scholarly journals Studies on the Antileishmanial Mechanism of Action of the Arylimidamide DB766: Azole Interactions and Role of CYP5122A1

2014 ◽  
Vol 58 (8) ◽  
pp. 4682-4689 ◽  
Author(s):  
Trupti Pandharkar ◽  
Xiaohua Zhu ◽  
Radhika Mathur ◽  
Jinmai Jiang ◽  
Thomas D. Schmittgen ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Mechanism Of Action ◽  
Leishmania Donovani ◽  
Synergistic Activity ◽  
Wild Type ◽  
Content Type ◽  
Axenic Amastigotes ◽  
Intracellular Parasites

ABSTRACTArylimidamides (AIAs) are inspired by diamidine antimicrobials but show superior activity against intracellular parasites. The AIA DB766 {2,5-bis[2-(2-i-propoxy)-4-(2-pyridylimino)aminophenyl]furan hydrochloride} displays outstanding potency against intracellularLeishmaniaparasites and is effective in murine and hamster models of visceral leishmaniasis when given orally, but its mechanism of action is unknown. In this study, through the use of continuous DB766 pressure, we raisedLeishmania donovaniaxenic amastigotes that displayed 12-fold resistance to this compound. These DB766-resistant (DB766R) parasites were 2-fold more sensitive to miltefosine than wild-type organisms and were hypersensitive to the sterol 14α-demethylase (CYP51) inhibitors ketoconazole and posaconazole (2,000-fold more sensitive and over 12,000-fold more sensitive than the wild type, respectively). Western blot analysis of DB766R parasites indicated that while expression of CYP51 is slightly increased in these organisms, expression of CYP5122A1, a recently identified cytochrome P450 associated with ergosterol metabolism inLeishmania, is dramatically reduced in DB766R parasites.In vitrosusceptibility assays demonstrated that CYP5122A1 half-knockoutL. donovanipromastigotes were significantly less susceptible to DB766 and more susceptible to ketoconazole than their wild-type counterparts, consistent with observations in DB766R parasites. Further, DB766-posaconazole combinations displayed synergistic activity in both axenic and intracellularL. donovaniamastigotes. Taken together, these studies implicate CYP5122A1 in the antileishmanial action of the AIAs and suggest that DB766-azole combinations are potential candidates for the development of synergistic antileishmanial therapy.

scholarly journals Fimbria-Encoding GeneyadCHas a Pleiotropic Effect on Several Biological Characteristics and Plays a Role in Avian Pathogenic Escherichia coli Pathogenicity

2015 ◽  
Vol 84 (1) ◽  
pp. 187-193 ◽  
Author(s):  
Renu Verma ◽  
Thaís Cabrera Galvão Rojas ◽  
Renato Pariz Maluta ◽  
Janaína Luisa Leite ◽  
Livia Pilatti Mendes da Silva ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Soft Agar ◽  
Pleiotropic Effect ◽  
Biological Characteristics ◽  
Wild Type ◽  
Content Type ◽  
Pathogenic Escherichia Coli

The extraintestinal pathogen termed avian pathogenicEscherichia coli(APEC) is known to cause colibacillosis in chickens. The molecular basis of APEC pathogenesis is not fully elucidated yet. In this work, we deleted a component of the Yad gene cluster (yadC) in order to understand the role of Yad in the pathogenicity of the APEC strain SCI-07.In vitro, the transcription level ofyadCwas upregulated at 41°C and downregulated at 22°C. TheyadCexpressionin vivowas more pronounced in lungs than in spleen, suggesting a role in the early steps of the infection. Chicks infected with the wild-type and mutant strains presented, respectively, 80% and 50% mortality rates. The ΔyadCstrain presented a slightly decreased ability to adhere to HeLa cells with or without thed-mannose analog compared with the wild type. Real-time PCR (RT-PCR) assays showed thatfimHwas downregulated (P< 0.05) andcsgAandecpAwere slightly upregulated in the mutant strain, showing thatyadCmodulates expression of other fimbriae. Bacterial internalization studies showed that the ΔyadCstrain had a lower number of intracellular bacteria recovered from Hep-2 cells and HD11 cells than the wild-type strain (P< 0.05). Motility assays in soft agar demonstrated that the ΔyadCstrain was less motile than the wild type (P< 0.01). Curiously, flagellum-associated genes were not dramatically downregulated in the ΔyadCstrain. Taken together, the results show that the fimbrial adhesin Yad contributes to the pathogenicity and modulates different biological characteristics of the APEC strain SCI-07.

scholarly journals Role of Cytosolic Glyceraldehyde-3-Phosphate Dehydrogenase in Visceral Organ Infection by Leishmania donovani

2012 ◽  
Vol 12 (1) ◽  
pp. 70-77 ◽  
Author(s):  
Wen-Wei Zhang ◽  
Laura-Isobel McCall ◽  
Greg Matlashewski
Keyword(s):  
Leishmania Donovani ◽  
Null Mutant ◽  
Wild Type ◽  
Visceral Organ ◽  
Content Type ◽  
Visceral Organs ◽  
Deficient Medium ◽  
Visceral Disease ◽  
Organ Infection

ABSTRACTThe initial 7 steps of the glycolytic pathway from glucose to 3-phosphoglycerate are localized in the glycosomes inLeishmania, including step 6, catalyzed by the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). InL. donovaniandL. mexicana, there exists a second GAPDH enzyme present in the cytosol that is absent inL. braziliensisand that has become a pseudogene inL. major.To investigate the role of the cytosolic GAPDH (cGAPDH), anL. donovanicGAPDH-null mutant was generated, and conversely, the functionalL. donovanicGAPDH was introduced intoL. majorand the resulting engineered parasites were characterized. TheL. donovanicGAPDH-null mutant was able to proliferate at the same rate as the wild-type parasite in glucose-deficient medium. However, in the presence of glucose, theL. donovanicGAPDH-null mutant consumed less glucose and proliferated more slowly than the wild-type parasite and displayed reduced infectivity in visceral organs of experimentally infected mice. This demonstrates that cGAPDH is functional inL. donovaniand is required for survival in visceral organs. Restoration of cGAPDH activity inL. major, in contrast, had an adverse effect onL. majorproliferation in glucose-containing medium, providing a possible explanation of why it has evolved into a pseudogene inL. major. This study indicates that there is a difference in glucose metabolism betweenL. donovaniandL. major, and this may represent an important factor in the ability ofL. donovanito cause visceral disease.

scholarly journals Role of Aspergillus fumigatus DvrA in Host Cell Interactions and Virulence

2010 ◽  
Vol 9 (10) ◽  
pp. 1432-1440 ◽  
Author(s):  
Daniele E. Ejzykowicz ◽  
Norma V. Solis ◽  
Fabrice N. Gravelat ◽  
Josee Chabot ◽  
Xuexian Li ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Type Strain ◽  
Wild Type Strain ◽  
Host Cells ◽  
Epithelial Cell Line ◽  
Wild Type ◽  
Content Type ◽  
Pulmonary Epithelial Cell

ABSTRACT The transcription factors that regulate Aspergillus fumigatus interactions with host cells and virulence are incompletely defined. We investigated the role of the putative C2H2 transcription factor DvrA in governing these processes. Although DvrA was identified by its limited homology to Candida albicans Bcr1, a ΔdvrA mutant strain of A. fumigatus had wild-type adherence to host constituents in vitro. However, it had increased capacity to damage both endothelial cells and a pulmonary epithelial cell line compared to the ability of the wild-type strain and a ΔdvrA::dvrA-complemented strain. This increase in damage required direct contact between the mutant and host cells. The ΔdvrA mutant also stimulated greater CCL20, interleukin-8, and tumor necrosis factor mRNA expression in a pulmonary epithelial cell line compared to levels induced by the control strains. Also, it was resistant to nikkomycin Z, suggesting an altered cell wall composition. As predicted by these in vitro results, the ΔdvrA mutant had increased virulence and stimulated a greater pulmonary inflammatory response than the wild-type strain and ΔdvrA::dvrA-complemented strains in the nonneutropenic mouse model of invasive pulmonary aspergillosis. These results indicate that DvrA influences A. fumigatus virulence as well as its capacity to damage host cells and stimulate a proinflammatory response.

scholarly journals New Insights into the Cyp51 Contribution to Azole Resistance in Aspergillus Section Nigri

2019 ◽  
Vol 63 (7) ◽  
Author(s):  
Alba Pérez-Cantero ◽  
Loida López-Fernández ◽  
Josep Guarro ◽  
Javier Capilla
Keyword(s):  
Resistance Mechanisms ◽  
Azole Resistance ◽  
Wild Type ◽  
Severe Condition ◽  
Content Type ◽  
Recommended Treatment ◽  
Highly Active ◽  
Expression Studies

ABSTRACT Invasive aspergillosis (IA) is a severe condition mainly caused by Aspergillus fumigatus, although other species of the genus, such as section Nigri members, can also be involved. Voriconazole (VRC) is the recommended treatment for IA; however, the prevalence of azole-resistant Aspergillus isolates has alarmingly increased in recent years, and the underlying resistance mechanisms in non-fumigatus species remain unclear. We have determined the in vitro susceptibility of 36 strains from section Nigri to VRC, posaconazole (POS), and itraconazole (ITC), and we have explored the role of Cyp51A and Cyp51B, both targets of azoles, in azole resistance. The three drugs were highly active; POS displayed the best in vitro activity, while ITC and VRC showed MICs above the established epidemiological cutoff values in 9 and 16% of the strains, respectively. Furthermore, expression studies of cyp51A and cyp51B in control condition and after VRC exposure were performed in 14 strains with different VRC susceptibility. We found higher transcription of cyp51A, which was upregulated upon VRC exposure, but no correlation between MICs and cyp51 transcription levels was observed. In addition, cyp51A sequence analyses revealed nonsynonymous mutations present in both, wild-type and non-wild-type strains of A. niger and A. tubingensis. Nevertheless, a few mutations were exclusively present in non-wild-type A. tubingensis strains. Altogether, our results suggest that azole resistance in section Nigri is not clearly explained by Cyp51A protein alteration or by cyp51 gene upregulation, which indicates that other mechanisms might be involved.

scholarly journals Characterization of Stress and Innate Immunity Resistance of Wild-Type and Δp66 Borrelia burgdorferi

2017 ◽  
Vol 86 (2) ◽  
Author(s):  
Michael W. Curtis ◽  
Beth L. Hahn ◽  
Kai Zhang ◽  
Chunhao Li ◽  
Richard T. Robinson ◽  
...  
Keyword(s):  
Borrelia Burgdorferi ◽  
Antimicrobial Peptide ◽  
Membrane Integrity ◽  
The United States ◽  
Laboratory Model ◽  
Wild Type ◽  
Content Type ◽  
Inoculation Site

ABSTRACTBorrelia burgdorferiis a causative agent of Lyme disease, the most common arthropod-borne disease in the United States.B. burgdorferievades host immune defenses to establish a persistent, disseminated infection. Previous work showed that P66-deficientB. burgdorferi(Δp66) is cleared quickly after inoculation in mice. We demonstrate that the Δp66strain is rapidly cleared from the skin inoculation site prior to dissemination. The rapid clearance of Δp66bacteria is not due to inherent defects in multiple properties that might affect infectivity: bacterial outer membrane integrity, motility, chemotactic response, or nutrient acquisition. This led us to the hypothesis that P66 has a role in mouse cathelicidin-related antimicrobial peptide (mCRAMP; a major skin antimicrobial peptide) and/or neutrophil evasion. Neither wild-type (WT) nor Δp66 B. burgdorferiwas susceptible to mCRAMP. To examine the role of neutrophil evasion, we administered neutrophil-depleting antibody anti-Ly6G (1A8) to C3H/HeN mice and subsequently monitored the course ofB. burgdorferiinfection. Δp66mutants were unable to establish infection in neutrophil-depleted mice, suggesting that the important role of P66 during early infection is through another mechanism. Neutrophil depletion did not affect WTB. burgdorferibacterial burdens in the skin (inoculation site), ear, heart, or tibiotarsal joint at early time points postinoculation. This was unexpected given that priorin vitrostudies demonstrated neutrophils phagocytose and killB. burgdorferi. These data, together with our previous work, suggest that despite thein vitroability of host innate defenses to killB. burgdorferi, individual innate immune mechanisms have limited contributions to controlling earlyB. burgdorferiinfection in the laboratory model used.

scholarly journals Role of Klebsiella pneumoniae Type 1 and Type 3 Fimbriae in Colonizing Silicone Tubes Implanted into the Bladders of Mice as a Model of Catheter-Associated Urinary Tract Infections

2013 ◽  
Vol 81 (8) ◽  
pp. 3009-3017 ◽  
Author(s):  
Caitlin N. Murphy ◽  
Martin S. Mortensen ◽  
Karen A. Krogfelt ◽  
Steven Clegg
Keyword(s):  
Urinary Tract ◽  
Klebsiella Pneumoniae ◽  
Urinary Tract Infections ◽  
Wild Type ◽  
Content Type ◽  
Tract Infections ◽  
Type 3

ABSTRACTCatheter-associated urinary tract infections are biofilm-mediated infections that cause a significant economic and health burden in nosocomial environments. Using a newly developed murine model of this type of infection, we investigated the role of fimbriae in implant-associated urinary tract infections by the Gram-negative bacteriumKlebsiella pneumoniae, which is a proficient biofilm former and a commonly isolated nosocomial pathogen. Studies have shown that type 1 and type 3 fimbriae are involved in attachment and biofilm formationin vitro, and these fimbrial types are suspected to be important virulence factors during infection. To test this hypothesis, the virulence of fimbrial mutants was assessed in independent challenges in which mouse bladders were inoculated with the wild type or a fimbrial mutant and in coinfection studies in which the wild type and fimbrial mutants were inoculated together to assess the results of a direct competition in the urinary tract. Using these experiments, we were able to show that both fimbrial types serve to enhance colonization and persistence. Additionally, a double mutant had an additive colonization defect under some conditions, indicating that both fimbrial types have unique roles in the attachment and persistence in the bladder and on the implant itself. All of these mutants were outcompeted by the wild type in coinfection experiments. Using these methods, we are able to show that type 1 and type 3 fimbriae are important colonization factors in the murine urinary tract when an implanted silicone tube is present.

scholarly journals Role of Sca2 and RickA in the Dissemination ofRickettsia parkeriinAmblyomma maculatum

2018 ◽  
Vol 86 (6) ◽  
Author(s):  
Emma K. Harris ◽  
Krit Jirakanwisal ◽  
Victoria I. Verhoeve ◽  
Chanida Fongsaran ◽  
Chanakan Suwanbongkot ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Actin Polymerization ◽  
Dependent Manner ◽  
Wild Type ◽  
Cell Infection ◽  
Rickettsia Parkeri ◽  
Content Type ◽  
Tick Infection

ABSTRACTThe Gram-negative obligate intracellular bacteriumRickettsia parkeriis an emerging tick-borne human pathogen. Recently,R. parkeriSca2 and RickA have been implicated in adherence and actin-based motility in vertebrate host cell infection models; however, the rickettsia-derived factors essential to tick infection are unknown. UsingR. parkerimutants lacking functional Sca2 or RickA to compare actin polymerization, replication, and cell-to-cell spreadin vitro, similar phenotypes in tick and mammalian cells were observed. Specifically, actin polymerization in cultured tick cells is controlled by the two separate proteins in a time-dependent manner. To assess the role of Sca2 and RickA in dissemination in the tick host,Rickettsia-freeAmblyomma maculatum, the natural vector ofR. parkeri, was exposed to wild-type,R. parkeri rickA::tn, orR. parkeri sca2::tnbacteria, and individual tick tissues, including salivary glands, midguts, ovaries, and hemolymph, were analyzed at 12 h and after continued bloodmeal acquisition for 3 or 7 days postexposure. Initially, ticks exposed to wild-typeR. parkerihad the highest rickettsial load across all organs; however, rickettsial loads decreased and wild-type rickettsiae were cleared from the ovaries at 7 days postexposure. In contrast, ticks exposed toR. parkeririckA::tnorR. parkerisca2::tnhad comparatively lower rickettsial loads, but bacteria persisted in all organs for 7 days. These data suggest that while RickA and Sca2 function in actin polymerization in tick cells, the absence of these proteins did not change dissemination patterns within the tick vector.

scholarly journals In VitroActivity of Imipenem-Relebactam Alone or in Combination with Amikacin or Colistin againstPseudomonas aeruginosa

2019 ◽  
Vol 63 (9) ◽  
Author(s):  
Tomefa E. Asempa ◽  
David P. Nicolau ◽  
Joseph L. Kuti
Keyword(s):  
Potential Role ◽  
Multidrug Resistant ◽  
Synergistic Activity ◽  
Content Type ◽  
Class A ◽  
Susceptible Isolate ◽  
Time Kill ◽  
Lactamase Inhibitor

ABSTRACTRelebactam is a novel class A/C β-lactamase inhibitor that restores imipenemin vitroactivity against multidrug-resistant and carbapenem-nonsusceptiblePseudomonas aeruginosa. Time-kill analyses were performed to evaluate the potential role of imipenem-relebactam in combination with amikacin or colistin againstP. aeruginosa. Ten clinicalP. aeruginosaisolates (9 imipenem nonsusceptible) with imipenem-relebactam MICs ranging from 1/4 to 8/4 μg/ml were included. The isolates had varied susceptibilities to imipenem (1 to 32 μg/ml), amikacin (4 to 128 μg/ml), and colistin (0.5 to 1 μg/ml). Duplicate 24-h time-kill studies were conducted using the average steady-state concentrations (Cssavg) observed after the administration of imipenem-relebactam at 500 mg/250 mg every 6 hours (q6h) alone and in combination with theCssavgof 25 mg/kg of body weight/day amikacin and 360 mg/day colistin in humans. Imipenem-relebactam alone resulted in 24-h bacterial densities of −2.93 ± 0.38, −1.67 ± 0.29, +0.38 ± 0.96, and +0.15 ± 0.65 log10CFU/ml at imipenem-relebactam MICs of 1/4, 2/4, 4/4, and 8/4 μg/ml, respectively. No synergy was demonstrated against the single imipenem-susceptible isolate. Against the imipenem-nonsusceptible isolates (n = 9), imipenem-relebactam combined with amikacin resulted in synergy (−2.61 ± 1.50 log10CFU/ml) against all amikacin-susceptible isolates and in two of three amikacin-intermediate (i.e., MIC, 32 μg/ml) isolates (−2.06 ± 0.19 log10CFU/ml). Synergy with amikacin was not observed when the amikacin MIC was >32 μg/ml. Imipenem-relebactam combined with colistin demonstrated synergy in eight out of the nine imipenem-resistant isolates (−3.17 ± 1.00 log10CFU/ml). Against these 10 P. aeruginosaisolates, imipenem-relebactam combined with either amikacin or colistin resulted in synergistic activity against the majority of strains. Further studies evaluating combination therapy with imipenem-relebactam are warranted.

scholarly journals Competition and Resilience between Founder and Introduced Bacteria in the Caenorhabditis elegans Gut

2011 ◽  
Vol 80 (3) ◽  
pp. 1288-1299 ◽  
Author(s):  
Cynthia Portal-Celhay ◽  
Martin J. Blaser
Keyword(s):  
Caenorhabditis Elegans ◽  
Wild Type ◽  
Content Type ◽  
E Coli ◽  
C Elegans ◽  
Serovar Typhimurium ◽  
Colonization Factors

The microbial communities that reside within the intestinal tract in vertebrates are complex and dynamic. In this report, we establish the utility ofCaenorhabditis elegansas a model system for identifying the factors that contribute to bacterial persistence and for host control of gut luminal populations. We found that for N2 worms grown on mixed lawns of bacteria,Salmonella entericaserovar Typhimurium substantially outcompetedEscherichia coli, even whenE. coliwas initially present at 100-fold-higher concentrations. To address whether innate immunity affects the competition, thedaf-2anddaf-16mutants were studied; their total gut bacterial levels reflect overall capacity for colonization, butSalmonellaoutcompetedE. colito an extent similar to wild-type worms. To address the role of virulence properties,SalmonellaΔspi-1Δspi-2was used to compete withE. coli. The net differential was significantly less than that for wild-typeSalmonella; thus,spi-1 spi-2encodesC. eleganscolonization factors. AnE. colistrain with repeatedin vivopassage had an enhanced ability to compete against anin vitro-passedE. colistrain and againstSalmonella. Our data provide evidence of active competition for colonization niches in theC. elegansgut, as determined by bacterial factors and subject toin vivoselection.

Stigmasterol as a potential biomarker for amphotericin B resistance in Leishmania donovani

2019 ◽  
Vol 75 (4) ◽  
pp. 942-950 ◽  
Author(s):  
Ruby Bansal ◽  
Shib Sankar Sen ◽  
Rohini Muthuswami ◽  
Rentala Madhubala
Keyword(s):  
Visceral Leishmaniasis ◽  
Amphotericin B ◽  
Resistant Strain ◽  
Drug Targets ◽  
Leishmania Donovani ◽  
New Drugs ◽  
Axenic Amastigotes ◽  
Potential Biomarker

Abstract Background Leishmania donovani, a protozoan parasite, is the primary causative agent for visceral leishmaniasis. Toxicity and increased resistance to existing drugs have led to an urgent need for identifying new drugs and drug targets. Understanding the risks and mechanisms of resistance is of great importance. Amphotericin B (AmB) is a polyene antimicrobial, the mainstay therapy for visceral leishmaniasis in several parts of India. Objectives In the present study, we established a line of AmB-resistant L. donovani promastigotes in vitro and demonstrated the molecular basis of resistance to AmB. Methods AmB-resistant promastigotes were generated and characterized to evaluate the mechanism of resistance to AmB. We examined the sterol composition of the promastigotes and the axenic amastigotes derived from the WT and AmB-resistant promastigotes. The role of the plant-like C-22 desaturase responsible for stigmasterol production was also evaluated in the AmB-resistant strain. Results The IC50 for resistant cells was four times higher than for the WT. AmB-resistant promastigotes showed an increase in the conversion of β-sitosterol into stigmasterol. The presence of higher amounts of stigmasterol in resistant promastigotes, as well as in axenic amastigotes, signifies its role in AmB resistance in Leishmania. The resistant strain showed reduced infectivity in vitro. Conclusions We have elucidated the mode of action and resistance mechanisms to the drug. However, further work is required to validate the potential role of stigmasterol in resistance and to help develop a diagnostic kit that can assist in diagnosing potentially resistant lines in the field.

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