scholarly journals The Helical Shape of Campylobacter jejuni PromotesIn VivoPathogenesis by Aiding Transit through Intestinal Mucus and Colonization of Crypts

2016 ◽  
Vol 84 (12) ◽  
pp. 3399-3407 ◽  
Author(s):  
Martin Stahl ◽  
Emilisa Frirdich ◽  
Jenny Vermeulen ◽  
Yuliya Badayeva ◽  
Xiaoxia Li ◽  
...  
Keyword(s):  
Mouse Model ◽  
Campylobacter Jejuni ◽  
Intestinal Inflammation ◽  
Critical Role ◽  
Bacterial Pathogen ◽  
Intestinal Lumen ◽  
Wild Type ◽  
Content Type ◽  
Intestinal Mucus ◽  
Straight Rod

Campylobacter jejuniis a helix-shaped enteric bacterial pathogen and a common cause of gastroenteritis. We recently developed a mouse model for this human pathogen utilizing the SIGIRR-deficient mouse strain, which exhibits significant intestinal inflammation in response to intestinalC. jejuniinfection. In the current study, this mouse model was used to define whetherC. jejuni's characteristic helical shape plays a role in its ability to colonize and elicit inflammation in the mouse intestine. Mice were infected with the previously characterized straight-rod Δpgp1and Δpgp2mutant strains, along with a newly characterized curved-rod Δ1228mutant strain. We also compared the resultant infections and pathology to those elicited by the helix-shaped wild-typeC. jejuniand complemented strains. Despite displaying wild-type colonization of the intestinal lumen, the straight-rod Δpgp1and Δpgp2mutants were essentially nonpathogenic, while all strains with a curved or helical shape retained their expected virulence. Furthermore, analysis ofC. jejunilocalization within the ceca of infected mice determined that the primary difference between the rod-shaped, nonpathogenic mutants and the helix-shaped, pathogenic strains was the ability to colonize intestinal crypts. Rod-shaped mutants appeared unable to colonize intestinal crypts due to an inability to pass through the intestinal mucus layer to directly contact the epithelium. Together, these results support a critical role forC. jejuni's helical morphology in enabling it to traverse and colonize the mucus-filled intestinal crypts of their host, a necessary step required to trigger intestinal inflammation in response toC. jejuni.

scholarly journals Critical Role of LuxS in the Virulence of Campylobacter jejuni in a Guinea Pig Model of Abortion

2011 ◽  
Vol 80 (2) ◽  
pp. 585-593 ◽  
Author(s):  
Paul Plummer ◽  
Orhan Sahin ◽  
Eric Burrough ◽  
Rachel Sippy ◽  
Kathy Mou ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Campylobacter Jejuni ◽  
Type Strain ◽  
Wild Type Strain ◽  
Critical Role ◽  
Wild Type ◽  
Direct Role ◽  
Content Type

ABSTRACTPrevious studies onCampylobacter jejunihave demonstrated the role of LuxS in motility, cytolethal distending toxin production, agglutination, and intestinal colonization; however, its direct involvement in virulence has not been reported. In this study, we demonstrate a direct role ofluxSin the virulence ofC. jejuniin two different animal hosts. The IA3902 strain, a highly virulent sheep abortion strain recently described by our laboratory, along with its isogenicluxSmutant andluxScomplement strains, was inoculated by the oral route into both a pregnant guinea pig virulence model and a chicken colonization model. In both cases, the IA3902luxSmutant demonstrated a complete loss of ability to colonize the intestinal tract. In the pregnant model, the mutant also failed to induce abortion, while the wild-type strain was highly abortifacient. Genetic complementation of theluxSgene fully restored the virulent phenotype in both models. Interestingly, when the organism was inoculated into guinea pigs by the intraperitoneal route, no difference in virulence (abortion induction) was observed between theluxSmutant and the wild-type strain, suggesting that the defect in virulence following oral inoculation is likely associated with a defect in colonization and/or translocation of the organism out of the intestine. These studies provide the first direct evidence that LuxS plays an important role in the virulence ofC. jejuniusing anin vivomodel of natural disease.

scholarly journals The Capsule Encoding the viaB Locus Reduces Interleukin-17 Expression and Mucosal Innate Responses in the Bovine Intestinal Mucosa during Infection with Salmonella enterica Serotype Typhi

2007 ◽  
Vol 75 (9) ◽  
pp. 4342-4350 ◽  
Author(s):  
Manuela Raffatellu ◽  
Renato L. Santos ◽  
Daniela Chessa ◽  
R. Paul Wilson ◽  
Sebastian E. Winter ◽  
...  
Keyword(s):  
Mouse Model ◽  
Salmonella Enterica ◽  
Intestinal Inflammation ◽  
Fluid Secretion ◽  
Interleukin 17 ◽  
Loop Model ◽  
Wild Type ◽  
Ileal Loop ◽  
Chemokine Production

ABSTRACT The viaB locus contains genes for the biosynthesis and export of the Vi capsular antigen of Salmonella enterica serotype Typhi. Wild-type serotype Typhi induces less CXC chemokine production in tissue culture models than does an isogenic viaB mutant. Here we investigated the in vivo relevance of these observations by determining whether the presence of the viaB region prevents inflammation in two animal models of gastroenteritis. Unlike S. enterica serotype Typhimurium, serotype Typhi or a serotype Typhi viaB mutant did not elicit marked inflammatory changes in the streptomycin-pretreated mouse model. In contrast, infection of bovine ligated ileal loops with a serotype Typhi viaB mutant resulted in more fluid accumulation and higher expression of the chemokine growth-related oncogene alpha (GROα) and interleukin-17 (IL-17) than did infection with the serotype Typhi wild type. There was a marked upregulation of IL-17 expression in both the bovine ligated ileal loop model and the streptomycin-pretreated mouse model, suggesting that this cytokine is an important component of the inflammatory response to infection with Salmonella serotypes. Introduction of the cloned viaB region into serotype Typhimurium resulted in a significant reduction of GROα and IL-17 expression and in reduced fluid secretion. Our data support the idea that the viaB region plays a role in reducing intestinal inflammation in vivo.

Two regulatory factors of Vibrio cholerae activating the mannose-sensitive haemagglutinin pilus expression is important for biofilm formation and colonization in mice

Microbiology ◽  
2021 ◽  
Vol 167 (10) ◽  
Author(s):  
Mengting Shi ◽  
Yue Zheng ◽  
Xianghong Wang ◽  
Zhengjia Wang ◽  
Menghua Yang
Keyword(s):  
Mouse Model ◽  
Vibrio Cholerae ◽  
Biofilm Formation ◽  
Type Species ◽  
Wild Type ◽  
Expression Library ◽  
Content Type ◽  
Genomic Expression ◽  
Infant Mouse ◽  
Link Type

Vibrio cholerae the causative agent of cholera, uses a large number of coordinated transcriptional regulatory events to transition from its environmental reservoir to the host intestine, which is its preferred colonization site. Transcription of the mannose-sensitive haemagglutinin pilus (MSHA), which aids the persistence of V. cholerae in aquatic environments, but causes its clearance by host immune defenses, was found to be regulated by a yet unknown mechanism during the infection cycle of V. cholerae . In this study, genomic expression library screening revealed that two regulators, VC1371 and VcRfaH, are able to positively activate the transcription of MSHA operon. VC1371 is localized and active in the cell membrane. Deletion of vc1371 or VcrfaH genes in V. cholerae resulted in less MshA protein production and less efficiency of biofilm formation compared to that in the wild-type strain. An adult mouse model showed that the mutants with vc1371 or VcrfaH deletion colonized less efficiently than the wild-type; the VcrfaH deletion mutant showed less colonization efficiency in the infant mouse model. The findings strongly suggested that the two regulators, namely VC1371 and VcRfaH, which are involved in the regulation of MSHA expression, play an important role in V. cholerae biofilm formation and colonization in mice.

scholarly journals Phagocytes from Mice Lacking the Sts Phosphatases Have an Enhanced Antifungal Response to Candida albicans

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
David Frank ◽  
Shamoon Naseem ◽  
Gian Luigi Russo ◽  
Cindy Li ◽  
Kaustubh Parashar ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Immune Response ◽  
Candida Albicans ◽  
Tyrosine Kinase ◽  
Critical Role ◽  
Inflammasome Activation ◽  
Wild Type ◽  
Content Type ◽  
Enhanced Production ◽  
Immunological Mechanisms

ABSTRACT Mice lacking expression of the homologous phosphatases Sts-1 and Sts-2 (Sts−/− mice) are resistant to disseminated candidiasis caused by the fungal pathogen Candida albicans. To better understand the immunological mechanisms underlying the enhanced resistance of Sts−/− mice, we examined the kinetics of fungal clearance at early time points. In contrast to the rapid C. albicans growth seen in normal kidneys during the first 24 h postinfection, we observed a reduction in kidney fungal CFU within Sts−/− mice beginning at 12 to 18 h postinfection. This corresponds to the time period when large numbers of innate leukocytes enter the renal environment to counter the infection. Because phagocytes of the innate immune system are important for host protection against pathogenic fungi, we evaluated responses of bone marrow leukocytes. Relative to wild-type cells, Sts−/− marrow monocytes and bone marrow-derived dendritic cells (BMDCs) displayed a heightened ability to inhibit C. albicans growth ex vivo. This correlated with significantly enhanced production of reactive oxygen species (ROS) by Sts−/− BMDCs downstream of Dectin-1, a C-type lectin receptor that plays a critical role in stimulating host responses to fungi. We observed no visible differences in the responses of other antifungal effector pathways, including cytokine production and inflammasome activation, despite enhanced activation of the Syk tyrosine kinase downstream of Dectin-1 in Sts−/− cells. Our results highlight a novel mechanism regulating the immune response to fungal infections. Further understanding of this regulatory pathway could aid the development of therapeutic approaches to enhance protection against invasive candidiasis. IMPORTANCE Systemic candidiasis caused by fungal Candida species is becoming an increasingly serious medical problem for which current treatment is inadequate. Recently, the Sts phosphatases were established as key regulators of the host antifungal immune response. In particular, genetic inactivation of Sts significantly enhanced survival of mice infected intravenously with Candida albicans. The Sts−/− in vivo resistance phenotype is associated with reduced fungal burden and an absence of inflammatory lesions. To understand the underlying mechanisms, we studied phagocyte responses. Here, we demonstrate that Sts−/− phagocytes have heightened responsiveness to C. albicans challenge relative to wild-type cells. Our data indicate the Sts proteins negatively regulate phagocyte activation via regulating selective elements of the Dectin-1–Syk tyrosine kinase signaling axis. These results suggest that phagocytes lacking Sts respond to fungal challenge more effectively and that this enhanced responsiveness partially underlies the profound resistance of Sts−/− mice to systemic fungal challenge.

scholarly journals An intestinally secreted host factor promotes microsporidia invasion of C. elegans

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Hala Tamim El Jarkass ◽  
Calvin Mok ◽  
Michael R Schertzberg ◽  
Andrew G Fraser ◽  
Emily R Troemel ◽  
...  
Keyword(s):  
Bacterial Pathogen ◽  
Oral Route ◽  
Intestinal Lumen ◽  
Wild Type ◽  
Parasite Invasion ◽  
Competitive Fitness ◽  
Obligate Intracellular ◽  
C Elegans ◽  
Fitness Advantage ◽  
Trade Offs

Microsporidia are ubiquitous obligate intracellular pathogens of animals. These parasites often infect hosts through an oral route, but little is known about the function of host intestinal proteins that facilitate microsporidia invasion. To identify such factors necessary for infection by Nematocida parisii, a natural microsporidian pathogen of Caenorhabditis elegans, we performed a forward genetic screen to identify mutant animals that have a Fitness Advantage with Nematocida (Fawn). We isolated four fawn mutants that are resistant to Nematocida infection and contain mutations in T14E8.4, which we renamed aaim-1 (Antibacterial and Aids invasion by Microsporidia). Expression of AAIM-1 in the intestine of aaim-1 animals restores N. parisii infectivity and this rescue of infectivity is dependent upon AAIM-1 secretion. N. parisii spores in aaim-1 animals are improperly oriented in the intestinal lumen, leading to reduced levels of parasite invasion. Conversely, aaim-1 mutants display both increased colonization and susceptibility to the bacterial pathogen Pseudomonas aeruginosa and overexpression of AAIM-1 reduces P. aeruginosa colonization. Competitive fitness assays show that aaim-1 mutants are favoured in the presence of N. parisii but disadvantaged on P. aeruginosa compared to wild type animals. Together, this work demonstrates how microsporidia exploits a secreted protein to promote host invasion. Our results also suggest evolutionary trade-offs may exist to optimizing host defense against multiple classes of pathogens.

scholarly journals Motility-Independent Formation of Antibiotic-TolerantPseudomonas aeruginosaAggregates

2019 ◽  
Vol 85 (14) ◽  
Author(s):  
Sally Demirdjian ◽  
Hector Sanchez ◽  
Daniel Hopkins ◽  
Brent Berwin
Keyword(s):  
Biofilm Formation ◽  
Bacterial Pathogen ◽  
Aggregate Formation ◽  
Flagellar Motility ◽  
Wild Type ◽  
Chronic Infections ◽  
Content Type ◽  
Temporal Adaptation ◽  
Bacterial Aggregates

ABSTRACTPseudomonas aeruginosais a bacterial pathogen that causes severe chronic infections in immunocompromised individuals. This bacterium is highly adaptable to its environments, which frequently select for traits that promote bacterial persistence. A clinically significant temporal adaptation is the formation of surface- or cell-adhered bacterial biofilms that are associated with increased resistance to immune and antibiotic clearance. Extensive research has shown that bacterial flagellar motility promotes formation of such biofilms, whereupon the bacteria subsequently become nonmotile. However, recent evidence shows that antibiotic-tolerant nonattached bacterial aggregates, distinct from surface-adhered biofilms, can form, and these have been reported in the context of lung infections, otitis media, nonhealing wounds, and soft tissue fillers. It is unclear whether the same bacterial traits are required for aggregate formation as for biofilm formation. In this report, using isogenic mutants, we demonstrate thatP. aeruginosaaggregates in liquid cultures are spontaneously formed independent of bacterial flagellar motility and independent of an exogenous scaffold. This contrasts with the role of the flagellum to initiate surface-adhered biofilms. Similarly to surface-attached biofilms, these aggregates exhibit increased antibiotic tolerance compared to planktonic cultures. These findings provide key insights into the requirements for aggregate formation that contrast with those for biofilm formation and that may have relevance for the persistence and dissemination of nonmotile bacteria found within chronic clinical infections.IMPORTANCEIn this work, we have investigated the role of bacterial motility with regard to antibiotic-tolerant bacterial aggregate formation. Previous work has convincingly demonstrated thatP. aeruginosaflagellar motility promotes the formation of surface-adhered biofilms in many systems. In contrast, aggregate formation byP. aeruginosawas observed for nonmotile but not for motile cells in the presence of an exogenous scaffold. Here, we demonstrate that both wild-typeP. aeruginosaand mutants that genetically lack motility spontaneously form antibiotic-tolerant aggregates in the absence of an exogenously added scaffold. Additionally, we also demonstrate that wild-type (WT) and nonmotileP. aeruginosabacteria can coaggregate, shedding light on potential physiological interactions and heterogeneity of aggregates.

scholarly journals VibA, a Homologue of a Transcription Factor for Fungal Heterokaryon Incompatibility, Is Involved in Antifungal Compound Production in the Plant-Symbiotic Fungus Epichloë festucae

2014 ◽  
Vol 14 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Jennifer T. Niones ◽  
Daigo Takemoto
Keyword(s):  
Transcription Factor ◽  
Antifungal Activity ◽  
Critical Role ◽  
Antifungal Compound ◽  
Symbiotic Association ◽  
Wild Type ◽  
Exogenous Dna ◽  
Content Type ◽  
Type Isolate ◽  
Epichloë Festucae

ABSTRACT Symbiotic association of epichloae endophytes ( Epichloë/Neotyphodium species) with cool-season grasses of the subfamily Pooideae confers bioprotective benefits to the host plants against abiotic and biotic stresses. While the production of fungal bioprotective metabolites is a well-studied mechanism of host protection from insect herbivory, little is known about the antibiosis mechanism against grass pathogens by the mutualistic endophyte. In this study, an Epichloë festucae mutant defective in antimicrobial substance production was isolated by a mutagenesis approach. In an isolated mutant that had lost antifungal activity, the exogenous DNA fragment was integrated into the promoter region of the vibA gene, encoding a homologue of the transcription factor VIB-1. VIB-1 in Neurospora crassa is a regulator of genes essential in vegetative incompatibility and promotion of cell death. Here we show that deletion of the vibA gene severely affected the antifungal activity of the mutant against the test pathogen Drechslera erythrospila . Further analyses showed that overexpressing vibA enhanced the antifungal activity of the wild-type isolate against test pathogens. Transformants overexpressing vibA showed an inhibitory activity on test pathogens that the wild-type isolate could not. Moreover, overexpressing vibA in a nonantifungal E. festucae wild-type Fl1 isolate enabled the transformant to inhibit the mycelial and spore germination of D. erythrospila . These results demonstrate that enhanced expression of vibA is sufficient for a nonantifungal isolate to obtain antifungal activity, implicating the critical role of VibA in antifungal compound production by epichloae endophytes.

scholarly journals SREBP-Dependent Triazole Susceptibility in Aspergillus fumigatus Is Mediated through Direct Transcriptional Regulation oferg11A(cyp51A)

2011 ◽  
Vol 56 (1) ◽  
pp. 248-257 ◽  
Author(s):  
Sara J. Blosser ◽  
Robert A. Cramer
Keyword(s):  
Aspergillus Fumigatus ◽  
Regulatory Element ◽  
Critical Role ◽  
Clinical Importance ◽  
Growth Defect ◽  
Ergosterol Biosynthesis ◽  
Wild Type ◽  
Transcript Levels ◽  
Content Type ◽  
Conditional Expression

ABSTRACTAs triazole antifungal drug resistance during invasiveAspergillus fumigatusinfection has become more prevalent, the need to understand mechanisms of resistance inA. fumigatushas increased. The presence of twoerg11(cyp51) genes inAspergillusspp. is hypothesized to account for the inherent resistance of this mold to the triazole fluconazole (FLC). Recently, anA. fumigatusnull mutant of a transcriptional regulator in the sterol regulatory element binding protein (SREBP) family, the ΔsrbAstrain, was found to have increased susceptibility to FLC and voriconazole (VCZ). In this study, we examined the mechanism engendering the observed increase inA. fumigatustriazole susceptibility in the absence of SrbA. We observed a significant reduction in theerg11Atranscript in the ΔsrbAstrain in response to FLC and VCZ. Transcript levels oferg11Bwere also reduced but not to the extent oferg11A. Interestingly,erg11Atranscript levels increased upon extended VCZ, but not FLC, exposure. Construction of anerg11Aconditional expression strain in the ΔsrbAstrain was able to restoreerg11Atranscript levels and, consequently, wild-type MICs to the triazole FLC. The VCZ MIC was also partially restored upon increasederg11Atranscript levels; however, total ergosterol levels remained significantly reduced compared to those of the wild type. Induction of theerg11Aconditional strain did not restore the hypoxia growth defect of the ΔsrbAstrain. Taken together, our results demonstrate a critical role for SrbA-mediated regulation of ergosterol biosynthesis and triazole drug interactions inA. fumigatusthat may have clinical importance.

scholarly journals ClpP is required for proteolytic regulation of type II toxin–antitoxin systems and persister cell formation in Streptococcus mutans

2019 ◽  
Vol 1 (8) ◽  
Author(s):  
Xiao-Lin Tian ◽  
Miao Li ◽  
Zachariah Scinocca ◽  
Heather Rutherford ◽  
Yung-Hua Li
Keyword(s):  
Streptococcus Mutans ◽  
Type Species ◽  
Critical Role ◽  
Cell Formation ◽  
Type Ii ◽  
Wild Type ◽  
Content Type ◽  
Link Type ◽  
Viability Assay ◽  
Persister Cell

The type II toxin–antitoxin (TA) modules, mazEF and relBE, in Streptococcus mutans have been implicated in stress response, antibiotic tolerance and persister cell formation. However, how S. mutans regulates these systems to prevent unwanted toxin activation and persister cell formation is unclear. In this study, we provide evidence that ClpP is required for the proteolytic regulation of these TA systems and persister cell formation in S. mutans following antibiotic challenge. A persister viability assay showed that S. mutans UA159 (WT) formed a larger quantity of persister cells than its isogenic mutant ΔclpP following antibiotic challenge. However, the lux reporter assay revealed that clpP deletion did not affect the transcriptional levels of mazEF and relBE, since no significant differences (P>0.05) in the reporter activities were detected between the wild-type and ΔclpP background. Instead, all antibiotics tested at a sub-minimum inhibitory concentration (sub-MIC) induced transcriptional levels of mazEF and relBE operons. We then examined the protein profiles of His-tagged MazE and RelB proteins in the UA159 and ΔclpP backgrounds by Western blotting analysis. The results showed that S. mutans strains grown under non-stress conditions expressed very low but detectable levels of MazE and RelB antitoxin proteins. Antibiotics at sub-MICs induced the levels of the MazE and RelB proteins, but the protein levels decreased rapidly in the wild-type background. In contrast, a stable level of MazE and RelB proteins could be detected in the ΔclpP mutant background, suggesting that both proteins accumulated in the ΔclpP mutant. We conclude that ClpP is required for the proteolytic regulation of cellular levels of the MazE and RelB antitoxins in S. mutans , which may play a critical role in modulating the TA activities and persister cell formation of this organism following antibiotic challenge.

scholarly journals Specific immune modulation of experimental colitis drives enteric alpha-synuclein accumulation and triggers age-related Parkinson-like brain pathology

2020 ◽  
Author(s):  
Stefan Grathwohl ◽  
Emmanuel Quansah ◽  
Nazia Maroof ◽  
Jennifer A Steiner ◽  
Liz Spycher ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Immune Modulation ◽  
Intestinal Inflammation ◽  
Critical Role ◽  
Experimental Colitis ◽  
Alpha Synuclein ◽  
Submucosal Plexus ◽  
Wild Type ◽  
Genetic Ablation ◽  
Dss Colitis

Abstract Background : Intraneuronal accumulation of a-synuclein (αSyn) is key in Parkinson’s disease (PD) pathogenesis. The pathogenic process is suggested to begin in the enteric nervous system decades before diagnosis of PD and then propagate into the brain. The triggers for these events are unclear but, in some patients, colitis might play a critical role. Methods : We administered lipopolysaccharide (LPS) or dextran sulfate sodium (DSS) to assess the effect of different types of experimental colitis on αSyn accumulation in the gut of αSyn transgenic and wild type mice and quantified local gene expression by RT-PCR and level of αSyn accumulation by immunofluorescence imaging. Immune modulation during the DSS colitis paradigm in the αSyn transgenic mice included genetic ablation of Cx3cr1 or treatment with recombinant IL-10. To determine long-term effects of experimental colitis, we induced DSS colitis in young αSyn transgenic mice and aged them under normal conditions up to nine or 21 months before analyzing their brains by immunohistochemistry. In vivo experiments were performed in randomized cohorts. Blinded experimenters performed image analysis and statistical analysis depended on data type (i.e., Student’s t-test, ANOVA, mixed-effects model). Results : We demonstrate that mild sustained or one strong insult of experimental DSS colitis triggers αSyn accumulation in the submucosal plexus of wild type and αSyn transgenic mice, while short-term mild DSS experimental colitis or inflammation induced by LPS does not have such an effect. Lack of macrophage-related Cx3cr1-signalling during DSS colitis increases accumulation of αSyn in the colonic submucosal plexus of αSyn transgenic mice while systemic treatment with immune-dampening IL-10 ameliorates this phenomenon. Additionally, DSS colitis-induced αSyn accumulation in young αSyn transgenic mice persists for months and is exacerbated by lack of Cx3cr1-signaling. Remarkably, experimental colitis at three months of age exacerbates the accumulation of aggregated phospho-Serine 129 αSyn in the midbrain (including the substantia nigra), in 21- but not 9-month-old αSyn transgenic mice. This increase in midbrain αSyn accumulation is accompanied by the loss of tyrosine hydroxylase-immunoreactive nigral neurons. Conclusions : Our data suggest that specific types of intestinal inflammation, mediated by monocyte/macrophage signaling, could play a critical role in the initiation and progression of PD.

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