scholarly journals Streptococcus pyogenes Arginine and Citrulline Catabolism Promotes Infection and Modulates Innate Immunity

2013 ◽  
Vol 82 (1) ◽  
pp. 233-242 ◽  
Author(s):  
Zachary T. Cusumano ◽  
Michael E. Watson ◽  
Michael G. Caparon
Keyword(s):  
Nitric Oxide ◽  
Innate Immunity ◽  
Streptococcus Pyogenes ◽  
Murine Model ◽  
Acid Stress ◽  
Arginine Deiminase ◽  
Content Type ◽  
Cutaneous Tissue

ABSTRACTA bacterium's ability to acquire nutrients from its host during infection is an essential component of pathogenesis. For the Gram-positive pathogenStreptococcus pyogenes, catabolism of the amino acid arginine via the arginine deiminase (ADI) pathway supplements energy production and provides protection against acid stressin vitro. Its expression is enhanced in murine models of infection, suggesting an important rolein vivo. To gain insight into the function of the ADI pathway in pathogenesis, the virulence of mutants defective in each of its enzymes was examined. Mutants unable to use arginine (ΔArcA) or citrulline (ΔArcB) were attenuated for carriage in a murine model of asymptomatic mucosal colonization. However, in a murine model of inflammatory infection of cutaneous tissue, the ΔArcA mutant was attenuated but the ΔArcB mutant was hyperattenuated, revealing an unexpected tissue-specific role for citrulline metabolism in pathogenesis. When mice defective for the arginine-dependent production of nitric oxide (iNOS−/−) were infected with the ΔArcA mutant, cutaneous virulence was rescued, demonstrating that the ability ofS. pyogenesto utilize arginine was dispensable in the absence of nitric oxide-mediated innate immunity. This work demonstrates the importance of arginine and citrulline catabolism and suggests a novel mechanism of virulence by whichS. pyogenesuses its metabolism to modulate innate immunity through depletion of an essential host nutrient.

scholarly journals The Transcriptional Regulator CpsY Is Important for Innate Immune Evasion in Streptococcus pyogenes

2016 ◽  
Vol 85 (3) ◽  
Author(s):  
Luis A. Vega ◽  
Kayla M. Valdes ◽  
Ganesh S. Sundar ◽  
Ashton T. Belew ◽  
Emrul Islam ◽  
...  
Keyword(s):  
Streptococcus Pyogenes ◽  
Immune Evasion ◽  
Immune Cell ◽  
Group A Streptococcus ◽  
Transcriptional Regulator ◽  
Innate Immune ◽  
Content Type ◽  
Human Host

ABSTRACTAs an exclusively human pathogen,Streptococcus pyogenes(the group A streptococcus [GAS]) has specifically adapted to evade host innate immunity and survive in multiple tissue niches, including blood. GAS can overcome the metabolic constraints of the blood environment and expresses various immunomodulatory factors necessary for survival and immune cell resistance. Here we present our investigation of one such factor, the predicted LysR family transcriptional regulator CpsY. The encoding gene,cpsY, was initially identified as being required for GAS survival in a transposon-site hybridization (TraSH) screen in whole human blood. CpsY is homologous with transcriptional regulators ofStreptococcus mutans(MetR),Streptococcus iniae(CpsY), andStreptococcus agalactiae(MtaR) that regulate methionine transport, amino acid metabolism, resistance to neutrophil-mediated killing, and survivalin vivo. Our investigation indicated that CpsY is involved in GAS resistance to innate immune cells of its human host. However, GAS CpsY does not manifest thein vitrophenotypes of its homologs in other streptococcal species. GAS CpsY appears to regulate a small set of genes that is markedly different from the regulons of its homologs. The differential expression of these genes depends on the growth medium, and CpsY modestly influences their expression. The GAS CpsY regulon includes known virulence factors (mntE,speB,spd,nga[spn],prtS[SpyCEP], andsse) and cell surface-associated factors of GAS (emm1,mur1.2,sibA[cdhA], andM5005_Spy0500). Intriguingly, the loss of CpsY in GAS does not result in virulence defects in murine models of infection, suggesting that CpsY function in immune evasion is specific to the human host.

scholarly journals Interplay of Nitric Oxide Synthase (NOS) and SrrAB in Modulation ofStaphylococcus aureusMetabolism and Virulence

2018 ◽  
Vol 87 (2) ◽  
Author(s):  
Kimberly L. James ◽  
Austin B. Mogen ◽  
Jessica N. Brandwein ◽  
Silvia S. Orsini ◽  
Miranda J. Ridder ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Double Mutant ◽  
Nitrate Assimilation ◽  
Arginine Deiminase ◽  
Growth Defect ◽  
Content Type ◽  
Metabolic Versatility ◽  
Oxide Synthase

ABSTRACTStaphylococcus aureusnitric oxide synthase (saNOS) is a major contributor to virulence, stress resistance, and physiology, yet the specific mechanism(s) by which saNOS intersects with other known regulatory circuits is largely unknown. The SrrAB two-component system, which modulates gene expression in response to the reduced state of respiratory menaquinones, is a positive regulator ofnosexpression. Several SrrAB-regulated genes were also previously shown to be induced in an aerobically respiringnosmutant, suggesting a potential interplay between saNOS and SrrAB. Therefore, a combination of genetic, molecular, and physiological approaches was employed to characterize anos srrABmutant, which had significant reductions in the maximum specific growth rate and oxygen consumption when cultured under conditions promoting aerobic respiration. Thenos srrABmutant secreted elevated lactate levels, correlating with the increased transcription of lactate dehydrogenases. Expression of nitrate and nitrite reductase genes was also significantly enhanced in thenos srrABdouble mutant, and its aerobic growth defect could be partially rescued with supplementation with nitrate, nitrite, or ammonia. Furthermore, elevated ornithine and citrulline levels and highly upregulated expression of arginine deiminase genes were observed in the double mutant. These data suggest that a dual deficiency in saNOS and SrrAB limitsS. aureusto fermentative metabolism, with a reliance on nitrate assimilation and the urea cycle to help fuel energy production. Thenos,srrAB, andnos srrABmutants showed comparable defects in endothelial intracellular survival, whereas thesrrABandnos srrABmutants were highly attenuated during murine sepsis, suggesting that SrrAB-mediated metabolic versatility is dominantin vivo.

scholarly journals Efficacy of Humanized High-Dose Meropenem, Cefepime, and Levofloxacin against Enterobacteriaceae Isolates Producing Verona Integron-Encoded Metallo-β-Lactamase (VIM) in a Murine Thigh Infection Model

2015 ◽  
Vol 59 (11) ◽  
pp. 7145-7147 ◽  
Author(s):  
Islam M. Ghazi ◽  
Jared L. Crandon ◽  
Emil P. Lesho ◽  
Patrick McGann ◽  
David P. Nicolau
Keyword(s):  
Murine Model ◽  
Infection Model ◽  
High Dose ◽  
Content Type ◽  
High Mics

ABSTRACTWe aimed to describe thein vivoactivity of humanized pharmacokinetic exposures of meropenem and comparators against Verona integron-encoded metallo-β-lactamase (MBL) (VIM)-producingEnterobacteriaceaein a murine model. Levofloxacin activity was predicted by its MIC, and cefepime activity displayed variability, whereas meropenem produced a >1 log CFU reduction against all isolates despite high MICs indicative of resistance. Our results suggest that despitein vitroresistance, high-dose meropenem may be a possible option against infections caused byEnterobacteriaceaeproducing MBL-type carbapenemases.

scholarly journals Stimulation of Innate Immunity byIn VivoCyclic di-GMP Synthesis Using Adenovirus

2014 ◽  
Vol 21 (11) ◽  
pp. 1550-1559 ◽  
Author(s):  
Benjamin J. Koestler ◽  
Sergey S. Seregin ◽  
David P. W. Rastall ◽  
Yasser A. Aldhamen ◽  
Sarah Godbehere ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Mammalian Cells ◽  
Immune Cell ◽  
Innate Immune ◽  
Host Cells ◽  
Content Type ◽  
Cytokines And Chemokines ◽  
Novel Approach

ABSTRACTThe bacterial second messenger cyclic di-GMP (c-di-GMP) stimulates inflammation by initiating innate immune cell recruitment and triggering the release of proinflammatory cytokines and chemokines. These properties make c-di-GMP a promising candidate for use as a vaccine adjuvant, and numerous studies have demonstrated that administration of purified c-di-GMP with different antigens increases protection against infection in animal models. Here, we have developed a novel approach to produce c-di-GMP inside host cells as an adjuvant to exploit a host-pathogen interaction and initiate an innate immune response. We have demonstrated that c-di-GMP can be synthesizedin vivoby transducing a diguanylate cyclase (DGC) gene into mammalian cells using an adenovirus serotype 5 (Ad5) vector. Expression of DGC led to the production of c-di-GMPin vitroandin vivo, and this was able to alter proinflammatory gene expression in murine tissues and increase the secretion of numerous cytokines and chemokines when administered to animals. Furthermore, coexpression of DGC modestly increased T-cell responses to aClostridium difficileantigen expressed from an adenovirus vaccine, although no significant differences in antibody titers were observed. This adenovirus c-di-GMP delivery system offers a novel method to administer c-di-GMP as an adjuvant to stimulate innate immunity during vaccination.

scholarly journals Enantiomers of Nifurtimox Do Not Exhibit Stereoselective Anti-Trypanosoma cruzi Activity, Toxicity, or Pharmacokinetic Properties

2015 ◽  
Vol 59 (6) ◽  
pp. 3645-3647 ◽  
Author(s):  
Carolina B. Moraes ◽  
Karen L. White ◽  
Stéphanie Braillard ◽  
Catherine Perez ◽  
Junghyun Goo ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
Chagas Disease ◽  
Murine Model ◽  
Therapeutic Benefit ◽  
Racemic Mixture ◽  
Content Type ◽  
Pharmacokinetic Properties

ABSTRACTWith the aim of improving the available drugs for the treatment of Chagas disease, individual enantiomers of nifurtimox were characterized. The results indicate that the enantiomers are equivalent in theirin vitroactivity against a panel ofTrypanosoma cruzistrains;in vivoefficacy in a murine model of Chagas disease;in vitrotoxicity and absorption, distribution, metabolism, and excretion characteristics; andin vivopharmacokinetic properties. There is unlikely to be any therapeutic benefit of an individual nifurtimox enantiomer over the racemic mixture.

scholarly journals Interaction of Antibiotics with Innate Host Defense Factors against Salmonella enterica Serotype Newport

mSphere ◽  
2017 ◽  
Vol 2 (6) ◽  
Author(s):  
George Sakoulas ◽  
Monika Kumaraswamy ◽  
Armin Kousha ◽  
Victor Nizet
Keyword(s):  
Innate Immunity ◽  
Immune System ◽  
Innate Immune System ◽  
Salmonella Enterica ◽  
Clinical Performance ◽  
Innate Immune ◽  
Content Type ◽  
Antimicrobial Assay

ABSTRACT It is becoming increasingly understood that the current paradigms of in vitro antimicrobial susceptibility testing may have significant shortcomings in predicting activity in vivo. This study evaluated the activity of several antibiotics alone and in combination against clinical isolates of Salmonella enterica serotype Newport (meningitis case) utilizing both conventional and physiological media. In addition, the interactions of these antibiotics with components of the innate immune system were evaluated. Azithromycin, which has performed quite well clinically despite high MICs in conventional media, was shown to be more active in physiological media and to enhance innate immune system killing. Alternatively, chloramphenicol did not show enhanced immune system killing, paralleling its inferior clinical performance to other antibiotics that have been used to treat Salmonella meningitis. These findings are important additions to the building understanding of current in vitro antimicrobial assay limitations that hopefully will amount to future improvements in these assays to better predict clinical efficacy and activity in vivo. This study examines the pharmacodynamics of antimicrobials that are used to treat Salmonella with each other and with key components of the innate immune system. Antimicrobial synergy was assessed using time-kill and checkerboard assays. Antimicrobial interactions with innate immunity were studied by employing cathelicidin LL-37, whole-blood, and neutrophil killing assays. Ceftriaxone and ciprofloxacin were found to be synergistic in vitro against Salmonella enterica serotype Newport. Ceftriaxone, ciprofloxacin, and azithromycin each demonstrated synergy with the human cathelicidin defense peptide LL-37 in killing Salmonella. Exposure of Salmonella to sub-MICs of ceftriaxone resulted in enhanced susceptibility to LL-37, whole blood, and neutrophil killing. The activity of antibiotics in vivo against Salmonella may be underestimated in bacteriologic media lacking components of innate immunity. The pharmacodynamic interactions of antibiotics used to treat Salmonella with each other and with components of innate immunity warrant further study in light of recent findings showing in vivo selection of antimicrobial resistance by single agents in this pathogen. IMPORTANCE It is becoming increasingly understood that the current paradigms of in vitro antimicrobial susceptibility testing may have significant shortcomings in predicting activity in vivo. This study evaluated the activity of several antibiotics alone and in combination against clinical isolates of Salmonella enterica serotype Newport (meningitis case) utilizing both conventional and physiological media. In addition, the interactions of these antibiotics with components of the innate immune system were evaluated. Azithromycin, which has performed quite well clinically despite high MICs in conventional media, was shown to be more active in physiological media and to enhance innate immune system killing. Alternatively, chloramphenicol did not show enhanced immune system killing, paralleling its inferior clinical performance to other antibiotics that have been used to treat Salmonella meningitis. These findings are important additions to the building understanding of current in vitro antimicrobial assay limitations that hopefully will amount to future improvements in these assays to better predict clinical efficacy and activity in vivo.

scholarly journals Macrolones Are a Novel Class of Macrolide Antibiotics Active against Key Resistant Respiratory PathogensIn VitroandIn Vivo

2016 ◽  
Vol 60 (9) ◽  
pp. 5337-5348 ◽  
Author(s):  
Hana Čipčić Paljetak ◽  
Donatella Verbanac ◽  
Jasna Padovan ◽  
Miroslava Dominis-Kramarić ◽  
Željko Kelnerić ◽  
...  
Keyword(s):  
Murine Model ◽  
Bacterial Resistance ◽  
Volume Of Distribution ◽  
Macrolide Antibiotics ◽  
Respiratory Pathogens ◽  
Protein Synthesis Inhibitors ◽  
Content Type ◽  
Tract Infections

ABSTRACTAs we face an alarming increase in bacterial resistance to current antibacterial chemotherapeutics, expanding the available therapeutic arsenal in the fight against resistant bacterial pathogens causing respiratory tract infections is of high importance. The antibacterial potency of macrolones, a novel class of macrolide antibiotics, against key respiratory pathogens was evaluatedin vitroandin vivo. MIC values againstStreptococcus pneumoniae,Streptococcus pyogenes,Staphylococcus aureus, andHaemophilus influenzaestrains sensitive to macrolide antibiotics and with defined macrolide resistance mechanisms were determined. The propensity of macrolones to induce the expression of inducibleermgenes was tested by the triple-disk method and incubation in the presence of subinhibitory concentrations of compounds.In vivoefficacy was assessed in a murine model ofS. pneumoniae-induced pneumonia, and pharmacokinetic (PK) profiles in mice were determined. Thein vitroantibacterial profiles of macrolones were superior to those of marketed macrolide antibiotics, including the ketolide telithromycin, and the compounds did not induce the expression of inducibleermgenes. They acted as typical protein synthesis inhibitors in anEscherichia colitranscription/translation assay. Macrolones were characterized by low to moderate systemic clearance, a large volume of distribution, a long half-life, and low oral bioavailability. They were highly efficacious in a murine model of pneumonia after intraperitoneal application even against anS. pneumoniaestrain with constitutive resistance to macrolide-lincosamide-streptogramin B antibiotics. Macrolones are the class of macrolide antibiotics with an outstanding antibacterial profile and reasonable PK parameters resulting in goodin vivoefficacy.

scholarly journals Citrulline Protects Streptococcus pyogenes from Acid Stress Using the Arginine Deiminase Pathway and the F1Fo-ATPase

2015 ◽  
Vol 197 (7) ◽  
pp. 1288-1296 ◽  
Author(s):  
Zachary T. Cusumano ◽  
Michael G. Caparon
Keyword(s):  
Soft Tissue ◽  
Streptococcus Pyogenes ◽  
Soft Tissue Infection ◽  
Bacterial Infections ◽  
Defense Mechanism ◽  
Acid Stress ◽  
Low Ph ◽  
Arginine Deiminase ◽  
Tissue Infection ◽  
Content Type

ABSTRACTA common stress encountered by both pathogenic and environmental bacteria is exposure to a low-pH environment, which can inhibit cell growth and lead to cell death. One major defense mechanism against this stress is the arginine deiminase (ADI) pathway, which catabolizes arginine to generate two ammonia molecules and one molecule of ATP. While this pathway typically relies on the utilization of arginine, citrulline has also been shown to enter into the pathway and contribute to protection against acid stress. In the pathogenic bacteriumStreptococcus pyogenes, the utilization of citrulline has been demonstrated to contribute to pathogenesis in a murine model of soft tissue infection, although the mechanism underlying its role in infection is unknown. To gain insight into this question, we analyzed a panel of mutants defective in different steps in the ADI pathway to dissect how arginine and citrulline protectS. pyogenesin a low-pH environment. While protection provided by arginine utilization occurred through the buffering of the extracellular environment, citrulline catabolism protection was pH independent, requiring the generation of ATP via the ADI pathway and a functional F1Fo-ATP synthase. This work demonstrates that arginine and citrulline catabolism protect against acid stress through distinct mechanisms and have unique contributions to virulence during an infection.IMPORTANCEAn important aspect of bacterial pathogenesis is the utilization of host-derived nutrients during an infection for growth and virulence. Previously published work from our lab identified a unique role for citrulline catabolism inStreptococcus pyogenesduring a soft tissue infection. The present article probes the role of citrulline utilization during this infection and its contribution to protection against acid stress. This work reveals a unique and concerted action between the catabolism of citrulline and the F1Fo-ATPase that function together to provide protection for bacteria in a low-pH environment. Dissection of these collaborative pathways highlights the complexity of bacterial infections and the contribution of atypical nutrients, such as citrulline, to pathogenesis.

scholarly journals Three Novel Candidate Probiotic Strains with Prophylactic Properties in a Murine Model of Cow's Milk Allergy

2016 ◽  
Vol 82 (6) ◽  
pp. 1722-1733 ◽  
Author(s):  
Elodie Neau ◽  
Johanne Delannoy ◽  
Candice Marion ◽  
Charles-Henry Cottart ◽  
Chantal Labellie ◽  
...  
Keyword(s):  
Murine Model ◽  
Food Allergies ◽  
T Helper ◽  
Murine Splenocytes ◽  
Content Type ◽  
Cellular Models ◽  
Probiotic Strains ◽  
The Impact

ABSTRACTFood allergies can have significant effects on morbidity and on quality of life. Therefore, the development of efficient approaches to reduce the risk of developing food allergies is of considerable interest. The aim of this study was to identify and select probiotic strains with preventive properties against allergies using a combination ofin vitroandin vivoapproaches. To that end, 31 strains of bifidobacteria and lactic acid bacteria were screened for their immunomodulatory properties in two cellular models, namely, human peripheral blood mononuclear cells (PBMCs) and T helper 2 (Th2)-skewed murine splenocytes. Six strains inducing a high interleukin-10 (IL-10)/IL-12p70 ratio and a low secretion of IL-4 on the two cellular models were selected, and their protective impact was testedin vivoin a murine model of food allergy to β-lactoglobulin. Three strains showed a protective impact on sensitization, with a decrease in allergen-specific IgE, and on allergy, with a decrease in mast cell degranulation. Analysis of the impact of these three strains on the T helper balance revealed different mechanisms of action. TheLactobacillus salivariusLA307 strain proved to block Th1 and Th2 responses, while theBifidobacterium longumsubsp.infantisLA308 strain induced a pro-Th1 profile and theLactobacillus rhamnosusLA305 strain induced pro-Th1 and regulatory responses. These results demonstrate that a combination ofin vitroandin vivoscreening is effective in probiotic strain selection and allowed identification of three novel probiotic strains that are active against sensitization in mice.

scholarly journals Antimalarial Activity of Small-Molecule Benzothiazole Hydrazones

2016 ◽  
Vol 60 (7) ◽  
pp. 4217-4228 ◽  
Author(s):  
Souvik Sarkar ◽  
Asim A. Siddiqui ◽  
Shubhra J. Saha ◽  
Rudranil De ◽  
Somnath Mazumder ◽  
...  
Keyword(s):  
Murine Model ◽  
Resistant Strain ◽  
Therapeutic Potential ◽  
Antimalarial Activity ◽  
Hematological Parameters ◽  
Plasmodium Yoelii ◽  
Multiple Drug ◽  
Content Type

ABSTRACTWe synthesized a new series of conjugated hydrazones that were found to be active against malaria parasitein vitro, as well asin vivoin a murine model. These hydrazones concentration-dependently chelated free iron and offered antimalarial activity. Upon screening of the synthesized hydrazones, compound 5f was found to be the most active iron chelator, as well as antiplasmodial. Compound 5f also interacted with free heme (KD[equilibrium dissociation constant] = 1.17 ± 0.8 μM), an iron-containing tetrapyrrole released after hemoglobin digestion by the parasite, and inhibited heme polymerization by parasite lysate. Structure-activity relationship studies indicated that a nitrogen- and sulfur-substituted five-membered aromatic ring present within the benzothiazole hydrazones might be responsible for their antimalarial activity. The dose-dependent antimalarial and heme polymerization inhibitory activities of the lead compound 5f were further validated by following [3H]hypoxanthine incorporation and hemozoin formation in parasite, respectively. It is worth mentioning that compound 5f exhibited antiplasmodial activityin vitroagainst a chloroquine/pyrimethamine-resistant strain ofPlasmodium falciparum(K1). We also evaluatedin vivoantimalarial activity of compound 5f in a murine model where a lethal multiple-drug-resistant strain ofPlasmodium yoeliiwas used to infect Swiss albino mice. Compound 5f significantly suppressed the growth of parasite, and the infected mice experienced longer life spans upon treatment with this compound. Duringin vitroandin vivotoxicity assays, compound 5f showed minimal alteration in biochemical and hematological parameters compared to control. In conclusion, we identified a new class of hydrazone with therapeutic potential against malaria.

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