Model Of Bacterial Infection Research Articles

Development of a bacterial infection model of Galleria mellonella larvae (greater wax moth)

Development of a bacterial infection model of Galleria mellonella larvae (greater wax moth)

Galleria mellonella as a Suitable Model of Bacterial Infection: Past, Present and Future.

The increasing interest for Galleria mellonella larvae as an infection model is evidenced by the number of papers reporting its use, which increases exponentially since the early 2010s. This popularity was initially linked to limitation of conventional animal models due to financial, technical and ethical aspects. In comparison, alternative models (e.g. models using Caenorhabditis elegans, Drosophila melanogaster or G. mellonella) were cheap, simple to use and not limited by ethical regulation. Since then, similar results have been established with G. mellonella model comparatively to vertebrates, and it is more and more often used as a robust model per se, not only as an alternative to the murine model. This review attempts to summarize the current knowledge supporting the development of this model, both on immunological and microbiological aspects. For that, we focus on investigation of virulence and new therapies for the most important pathogenic bacteria. We also discuss points out directions for standardization, as well as recent advances and new perspectives for monitoring host-pathogen interactions.

Investigating the mechanisms of brain innate immune activation following bacterial infection in Drosophila

AbstractBackgroundCentral Nervous System (CNS) infections caused by bacteria and resulting immune responses could underlie neurodegenerative diseases such as Alzheimer’s disease (AD). Neuroinflammation is a well‐known component of AD furthering disease pathology and progression. However, the mechanisms by which infectious agents contribute to neuroinflammatory reactions and neurodegeneration are not fully understood. The model organism Drosophila melanogaster shares conserved mechanisms of innate immune activation and neural development with mammals, and thus represents an excellent system for the investigation of pathogen‐associated neurodegeneration. Previous work in flies has shown that bacterial brain injection results in age‐dependent neurodegeneration and impaired locomotor activity. Furthermore, these phenotypes depend on NF‐κB in both glia and neurons, suggesting that long‐term inflammatory processes take place in both cell types. However, a detailed picture of innate immune pathway activation in the Drosophila brain following bacterial infection is lacking. Here, we investigate the activation in the brain of the two Drosophila NF‐ κB pathways, Toll and Immune deficiency (IMD), in response to infection with Gram‐positive and Gram‐negative bacteria, respectively.MethodFly brains are infected by pricking heads with a thin, metal needle, dipped into concentrated pellets of overnight cultured bacterial solutions. Activation of NF‐κB pathways in brain cell types is assayed using immunohistochemistry and confocal microscopy of flies carrying fluorescent NF‐κB reporters. The dependence of canonical NF‐κB pathway components is assayed using quantitative reverse‐transcription PCR (RT‐qPCR) using RNA isolated from dissected brains of control‐injected or bacterially injected flies.ResultOur preliminary results show that brain bacterial injection leads to the activation of GFP reporters for both Toll and IMD pathways in multiple glial subtypes in the fly brain 24h following infection. We have optimized a protocol for brain‐specific gene expression of NF‐κB targets and are currently examining the response to bacterial challenge of multiple mutants for components of the Toll and IMD pathways.ConclusionWe have established a Drosophila model of bacterial brain infection that allows studying the long‐term consequences of pathogen‐mediated neuroinflammatory reactions associated with neurodegeneration. Our system could be used to identify the processes of immediate protection as well as the long‐term effects of brain infection.

Anti-Virulence Properties of Plant Species: Correlation between In Vitro Activity and Efficacy in a Murine Model of Bacterial Infection.

Several plant extracts exhibit anti-virulence properties due to the interruption of bacterial quorum sensing (QS). However, studies on their effects at the preclinical level are scarce. Here, we used a murine model of abscess/necrosis induced by Pseudomonas aeruginosa to evaluate the anti-pathogenic efficacy of 24 plant extracts at a sub-inhibitory concentration. We analyzed their ability to inhibit QS-regulated virulence factors such as swarming, pyocyanin production, and secretion of the ExoU toxin via the type III secretion system (T3SS). Five of the seven extracts with the best anti-pathogenic activity reduced ExoU secretion, and the extracts of Diphysa americana and Hibiscus sabdariffa were identified as the most active. Therefore, the abscess/necrosis model allows identification of plant extracts that have the capacity to reduce pathogenicity of P. aeruginosa. Furthermore, we evaluated the activity of the plant extracts on Chromobacterium violaceum. T3SS (ΔescU) and QS (ΔcviI) mutant strains were assessed in both the abscess/necrosis and sepsis models. Only the ΔescU strain had lower pathogenicity in the animal models, although no activity of plant extracts was observed. These results demonstrate differences between the anti-virulence activity recorded in vitro and pathogenicity in vivo and between the roles of QS and T3S systems as virulence determinants.

Abstract 8876: Role of Device Temperature Sensor and Impedance in a Rabbit Model of Bacterial Pocket Infection versus Systemic Endotoxemia

Introduction: Device infections are associated with considerable morbidity, mortality, and cost. The feasibility of temperature sensor performance and impedance measurements in the dual chamber pacemaker was evaluated. Hypothesis: An infection can cause local temperature to rise around the implanted device. Methods: All rabbits received two subcutaneous pacemaker implants in the thoracic region. The prototype device measured both temperature and local pocket impedance. A control device measured only temperature. After collecting baseline data, rabbits were assigned to either pocket infection (n=6) or systemic infection (n=6) groups. In the pocket infection group, one implant site was inoculated with Staphylococcus aureus suspension (5x106 CFU/mL) and the other control site received saline. In the systemic infection group, each animal received intravenous injections (17.7-35 μg/kg body weight) of E. coli endotoxin for 5 consecutive days. Animals were recovered and monitored for 14 days. The device temperature and pocket impedance data were logged every 10 minutes. Results: The temperature measurements increased significantly in all the rabbits, by 15.4 hours after the bacterial inoculation in the pocket. Compared to 24-hour baseline temperature of 38.83±0.04°C, the temperature increased by 2.03°C (40.86±0.25; P=0.005). The mean pocket impedance decreased significantly by 26 Ohms compared to baseline. In the systemic infection animals, significant increases in temperatures (~1.5 °C; P=<0.01) after each endotoxin challenge were observed, compared to baseline. Conclusions: These results show that shifts in temperature and impedance can be used to detect pocket or systemic infections. It is feasible that an “infection status” may be determined from longitudinal temperature measurements. Prospective data are needed to demonstrate performance of the temperature algorithm following device implantations.

Co3 O4 Nanowires Capable of Discharging Low Voltage Electricity Showing Potent Antibacterial Activity for Treatment of Bacterial Skin Infection.

Overuse of antibiotics has led to multidrug resistance in bacteria, posing a tremendous challenge to the healthcare system. There is an urgent need to explore unconventional strategies to overcome this issue. Herein, for the first time, we report a capacitive Co3 O4 nanowire (NW) electrode coated on flexible carbon cloth, which is capable of eliminating bacteria while discharging, for the treatment of skin infection. Benefiting from the unique NW-like morphology, the Co3 O4 NW electrode with increased active sites and enhanced capacitive property exhibits a prominent antibacterial effect against both Gram-positive and Gram-negative bacteria after charging at a low voltage of 2V for 30min. Furthermore, the electrode is demonstrated to be recharged for multiple antibacterial treatment cycles without significant change of antibacterial activity, allowing for practical use in a non-clinical setting. More importantly, this Co3 O4 NW electrode is capable of damaging bacterial cell membrane and inducing the accumulation of intracellular reactive oxygen species without impairing viability of skin keratinocytes. In a mouse model of bacterial skin infection, the Co3 O4 electrode shows significant therapeutic efficacy by eradicating colonized bacteria, thus accelerating the healing process of infected wounds. This nanostructured capacitive electrode provides an antibiotic-free, rechargeable, and wearable approach to treat bacterial skin infection.

Mitochondrial respiration restricts Listeria monocytogenes infection by slowing down host cell receptor recycling.

SummaryMutations in mitochondrial genes impairing energy production cause mitochondrial diseases (MDs), and clinical studies have shown that MD patients are prone to bacterial infections. However, the relationship between mitochondrial (dys)function and infection remains largely unexplored, especially in epithelial cells, the first barrier to many pathogens. Here, we generate an epithelial cell model for one of the most common mitochondrial diseases, Leigh syndrome, by deleting surfeit locus protein 1 (SURF1), an assembly factor for respiratory chain complex IV. We use this genetic model and a complementary, nutrient-based approach to modulate mitochondrial respiration rates and show that impaired mitochondrial respiration favors entry of the human pathogen Listeria monocytogenes, a well-established bacterial infection model. Reversely, enhanced mitochondrial energy metabolism decreases infection efficiency. We further demonstrate that endocytic recycling is reduced in mitochondrial respiration-dependent cells, dampening L. monocytogenes infection by slowing the recycling of its host cell receptor c-Met, highlighting a previously undescribed role of mitochondrial respiration during infection.

Retraction Note: IspH inhibitors kill Gram-negative bacteria and mobilize immune clearance.

Isoprenoids are vital for all organisms, in which they maintain membrane stability and support core functions such as respiration1. IspH, an enzyme in the methyl erythritol phosphate pathway of isoprenoid synthesis, is essential for Gram-negative bacteria, mycobacteria and apicomplexans2,3. Its substrate, (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), is not produced in metazoans, and in humans and other primates it activates cytotoxic Vγ9Vδ2 T cells at extremely low concentrations4–6. Here we describe a class of IspH inhibitors and refine their potency to nanomolar levels through structure-guided analogue design. After modification of these compounds into prodrugs for delivery into bacteria, we show that they kill clinical isolates of several multidrug-resistant bacteria—including those from the genera Acinetobacter, Pseudomonas, Klebsiella, Enterobacter, Vibrio, Shigella, Salmonella, Yersinia, Mycobacterium and Bacillus—yet are relatively non-toxic to mammalian cells. Proteomic analysis reveals that bacteria treated with these prodrugs resemble those after conditional IspH knockdown. Notably, these prodrugs also induce the expansion and activation of human Vγ9Vδ2 T cells in a humanized mouse model of bacterial infection. The prodrugs we describe here synergize the direct killing of bacteria with a simultaneous rapid immune response by cytotoxic γδ T cells, which may limit the increase of antibiotic-resistant bacterial populations. A class of compounds with a dual mechanism of action—direct targeting of IspH and stimulation of cytotoxic γδ T cells to enhance pathogen clearance—are active against multidrug-resistant bacteria.

An efficient method to screen for the soil bacteria producing therapeutically effective antibiotics.

The discovery of novel therapeutic antimicrobials has become an urgent issue in response to the global crisis of the spread of multi-drug-resistant bacteria. In this report, we propose an efficient screening method for antimicrobial agents with therapeutic potential from soil bacteria. With this method, colonies of the soil bacteria were formed first on agar plates containing only an extract of soil, followed by an overlay of soft agar containing the pathogens, an antibiotic target. Then, we selected the colonies that formed the inhibitory zones on soft agar and evaluated the therapeutic efficacy of their culture supernatants using a silkworm bacterial infection model. Using Staphylococcus aureus as an indicator strain to obtain bacteria that produce therapeutically effective antimicrobials, we succeeded in reducing the screening size by 20-fold compared to the conventional method. An analysis of 86 antibiotics producers identified in this study indicated that the majority belonged to Streptomyces sp. and Lysobacter sp., well-known producers of secondary metabolites. Besides, the presence of eight genera and 37 species among the identified species indicated the diversity of antibiotic producers. Based on the finding of our study, we propose this method as an efficient way to discover novel antimicrobial agents that are therapeutically effective.

Pulmonary infection induces persistent, pathogen-specific lipidomic changes influencing trained immunity

SummaryResolution of infection results in development of trained innate immunity which is typically beneficial for defense against unrelated secondary infection. Epigenetic changes including modification of histones via binding of various polar metabolites underlie the establishment of trained innate immunity. Therefore, host metabolism and this response are intimately linked. However, little is known regarding the influence of lipids on the development and function of trained immunity. Utilizing two models of pulmonary bacterial infection combined with multi-omic approaches, we identified persistent, pathogen-specific changes to the lung lipidome that correlated with differences in the trained immune response against a third unrelated pathogen. Further, we establish the specific cellular populations in the lung that contribute to this altered lipidome. Together these results expand our understanding of the pulmonary trained innate immune response and the contributions of host lipids in informing that response.

Significance of the Gut Microbiome for Viral Diarrheal and Extra-Intestinal Diseases.

The composition of the mammalian gut microbiome is very important for the health and disease of the host. Significant correlations of particular gut microbiota with host immune responsiveness and various infectious and noninfectious host conditions, such as chronic enteric infections, type 2 diabetes, obesity, asthma, and neurological diseases, have been uncovered. Recently, research has moved on to exploring the causalities of such relationships. The metabolites of gut microbiota and those of the host are considered in a ‘holobiontic’ way. It turns out that the host’s diet is a major determinant of the composition of the gut microbiome and its metabolites. Animal models of bacterial and viral intestinal infections have been developed to explore the interrelationships of diet, gut microbiome, and health/disease phenotypes of the host. Dietary fibers can act as prebiotics, and certain bacterial species support the host’s wellbeing as probiotics. In cases of Clostridioides difficile-associated antibiotic-resistant chronic diarrhea, transplantation of fecal microbiomes has sometimes cured the disease. Future research will concentrate on the definition of microbial/host/diet interrelationships which will inform rationales for improving host conditions, in particular in relation to optimization of immune responses to childhood vaccines.

A Novel Anti-Infective Peptide BCCY-1 With Immunomodulatory Activities.

Antibiotic resistance has been considered to be a global threat which underscores the need to develop novel anti-infective therapeutics. Modulation of innate immunity by synthetic peptides is an attractive strategy to overcome this circumstance. We recently reported that BCCY-1, a human β-casein-derived peptide displays regulatory activities on monocytes, thereby enhancing their actions in innate immune responses. However, the function of peptide BCCY-1 in host defense against infection remains unknown. In this study, we investigated the in vivo characteristics and effects of peptide BCCY-1 in mouse models of bacterial infection. Following intraperitoneal injection, the peptide BCCY-1 exhibited high level of cellular uptake by monocytes without obvious toxicities. Results revealed that peptide BCCY-1, but not the scrambled version, stimulated the chemokine production and monocyte recruitment in vivo. Treatment with BCCY-1 enhanced the pathogen clearance and protected mice against lethal infections. Because the anti-infective effects of BCCY-1 was abolished by in vivo depletion of monocytes/macrophages rather than lymphocytes and granulocytes, we conclude that monocytes/macrophages are key effector cells in BCCY-1-mediated anti-infective protection. Additionally, BCCY-1 lacks direct antimicrobial activity. To our knowledge, a human β-casein-derived peptide that counters infection by selective regulation of innate immunity has not been reported previously. These results suggest peptide BCCY-1 as a promising alternative approach and a valuable complement to current anti-infective strategy.

Sinusoidal Endothelial Cells as Orchestrators of the Gut Liver Immune Axis.

The paper by Gola and colleagues published recently in Nature uses an array of state-of-the-art techniques to demonstrate how commensal organisms shape protective immunity in the liver by organising immune cells into anatomical zones that are closely related to blood flow into the liver from the gut via the portal venous system. Sophisticated confocal imaging is used to map leukocyte distribution within the liver, targeted disruption of critical signalling pathways and RNA sequencing of specific cell types to determine molecular and cellular mechanisms and murine models of bacterial and malarial infection to demonstrate functional relevance.

Caerin 1.1 and 1.9 Peptides from Australian Tree Frog Inhibit Antibiotic-Resistant Bacteria Growth in a Murine Skin Infection Model.

ABSTRACTThe host defense peptide caerin 1.9 was originally isolated from skin secretions of an Australian tree frog and inhibits the growth of a wide range of bacteria in vitro. In this study, we demonstrated that caerin 1.9 shows high bioactivity against several bacteria strains, such as Staphylococcus aureus, Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus haemolyticus in vitro. Importantly, unlike the antibiotic Tazocin, caerin 1.9 does not induce bacterial resistance after 30 rounds of in vitro culture. Moreover, caerin 1.1, another peptide of the caerin family, has an additive antibacterial effect when used together with caerin 1.9. Furthermore, caerin 1.1 and 1.9 prepared in the form of a temperature-sensitive gel inhibit MRSA growth in a skin bacterial infection model of two murine strains. These results indicate that caerin 1.1 and 1.9 peptides could be considered an alternative for conventional antibiotics.IMPORTANCE Antibiotic-resistant bacteria cause severe problems in the clinic. We show in our paper that two short peptides isolated from an Australian frog and prepared in the form of a gel are able to inhibit the growth of antibiotic-resistant bacteria in mice, and, unlike antibiotics, these peptides do not lead to the development of peptide-resistant bacteria strains.

Development and multimodal characterization of an elastase-induced emphysema mouse disease model for the COPD frequent bacterial exacerbator phenotype

ABSTRACT Chronic obstructive pulmonary disease (COPD) patients undergo infectious exacerbations whose frequency identifies a clinically meaningful phenotype. Mouse models have been mostly used to separately study both COPD and the infectious processes, but a reliable model of the COPD frequent exacerbator phenotype is still lacking. Accordingly, we first established a model of single bacterial exacerbation by nontypeable Haemophilus influenzae (NTHi) infection on mice with emphysema-like lesions. We characterized this single exacerbation model combining both noninvasive in vivo imaging and ex vivo techniques, obtaining longitudinal information about bacterial load and the extent of the developing lesions and host responses. Bacterial load disappeared 48 hours post-infection (hpi). However, lung recovery, measured using tests of pulmonary function and the disappearance of lung inflammation as revealed by micro-computed X-ray tomography, was delayed until 3 weeks post-infection (wpi). Then, to emulate the frequent exacerbator phenotype, we performed two recurrent episodes of NTHi infection on the emphysematous murine lung. Consistent with the amplified infectious insult, bacterial load reduction was now observed 96 hpi, and lung function recovery and disappearance of lesions on anatomical lung images did not happen until 12 wpi. Finally, as a proof of principle of the use of the model, we showed that azithromycin successfully cleared the recurrent infection, confirming this macrolide utility to ameliorate infectious exacerbation. In conclusion, we present a mouse model of recurrent bacterial infection of the emphysematous lung, aimed to facilitate investigating the COPD frequent exacerbator phenotype by providing complementary, dynamic information of both infectious and inflammatory processes.

Applying the silkworm model for the search of immunosuppressants.

Various stresses (high temperature, starvation, or sublethal Cryptococcal infection) increased the susceptibility of silkworms to bacterial infection by up to 100-fold, confirming the stress-induced immunosuppression reported in a range of species. When the silkworm was injected with a steroidal drug, betamethasone (1 mg/larva), the susceptibility of the silkworm to bacterial infection increased about 100-fold. This indicates that the immune function of the silkworm can be suppressed by a known compound that shows immunosuppressive effects in humans. We further tested the immunosuppressive effect of the culture supernatants (acetone extracts) of soil bacteria, and 24 out of 193 isolates showed the immunosuppressive activity. These results suggest that it is possible to search for immunosuppressive agents targeting innate immunity by using a silkworm bacterial infection model as a screening system, and that there may be candidate compounds for immunosuppressive agents among the substances produced by soil bacteria.

Developing fluoromodule-based probes for in vivo monitoring the bacterial infections and antibiotic responses

Recently, antibiotic resistant has become a serious public health concern, which warrants new generations of antibiotics to be developed. Pharmacodynamic evaluation is crucial in drug discovery processes. Despite numerous advanced imaging systems are available nowadays, technologies for the sensitive in vivo diagnosis of bacterial infections and direct visualization of drug efficacy are yet to be developed. In this study, we have developed novel near-infrared (NIR) fluorogenic probes. These probes are dark in solution but highly fluorescent when bound to the cognate reporter, fluorogen-activating protein (FAP). We established the in vivo bacterial infection model using FAP_dH6.2 recombinantly expressed E. coli and applied this NIR fluoromodule-based system for diagnosing bacterial infections and monitoring disease progressions and its responses to a type of antibiotics through classic mechanism of membrane lysis. This NIR fluoromodule-based system will discover new information on bacterial infections and identify newer antibacterial entities.

Immunopeptidomics for next-generation bacterial vaccine development.

Antimicrobial resistance is an increasing global threat and alternative treatments substituting failing antibiotics are urgently needed. Vaccines are recognized as highly effective tools to mitigate antimicrobial resistance; however, the selection of bacterial antigens as vaccine candidates remains challenging. In recent years, advances in mass spectrometry-based proteomics have led to the development of so-called immunopeptidomics approaches that allow the untargeted discovery of bacterial epitopes that are presented on the surface of infected cells. Especially for intracellular bacterial pathogens, immunopeptidomics holds great promise to uncover antigens that can be encoded in viral vector- or nucleic acid-based vaccines. This review provides an overview of immunopeptidomics studies on intracellular bacterial pathogens and considers future directions and challenges in advancing towards next-generation vaccines.

Development and Validation of a Clinical Predictive Model for Bacterial Infection in HepatitisB Virus-Related Acute-on-Chronic Liver Failure.

IntroductionBacterial infection is one of the most frequent complications in hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF), which leads to high mortality. However, a predictive model for bacterial infection in HBV-ACLF has not been well established. This study aimed to establish and validate a predictive model for bacterial infection in two independent patient cohorts.MethodsAdmission data from a prospective cohort of patients with HBV-ACLF without bacterial infection on admission was used for derivation. Bacterial infection development from day 3 to 7 of admission was captured. Independent predictors of bacterial infection development on multivariate logistic regression were used to develop the predictive model. External validation was performed on a separate retrospective cohort.ResultsA total of 377 patients were enrolled into the derivation cohort, including 88 patients (23.3%) who developed bacterial infection from day 3 to 7 of admission. On multivariate regression analysis, admission serum globulin (OR 0.862, 95% CI 0.822–0.904; P < 0.001), interleukin-6 (OR 1.023, 95% CI 1.006–1.040; P = 0.009), and C-reactive protein (OR 1.123, 95% CI 1.081–1.166; P < 0.001) levels were independent predictors for the bacterial infection development, which were adopted as parameters of the predictive model (GIC). In the derivation cohort, the area under the curve (AUC) of GIC was 0.861 (95% CI 0.821–0.902). A total of 230 patients were enrolled into the validation cohort, including 57 patients (24.8%) who developed bacterial infection from day 3 to 7 of admission, and the AUC of GIC was 0.836 (95% CI 0.782–0.881). The Hosmer–Lemeshow test showed a good calibration performance of the predictive model in the two cohorts (P = 0.199, P = 0.746). Decision curve analysis confirmed the clinical utility of the predictive model.ConclusionGIC was established and validated for the prediction of bacterial infection development in HBV-ACLF, which may provide a potential auxiliary solution for the primary complication of HBV-ACLF.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40121-021-00454-2.

Therapeutic Potential of Vasoactive Intestinal Peptide and its Derivative Stearyl-Norleucine-VIP in Inflammation-Induced Osteolysis.

The common use of dental and orthopedic implants calls for special attention to the immune response leading to peri-prosthetic bone loss and implant failure. In addition to the well-established microbial etiology for oral implant failure, wear debris and in particular titanium (Ti) particles (TiP) in the implant vicinity are an important trigger of inflammation and activation of bone resorption around oral and orthopedic implants, presenting an unmet medical need. Here, we employed bacterial-derived lipopolysaccharides (LPS) to model infection and TiP to model aseptic inflammation and osteolysis. We assessed inflammation in vitro by measuring IL1β, IL6 and TNFα mRNA expression in primary macrophages, osteoclastogenesis in RANKL-induced bone marrow derived pre-osteoclasts and osteolysis in vivo in a mouse calvarial model. We also assessed the trans-epithelial penetrability and safety of the tested compound in rats. Our results show that a lipophilic super-active derivative of vasoactive intestinal peptide (VIP), namely stearyl-norleucine-VIP (SNV) presented superior anti-inflammatory and anti-osteoclastogenic effects compared to VIP in vitro. In the bacterial infection model (LPS), SNV significantly reduced IL1β expression, while VIP increased IL6 expression. In the aseptic models of osteolysis, SNV showed greater suppression of in vitro osteoclastogenesis than VIP, and significantly inhibited inflammation-induced osteolysis in vivo. We also observed that expression levels of the VIP receptor VPAC-2, but not that of VPAC-1, dramatically decreased during osteoclast differentiation. Importantly, SNV previously shown to have an increased stability compared to VIP, showed here significant trans-epithelial penetration and a clean toxicological profile, presenting a novel drug candidate that could be applied topically to counter both aseptic and infection-related bone destruction.