SadA, a Trimeric Autotransporter from Salmonella enterica Serovar Typhimurium, Can Promote Biofilm Formation and Provides Limited Protection against Infection

ABSTRACTSalmonella entericais a major cause of morbidity worldwide and mortality in children and immunocompromised individuals in sub-Saharan Africa. Outer membrane proteins ofSalmonellaare of significance because they are at the interface between the pathogen and the host, they can contribute to adherence, colonization, and virulence, and they are frequently targets of antibody-mediated immunity. In this study, the properties of SadA, a purported trimeric autotransporter adhesin ofSalmonella entericaserovar Typhimurium, were examined. We demonstrated that SadA is exposed on theSalmonellacell surfacein vitroandin vivoduring infection of mice. Expression of SadA resulted in cell aggregation, biofilm formation, and increased adhesion to human intestinal Caco-2 epithelial cells. Immunization of mice with folded, full-length, purified SadA elicited an IgG response which provided limited protection against bacterial challenge. When anti-SadA IgG titers were enhanced by administering alum-precipitated protein, a modest additional protection was afforded. Therefore, despite SadA having pleiotropic functions, it is not a dominant, protective antigen for antibody-mediated protection againstSalmonella.

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Terminal Deoxynucleotidyl Transferase Is Not Required for Antibody Response to Polysaccharide Vaccines againstStreptococcus pneumoniaeandSalmonella entericaSerovar Typhi

Infection and Immunity ◽

10.1128/iai.00211-18 ◽

2018 ◽

Vol 86 (9) ◽

Author(s):

Vivek Belde ◽

Matthew P. Cravens ◽

Dania Gulandijany ◽

Justin A. Walker ◽

Isabel Palomo-Caturla ◽

...

Keyword(s):

Antibody Response ◽

B Cell ◽

Salmonella Enterica ◽

Passive Immunization ◽

Terminal Deoxynucleotidyl Transferase ◽

Human Infants ◽

Content Type ◽

Serovar Typhimurium

ABSTRACTB cell antigen receptor (BCR) diversity increases by several orders of magnitude due to the action of terminal deoxynucleotidyl transferase (TdT) during V(D)J recombination. Unlike adults, infants have limited BCR diversity, in part due to reduced expression of TdT. Since human infants and young mice respond poorly to polysaccharide vaccines, such as the pneumococcal polysaccharide vaccine Pneumovax23 and Vi polysaccharide (ViPS) ofSalmonella entericaserovar Typhi, we tested the contribution of TdT-mediated BCR diversity in response to these vaccines. We found that TdT+/−and TdT−/−mice generated comparable antibody responses to Pneumovax23 and survivedStreptococcus pneumoniaechallenge. Moreover, passive immunization of B cell-deficient mice with serum from Pneumovax23-immunized TdT+/−or TdT−/−mice conferred protection. TdT+/−and TdT−/−mice generated comparable levels of anti-ViPS antibodies and antibody-dependent, complement-mediated bactericidal activity againstS. Typhiin vitro. To test the protective immunity conferred by ViPS immunizationin vivo, TdT+/−and TdT−/−mice were challenged with a chimericSalmonella entericaserovar Typhimurium strain expressing ViPS, since mice are nonpermissive hosts forS. Typhi infection. Compared to their unimmunized counterparts, immunized TdT+/−and TdT−/−mice challenged with ViPS-expressingS. Typhimurium exhibited a significant reduction in the bacterial burden and liver pathology. These data suggest that the impaired antibody response to the Pneumovax23 and ViPS vaccines in the young is not due to limited TdT-mediated BCR diversification.

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Salmonella Extracellular Matrix Components Influence Biofilm Formation and Gallbladder Colonization

Infection and Immunity ◽

10.1128/iai.00532-16 ◽

2016 ◽

Vol 84 (11) ◽

pp. 3243-3251 ◽

Cited By ~ 13

Author(s):

Haley E. Adcox ◽

Erin M. Vasicek ◽

Varun Dwivedi ◽

Ky V. Hoang ◽

Joanne Turner ◽

...

Keyword(s):

Extracellular Matrix ◽

Typhoid Fever ◽

Salmonella Enterica ◽

Biofilm Formation ◽

Bacterial Survival ◽

Content Type ◽

Extracellular Matrix Components ◽

Matrix Components

Salmonella enterica serovar Typhi, the causative agent of typhoid fever in humans, forms biofilms encapsulated by an extracellular matrix (ECM). Biofilms facilitate colonization and persistent infection in gallbladders of humans and mouse models of chronic carriage. Individual roles of matrix components have not been completely elucidated in vitro or in vivo . To examine individual functions, strains of Salmonella enterica serovar Typhimurium, the murine model of S . Typhi, in which various ECM genes were deleted or added, were created to examine biofilm formation, colonization, and persistence in the gallbladder. Studies show that curli contributes most significantly to biofilm formation. Expression of Vi antigen decreased biofilm formation in vitro and virulence and bacterial survival in vivo without altering the examined gallbladder pro- or anti-inflammatory cytokines. Oppositely, loss of all ECM components (Δ wcaM Δ csgA Δ yihO Δ bcsE ) increased virulence and bacterial survival in vivo and reduced gallbladder interleukin-10 (IL-10) levels. Colanic acid and curli mutants had the largest defects in biofilm-forming ability and contributed most significantly to the virulence increase of the Δ wcaM Δ csgA Δ yihO Δ bcsE mutant strain. While the Δ wcaM Δ csgA Δ yihO Δ bcsE mutant was not altered in resistance to complement or growth in macrophages, it attached and invaded macrophages better than the wild-type (WT) strain. These data suggest that ECM components have various levels of importance in biofilm formation and gallbladder colonization and that the ECM diminishes disseminated disease in our model, perhaps by reducing cell attachment/invasion and dampening inflammation by maintaining/inducing IL-10 production. Understanding how ECM components aid acute disease and persistence could lead to improvements in therapeutic treatment of typhoid fever patients.

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In Salmonella enterica, the Gcn5-Related Acetyltransferase MddA (Formerly YncA) Acetylates Methionine Sulfoximine and Methionine Sulfone, Blocking Their Toxic Effects

Journal of Bacteriology ◽

10.1128/jb.02311-14 ◽

2014 ◽

Vol 197 (2) ◽

pp. 314-325 ◽

Cited By ~ 19

Author(s):

Kristy L. Hentchel ◽

Jorge C. Escalante-Semerena

Keyword(s):

Salmonella Enterica ◽

Physiological Role ◽

Methionine Sulfoximine ◽

Amino Acid Transporters ◽

Content Type ◽

Methionine Sulfone ◽

Serovar Typhimurium ◽

Acylation Reactions

Protein and small-molecule acylation reactions are widespread in nature. Many of the enzymes catalyzing acylation reactions belong to theGcn5-relatedN-acetyltransferase (GNAT; PF00583) family, named after the yeast Gcn5 protein. The genome ofSalmonella entericaserovar Typhimurium LT2 encodes 26 GNATs, 11 of which have no known physiological role. Here, we providein vivoandin vitroevidence for the role of the MddA (methioninederivativedetoxifier; formerly YncA) GNAT in the detoxification of oxidized forms of methionine, including methionine sulfoximine (MSX) and methionine sulfone (MSO). MSX and MSO inhibited the growth of anS. entericaΔmddAstrain unless glutamine or methionine was present in the medium. We used anin vitrospectrophotometric assay and mass spectrometry to show that MddA acetylated MSX and MSO. AnmddA+strain displayed biphasic growth kinetics in the presence of MSX and glutamine. Deletion of two amino acid transporters (GlnHPQ and MetNIQ) in a ΔmddAstrain restored growth in the presence of MSX. Notably, MSO was transported by GlnHPQ but not by MetNIQ. In summary, MddA is the mechanism used byS. entericato respond to oxidized forms of methionine, which MddA detoxifies by acetyl coenzyme A-dependent acetylation.

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Phosphate Groups of Lipid A Are Essential for Salmonella enterica Serovar Typhimurium Virulence and Affect Innate and Adaptive Immunity

Infection and Immunity ◽

10.1128/iai.00123-12 ◽

2012 ◽

Vol 80 (9) ◽

pp. 3215-3224 ◽

Cited By ~ 46

Author(s):

Qingke Kong ◽

David A. Six ◽

Qing Liu ◽

Lillian Gu ◽

Shifeng Wang ◽

...

Keyword(s):

Outer Membrane ◽

Adaptive Immunity ◽

Salmonella Enterica ◽

Lipid A ◽

Outer Membrane Proteins ◽

Polymyxin B ◽

Content Type ◽

Serovar Typhimurium ◽

Phosphate Groups

ABSTRACTLipid A is a key component of the outer membrane of Gram-negative bacteria and stimulates proinflammatory responses via the Toll-like receptor 4 (TLR4)-MD2-CD14 pathway. Its endotoxic activity depends on the number and length of acyl chains and its phosphorylation state. InSalmonella entericaserovar Typhimurium, removal of the secondary laurate or myristate chain in lipid A results in bacterial attenuation and growth defectsin vitro. However, the roles of the two lipid A phosphate groups in bacterial virulence and immunogenicity remain unknown. Here, we used anS. TyphimuriummsbB pagL pagP lpxRmutant, carrying penta-acylated lipid A, as the parent strain to construct a series of mutants synthesizing 1-dephosphorylated, 4′-dephosphorylated, or nonphosphorylated penta-acylated lipid A. Dephosphorylated mutants exhibited increased sensitivity to deoxycholate and showed increased resistance to polymyxin B. Removal of both phosphate groups severely attenuated the mutants when administered orally to BALB/c mice, but the mutants colonized the lymphatic tissues and were sufficiently immunogenic to protect the host from challenge with wild-typeS. Typhimurium. Mice receivingS. Typhimurium with 1-dephosphorylated or nonphosphorylated penta-acylated lipid A exhibited reduced levels of cytokines. Attenuated and dephosphorylatedSalmonellavaccines were able to induce adaptive immunity against heterologous (PspA ofStreptococcus pneumoniae) and homologous antigens (lipopolysaccharide [LPS] and outer membrane proteins [OMPs]).

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Palmitoylation State Impacts Induction of Innate and Acquired Immunity by the Salmonella enterica Serovar TyphimuriummsbBMutant

Infection and Immunity ◽

10.1128/iai.05524-11 ◽

2011 ◽

Vol 79 (12) ◽

pp. 5027-5038 ◽

Cited By ~ 25

Author(s):

Qingke Kong ◽

David A. Six ◽

Qing Liu ◽

Lillian Gu ◽

Kenneth L. Roland ◽

...

Keyword(s):

Salmonella Enterica ◽

Lipid A ◽

Inflammatory Responses ◽

Outer Membrane Proteins ◽

Acyl Chain ◽

Wild Type ◽

Proinflammatory Response ◽

Content Type ◽

Serovar Typhimurium

ABSTRACTLipopolysaccharide (LPS), composed of lipid A, core, and O-antigen, is a major virulence factor ofSalmonella entericaserovar Typhimurium, with lipid A being a major stimulator to induce the proinflammatory response via the Toll-like receptor 4 (TLR4)-MD2-CD14 pathway. WhileSalmonella msbBmutants lacking the myristate chain in lipid A were investigated widely as an anticancer vaccine, inclusion of themsbBmutation in aSalmonellavaccine to deliver heterologous antigens has not yet been investigated. We introduced themsbBmutation alone or in combination with mutations in other lipid A acyl chain modification genes encoding PagL, PagP, and LpxR into wild-typeS. entericaserovar Typhimurium. ThemsbBmutation reduced virulence, while thepagL,pagP, andlpxRmutations did not affect virulence in themsbBmutant background when administered orally to BALB/c mice. Also, all mutants exhibited sensitivity to polymyxin B but did not display sensitivity to deoxycholate. LPS derived frommsbBmutants induced less inflammatory responses in human Mono Mac 6 and murine macrophage RAW264.7 cellsin vitro. However, anmsbBmutant did not decrease the induction of inflammatory responses in mice compared to the levels induced by the wild-type strain, whereas anmsbB pagPmutant induced less inflammatory responsesin vivo. The mutations were moved to an attenuatedSalmonellavaccine strain to evaluate their effects on immunogenicity. Lipid A modification caused by themsbBmutation alone and in combination withpagL,pagP, andlpxRmutations led to higher IgA production in the vaginal tract but still retained the same IgG titer level in serum to PspA, a test antigen fromStreptococcus pneumoniae, and to outer membrane proteins (OMPs) fromSalmonella.

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The Stringent Response Regulator DksA Is Required for Salmonella enterica Serovar Typhimurium Growth in Minimal Medium, Motility, Biofilm Formation, and Intestinal Colonization

Infection and Immunity ◽

10.1128/iai.01135-15 ◽

2015 ◽

Vol 84 (1) ◽

pp. 375-384 ◽

Cited By ~ 26

Author(s):

Shalhevet Azriel ◽

Alina Goren ◽

Galia Rahav ◽

Ohad Gal-Mor

Keyword(s):

Salmonella Enterica ◽

Biofilm Formation ◽

Early Stage ◽

Response Regulator ◽

Stringent Response ◽

Negative Regulator ◽

Logarithmic Phase ◽

Content Type ◽

Serovar Typhimurium

Salmonella entericaserovar Typhimurium is a facultative intracellular human and animal bacterial pathogen posing a major threat to public health worldwide.Salmonellapathogenicity requires complex coordination of multiple physiological and virulence pathways. DksA is a conserved Gram-negative regulator that belongs to a distinct group of transcription factors that bind directly to the RNA polymerase secondary channel, potentiating the effect of the signaling molecule ppGpp during a stringent response. Here, we established that inS.Typhimurium,dksAis induced during the logarithmic phase and DksA is essential for growth in minimal defined medium and plays an important role in motility and biofilm formation. Furthermore, we determined that DksA positively regulates theSalmonellapathogenicity island 1 and motility-chemotaxis genes and is necessary forS.Typhimurium invasion of human epithelial cells and uptake by macrophages. In contrast, DksA was found to be dispensable forS.Typhimurium host cell adhesion. Finally, using the colitis mouse model, we found thatdksAis spatially induced at the midcecum during the early stage of the infection and required for gastrointestinal colonization and systemic infectionin vivo. Taken together, these data indicate that the ancestral stringent response regulator DksA coordinates various physiological and virulenceS.Typhimurium programs and therefore is a key virulence regulator ofSalmonella.

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Role of Mouse Peptidoglycan Recognition Protein PGLYRP2 in the Innate Immune Response to Salmonella enterica Serovar Typhimurium InfectionIn Vivo

Infection and Immunity ◽

10.1128/iai.00168-12 ◽

2012 ◽

Vol 80 (8) ◽

pp. 2645-2654 ◽

Cited By ~ 19

Author(s):

Jooeun Lee ◽

Kaoru Geddes ◽

Catherine Streutker ◽

Dana J. Philpott ◽

Stephen E. Girardin

Keyword(s):

Salmonella Enterica ◽

Fluorescent Protein ◽

Intraepithelial Lymphocytes ◽

Innate Immune ◽

Th17 Response ◽

Content Type ◽

Serovar Typhimurium

ABSTRACTPeptidoglycan recognition proteins (PGRPs) are a family of innate pattern recognition molecules that bind bacterial peptidoglycan. While the role of PGRPs inDrosophilainnate immunity has been extensively studied, how the four mammalian PGRP proteins (PGLYRP1 to PGLYRP4) contribute to host defense against bacterial pathogensin vivoremains poorly understood. PGLYRP1, PGLYRP3, and PGLYRP4 are directly bactericidalin vitro, whereas PGLYRP2 is anN-acetylmuramyl-l-alanine amidase that cleaves peptidoglycan between the sugar backbone and the peptide stem. Because PGLYRP2 cleaves muramyl peptides detected by host peptidoglycan sensors Nod1 and Nod2, we speculated that PGLYRP2 may act as a modifier of Nod1/Nod2-dependent innate immune responses. We investigated the role of PGLYRP2 inSalmonella entericaserovar Typhimurium-induced colitis, which is regulated by Nod1/Nod2 through the induction of an early Th17 response. PGLYRP2 did not contribute to expression of Th17-associated cytokines, interleukin-22 (IL-22)-dependent antimicrobial proteins, or inflammatory cytokines. However, we found thatPglyrp2-deficient mice displayed significantly enhanced inflammation in the cecum at 72 h postinfection, reflected by increased polymorphonuclear leukocyte (PMN) infiltration and goblet cell depletion.Pglyrp2expression was also induced in the cecum ofSalmonella-infected mice, and expression of green fluorescent protein under control of thePglyrp2promoter was increased in discrete populations of intraepithelial lymphocytes. Lastly,Nod2−/−Pglyrp2−/−mice displayed increased susceptibility to infection at 24 h postinfection compared toPglyrp2−/−mice, which correlated with increased PMN infiltration and submucosal edema. Thus, PGLYRP2 plays a protective rolein vivoin the control ofS. Typhimurium infection through a Nod1/Nod2-independent mechanism.

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Cathelicidin Antimicrobial Peptide Expression Is Not Induced or Required for Bacterial Clearance during Salmonella enterica Infection of Human Monocyte-Derived Macrophages

Infection and Immunity ◽

10.1128/iai.00672-12 ◽

2012 ◽

Vol 80 (11) ◽

pp. 3930-3938 ◽

Cited By ~ 11

Author(s):

Kristi L. Strandberg ◽

Susan M. Richards ◽

John S. Gunn

Keyword(s):

Antimicrobial Peptide ◽

Salmonella Enterica ◽

Active Form ◽

Human Monocyte ◽

Content Type ◽

Mutant Strains ◽

Serovar Typhimurium ◽

Proinflammatory Responses

ABSTRACTSalmonella entericaserovar Typhimurium is able to resist antimicrobial peptide killing by induction of the PhoP-PhoQ and PmrA-PmrB two-component systems and the lipopolysaccharide (LPS) modifications they mediate. Murine cathelin-related antimicrobial peptide (CRAMP) has been reported to inhibitS. Typhimurium growthin vitroandin vivo. We hypothesize that infection of human monocyte-derived macrophages (MDMs) withSalmonella entericaserovar Typhi andS. Typhimurium will induce human cathelicidin antimicrobial peptide (CAMP) production, and exposure to LL-37 (processed, active form of CAMP/hCAP18) will lead to upregulation of PmrAB-mediated LPS modifications and increased survivalin vivo. Unlike in mouse macrophages, in which CRAMP is upregulated during infection,campgene expression was not induced in human MDMs infected withS. Typhi orS. Typhimurium. Upon infection, intracellular levels of ΔphoPQ, ΔpmrAB, and PhoPcS. Typhi decreased over time but were not further inhibited by the vitamin D3-induced increase incampexpression. MDMs infected with wild-type (WT)S. Typhi orS. Typhimurium released similar levels of proinflammatory cytokines; however, the LPS modification mutant strains dramatically differed in MDM-elicited cytokine levels. Overall, these findings indicate thatcampis not induced duringSalmonellainfection of MDMs nor is key toSalmonellaintracellular clearance. However, the cytokine responses from MDMs infected with WT or LPS modification mutant strains differ significantly, indicating a role for LPS modifications in altering the host inflammatory response. Our findings also suggest thatS. Typhi andS. Typhimurium elicit different proinflammatory responses from MDMs, despite being capable of adding similar modifications to their LPS structures.

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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

Infection and Immunity ◽

10.1128/iai.00784-17 ◽

2017 ◽

Vol 86 (1) ◽

Cited By ~ 5

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.

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Identification of Salmonella enterica Serovar Typhimurium Genes Regulated during Biofilm Formation on Cholesterol Gallstone Surfaces

Infection and Immunity ◽

10.1128/iai.00647-13 ◽

2013 ◽

Vol 81 (10) ◽

pp. 3770-3780 ◽

Cited By ~ 18

Author(s):

Geoffrey Gonzalez-Escobedo ◽

John S. Gunn

Keyword(s):

Salmonella Enterica ◽

Biofilm Formation ◽

Cholesterol Gallstone ◽

Structural Genes ◽

Content Type ◽

Serovar Typhimurium ◽

Coated Surfaces ◽

Biofilm Development

ABSTRACTSalmonellaspp. are able to form biofilms on abiotic and biotic surfaces.In vivostudies in our laboratory have shown thatSalmonellacan form biofilms on the surfaces of cholesterol gallstones in the gallbladders of mice and human carriers. Biofilm formation on gallstones has been demonstrated to be a mechanism of persistence. The purpose of this work was to identify and evaluateSalmonellasp. cholesterol-dependent biofilm factors. Differential gene expression analysis between biofilms on glass or cholesterol-coated surfaces and subsequent quantitative real-time PCR (qRT-PCR) revealed that type 1 fimbria structural genes and a gene encoding a putative outer membrane protein (ycfR) were specifically upregulated inSalmonella entericaserovar Typhimurium biofilms grown on cholesterol-coated surfaces. Spatiotemporal expression ofycfRand FimA verified their regulation during biofilm development on cholesterol-coated surfaces. Surprisingly, confocal and scanning electron microscopy demonstrated that a mutant of type 1 fimbria structural genes (ΔfimAICDHF) and aycfRmutant showed increased biofilm formation on cholesterol-coated surfaces.In vivoexperiments usingNramp1+/+mice harboring gallstones showed that only the ΔycfRmutant formed extensive biofilms on mouse gallstones at 7 and 21 days postinfection; ΔfimAICDHFwas not observed on gallstone surfaces after the 7-day-postinfection time point. These data suggest that inSalmonellaspp., wild-type type 1 fimbriae are important for attachment to and/or persistence on gallstones at later points of chronic infection, whereas YcfR may represent a specific potential natural inhibitor of initial biofilm formation on gallstones.

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