Immunomodulatory regulation by heat-labile enterotoxins and potential therapeutic applications.

Introduction: Heat-labile enterotoxins (HLTs) and their cognate ganglioside receptors have been extensively studied because of their therapeutic potential. Gangliosides play arole in modulating effector cells of the immune system, and HLTs provide a novel means for stimulating ganglioside-mediated responses in immunocompetent cells.Areas covered: To evaluate the mechanisms of HLT adjuvanticity, a systemic literature review was performed using relevant keyword searches of the PubMed database, accessing literature published as recently as late 2020. Since HLTs bind to specific ganglioside receptors on immunocytes, they can act as regulators via stimulation or tapering of immune responses from associated signal transduction events. Binding of HLTs to gangliosides can increase proliferation of T-cells, increase cytokine release, augment mucosal/systemic antibody responses, and increase the effectiveness of antigen presenting cells. Subunit components also independently stimulate certain immune responses. Mutant forms of HLTs have potent immunomodulatory effects without the toxicity associated with holotoxins.Expert opinion: HLTs have been the subject of abundant research exploring their use as vaccine adjuvants, in the treatment of autoimmune conditions, in cancer therapy, and for weight loss, proving that these molecules are promising tools in the field of immunotherapy.

Community-Acquired, Extended-Spectrum ß-Lactamase-Producing and Extensively Drug-Resistant Escherichia coli in a 28-Year-Old Pyelonephritis Patient Lacking Risk Factors.

While Escherichia coli is a common cause of urinary tract infections and pyelonephritis, there are few documented cases of extended-spectrum ß-lactamase (ESBL)-producing and extensively drug-resistant (XDR) isolates from the community resulting in infection requiring hospitalization, especially in individuals lacking risk factors. In the United States, exposure to ESBL-producing E. coli is typically nosocomial, whereas patients from developing countries often encounter ESBL-producing E. coli in the community through the consumption of contaminated food or water. Considering the rarity at which XDR E. coli isolates are encountered, there is also a scarcity of literature describing the successful treatment of ESBL-producing XDR E. coli. Here we present a case of an otherwise healthy 28-year-old female delicatessen worker infected with ESBL-producing and XDR E. coli without recent travel, antibiotic use, or healthcare contact, who required admission to the intensive care unit (ICU) with pyelonephritis and septic shock. Treatment with intravenous meropenem through a peripherally inserted central catheter (PICC) line at home was curative and follow up thereafter unremarkable. Given the patient's lack of obvious exposure to and risk factors for an ESBL-producing XDR E. coli infection and the specific lack of risk factors for severe pyelonephritis requiring hospitalization, this case represents a unique addition to the literature and is of value to clinicians by describing successful treatment.

Two Acinetobacter baumannii Isolates Obtained From a Fatal Necrotizing Fasciitis Infection Display Distinct Genomic and Phenotypic Characteristics in Comparison to Type Strains.

Acinetobacter baumannii has been recognized as a critical pathogen that causes severe infections worldwide not only because of the emergence of extensively drug-resistant (XDR) derivatives, but also because of its ability to persist in medical environments and colonize compromised patients. While there are numerous reports describing the mechanisms by which this pathogen acquires resistance genes, little is known regarding A. baumannii's virulence functions associated with rare manifestations of infection such as necrotizing fasciitis, making the determination and implementation of alternative therapeutic targets problematic. To address this knowledge gap, this report describes the analysis of the NFAb-1 and NFAb-2 XDR isolates, which were obtained at two time points during a fatal case of necrotizing fasciitis, at the genomic and functional levels. The comparative genomic analysis of these isolates with the ATCC 19606T and ATCC 17978 strains showed that the NFAb-1 and NFAb-2 isolates are genetically different from each other as well as different from the ATCC 19606T and ATCC 17978 clinical isolates. These genomic differences could be reflected in phenotypic differences observed in these NFAb isolates. Biofilm, cell viability and flow cytometry assays indicate that all tested strains caused significant decreases in A549 human alveolar epithelial cell viability with ATCC 17978, NFAb-1 and NFAb-2 producing significantly less biofilm and significantly more hemolysis and capacity for intracellular invasion than ATCC 19606T. NFAb-1 and NFAb-2 also demonstrated negligible surface motility but significant twitching motility compared to ATCC 19606T and ATCC 17978, likely due to the presence of pili exceeding 2 µm in length, which are significantly longer and different from those previously described in the ATCC 19606T and ATCC 17978 strains. Interestingly, infection with cells of the NFAb-1 isolate, which were obtained from a premortem blood sample, lead to significantly higher mortality rates than NFAb-2 bacteria, which were obtained from postmortem tissue samples, when tested using the Galleria mellonella in vivo infection model. These observations suggest potential changes in the virulence phenotype of the A. baumannii necrotizing fasciitis isolates over the course of infection by mechanisms and cell processes that remain to be identified.

Fatal Coronary Artery Vasculitis With Mixed Features.

ABSTRACT: Atherosclerotic cardiovascular disease (ASCVD) is often investigated by medical examiners as a cause of sudden death. Because of the variation in presentation of atherosclerotic cardiovascular disease, the examiner must be cautious when assigning a final diagnosis. The presented case depended upon histologic examination of coronary artery lesions to reach an appropriate final diagnosis of vasculitis with mixed features. Autopsy findings showed hepatosplenic vasculitis with noncaseating granulomas, and multifocal diffuse coronary fibrosis with histologic findings consistent with late-stage polyarteritis nodosa (PAN). However, the patient lacked the hallmark renal involvement observed in PAN. Furthermore, the vasculitis within the liver showed a highly granulomatous appearance, more consistent with IgG4 disease. In these mixed-appearance cases with limited history, exact categorization of the disease may prove difficult to impossible. Herein, we review a differential diagnosis of classic vasculitides with a focus on those that commonly affect the coronary arteries in adults, namely, PAN.

Glyphosate and Polyoxyethyleneamine Ingestion Leading to Renal, Hepatic, and Pulmonary Failure.

ABSTRACT: Glyphosate is an organophosphorus compound and the active ingredient in commonly used herbicides, whereas polyoxyethyleneamine (POEA) is a nonionic surfactant often coupled with glyphosate in these herbicides to increase their efficacy. Cases of glyphosate-POEA ingestion have shown a variety of outcomes, ranging from skin and mucosal surface irritation to death. Here, we report mortality after ingestion of at least 237 mL of an herbicide confirmed to contain both glyphosate and POEA. The decedent's electronic medical record indicates presentation to the emergency department shortly after ingestion and rapid decompensation, with death occurring on the fourth day of admission. The autopsy report showed extensive pulmonary edema and congestion with no alimentary tract abnormalities. Microscopically, airway inflammation, edema, and hemorrhage were shown as well as pericentral necrosis and macrovascular hepatic steatosis. This case is unusual for several reasons including the fatal outcome in a young 30-year-old patient, the large volume of the herbicide consumed, the associated large volume aspirated, and the lung pathology associated with exposure to glyphosate-POEA since inhalation, and in this case, aspiration is an uncommon route of glyphosate-POEA exposure. This report therefore offers rare respiratory tract pathological findings and the clinical course after aspiration of a large volume of glyphosate-POEA.

Draft Genome Sequences of Two Acinetobacter baumannii Isolates from a Fatal Case of Necrotizing Fasciitis.

Carbapenem-resistant Acinetobacter baumannii is a bacterial pathogen with serious implications for human health and is recognized as an urgent threat by the Centers for Disease Control and Prevention (CDC). Total DNA from two A. baumannii clinical isolates collected over 3 days from a fatal case of necrotizing fasciitis has been sequenced to >30× coverage.

Acanthamoeba spp. and Balamuthia mandrillaris leading to fatal granulomatous amebic encephalitis.

Acanthamoeba spp. and Balamuthia mandrillaris are free-living amebae known to cause disseminated and fatal central nervous system dysfunction which manifests as granulomatous amebic encephalitis (GAE) with exceedingly rare frequency. We report two lethal cases of infection with free-living amebae: an acute case of Acanthamoeba spp. infection in an immunocompromised female and a subacute case of B. mandrillaris in a Hispanic male. The Acanthamoeba spp. infection presented with an atypical lesion in the thalamus that caused rapid deterioration of the patient while the case of B. mandrillaris had a prolonged clinical course with multifocal lesions beginning in the frontal lobe. Cerebrospinal fluid results were non-specific in both cases, however, post-mortem histology demonstrated the presence of trophozoites along a perivascular distribution of necrosis and infiltrate composed primarily of neutrophils. In addition to detailing the clinical presentations of these infrequent amebic infections, we offer insight into the difficulties surrounding their diagnoses in order to aid the clinician in accurate and timely identification.

Mortality from neonatal herpes simplex viremia causing severe hepatitis.

Neonatal herpes simplex viral infections are rare in the setting of appropriate prenatal care; however, under circumstances where prenatal care is not delivered, these infections can lead to significant disease. We report a fatal case of herpes simplex virus with severe herpes hepatitis in a 14-day old male neonate. The clinical history was limited and nonspecific, however there was no prenatal care and a known history of drug abuse in the family. Autopsy revealed extensive necrosis and hemorrhage of the liver and cerebellum. Histologically, the liver revealed viral intranuclear ground glass inclusions, characteristic of herpes virus. Immunohistochemistry for herpes simplex virus performed on the both the liver and cerebellum showed strong diffuse staining in the liver and negative staining in the cerebellum. Neonatal herpes simplex virus infection is a disease of low prevalence with significant morbidity and mortality, and an exceptionally high rate of fatality in those with disseminated disease with associated fulminant hepatic failure.

Miliary pattern MRSA sepsis following clandestine intravenous infusion.

Intravascular devices aid in drug administration and fluid replacement for hospitalized patients and are thus an integral part of modern medical care; however, poor aseptic technique and improper manipulation of infusion devices increase the risk of infections secondary to catheterization that can progress to sepsis and septic shock. We report the case of a woman who presented with altered mental status after receiving normal saline through an intravenous catheter placed by a medically untrained individual. Less than 24 h following her initial presentation to emergency medical services the patient became unresponsive to multiple vasopressors and broad-spectrum antibiotics and succumbed to septic shock. At autopsy, the decedent had enumerable hemorrhagic lesions consistent with septic emboli, and microscopic examination revealed clusters of coccoid-appearing bacteria. Cultures of the intravenous fluid and IV tubing collected at the decedent's home grew methicillin-resistant Staphylococcus aureus (MRSA), which was consistent with ante-mortem cultures. This case highlights the rapid clinical deterioration and autopsy presentation of MRSA sepsis due to contamination of the intravenous delivery system.

Embolization of Endocardial Vegetation With Stroke Presentation.

This case report details the unique cause of death of a 37-year-old Caucasian woman with a history significant for intravenous drug abuse. Before her death, she complained of extremity weakness and pain. Although her death was discovered to be the result of endocarditis, her symptoms were similar to that of a stroke. Autopsy revealed a large endocardial vegetation infecting both the tricuspid and mitral valves and a patent foramen ovale. The subsequent embolization of this vegetation caused blockages in the lungs, liver, and brain. An acute embolization of these vegetations to the bilateral middle cerebral arteries is the cause of the stroke presentation. Other comorbidities, such as cardiomegaly, microscopic evidence of myocardial infarction, and atherosclerotic disease, also contributed to the cause of death. As the opioid crisis continues in the United States, it is important to review cases involving the effects of drug use. The multiple interactions between endocarditis and the aforementioned conditions are documented to not only serve as references for future autopsies but also for the treatment of patients who have similar symptoms and comorbidities.

Miltefosine Reduces the Cytolytic Activity and Virulence of Acinetobacter baumannii.

Stagnation in antimicrobial development has led to a serious threat to public health because some Acinetobacter baumannii infections have become untreatable. New therapeutics with alternative mechanisms of action to combat A. baumannii are therefore necessary to treat these infections. To this end, the virulence of A. baumannii isolates with various antimicrobial susceptibilities was assessed when the isolates were treated with miltefosine, a phospholipase C inhibitor. Phospholipase C activity is a contributor to A. baumannii virulence associated with hemolysis, cytolysis of A549 human alveolar epithelial cells, and increased mortality in the Galleria mellonella experimental infection model. While the effects on bacterial growth were variable among strains, miltefosine treatment significantly reduced both the hemolytic and cytolytic activity of all treated A. baumannii strains. Additionally, scanning electron microscopy of polarized A549 cells infected with bacteria of the A. baumannii ATCC 19606T strain or the AB5075 multidrug-resistant isolate showed a decrease in A549 cell damage with a concomitant increase in the presence of A549 surfactant upon administration of miltefosine. The therapeutic ability of miltefosine was further supported by the results of G. mellonella infections, wherein miltefosine treatment of animals infected with ATCC 19606T significantly decreased mortality. These data demonstrate that inhibition of phospholipase C activity results in the overall reduction of A. baumannii virulence in both in vitro and in vivo models, making miltefosine a viable option for the treatment of A. baumannii infections, particularly those caused by multidrug-resistant isolates.

Methicillin-Resistant Staphylococcus aureus Parotitis Leading to Mortality in an Adolescent Male.

A case of toxic shock syndrome associated with methicillin-resistant Staphylococcus aureus parotitis in a 13-year-old male is presented. He was initially diagnosed with left-sided parotitis by his primary care physician, was started on sulfamethoxazole/trimethoprim, and became severely ill the following day. He was transported to the hospital after a syncopal episode at home and was found to have altered mental status, hypotension, and hypoxia. He was transferred to a larger care facility and died en route despite aggressive resuscitation. At autopsy, he was found to have a severe left-sided parotitis, severe pulmonary congestion, edema, and pneumonia, as well as bilateral lower limb hemorrhagic lesions. Blood cultures from the time of admission and at autopsy grew methicillin-resistant Staphylococcus aureus, which is rarely reported as the sole cause of parotitis. In addition, although S. aureus bacteremia is not necessarily a rare complication of a parotid gland infection, it is exceedingly rare in an immunocompetent adolescent.

Mucin acts as a nutrient source and a signal for the differential expression of genes coding for cellular processes and virulence factors in Acinetobacter baumannii.

The capacity of Acinetobacter baumannii to persist and cause infections depends on its interaction with abiotic and biotic surfaces, including those found on medical devices and host mucosal surfaces. However, the extracellular stimuli affecting these interactions are poorly understood. Based on our previous observations, we hypothesized that mucin, a glycoprotein secreted by lung epithelial cells, particularly during respiratory infections, significantly alters A. baumannii's physiology and its interaction with the surrounding environment. Biofilm, virulence and growth assays showed that mucin enhances the interaction of A. baumannii ATCC 19606T with abiotic and biotic surfaces and its cytolytic activity against epithelial cells while serving as a nutrient source. The global effect of mucin on the physiology and virulence of this pathogen is supported by RNA-Seq data showing that its presence in a low nutrient medium results in the differential transcription of 427 predicted protein-coding genes. The reduced expression of ion acquisition genes and the increased transcription of genes coding for energy production together with the detection of mucin degradation indicate that this host glycoprotein is a nutrient source. The increased expression of genes coding for adherence and biofilm biogenesis on abiotic and biotic surfaces, the degradation of phenylacetic acid and the production of an active type VI secretion system further supports the role mucin plays in virulence. Taken together, our observations indicate that A. baumannii recognizes mucin as an environmental signal, which triggers a response cascade that allows this pathogen to acquire critical nutrients and promotes host-pathogen interactions that play a role in the pathogenesis of bacterial infections.

Contribution of the A. baumannii A1S_0114 Gene to the Interaction with Eukaryotic Cells and Virulence.

Genetic and functional studies showed that some components of the Acinetobacter baumannii ATCC 17978 A1S_0112-A1S_0119 gene cluster are critical for biofilm biogenesis and surface motility. Recently, our group has shown that the A1S_0114 gene was involved in biofilm formation, a process related with pathogenesis. Confirming our previous results, microscopy images revealed that the ATCC 17978 Δ0114 derivative lacking this gene was unable to form a mature biofilm structure. Therefore, other bacterial phenotypes were analyzed to determine the role of this gene in the pathogenicity of A. baumannii ATCC 17978. The interaction of the ATCC 17978 parental strain and the Δ0114 mutant with A549 human alveolar epithelial cells was quantified revealing that the A1S_0114 gene was necessary for proper attachment to A549 cells. This dependency correlates with the negative effect of the A1S_0114 deletion on the expression of genes coding for surface proteins and pili-assembly systems, which are known to play a role in adhesion. Three different experimental animal models, including vertebrate and invertebrate hosts, confirmed the role of the A1S_0114 gene in virulence. All of the experimental infection assays indicated that the virulence of the ATCC 17978 was significantly reduced when this gene was inactivated. Finally, we discovered that the A1S_0114 gene was involved in the production of a small lipopeptide-like compound herein referred to as acinetin 505 (Ac-505). Ac-505 was isolated from ATCC 17978 spent media and its chemical structure was interpreted by mass spectrometry. Overall, our observations provide novel information on the role of the A1S_0114 gene in A. baumannii's pathobiology and lay the foundation for future work to determine the mechanisms by which Ac-505, or possibly an Ac-505 precursor, could execute critical functions as a secondary metabolite.

Iron-Regulated Phospholipase C Activity Contributes to the Cytolytic Activity and Virulence of Acinetobacter baumannii.

Acinetobacter baumannii is an opportunistic Gram-negative pathogen that causes a wide range of infections including pneumonia, septicemia, necrotizing fasciitis and severe wound and urinary tract infections. Analysis of A. baumannii representative strains grown in Chelex 100-treated medium for hemolytic activity demonstrated that this pathogen is increasingly hemolytic to sheep, human and horse erythrocytes, which interestingly contain increasing amounts of phosphatidylcholine in their membranes. Bioinformatic, genetic and functional analyses of 19 A. baumannii isolates showed that the genomes of each strain contained two phosphatidylcholine-specific phospholipase C (PC-PLC) genes, which were named plc1 and plc2. Accordingly, all of these strains were significantly hemolytic to horse erythrocytes and their culture supernatants tested positive for PC-PLC activity. Further analyses showed that the transcriptional expression of plc1 and plc2 and the production of phospholipase and thus hemolytic activity increased when bacteria were cultured under iron-chelation as compared to iron-rich conditions. Testing of the A. baumannii ATCC 19606T plc1::aph-FRT and plc2::aph isogenic insertion derivatives showed that these mutants had a significantly reduced PC-PLC activity as compared to the parental strain, while testing of plc1::ermAM/plc2::aph demonstrated that this double PC-PLC isogenic mutant expressed significantly reduced cytolytic and hemolytic activity. Interestingly, only plc1 was shown to contribute significantly to A. baumannii virulence using the Galleria mellonella infection model. Taken together, our data demonstrate that both PLC1 and PLC2, which have diverged from a common ancestor, play a concerted role in hemolytic and cytolytic activities; although PLC1 seems to play a more critical role in the virulence of A. baumannii when tested in an invertebrate model. These activities would provide access to intracellular iron stores this pathogen could use during growth in the infected host.

Draft Genome Sequences of Acinetobacter baumannii Isolates from Wounded Military Personnel.

Acinetobacter baumannii is a Gram-negative bacterium capable of causing hospital-acquired infections that has been grouped with Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species as ESKAPE pathogens because of their extensive drug resistance phenotypes and increasing risk to human health. Twenty-four multidrug-resistant A. baumannii strains isolated from wounded military personnel were sequenced and annotated.

Draft Genome Sequences of Escherichia coli Isolates from Wounded Military Personnel.

Members of the Escherichia coli bacterial family have been grouped as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens because of their extensive drug resistance phenotypes and increasing threat to human health. The genomes of six extended-spectrum ß-lactamase (ESBL)-producing E. coli strains isolated from wounded military personnel were sequenced and annotated.

Draft Genome Sequences of Pseudomonas aeruginosa Isolates from Wounded Military Personnel.

Pseudomonas aeruginosa, a Gram-negative bacterium that causes severe hospital-acquired infections, is grouped as an ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogen because of its extensive drug resistance phenotypes and effects on human health worldwide. Five multidrug resistant P. aeruginosa strains isolated from wounded military personnel were sequenced and annotated in this work.

Antimicrobial Activity of Gallium Protoporphyrin IX against Acinetobacter baumannii Strains Displaying Different Antibiotic Resistance Phenotypes.

A paucity of effective, currently available antibiotics and a lull in antibiotic development pose significant challenges for treatment of patients with multidrug-resistant (MDR) Acinetobacter baumannii infections. Thus, novel therapeutic strategies must be evaluated to meet the demands of treatment of these often life-threatening infections. Accordingly, we examined the antibiotic activity of gallium protoporphyrin IX (Ga-PPIX) against a collection of A. baumannii strains, including nonmilitary and military strains and strains representing different clonal lineages and isolates classified as susceptible or MDR. Susceptibility testing demonstrated that Ga-PPIX inhibits the growth of all tested strains when cultured in cation-adjusted Mueller-Hinton broth, with a MIC of 20 µg/ml. This concentration significantly reduced bacterial viability, while 40 µg/ml killed all cells of the A. baumannii ATCC 19606(T) and ACICU MDR isolate after 24-h incubation. Recovery of ATCC 19606(T) and ACICU strains from infected A549 human alveolar epithelial monolayers was also decreased when the medium was supplemented with Ga-PPIX, particularly at a 40-µg/ml concentration. Similarly, the coinjection of bacteria with Ga-PPIX increased the survival of Galleria mellonella larvae infected with ATCC 19606(T) or ACICU. Ga-PPIX was cytotoxic only when monolayers or larvae were exposed to concentrations 16-fold and 1,250-fold higher than those showing antibacterial activity, respectively. These results indicate that Ga-PPIX could be a viable therapeutic option for treatment of recalcitrant A. baumannii infections regardless of the resistance phenotype, clone lineage, time and site of isolation of strains causing these infections and their iron uptake phenotypes or the iron content of the media.