scholarly journals Salmonella enterica Serovar Kentucky Flagella Are Required for Broiler Skin Adhesion and Caco-2 Cell Invasion

2016 ◽  
Vol 83 (2) ◽  
Author(s):  
Sanaz Salehi ◽  
Kevin Howe ◽  
Mark L. Lawrence ◽  
John P. Brooks ◽  
R. Hartford Bailey ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Flagellar Motor ◽  
Structural Genes ◽  
Wild Type ◽  
Content Type ◽  
Flagellar Assembly ◽  
Adhesion And Invasion

ABSTRACT Nontyphoidal Salmonella strains are the main source of pathogenic bacterial contamination in the poultry industry. Recently, Salmonella enterica serovar Kentucky has been recognized as the most prominent serovar on carcasses in poultry-processing plants. Previous studies showed that flagella are one of the main factors that contribute to bacterial attachment to broiler skin. However, the precise role of flagella and the mechanism of attachment are unknown. There are two different flagellar subunits (fliC and fljB) expressed alternatively in Salmonella enterica serovars using phase variation. Here, by making deletions in genes encoding flagellar structural subunits (flgK, fliC, and fljB), and flagellar motor (motA), we were able to differentiate the role of flagella and their rotary motion in the colonization of broiler skin and cellular attachment. Utilizing a broiler skin assay, we demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the alternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate tight attachment. Deletion of the flgK gene prevents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S. Kentucky with deletions in all three structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while an fljB mutant was as adherent and invasive as the wild-type strain. IMPORTANCE In this work, we answered clearly the role of flagella in S. Kentucky attachment to the chicken skin and Caco-2 cells. We demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the alternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate strong attachment. Deletion of the flgK gene prevents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S. Kentucky with deletions in all three structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while an fljB mutant was as adherent and invasive as the wild-type strain. We expect these results will contribute to the understanding of the mechanisms of Salmonella attachment to food products.

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 Temperature-Sensitive Salmonella enterica Serovar Enteritidis PT13a Expressing Essential Proteins of Psychrophilic Bacteria

2015 ◽  
Vol 81 (19) ◽  
pp. 6757-6766 ◽  
Author(s):  
Barry N. Duplantis ◽  
Stephanie M. Puckett ◽  
Everett L. Rosey ◽  
Keith A. Ameiss ◽  
Angela D. Hartman ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Phage Type ◽  
The Body ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Wild Type ◽  
Psychrophilic Bacteria ◽  
Content Type

ABSTRACTSynthetic genes based on deduced amino acid sequences of the NAD-dependent DNA ligase (ligA) and CTP synthetase (pyrG) of psychrophilic bacteria were substituted for their native homologues in the genome ofSalmonella entericaserovar Enteritidis phage type 13a (PT13a). The resulting strains were rendered temperature sensitive (TS) and did not revert to temperature resistance at a detectable level. At permissive temperatures, TS strains grew like the parental strain in broth medium and in macrophage-like cells, but their growth was slowed or stopped when they were shifted to a restrictive temperature. When injected into BALB/c mice at the base of the tail, representing a cool site of the body, the strains with restrictive temperatures of 37, 38.5, and 39°C persisted for less than 1 day, 4 to 7 days, and 20 to 28 days, respectively. The wild-type strain persisted at the site of inoculation for at least 28 days. The wild-type strain, but not the TS strains, was also found in spleen-plus-liver homogenates within 1 day of inoculation of the tail and was detectable in these organs for at least 28 days. Intramuscular vaccination of White Leghorn chickens with the PT13a strain carrying the psychrophilicpyrGgene provided some protection against colonization of the reproductive tract and induced an anti-S. entericaantibody response.

scholarly journals Characterization and Evaluation of a Salmonella enterica Serotype Senftenberg Mutant Created by Deletion of Virulence-Related Genes for Use as a Live Attenuated Vaccine

2016 ◽  
Vol 23 (10) ◽  
pp. 802-812 ◽  
Author(s):  
Nitin M. Kamble ◽  
John Hwa Lee
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Protective Efficacy ◽  
Control Group ◽  
Intestinal Loop ◽  
Wild Type ◽  
Exchange Method ◽  
Content Type

ABSTRACTNatural infections of chickens withSalmonella entericasubsp.entericaserovar Senftenberg (S.Senftenberg) are characterized by low-level intestinal invasiveness and insignificant production of antibodies. In this study, we investigated the potential effects oflonandcpxRgene deletions on the invasiveness ofS. Senftenberg into the intestinal epithelium of chickens and its ability to induce an immune response, conferring protection againstS. Senftenberg infection. With the allelic exchange method, we developed JOL1596 (Δlon), JOL1571 (ΔcpxR), and JOL1587 (ΔlonΔcpxR) deletion mutants from wild-typeS. Senftenberg. Deletion of thelongene fromS. Senftenberg produced increased frequency of elongated cells, with significantly greater amounts of exopolysaccharide (EPS) than in thecpxR-deleted strain and the wild-type strain. Thein vivointestinal loop invasion assay showed a significant increase in epithelial invasiveness for JOL1596 (Δlon) and JOL1587 (ΔlonΔcpxR), compared to JOL1571 (ΔcpxR) and the wild-type strain. Furthermore, theS. Senftenberg wild-type and mutant strains were internalized at high levels inside activated abdominal macrophages from chicken. Thein vivoinoculation of JOL1587 (ΔlonΔcpxR) into chickens led to colonization of the liver, spleen, and cecum for a short time. Chickens inoculated with JOL1587 (ΔlonΔcpxR) showed significant increases in humoral, mucosal, and cellular immune responses specific toS. Senftenberg antigens. Postchallenge, compared to the control group, the JOL1587 (ΔlonΔcpxR)-inoculated chickens showed not only lower persistence but also faster clearance of wild-typeS. Senftenberg from the cecum. We conclude that the increased intestinal invasiveness and colonization of internal organs exhibited by JOL1587 (ΔlonΔcpxR) led to the establishment of immunogenicity and conferred protective efficacy againstS. Senftenberg infections in chickens.

scholarly journals Virulence Traits of a Serogroup C Meningococcus and IsogeniccssAMutant, Defective in Surface-Exposed Sialic Acid, in a Murine Model of Meningitis

2019 ◽  
Vol 87 (4) ◽  
Author(s):  
Roberta Colicchio ◽  
Chiara Pagliuca ◽  
Susanna Ricci ◽  
Elena Scaglione ◽  
Denis Grandgirard ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Corpus Callosum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Lethal Dose ◽  
Sialic Acids ◽  
Wild Type ◽  
Knockout Mutant ◽  
Content Type

ABSTRACTIn serogroup CNeisseria meningitidis, thecssA(siaA) gene codes for an UDP-N-acetylglucosamine 2-epimerase that catalyzes the conversion of UDP-N-acetyl-α-d-glucosamine intoN-acetyl-d-mannosamine and UDP in the first step in sialic acid biosynthesis. This enzyme is required for the biosynthesis of the (α2→9)-linked polysialic acid capsule and for lipooligosaccharide (LOS) sialylation. In this study, we have used a reference serogroup C meningococcal strain and an isogeniccssAknockout mutant to investigate the pathogenetic role of surface-exposed sialic acids in a model of meningitis based on intracisternal inoculation of BALB/c mice. Results confirmed the key role of surface-exposed sialic acids in meningococcal pathogenesis. The 50% lethal dose (LD50) of the wild-type strain 93/4286 was about four orders of magnitude lower than that of thecssAmutant. Compared to the wild-type strain, the ability of this mutant to replicate in brain and spread systemically was severely impaired. Evaluation of brain damage evidenced a significant reduction in cerebral hemorrhages in mice infected with the mutant in comparison with the levels in those challenged with the wild-type strain. Histological analysis showed the typical features of bacterial meningitis, including inflammatory cells in the subarachnoid, perivascular, and ventricular spaces especially in animals infected with the wild type. Noticeably, 80% of mice infected with the wild-type strain presented with massive bacterial localization and accompanying inflammatory infiltrate in thecorpus callosum, indicating high tropism of meningococci exposing sialic acids toward this brain structure and a specific involvement of thecorpus callosumin the mouse model of meningococcal meningitis.

scholarly journals The RNA Chaperone Hfq Promotes Fitness of Actinobacillus pleuropneumoniae during Porcine Pleuropneumonia

2013 ◽  
Vol 81 (8) ◽  
pp. 2952-2961 ◽  
Author(s):  
Sargurunathan Subashchandrabose ◽  
Rhiannon M. Leveque ◽  
Roy N. Kirkwood ◽  
Matti Kiupel ◽  
Martha H. Mulks
Keyword(s):  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Actinobacillus Pleuropneumoniae ◽  
Wild Type ◽  
Content Type ◽  
Porcine Pleuropneumonia ◽  
Porcine Lungs

ABSTRACTActinobacillus pleuropneumoniaeis the etiological agent of porcine pleuropneumonia, an economically important disease of pigs. Thehfqgene inA. pleuropneumoniae, encoding the RNA chaperone and posttranscriptional regulator Hfq, is upregulated during infection of porcine lungs. To investigate the role of thisin vivo-induced gene inA. pleuropneumoniae, anhfqmutant strain was constructed. Thehfqmutant was defective in biofilm formation on abiotic surfaces. The level ofpgaCtranscript, encoding the biosynthesis of poly-β-1,6-N-acetylglucosamine (PNAG), a major biofilm matrix component, was lower and PNAG content was 10-fold lower in thehfqmutant than in the wild-type strain. When outer membrane proteins were examined, cysteine synthase, implicated in resistance to oxidative stress and tellurite, was not found at detectable levels in the absence of Hfq. Thehfqmutant displayed enhanced sensitivity to superoxide generated by methyl viologen and tellurite. These phenotypes were readily reversed by complementation with thehfqgene expressed from its native promoter. The role of Hfq in the fitness ofA. pleuropneumoniaewas assessed in a natural host infection model. Thehfqmutant failed to colonize porcine lungs and was outcompeted by the wild-type strain (median competitive index of 2 × 10−5). Our data demonstrate that thein vivo-induced genehfqis involved in the regulation of PNAG-dependent biofilm formation, resistance to superoxide stress, and the fitness and virulence ofA. pleuropneumoniaein pigs and begin to elucidate the role of anin vivo-induced gene in the pathogenesis of pleuropneumonia.

scholarly journals Role of Mrx Fimbriae of Xenorhabdus nematophila in Competitive Colonization of the Nematode Host

2011 ◽  
Vol 77 (20) ◽  
pp. 7247-7254 ◽  
Author(s):  
Holly Snyder ◽  
Hongjun He ◽  
Heather Owen ◽  
Chris Hanna ◽  
Steven Forst
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Infective Juvenile ◽  
Xenorhabdus Nematophila ◽  
Wild Type ◽  
Content Type ◽  
Mutant Strains ◽  
Phenotypic Variant

ABSTRACTXenorhabdus nematophilaengages in mutualistic associations with the infective juvenile (IJ) stage of specific entomopathogenic nematodes. Mannose-resistant (Mrx) chaperone-usher-type fimbriae are produced when the bacteria are grown on nutrient broth agar (NB agar). The role of Mrx fimbriae in the colonization of the nematode host has remained unresolved. We show thatX. nematophilagrown on LB agar produced flagella rather than fimbriae. IJs propagated onX. nematophilagrown on LB agar were colonized to the same extent as those propagated on NB agar. Further, progeny IJs were normally colonized bymrxmutant strains that lacked fimbriae both when bacteria were grown on NB agar and when coinjected into the insect host with aposymbiotic nematodes. Themrxstrains were not competitively defective for colonization when grown in the presence of wild-type cells on NB agar. In addition, a phenotypic variant strain that lacked fimbriae colonized as well as the wild-type strain. In contrast, themrxstrains displayed a competitive colonization defectin vivo. IJ progeny obtained from insects injected with comixtures of nematodes carrying either the wild-type or themrxstrain were colonized almost exclusively with the wild-type strain. Likewise, when insects were coinjected with aposymbiotic IJs together with a comixture of the wild-type andmrxstrains, the resulting IJ progeny were predominantly colonized with the wild-type strain. These results revealed that Mrx fimbriae confer a competitive advantage during colonizationin vivoand provide new insights into the role of chaperone-usher fimbriae in the life cycle ofX. nematophila.

scholarly journals Identification of the Amidotransferase AsnB1 as Being Responsible formeso-Diaminopimelic Acid Amidation in Lactobacillus plantarum Peptidoglycan

2011 ◽  
Vol 193 (22) ◽  
pp. 6323-6330 ◽  
Author(s):  
Elvis Bernard ◽  
Thomas Rolain ◽  
Pascal Courtin ◽  
Pascal Hols ◽  
Marie-Pierre Chapot-Chartier
Keyword(s):  
Lactobacillus Plantarum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Bacterial Species ◽  
Critical Role ◽  
Innate Immune ◽  
Diaminopimelic Acid ◽  
Wild Type ◽  
Content Type

The peptidoglycan (PG) ofLactobacillus plantarumcontains amidatedmeso-diaminopimelic acid (mDAP). The functional role of this PG modification has never been characterized in any bacterial species, except for its impact on PG recognition by receptors of the innate immune system.In silicoanalysis of loci carrying PG biosynthesis genes in theL. plantarumgenome revealed the colocalization of themurEgene, which encodes the ligase catalyzing the addition of mDAP to UDP-N-muramoyl-d-glutamate PG precursors, withasnB1, which encodes a putative asparagine synthase with an N-terminal amidotransferase domain. By gene disruption and complementation experiments, we showed thatasnB1is the amidotransferase involved in mDAP amidation. PG structural analysis revealed that mDAP amidation plays a key role in the control of thel,d-carboxypeptidase DacB activity. In addition, a mutant strain with a defect in mDAP amidation is strongly affected in growth and cell morphology, with filamentation and cell chaining, while a DacB-negative strain displays a phenotype very similar to that of a wild-type strain. These results suggest that mDAP amidation may play a critical role in the control of the septation process.

scholarly journals The Homolog of the Gene bstA of the BTP1 Phage from Salmonella enterica Serovar Typhimurium ST313 Is an Antivirulence Gene in Salmonella enterica Serovar Dublin

2017 ◽  
Vol 86 (1) ◽  
Author(s):  
Ana Herrero-Fresno ◽  
Irene Cartas Espinel ◽  
Malene Roed Spiegelhauer ◽  
Priscila Regina Guerra ◽  
Karsten Wiber Andersen ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Luria Bertani ◽  
Wild Type ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Cattle Blood

ABSTRACTIn a previous study, a novel virulence gene,bstA, identified in aSalmonella entericaserovar Typhimurium sequence type 313 (ST313) strain was found to be conserved in all publishedSalmonella entericaserovar Dublin genomes. In order to analyze the role of this gene in the host-pathogen interaction inS. Dublin, a mutant where this gene was deleted (S. Dublin ΔbstA) and a mutant which was further genetically complemented withbstA(S. Dublin 3246-C) were constructed and tested in models ofin vitroandin vivoinfection as well as during growth competition assays in M9 medium, Luria-Bertani broth, and cattle blood. In contrast to the results obtained for a strain ofS. Typhimurium ST313, the lack ofbstAwas found to be associated with increased virulence inS. Dublin. Thus,S. Dublin ΔbstAshowed higher levels of uptake than the wild-type strain during infection of mouse and cattle macrophages and higher net replication within human THP-1 cells. Furthermore, during mouse infections,S. Dublin ΔbstAwas more virulent than the wild type following a single intraperitoneal infection and showed an increased competitive index during competitive infection assays. Deletion ofbstAdid not affect either the amount of cytokines released by THP-1 macrophages or the cytotoxicity toward these cells. The histology of the livers and spleens of mice infected with the wild-type strain and theS. Dublin ΔbstAmutant revealed similar levels of inflammation between the two groups. The gene was not important for adherence to or invasion of human epithelial cells and did not influence bacterial growth in rich medium, minimal medium, or cattle blood. In conclusion, a lack ofbstAaffects the pathogenicity ofS. Dublin by decreasing its virulence. Therefore, it might be regarded as an antivirulence gene in this serovar.

scholarly journals Role of Aspergillus lentulus 14-α Sterol Demethylase (Cyp51A) in Azole Drug Susceptibility

2011 ◽  
Vol 55 (12) ◽  
pp. 5459-5468 ◽  
Author(s):  
Emilia Mellado ◽  
Laura Alcazar-Fuoli ◽  
Manuel Cuenca-Estrella ◽  
Juan L. Rodriguez-Tudela
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Gene Knockout ◽  
Corticosteroid Treatment ◽  
Drug Susceptibility ◽  
Wild Type ◽  
Primary Resistance ◽  
Content Type ◽  
Aspergillus Lentulus

ABSTRACTRecent studies have demonstrated that some morphologically atypicalAspergillus fumigatusstrains are different species belonging to the sectionFumigati.Aspergillus lentulus, one of these sibling species, is increasingly reported in patients under corticosteroid treatment. MICs of most antifungals in clinical use are elevated againstA. lentulus, and it shows primary resistance to azole drugs. TwoA. lentuluscytochrome P450 14-α sterol demethylases, encoded byA. lentuluscyp51A (Alcyp51A) and Alcyp51Bgenes, were identified. Targetedcyp51Agene knockout inA. lentulusshowed that the intrinsic azole resistance of this species iscyp51Adependent. The Δcyp51Astrain was morphologically indistinguishable from theA. lentuluswild-type strain, retaining the ability to cause pulmonary disease in neutropenic mice. The heterologous expression ofA. lentuluscyp51Awas performed in anA. fumigatuscyp51A-deficient strain, confirming that Cyp51A is responsible for the differences inA. lentulus-azole drug interaction.

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.

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