a role for Akt in viral assembly.
Subject(s)
Caliciviridae Infections/metabolism , Caliciviridae Infections/virology , Macrophages/metabolism , Macrophages/virology , Norovirus/physiology , Proto-Oncogene Proteins c-akt/metabolism , Virus Replication , Animals , Caliciviridae Infections/immunology , Disease Susceptibility , Host-Pathogen Interactions , Macrophage Activation , Macrophages/immunology , Mice , Phosphorylation , Proto-Oncogene Proteins c-akt/antagonists & inhibitors , Species SpecificityABSTRACT
In Nature, Gerlach et al. (Nature 2018;563:705-709) report that methicillin-resistant Staphylococcus aureus camouflages its surface by displaying a 'stealth' wall teichoic acid (WTA) isomer. WTA can act as a cloak to limit exposure of surface antigens to the immune system, but this report indicates that even the cloak can become immunologically silent.
Subject(s)
Methicillin-Resistant Staphylococcus aureus , Cell Wall , Glycosylation , Methicillin , Teichoic AcidsABSTRACT
Health systems were abruptly plunged into a crisis as SARS-CoV-2 exploded into a pandemic in spring 2020. In March-April 2020, Metropolitan Detroit was a US "hotspot." As a large health system with five hospitals and two behavioural health inpatient facilities, a health insurance company, a medical group and physician network, and 41 ambulatory clinics normally hosting over 10,000 daily patient encounters, the Henry Ford Health System deployed numerous strategies in the management of this upheaval. As hospitals and Emergency Departments were inundated with COVID-19 patients, other services and activities needed to shut down as state-mandated policies were promulgated, new internal and external communication networks established, and management of employees and resources such as ventilators, ICU beds, personal protective equipment, and laboratory supplies became critical challenges. We describe herein the system-wide strategies implemented and lessons learned in the operation of a health system in the initial throes of a global pandemic.
Subject(s)
COVID-19 , Humans , Pandemics , Personal Protective Equipment , SARS-CoV-2 , Ventilators, MechanicalABSTRACT
A long-standing paradigm in virology was that non-enveloped viruses induce cell lysis to release progeny virions. However, emerging evidence indicates that some non-enveloped viruses exit cells without inducing cell lysis, while others engage both lytic and non-lytic egress mechanisms. Enteric viruses are transmitted via the faecal-oral route and are important causes of a wide range of human infections, both gastrointestinal and extra-intestinal. Virus cellular egress, when fully understood, may be a relevant target for antiviral therapies, which could minimize the public health impact of these infections. In this review, we outline lytic and non-lytic cell egress mechanisms of non-enveloped enteric RNA viruses belonging to five families: Picornaviridae, Reoviridae, Caliciviridae, Astroviridae and Hepeviridae. We discuss factors that contribute to egress mechanisms and the relevance of these mechanisms to virion stability, infectivity and transmission. Since most data were obtained in traditional two-dimensional cell cultures, we will further attempt to place them into the context of polarized cultures and in vivo pathogenesis. Throughout the review, we highlight numerous knowledge gaps to stimulate future research into the egress mechanisms of these highly prevalent but largely understudied viruses.
Subject(s)
RNA Virus Infections/virology , RNA Viruses/classification , Virion/physiology , Virus Release , Animals , Humans , RNA Viruses/physiologyABSTRACT
Human astroviruses (HAstV) are understudied positive-strand RNA viruses that cause gastroenteritis mostly in children and the elderly. Three clades of astroviruses, classic, MLB-type and VA-type have been reported in humans. One limitation towards a better understanding of these viruses has been the lack of a physiologically relevant cell culture model that supports growth of all clades of HAstV. Herein, we demonstrate infection of HAstV strains belonging to all three clades in epithelium-only human intestinal enteroids (HIE) isolated from biopsy-derived intestinal crypts. A detailed investigation of infection of VA1, a member of the non-canonical HAstV-VA/HMO clade, showed robust replication in HIE derived from different patients and from different intestinal regions independent of the cellular differentiation status. Flow cytometry and immunofluorescence analysis revealed that VA1 infects several cell types, including intestinal progenitor cells and mature enterocytes, in HIE cultures. RNA profiling of VA1-infected HIE uncovered that the host response to infection is dominated by interferon (IFN)-mediated innate immune responses. A comparison of the antiviral host response in non-transformed HIE and transformed human colon carcinoma Caco-2 cells highlighted significant differences between these cells, including an increased magnitude of the response in HIE. Additional studies confirmed the sensitivity of VA1 to exogenous IFNs, and indicated that the endogenous IFN response of HIE to curtail the growth of strains from all three clades. Genotypic variation in the permissiveness of different HIE lines to HAstV could be overcome by pharmacologic inhibition of JAK/STAT signaling. Collectively, our data identify HIE as a universal infection model for HAstV and an improved model of the intestinal epithelium to investigate enteric virus-host interactions.
Subject(s)
Astroviridae Infections/immunology , Astroviridae Infections/veterinary , Intestinal Mucosa/immunology , Intestine, Small/immunology , Mamastrovirus/physiology , Viral Tropism/genetics , Animals , Caco-2 Cells , Cell Line , Chlorocebus aethiops , Enterocytes/virology , Gastroenteritis/virology , Humans , Immunity, Innate/immunology , Interferons/immunology , Intestinal Mucosa/cytology , Intestinal Mucosa/virology , Intestine, Small/cytology , Intestine, Small/virology , Mamastrovirus/genetics , Mamastrovirus/immunology , Vero Cells , Viral Tropism/immunologyABSTRACT
BACKGROUND: Legalization of medical and recreational cannabis is a major contributor to pediatric cannabis exposures. The trends and magnitude of pediatric cannabis exposures in Michigan after medical cannabis legalization in 2008 have not been assessed. OBJECTIVE: To describe the temporal trends of pediatric cannabis exposures reported to the Michigan Poison Center (MiPC) after medical cannabis was legalized in 2008 and 1 year after legalization of recreational cannabis in 2018. METHODS: Retrospective electronic chart review of pediatric (<18 years old) single-substance cannabis exposures reported to the MiPC from January 1, 2008 to December 31, 2019. Routes of cannabis exposure were reported as ingestion, inhalation, and unknown. Types of ingested cannabis products were also documented. RESULTS: Between 2008 and 2019, 426 pediatric cannabis single exposures were reported. The median patient age was 6.0 years (interquartile range 2-15 years). Age distribution was bimodal. A total of 327 (76.8%) exposures were from cannabis ingestion, 79 (18.5%) from inhalation, 2 (0.5%) from both ingestion and inhalation, and 18 (4.2%) from unknown route. The doubling time for number of cases was 2.1 years, and the total number of annual reported cases increased after 2016. Teenagers (13-17 years) had the highest number of inhalational exposures, whereas young children (0-5 years) had the highest number of ingestions. CONCLUSION: Single-substance pediatric cannabis exposures reported to the Michigan Poison Center increased after medical cannabis was legalized in 2008 through recreational legalization in 2018.
Subject(s)
Cannabis , Medical Marijuana , Poisons , Adolescent , Child , Child, Preschool , Humans , Michigan/epidemiology , Retrospective StudiesABSTRACT
Performic acid (PFA) is an emerging disinfectant to inactivate bacterial and viral microorganisms in wastewater. In this study, the inactivation kinetics of murine norovirus (MNV) by PFA, in phosphate buffer and municipal secondary effluent wastewater, are reported for the first time. PFA decay followed first-order kinetics and the inactivation of MNV was governed by the exposure of microorganisms to PFA, i.e., the integral of the PFA concentration over time (integral CT or ICT). The extension of the Chick-Watson model, in the ICT domain, described well the reduction of MNV by PFA, with determined ICT-based inactivation rate constants, kd, of 1.024 ± 0.038 L/(mg·min) and 0.482 ± 0.022 L/(mg·min) in phosphate buffer and wastewater, respectively, at pH 7.2. Furthermore, the simultaneous PFA inactivation of MNV and fecal indicators indigenously present in wastewater such as fecal coliforms and enterococci showed that 1-log reduction could be achieved with ICT of 2, 1.5, and 3.5 mg·min/L, respectively. When compared with the most commonly used peracid disinfectant of municipal wastewater, peracetic acid (PAA), the ICT requirements determined using the fitted ICT-based kinetic models were â¼20 times higher for PAA than PFA, indicating a much stronger inactivation power of the PFA molecule.
Subject(s)
Disinfectants , Norovirus , Animals , Disinfection , Enterococcus , Formates , Mice , Peracetic Acid , Virus Inactivation , WastewaterABSTRACT
Ferrate(VI) (FeVIO42, Fe(VI)) is an emerging oxidant/disinfectant to treat a wide range of contaminants and microbial pollutants in wastewater. This study describes the inactivation of murine norovirus (MNV) by Fe(VI) in phosphate buffer (PB) and secondary effluent wastewater (SEW). The decay of Fe(VI) had second-order kinetics in PB while Fe(VI) underwent an initial demand followed by first-order decay kinetics in SEW. The Chick-Watson inactivation kinetic model, based on integral CT (ICT) dose, well fitted the inactivation of MNV in both PB and SEW. In PB, the values of the inactivation rate constant (kd) decreased with an increase in pH, which was related to the reaction of protonated Fe(VI) species (HFeO4-) with MNV. Higher kd was observed in SEW than in PB. The inactivation of indigenous fecal coliforms (FC) in SEW was also measured. A two-population double-exponential model that accounted for both dispersed and particle-associated FC well fitted the inactivation data with determined kd and particle-associated inactivation rate constant (kp). Results show that Fe(VI) was more effective in inactivating dispersed FC than MNV. The MNV inactivation results obtained herein, coupled with the detailed modeling, provide important information in designing an Fe(VI) wastewater disinfection process.
Subject(s)
Norovirus , Water Purification , Animals , Iron , Kinetics , Mice , Oxidation-Reduction , WastewaterABSTRACT
Due to the rise of antibiotic resistance and the small number of effective antiviral drugs, new approaches for treating infectious diseases are urgently needed. Identifying targets for host-based therapies represents an emerging strategy for drug discovery. The ubiquitin-proteasome system is a central mode of signaling in the eukaryotic cell and may be a promising target for therapies that bolster the host's ability to control infection. Deubiquitinase (DUB) enzymes are key regulators of the host inflammatory response, and we previously demonstrated that a selective DUB inhibitor and its derivative promote anti-infective activities in host cells. To find compounds with anti-infective efficacy but improved toxicity profiles, we tested a library of predominantly 2-cyano-3-acrylamide small-molecule DUB inhibitors for anti-infective activity in macrophages against two intracellular pathogens: murine norovirus (MNV) and Listeria monocytogenes We identified compound C6, which inhibited DUB activity in human and murine cells and reduced intracellular replication of both pathogens with minimal toxicity in cell culture. Treatment with C6 did not significantly affect the ability of macrophages to internalize virus, suggesting that the anti-infective activity interferes with postentry stages of the MNV life cycle. Metabolic stability and pharmacokinetic assays showed that C6 has a half-life in mouse liver microsomes of â¼20 min and has a half-life of approximately 4 h in mice when administered intravenously. Our results provide a framework for targeting the host ubiquitin system in the development of host-based therapies for infectious disease. Compound C6 represents a promising tool with which to elucidate the role of DUBs in the macrophage response to infection.
Subject(s)
Antiviral Agents/pharmacology , Animals , Deubiquitinating Enzymes/metabolism , Humans , Listeria monocytogenes/drug effects , Listeria monocytogenes/metabolism , Macrophages/virology , Mice , Norovirus/drug effects , Norovirus/metabolism , Virus Replication/drug effectsSubject(s)
Host Microbial Interactions/physiology , Viruses/metabolism , Viruses/pathogenicity , Animals , Antiviral Agents/metabolism , Cell Death , Communicable Diseases/etiology , Communicable Diseases/metabolism , Disease Progression , Disease Reservoirs/virology , Eating/physiology , Fasting/metabolism , HIV-1/metabolism , HIV-1/pathogenicity , Humans , Models, Biological , Succinates/metabolismABSTRACT
Whole-genome sequencing was used to compare longitudinal isolates of Staphylococcus aureus that developed resistance to oxacillin (MIC up to 16 µg/ml). The mecA gene was absent. A novel 5-bp TATCC frameshift insertion in a gene encoding an ABC transporter similar to that of the teichoic acid translocation ATP-binding protein TagH and a 3-bp GCT nonframeshift insertion in the pdhA pyruvate dehydrogenase gene were detected in the oxacillin-resistant isolates.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacteremia/microbiology , Drug Resistance, Bacterial , Oxacillin/pharmacology , Staphylococcal Infections/microbiology , Staphylococcus aureus/drug effects , ATP-Binding Cassette Transporters/genetics , Aged, 80 and over , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Frameshift Mutation , Genome, Bacterial , Humans , Longitudinal Studies , Male , Microbial Sensitivity Tests , Molecular Sequence Data , Mutagenesis, Insertional , Recurrence , Sequence Analysis, DNA , Staphylococcus aureus/isolation & purificationABSTRACT
The development of new vaccines against the SARS-CoV-2 virus in response to the COVID-19 pandemic represents a milestone in the history of public health. However, due to the rapid development and short duration of these new vaccines, the full spectrum of side effects is not yet known. A 76-year-old man presented to the clinic for follow-up after being discharged from the emergency department for hyperglycemia. His medical history included well-controlled type 2 diabetes for two years, hypertension, and hyperlipidemia. He had recently noticed high home blood glucose readings over 400 mg/dL, and his hemoglobin A1c (mean 90-day glucose level) had increased from 6.5% to 12.6%. Notably, the patient reported having excellent health behaviors, including daily exercise, a closely monitored healthy diet, and regular blood glucose testing. After extensive endocrinology workup, the rapid change in blood glucose was thought to be due to his having recently received the COVID-19 messenger RNA (mRNA) vaccine. He was started on long- and short-acting insulin and a glucagon-like peptide-1 agonist (novel injectable type 2 diabetes medication), with improvement in blood glucose. He was tapered off all medications and remains on metformin 1,000 mg twice daily after one year.Whether the new COVID-19 mRNA vaccines directly incur hyperglycemia within certain groups of patients with diabetes is not known; thus, studies exploring the relationship between vaccine antigen binding and pancreatic function are needed.
ABSTRACT
PROBLEM: Systematically investigating annual Accreditation Council for Graduate Medical Education (ACGME) Resident/Fellow Survey results by directly gathering trainee feedback could uncover training program problems and clarify misunderstandings as they arise, leading to faster corrective actions and program improvement. APPROACH: The Focus Group Forum (FGF) was created based on the utilization-focused evaluation approach to systematically gather comprehensive, high-quality, actionable trainee feedback on specific annual ACGME survey results and involve trainees in program improvement (Henry Ford Hospital, 2021). Trainees from programs with survey results indicating <80% compliance within several content areas were invited to attend FGF sessions. During FGF sessions, neutral moderators experienced in conducting focus groups and creating psychologically safe spaces and neutral scribes gathered trainee feedback on survey results through structured, iterative discussions and an anonymous electronic polling system. Summaries of FGF findings were created, combined with actual annual ACGME survey data, and used to develop recommended corrective actions and monitoring plans. OUTCOMES: In 2021, 6 training programs had survey results below the institution's compliance threshold for 4-8 of the 9 content areas. Of the 180 trainees (from the 6 programs) invited to attend an FGF session, 79 (44%) participated. Five key issues were identified: misinterpretation of several survey questions, lack of knowledge of institutional policies and procedures, perceived inability to share feedback with faculty, feelings of being overwhelmed with administrative duties, and lack of sufficient protected time for educational activities and requirements. NEXT STEPS: The authors are developing an FGF process for faculty so that all stakeholders have a voice regarding annual ACGME survey results. They are also improving scheduling processes so that feedback from experienced trainees who are leaving the institution will not be missed and developing longer-term processes for tracking outcomes since time for implementing corrective actions before the next ACGME survey is limited.
Subject(s)
Internship and Residency , Humans , Pilot Projects , Feedback , Education, Medical, Graduate/methods , AccreditationABSTRACT
OBJECTIVES: Educational approaches for training physicians in clinical communications vary, and whether physicians apply the communication skills they learn or find them useful in the clinic is not well known. The aim of this study was to determine how first-year residents who received explicit instruction in 7 communication strategies would apply them in a simulation exercise and in clinical practice. METHODS: First-year Internal Medicine residents at an urban teaching hospital received instruction in 7 systematic communication strategies: Ask-Tell-Ask, Teach-back, open-ended questioning, NURSE, open body language, pausing, and plain language. Residents were evaluated on their use of specific communication behaviors associated with the 7 strategies during a simulation exercise of disclosing a medical error to a standardized patient. Control group residents who did the simulation before attending the training program and training group residents who did the simulation after the training were compared. Residents were queried 6 months after the training program on their use of communication strategies during clinical practice. RESULTS: A total of 27 residents participated (n = 13 control group; n = 14 training group). The training group performed behaviors for "establishing patient understanding" significantly more often than the control group. Both groups used non-verbal communication and behaviors for addressing patient emotions at similar levels. Of the 24 residents who responded to the 6-month follow-up questionnaire, 24 (100%) reported using Ask-Tell-Ask, open-ended questioning, and Teach-back, and 22 (92%) reported using NURSE statements and non-verbal communication. Most respondents reported using the strategies in clinical practice often or very often (79%) and found the strategies useful or very useful (96%). CONCLUSION: Providing explicit instruction in systematic communication strategies, particularly those focused on establishing patient understanding, may be an efficient approach for helping early career physicians develop effective communication skills that can be readily implemented during clinical training and practice.
ABSTRACT
BACKGROUND: The genetic network involved in the bacterial cell cycle is poorly understood even though it underpins the remarkable ability of bacteria to proliferate. How such network evolves is even less clear. The major aims of this work were to identify and examine the genes and pathways that are differentially expressed during the Caulobacter crescentus cell cycle, and to analyze the evolutionary features of the cell cycle network. RESULTS: We used deep RNA sequencing to obtain high coverage RNA-Seq data of five C. crescentus cell cycle stages, each with three biological replicates. We found that 1,586 genes (over a third of the genome) display significant differential expression between stages. This gene list, which contains many genes previously unknown for their cell cycle regulation, includes almost half of the genes involved in primary metabolism, suggesting that these "house-keeping" genes are not constitutively transcribed during the cell cycle, as often assumed. Gene and module co-expression clustering reveal co-regulated pathways and suggest functionally coupled genes. In addition, an evolutionary analysis of the cell cycle network shows a high correlation between co-expression and co-evolution. Most co-expression modules have strong phylogenetic signals, with broadly conserved genes and clade-specific genes predominating different substructures of the cell cycle co-expression network. We also found that conserved genes tend to determine the expression profile of their module. CONCLUSION: We describe the first phylogenetic and single-nucleotide-resolution transcriptomic analysis of a bacterial cell cycle network. In addition, the study suggests how evolution has shaped this network and provides direct biological network support that selective pressure is not on individual genes but rather on the relationship between genes, which highlights the importance of integrating phylogenetic analysis into biological network studies.
Subject(s)
Bacterial Proteins/genetics , Caulobacter crescentus/genetics , Transcriptome , Bacterial Proteins/metabolism , Caulobacter crescentus/cytology , Caulobacter crescentus/metabolism , Cell Cycle , Chromosome Mapping , Evolution, Molecular , Gene Expression Regulation, Bacterial , Gene Ontology , Gene Regulatory Networks , Genes, Bacterial , Genes, Essential , Metabolic Networks and Pathways/genetics , Multigene Family , Phylogeny , RNA, Bacterial/genetics , Sequence Analysis, RNAABSTRACT
BACKGROUND: Research has explored the problems that women encounter during a medical career; however, the advice that experienced women physicians would give to women who have not yet entered the field is needed to reveal how the medical work landscape is evolving and to provide real-world narratives to help career seekers make informed choices. OBJECTIVE: By eliciting women's perspectives on their medical careers by asking them what advice they would give to aspiring women physicians, we aimed to reveal areas for improving career satisfaction of women physicians and to inform those who advise women considering a medical career. METHODS: In this qualitative study, we used a phenomenological approach to conduct semi-structured one-on-one interviews with 24 women physicians to query the advice they would give to women contemplating a career in medicine. RESULTS: Thematic analysis of interview transcriptions revealed 10 themes that women physicians communicated as being important to consider before deciding to become a physician. Although some advice had a cautionary tone, encouraging and practical advice was also conveyed. The most abundant themes concerned the centrality of patient care, a passion for practicing medicine, and the importance of planning. Other key topics included family and friends, self-reflection, life balance, finances, ethics, maintaining presence, and two overt cautionary statements. CONCLUSION: Interviews revealed that meaning and purpose derived from a medical career and maintaining work-life balance are valued by some women physicians. Participants were encouraging in recommending medicine as a career choice for women, while highlighting some challenges.
Subject(s)
Physicians, Women , Physicians , Humans , Female , Career Choice , Qualitative Research , EmotionsABSTRACT
Viruses are obligate intracellular parasites that rely on host cell metabolism for successful replication. Thus, viruses rewire host cell pathways involved in central carbon metabolism to increase the availability of building blocks for replication. However, the underlying mechanisms of virus-induced alterations to host metabolism are largely unknown. Noroviruses (NoVs) are highly prevalent pathogens that cause sporadic and epidemic viral gastroenteritis. In the present study, we uncovered several strain-specific and shared host cell metabolic requirements of three murine norovirus (MNV) strains, the acute MNV-1 strain and the persistent CR3 and CR6 strains. While all three strains required glycolysis, glutaminolysis, and the pentose phosphate pathway for optimal infection of macrophages, only MNV-1 relied on host oxidative phosphorylation. Furthermore, the first metabolic flux analysis of NoV-infected cells revealed that both glycolysis and glutaminolysis are upregulated during MNV-1 infection of macrophages. Glutamine deprivation affected the MNV lifecycle at the stage of genome replication, resulting in decreased non-structural and structural protein synthesis, viral assembly, and egress. Mechanistic studies further showed that MNV infection and overexpression of the MNV non-structural protein NS1/2 increased the enzymatic activity of the rate-limiting enzyme glutaminase. In conclusion, the inaugural investigation of NoV-induced alterations to host glutaminolysis identified the first viral regulator of glutaminolysis for RNA viruses, which increases our fundamental understanding of virus-induced metabolic alterations.
ABSTRACT
Methicillin-resistant Staphylococcus aureus (MRSA) strains with reduced susceptibility to vancomycin (MIC of 4 to 8 µg/ml) are referred to as vancomycin-intermediate S. aureus (VISA). In this study, we characterized two isogenic USA300 S. aureus isolates collected sequentially from a single patient with endocarditis where the S. aureus isolate changed from being susceptible to vancomycin (VSSA) (1 µg/ml) to VISA (8 µg/ml). In addition, the VISA isolate lost beta-lactamase activity and showed increased resistance to daptomycin and linezolid. The two strains did not differ in growth rate, but the VISA isolate had a thickened cell wall and was less autolytic. Transcriptome sequencing (RNA-seq) analysis comparing the two isolates grown to late exponential phase showed significant differences in transcription of cell surface protein genes (spa, SBI [second immunoglobulin-binding protein of S. aureus], and fibrinogen-binding proteins), regulatory genes (agrBCA, RNAIII, sarT, and saeRS), and others. Using whole-genome shotgun resequencing, we identified 6 insertion/deletion mutations between the VSSA and VISA isolates. A protein phosphatase 2C (PP2C) family phosphatase had a 6-bp (nonframeshift) insertion mutation in a highly conserved metal binding domain. Complementation of the clinical VISA isolate with a wild-type copy of the PP2C gene reduced the vancomycin and daptomycin MICs and increased autolytic activity, suggesting that this gene contributed to the reduced vancomycin susceptibility phenotype acquired in vivo. Creation of de novo mutants from the VSSA strain resulted in different mutations, demonstrating that reduced susceptibility to vancomycin in USA300 strains can occur via multiple routes, highlighting the complex nature of the VISA phenotype.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Daptomycin/pharmacology , Phosphoprotein Phosphatases/genetics , Staphylococcus aureus/drug effects , Staphylococcus aureus/enzymology , Vancomycin/pharmacology , Mutation , Protein Phosphatase 2C , Staphylococcus aureus/geneticsABSTRACT
The Henry Ford Health System provides patients with a safe, improved system of continuous kidney replacement therapy using a proprietary, 24-hour sustained low-efficiency dialysis (SLED). The SLED system utilizes regional citrate anticoagulation (RCA) in conventional hemodialysis machines that have been configured to provide slow dialytic therapy. Within our hospital complex, SLED-RCA systems are deployed in intensive care units distributed over 4 floors in 2 buildings. This widespread footprint represents a spatial challenge for hemodialysis technicians. Fifteen SLED-RCA machines may be running at one time, and each deployed unit may signal an alarm for multiple reasons. Previously, audible alarms prompted intensive care unit nurses to identify the alarming machine and manually notify technicians by telephone. Technicians would then travel to resolve the alarm. To improve the process of addressing SLED-RCA machine alarms, we developed a remote alert alarm system that wirelessly notifies hemodialysis technicians of specific machine alarms. A quality improvement analysis of nearly 1,000 SLED-RCA alarms over a 1-week period revealed that the average time for alarm correction with a remote alert alarm system was approximately 5 minutes. Reducing alarm resolution time may free technicians and nurses for other critical duties.