Influence of Gastric Acid on Susceptibility to Infection with Ingested Bacterial Pathogens

ABSTRACT Despite the widely held belief that gastric acid serves as a barrier to bacterial pathogens, there are almost no experimental data to support this hypothesis. We have developed a mouse model to quantify the effectiveness of gastric acid in mediating resistance to infection with ingested bacteria. Mice that were constitutively hypochlorhydric due to a mutation in a gastric H+/K+-ATPase (proton pump) gene were infected with Yersinia enterocolitica, Salmonella enterica serovar Typhimurium, Citrobacter rodentium, or Clostridium perfringens cells or spores. Significantly greater numbers of Yersinia, Salmonella, and Citrobacter cells (P ≤ 0.006) and Clostridium spores (P = 0.02) survived in hypochlorhydric mice, resulting in reduced median infectious doses. Experiments involving intraperitoneal infection or infection of mice treated with antacids indicated that the increased sensitivity of hypochlorhydric mice to infection was entirely due to the absence of stomach acid. Apart from establishing the role of gastric acid in nonspecific immunity to ingested bacterial pathogens, our model provides an excellent system with which to investigate the effects of hypochlorhydria on susceptibility to infection and to evaluate the in vivo susceptibility to gastric acid of orally administered therapies, such as vaccines and probiotics.

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Role of sapA and yfgA in Susceptibility to Antibody-Mediated Complement-Dependent Killing and Virulence of Salmonella enterica Serovar Typhimurium

Infection and Immunity ◽

10.1128/iai.00419-17 ◽

2017 ◽

Vol 85 (9) ◽

Cited By ~ 1

Author(s):

Edna M. Ondari ◽

Jennifer N. Heath ◽

Elizabeth J. Klemm ◽

Gemma Langridge ◽

Lars Barquist ◽

...

Keyword(s):

Salmonella Enterica ◽

Protein Translocation ◽

Invasive Disease ◽

Immune Serum ◽

Insertion Mutant ◽

Content Type ◽

Serovar Typhimurium ◽

Serum Killing ◽

Increased Sensitivity

ABSTRACT The ST313 pathovar of Salmonella enterica serovar Typhimurium contributes to a high burden of invasive disease among African infants and HIV-infected adults. It is characterized by genome degradation (loss of coding capacity) and has increased resistance to antibody-dependent complement-mediated killing compared with enterocolitis-causing strains of S. Typhimurium. Vaccination is an attractive disease-prevention strategy, and leading candidates focus on the induction of bactericidal antibodies. Antibody-resistant strains arising through further gene deletion could compromise such a strategy. Exposing a saturating transposon insertion mutant library of S. Typhimurium to immune serum identified a repertoire of S. Typhimurium genes that, when interrupted, result in increased resistance to serum killing. These genes included several involved in bacterial envelope biogenesis, protein translocation, and metabolism. We generated defined mutant derivatives using S. Typhimurium SL1344 as the host. Based on their initial levels of enhanced resistance to killing, yfgA and sapA mutants were selected for further characterization. The S. Typhimurium yfgA mutant lost the characteristic Salmonella rod-shaped appearance, exhibited increased sensitivity to osmotic and detergent stress, lacked very long lipopolysaccharide, was unable to invade enterocytes, and demonstrated decreased ability to infect mice. In contrast, the S. Typhimurium sapA mutants had similar sensitivity to osmotic and detergent stress and lipopolysaccharide profile and an increased ability to infect enterocytes compared with the wild type, but it had no increased ability to cause in vivo infection. These findings indicate that increased resistance to antibody-dependent complement-mediated killing secondary to genetic deletion is not necessarily accompanied by increased virulence and suggest the presence of different mechanisms of antibody resistance.

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The enzyme phosphoglucomutase (Pgm) is required by Salmonella enterica serovar Typhimurium for O-antigen production, resistance to antimicrobial peptides and in vivo fitness

Microbiology ◽

10.1099/mic.0.029553-0 ◽

2009 ◽

Vol 155 (10) ◽

pp. 3403-3410 ◽

Cited By ~ 22

Author(s):

G. K. Paterson ◽

D. B. Cone ◽

S. E. Peters ◽

D. J. Maskell

Keyword(s):

Antimicrobial Peptides ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Live Attenuated Vaccine ◽

Antigen Production ◽

O Antigen ◽

Serovar Typhimurium

The enzyme phosphoglucomutase (Pgm) catalyses the interconversion of glucose 1-phosphate and glucose 6-phosphate and contributes to glycolysis and the generation of sugar nucleotides for biosynthesis. To assess the role of this enzyme in the biology of the pathogen Salmonella enterica serovar Typhimurium we have characterized a pgm deletion mutant in strain SL1344. Compared to SL1344, SL1344 pgm had impaired growth in vitro, was deficient in the ability to utilize galactose as a carbon source and displayed reduced O-antigen polymer length. The mutant was also more susceptible to antimicrobial peptides and showed decreased fitness in the mouse typhoid model. The in vivo phenotype of SL1344 pgm indicated a role for pgm in the early stages of infection, most likely through deficient O-antigen production. Although pgm mutants in other pathogens have potential as live attenuated vaccine strains, SL1344 pgm was not sufficiently attenuated for such use.

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Bacterial Pathogens Induce Abscess Formation by CD4+ T-Cell Activation via the CD28–B7-2 Costimulatory Pathway

Infection and Immunity ◽

10.1128/iai.68.12.6650-6655.2000 ◽

2000 ◽

Vol 68 (12) ◽

pp. 6650-6655 ◽

Cited By ~ 37

Author(s):

Arthur O. Tzianabos ◽

Anil Chandraker ◽

Wiltrud Kalka-Moll ◽

Francesca Stingele ◽

Victor M. Dong ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Pathogenic Bacteria ◽

Cell Activation ◽

Bacterial Pathogens ◽

Abscess Formation

ABSTRACT Abscesses are a classic host response to infection by many pathogenic bacteria. The immunopathogenesis of this tissue response to infection has not been fully elucidated. Previous studies have suggested that T cells are involved in the pathologic process, but the role of these cells remains unclear. To delineate the mechanism by which T cells mediate abscess formation associated with intra-abdominal sepsis, the role of T-cell activation and the contribution of antigen-presenting cells via CD28-B7 costimulation were investigated. T cells activated in vitro by zwitterionic bacterial polysaccharides (Zps) known to induce abscess formation required CD28-B7 costimulation and, when adoptively transferred to the peritoneal cavity of naı̈ve rats, promoted abscess formation. Blockade of T-cell activation via the CD28-B7 pathway in animals with CTLA4Ig prevented abscess formation following challenge with different bacterial pathogens, including Staphylococcus aureus,Bacteroides fragilis, and a combination ofEnterococcus faecium and Bacteroides distasonis. In contrast, these animals had an increased abscess rate following in vivo T-cell activation via CD28 signaling. Abscess formation in vivo and T-cell activation in vitro required costimulation by B7-2 but not B7-1. These results demonstrate that abscess formation by pathogenic bacteria is under the control of a common effector mechanism that requires T-cell activation via the CD28–B7-2 pathway.

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Abstract 277: MicroRNA-125a-5p Protects the Mouse Heart From Ischemic Injury by Repressing Pro-apoptotic Bak1 and Klf13 in Cardiomyocytes

Circulation Research ◽

10.1161/res.127.suppl_1.277 ◽

2020 ◽

Vol 127 (Suppl_1) ◽

Author(s):

Bruno Moukette ◽

Tatsuya Aonuma ◽

Il-man Kim

Keyword(s):

Target Genes ◽

Cardiac Injury ◽

Cell Types ◽

Mouse Heart ◽

Small Noncoding Rnas ◽

Increased Sensitivity ◽

Β Blocker ◽

Apoptotic Genes

Background: Cardiac injury is accompanied by dynamic changes in the expression of microRNAs (miRs), which are small noncoding RNAs to downregulate target genes. MiR-125a-5p (miR-125a) is downregulated in patients with myocardial infarction (MI). We reported that miR-125a is upregulated by the β-blocker carvedilol (Carv) acting through β-arrestin1-biased β1-adrenergic receptor (β1AR; receptor found mainly in cardiomyocytes [CMs]) cardioprotective signaling (Figure A). We also showed that pro-apoptotic genes bak1 and klf13 are downregulated by Carv and are upregulated after MI. Here, we hypothesize that miR-125a in CMs favorably regulates cardiac functional and structural remodeling after MI by repressing bak1 and klf13. Methods and Results: Fractionation of cardiac cell types from heart tissues reveals that the expression of miR-125a is higher in CMs than other myocardial cells. Using cultured CM and in vivo approaches, we show that miR-125a is an ischemic stress-responsive protector against CM apoptosis. CMs lacking miR-125a exhibit an increased sensitivity to apoptosis, while CMs overexpressing miR-125a have increased phospho-AKT pro-survival signaling. Moreover, we show that miR-125a is downregulated in post-MI mouse hearts and miR-125a overexpression protects mouse hearts against MI. We also show that global genetic deletion of miR-125a in mice worsens maladaptive post-MI remodeling. Mechanistically, the cardioprotective role of miR-125a during MI is in part attributed to direct repression of the pro-apoptotic genes bak1 and klf13 in CMs (Figure B). Conclusions: These findings reveal a pivotal role for miR-125a in regulating CM survival during MI.

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Acquisition of Mn(II) in Addition to Fe(II) Is Required for Full Virulence of Salmonella enterica Serovar Typhimurium

Infection and Immunity ◽

10.1128/iai.70.11.6032-6042.2002 ◽

2002 ◽

Vol 70 (11) ◽

pp. 6032-6042 ◽

Cited By ~ 157

Author(s):

E. Boyer ◽

I. Bergevin ◽

D. Malo ◽

P. Gros ◽

M. F. M. Cellier

Keyword(s):

Salmonella Enterica ◽

Ferrous Iron ◽

Double Mutant ◽

Divalent Cations ◽

Intracellular Survival ◽

Iron Transporter ◽

Serovar Typhimurium ◽

Increased Sensitivity

ABSTRACT The roles of the genes feoB (ABC ferrous iron transporter), mntH (proton-dependent manganese transporter), and sitABCD (putative ABC iron and/or manganese transporter) in Salmonella pathogenicity were investigated by using mutant strains deficient in one, two, or three transporters. Our results indicated that sitABCD encodes an important transporter of Mn(II) and Fe(II) which is required for full virulence in susceptible animals (Nramp1 −/−) and for replication inside Nramp1 −/− macrophages in vitro. The mntH sitABCD double mutant (mutant MS) showed minimal Mn(II) uptake and increased sensitivity to H2O2 and to the divalent metal chelator 2,2′-dipyridyl (DP) and was defective for replication in macrophages. In vivo MS appeared to be as virulent as the sitABCD mutant in Nramp1 −/− animals. The ferrous iron transporter Feo was required for full virulence in 129/Sv Nramp1 −/− mice, and infection with multiple mutants lacking FeoB was not fatal. The sitABCD feoB mutant (mutant SF) and the mntH sitABCD feoB mutant (mutant MSF) showed minimal Fe(II) uptake and were slightly impaired for replication in susceptible macrophages. MSF showed reduced growth in minimal medium deficient in divalent cations. The role of the mntH gene, which is homologous to mammalian Nramp genes, was also investigated after overexpression in the double mutant MS. MntH preferred Mn(II) over Fe(II) and could suppress MS sensitivity to H2O2 and to DP, and it also improved the intracellular survival in Nramp1 −/− macrophages. This study indicates that acquisition of Mn(II), in addition to Fe(II), is required for intracellular survival and replication of Salmonella enterica serovar Typhimurium in macrophages in vitro and for virulence in vivo.

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Aggregation via the Red, Dry, and Rough Morphotype Is Not a Virulence Adaptation in Salmonella enterica Serovar Typhimurium

Infection and Immunity ◽

10.1128/iai.01383-07 ◽

2008 ◽

Vol 76 (3) ◽

pp. 1048-1058 ◽

Cited By ~ 44

Author(s):

A. P. White ◽

D. L. Gibson ◽

G. A. Grassl ◽

W. W. Kay ◽

B. B. Finlay ◽

...

Keyword(s):

In Vivo Imaging ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Primary Role ◽

Wild Type ◽

Serovar Typhimurium ◽

Cell Densities ◽

Two Populations

ABSTRACT The Salmonella rdar (red, dry, and rough) morphotype is an aggregative and resistant physiology that has been linked to survival in nutrient-limited environments. Growth of Salmonella enterica serovar Typhimurium was analyzed in a variety of nutrient-limiting conditions to determine whether aggregation would occur at low cell densities and whether the rdar morphotype was involved in this process. The resulting cultures consisted of two populations of cells, aggregated and nonaggregated, with the aggregated cells preferentially displaying rdar morphotype gene expression. The two groups of cells could be separated based on the principle that aggregated cells were producing greater amounts of thin aggregative fimbriae (Tafi or curli). In addition, the aggregated cells retained some physiological characteristics of the rdar morphotype, such as increased resistance to sodium hypochlorite. Competitive infection experiments in mice showed that nonaggregative ΔagfA cells outcompeted rdar-positive wild-type cells in all tissues analyzed, indicating that aggregation via the rdar morphotype was not a virulence adaptation in Salmonella enterica serovar Typhimurium. Furthermore, in vivo imaging experiments showed that Tafi genes were not expressed during infection but were expressed once Salmonella was passed out of the mice into the feces. We hypothesize that the primary role of the rdar morphotype is to enhance Salmonella survival outside the host, thereby aiding in transmission.

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Bactericidal and Antiendotoxic Properties of Short Cationic Peptides Derived from a Snake Venom Lys49 Phospholipase A2

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.49.4.1340-1345.2005 ◽

2005 ◽

Vol 49 (4) ◽

pp. 1340-1345 ◽

Cited By ~ 37

Author(s):

Carlos Santamaría ◽

Silda Larios ◽

Steve Quirós ◽

Javier Pizarro-Cerda ◽

Jean-Pierre Gorvel ◽

...

Keyword(s):

Bactericidal Activity ◽

Aromatic Amino Acids ◽

Polymyxin B ◽

Phospholipase A ◽

Necrosis Factor Alpha ◽

Parent Protein ◽

Serovar Typhimurium ◽

Microbial Infections ◽

Intraperitoneal Infection

ABSTRACT The activities of short synthetic, nonhemolytic peptides derived from the C-terminal region of myotoxin II, a catalytically inactive phospholipase A2 homologue present in the venom of the snake Bothrops asper, have been shown to reproduce the bactericidal activity of the parent protein. They combine cationic and hydrophobic-aromatic amino acids, thus functionally resembling the antimicrobial peptides of innate defenses. This study evaluated the antimicrobial and antiendotoxic properties of a 13-mer derivative peptide of the C-terminal sequence from positions 115 to 129 of myotoxin II, named pEM-2. This peptide (KKWRWWLKALAKK) showed bactericidal activity against both gram-positive and gram-negative bacteria. In comparison to previously described peptide variants derived from myotoxin II, the toxicity of pEM-2 toward eukaryotic cells in culture was significantly reduced, being similar to that of lactoferricin B but lower than that of polymyxin B. The all-d enantiomer of pEM-2 [pEM-2 (d)] retained the same bactericidal potency of its l-enantiomeric counterpart, but it showed an enhanced ability to counteract the lethal activity of an intraperitoneal lipopolysaccharide challenge in mice, which correlated with a significant reduction of the serum tumor necrosis factor alpha levels triggered by this endotoxin. Lethality induced by intraperitoneal infection of mice with Escherichia coli or Salmonella enterica serovar Typhimurium was reduced by the administration of pEM-2 (d). These results demonstrate that phospholipase A2-derived peptides may have the potential to counteract microbial infections and encourage further evaluations of their actions in vivo.

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The Development Of The Humanized Darc Transgenic Mouse

Blood ◽

10.1182/blood.v122.21.2188.2188 ◽

2013 ◽

Vol 122 (21) ◽

pp. 2188-2188

Author(s):

Igor N Novitzky-Basso ◽

Maria H Ulvmar ◽

Andrea Bacon ◽

Sridhar Chaganti ◽

Paul AH Moss ◽

...

Keyword(s):

Advisory Committees ◽

Downstream Signaling ◽

Cc Chemokines ◽

Travel Grant ◽

Resistance To Infection ◽

Portal Of Entry ◽

Kidney Liver ◽

The Impact

Abstract The Duffy Antigen Receptor for Chemokines (DARC) is an atypical chemokine receptor which binds CXC and CC chemokines with no measurable downstream signaling. Erythrocyte DARC serves as a chemokine sink and reservoir. DARC on endothelial cells transports chemokines thus promoting transendothelial leukocyte migration. Two common polymorphisms define the Duffy blood group, FYA and FYB, whilst the third polymorphism which is widely prevalent in West Africa, FYB(ES), abolishes erythrocyte expression of DARC. DARC is a portal of entry for plasmodium vivax suggesting that FYB(ES) was selected due to it conferring resistance to infection. The impact of the FYB(ES) polymorphism extends to a genetic association with the benign ethnic neutropenia. In order to study the mechanisms of this association we have developed a murine transgenic models of the Fy(a-b-) phenotype as encoded by FYB(ES), and Fy(a-b+) phenotype as encoded by FYB. Cloned genes were introduced by pronuclear micro-injection into fertilized oocytes of murine-DARC knockouts. The resulting embryos were transferred into pseudopregnant mice and offspring screened for transgene insertion by PCR genotyping. Gene expression in founder animals was measured by qPCR, demonstrating expression in lung, kidney, liver, spleen, skin and cerebellum. Protein expression was confirmed by immunofluorescence on frozen sections in spleen and skin in a distribution identical to human. Erythrocyte phenotyping by FACS using anti-Fy3 and anti-Fy6 monoclonal antibodies demonstrated the lack of DARC expression in mice with FYB(ES) and confirmed expression on FYB transgenic erythrocytes. We show that murine chemokines bind to human DARC and we plan to use this model to investigate the impact of FYB(ES) on in vivo chemokine functions and equilibria. These models will prove useful in the dissection of the mechanisms of ethnic neutropenia and improve the understanding in the role of DARC in chemokine homeostasis. Disclosures: Chaganti: Roche: Membership on an entity’s Board of Directors or advisory committees, Receipt of travel grant Other.

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Increased Susceptibility of C1q-Deficient Mice to Salmonella enterica Serovar Typhimurium Infection

Infection and Immunity ◽

10.1128/iai.70.2.551-557.2002 ◽

2002 ◽

Vol 70 (2) ◽

pp. 551-557 ◽

Cited By ~ 32

Author(s):

Joanna Warren ◽

Pietro Mastroeni ◽

Gordon Dougan ◽

Mahdad Noursadeghi ◽

Jonathan Cohen ◽

...

Keyword(s):

Salmonella Enterica ◽

Fluorescent Protein ◽

Alternative Pathway ◽

No Production ◽

Classical Pathway ◽

Serovar Typhimurium ◽

Deficient Mice

ABSTRACT The role of the complement system in host defense against Salmonella infection is poorly defined. Bacterial cell wall O-antigen polysaccharide can activate the alternative pathway in vitro. No studies, however, have elucidated the role of the classical pathway in immunity to Salmonella spp. in vivo. C1q-deficient mice (C1qa −/−) on a 129/Sv genetic background and strain-matched controls were infected intraperitoneally and intravenously with Salmonella enterica serovar Typhimurium and monitored over a 14-day period. After inoculation by either route, the C1qa −/− mice were found to be significantly more susceptible to Salmonella infection. Hepatic and splenic bacterial counts, performed at various time points, showed increased numbers of colonies in complement-deficient mice compared to controls. Analysis of blood clearance showed no difference between the two experimental groups during the first 15 min. However, after 20 min and until 6 h postinfection, numbers of circulating bacteria were significantly higher in complement-deficient mice. In vitro experiments using either resident or thioglycolate-elicited peritoneal macrophages showed a significant increase in the number of bacteria inside C1q-deficient macrophages compared to controls irrespective of the serum used for opsonizing the bacteria. These findings could not be explained either by an increased bacterial uptake, analyzed in vitro and in vivo using green fluorescent protein-tagged salmonellae, or by a defect in the respiratory burst or in NO production. The data presented here suggest the possibility of novel pathways by which C1q may modulate the pathogenesis of infectious diseases caused by intracellular pathogens.

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Role of gastrin/CCK-B receptors in meal-stimulated acid secretion in rats

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1997.272.5.g1243 ◽

1997 ◽

Vol 272 (5) ◽

pp. G1243-G1248 ◽

Cited By ~ 2

Author(s):

K. Aurang ◽

C. F. Spraggs ◽

C. Jordan ◽

K. C. Lloyd

Keyword(s):

Acid Secretion ◽

Gastric Acid Secretion ◽

Gastric Acid ◽

Rat Model ◽

Acid Output ◽

Male Rats ◽

Plasma Histamine ◽

Plasma Gastrin

Gastrin is the principal hormonal mediator of gastric acid secretion. Using an in vivo, intact, anesthetized rat model, we studied the role of gastrin/cholecystokinin (CCK)-B receptors in regulating the release of histamine and somatostatin during intragastric stimulation of acid secretion during a peptone meal. In pylorusligated, adult male rats (each implanted with a gastric cannula and portal venous and splenic artery catheters), after a 30-min basal period, gastric acid secretion was stimulated for 90 min either by an intravenous infusion of gastrin-17 (15 micrograms.kg-1.h-1) or by extragastric titration of 5 ml 8% peptone meal at pH 5.5. Basal and stimulated acid outputs and portal venous plasma gastrin, histamine, and somatostatin concentrations were measured before and after close-arterial injection of a new, relatively selective, gastrin/CCK-B receptor antagonist GR143330X. GR143330X reduced basal acid output by 50% but not basal plasma gastrin, histamine, or somatostatin concentrations. GR143330X reduced gastrin-stimulated acid output by 80%, plasma histamine by 70%, and plasma somatostatin by 34%. During intragastric peptone meal stimulation GR143330X reduced the acid response by 42% during the 30- to 60-min period but not during the 60- to 90-min period. GR143330X reduced the plasma histamine response by 72 and 68%, and the plasma somatostatin response by 32 and 54% during the 30- to 60- and 60- to 90-min periods, respectively. GR143330X did not block the gastrin response to peptone at any time. These results indicate that GR143330X is an effective agent for blocking gastrin-stimulated acid secretion and histamine and somatostatin release in rats. Furthermore, we show for the first time in an intact, in vivo, anesthetized rat model that meal-stimulated activation of gastrin/CCK-B receptors stimulates acid secretion in part by regulating the release of histamine and somatostatin.

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