bluuebunny/crossref_metadata_2025_split huggingface dataset:
2,3-Butanediol Synthesis and the Emergence of the
Vibrio cholerae
El Tor Biotype
Authors: Yoon Sang Sun , Mekalanos John J. 
Published: November 2006

ABSTRACT

Vibrio cholerae
is an aquatic bacterium that causes the severe diarrheal disease cholera.
V. cholerae
strains of the O1 serogroup exist as two biotypes, classical and El Tor. Toxigenic strains of the El Tor biotype emerged to cause the seventh pandemic of cholera in 1961 and subsequently displaced strains of the classical biotype both in the environment and as a cause of cholera within a decade. The factors that drove emergence of the El Tor biotype and the displacement of the classical biotype are unknown. Here, we show a unique difference in carbohydrate metabolism between these two biotypes. When grown with added carbohydrates, classical biotype strains generated a sharp decrease in medium pH, resulting in loss of viability. However, growth of El Tor biotype strain N16961 was enhanced due to its ability to produce 2,3-butanediol, a neutral fermentation end product, and suppress the accumulation of organic acids. An N16961 mutant (SSY01) defective in 2,3-butanediol synthesis showed the same defect in growth that classical biotype strains show in media rich in carbohydrates. Importantly, the SSY01 mutant was attenuated in its ability to colonize the intestines of infant mice, suggesting that host carbohydrates may be available to
V. cholerae
within the intestinal environment. Similarly, the SSY01 mutant failed to develop biofilms when utilizing
N
-acetyl-
d
-glucosamine as a carbon source. Because growth on
N
-acetyl-
d
-glucosamine likely reflects the ability of a strain to grow on chitin in certain aquatic environments, we conclude that the strains of classical biotype are likely defective compared to those of El Tor in growth in any environmental niche that is rich in chitin and/or other metabolizable carbohydrates. We propose that the ability to metabolize sugars without production of acid by-products might account for the improved evolutionary fitness of the
V. cholerae
El Tor biotype compared to that of the classical biotype both as a global cause of cholera and as an environmental organism.
Ascaris suum-Derived Products Suppress Mucosal Allergic Inflammation in an Interleukin-10-Independent Manner via Interference with Dendritic Cell Function
Authors: McConchie Brittany W. , Norris Hillary H. , Bundoc Virgilio G. , Trivedi Shweta , Boesen Agnieszka , Urban Joseph F. , Keane-Myers Andrea M. 
Published: November 2006

ABSTRACTWe have previously demonstrated that protection from allergic inflammation byAscaris suuminfection was characterized by a global increase in interleukin-10 (IL-10) and the development of protective CD4+/CD25+T cells (L. Schopf, S. Luccioli, V. Bundoc, P. Justice, C. C. Chan, B. J. Wetzel, H. H. Norris, J. F. Urban, Jr., and A. Keane-Myers, Investig. Ophthalmol. Vis. Sci.46:2772-2780, 2005). Here, we usedA. suumpseudocoelomic fluid (PCF) in lieu of infection to define molecular mechanisms of allergic protection in a mouse model of allergic inflammation. Mice were sensitized with ragweed (RW) and PCF (RW/PCF), PCF alone, or RW alone and then challenged intratracheally, intranasally, and supraocularly with RW. Histological examination of the eyes and lungs, analysis of the bronchoalveolar lavage fluid (BALF), and characterization of ex vivo cytokine responses were performed to determine allergic inflammatory responses. RW/PCF-treated mice had suppressed allergic immune responses compared to mice given RW alone. To investigate whether IL-10 was involved in PCF-mediated allergic protection, similar experiments were performed using mice genetically deficient for IL-10. Persistent protection from allergic disease was observed in the absence of IL-10, indicating the primary mechanism of PCF protection is IL-10 independent. Ex vivo and in vitro analysis of PCF-treated dendritic cells (DC) demonstrated reduced activation receptor expression and cytokine production in response to either RW or lipopolysaccharide stimulation. These findings extend previous studies that showed infection withA. suumalters expression of allergic disease and suggest that PCF can contribute to this effect by interference with DC function.
Oral Immunization withAcanthamoeba castellaniiMannose-Binding Protein Ameliorates Amoebic Keratitis
Authors: Garate M. , Alizadeh H. , Neelam S. , Niederkorn J. Y. , Panjwani N. 
Published: November 2006

ABSTRACTAcanthamoeba castellaniimannose-binding protein (MBP) mediates adhesion of the amoebae to corneal epithelial cells, a key first step in the pathogenesis ofAcanthamoebakeratitis (AK), a devastating corneal infection. In the present study, we demonstrate that oral immunization with recombinant MBP ameliorates AK in a hamster animal model and that this protection is associated with the presence of elevated levels of anti-MBP immunoglobulin A in the tear fluid of the immunized animals.
Identification and Characterization of a Novel ABC Iron Transport System,
fit
, in
Escherichia coli
Authors: Ouyang Zhiming , Isaacson Richard 
Published: November 2006

ABSTRACT

A putative ABC transporter,
fit
, with significant homology to several bacterial iron transporters was identified in
Escherichia coli
. The
E. coli fit
system consists of six genes designated
fitA
,
-B
,
-C
,
-D
,
-E
, and -
R
. Based on DNA sequence analysis,
fit
encodes an outer membrane protein (FitA), a periplasmic binding protein (FitE), two permease proteins (FitC and -D), an ATPase (FitB), and a hypothetical protein (FitR). Introduction of the
E. coli fit
system into
E. coli
strain K-12 increased intracellular iron content and transformed bacteria were more sensitive to streptonigrin, which suggested that
fit
transports iron in
E. coli
. Expression of
fit
was studied using a
lacZ
reporter assay. A functional, bidirectional promoter was identified in the intergenic region between genes
fitA
and
fitB.
The expression of the
E. coli fit
system was found to be induced by iron limitation and repressed when Fe
2+
was added to minimal medium. Several
fit
mutants were created in
E. coli
using an in vitro transposon mutagenesis strategy. Mutations in
fit
did not affect bacterial growth in iron-restricted media. Using a growth promotion test, it was found that
fit
was not able to transport enterobactin, ferrichrome, transferrin, and lactoferrin in
E. coli
.
Mac-1+Cells Are the Predominant Subset in the Early Hepatic Lesions of Mice Infected withFrancisella tularensis
Authors: Rasmussen John W. , Cello Jeronimo , Gil Horacio , Forestal Colin A. , Furie Martha B. , Thanassi David G. , Benach Jorge L. 
Published: November 2006

ABSTRACTThe cell composition of early hepatic lesions of experimental murine tularemia has not been characterized with specific markers. The appearance of multiple granulomatous-necrotic lesions in the liver correlates with a marked increase in the levels of serum alanine transferase and lactate dehydrogenase.Francisella tularensis, detected by specific antibodies, can be first noted by day 1 and becomes associated with the lesions by 5 days postinoculation. These lesions become necrotic, with some evidence of in situ apoptosis. The lesions do not contain B, T, or NK cells. Rather, the lesions are largely composed of two subpopulations of Mac-1+cells that are associated with the bacteria. Gr-1+Mac-1+immature myeloid cells and major histocompatibility complex class II-positive (MHC-II+) Mac-1+macrophages were the most abundant cell phenotypes found in the granuloma and are likely major contributors in controlling the infection in its early stages. Our findings have shown that there is an early development of hepatic lesions whereF. tularensiscolocalizes with both Gr-1+Mac-1+and MHC-II+Mac-1+cells.
Listeria monocytogenesFlagella Are Used for Motility, Not as Adhesins, To Increase Host Cell Invasion
Authors: O'Neil Heather S. , Marquis Hélène 
Published: November 2006

ABSTRACTFlagellar structures contribute to the virulence of multiple gastrointestinal pathogens either as the effectors of motility, as adhesins, or as a secretion apparatus for virulence factors.Listeria monocytogenesis a food-borne, gram-positive pathogen that uses flagella to increase the efficiency of epithelial cell invasion (A. Bigot, H. Pagniez, E. Botton, C. Frehel, I. Dubail, C. Jacquet, A. Charbit, and C. Raynaud, Infect. Immun.73:5530-5539, 2005; L. Dons, E. Eriksson, Y. Jin, M. E. Rottenberg, K. Kristensson, C. N. Larsen, J. Bresciani, and J. E. Olsen, Infect. Immun.72:3237-3244, 2004). In this study, we aimed to elucidate the mechanism by which flagella contribute toL. monocytogenesinvasion. To examine the role of flagella as adhesins, invasion and adhesion assays were performed with flagellated motile and nonmotile bacteria and nonflagellated bacteria. We observed that flagellated but nonmotile bacteria do not adhere to or invade human epithelial cells more efficiently than nonflagellated bacteria. These results indicated that flagella do not function as adhesins to enhance the adhesion ofL. monocytogenesto targeted host cells. Instead, it appears that motility is important for tissue culture invasion. Furthermore, we tested whether motility contributes to early colonization of the gastrointestinal tract using a competitive index assay in which mice were infected orally with motile and nonmotile bacteria in a 1:1 ratio. Differential bacterial counts demonstrated that motile bacteria outcompete nonmotile bacteria in the colonization of the intestines at early time points postinfection. This difference is also reflected in invasion of the liver 12 h later, suggesting that flagellum-mediated motility enhancesL. monocytogenesinfectivity soon after bacterial ingestion in vivo.
Antibodies Enhance Interaction of
Vibrio cholerae
with Intestinal M-Like Cells
Authors: Blanco Luz P. , DiRita Victor J. 
Published: November 2006

ABSTRACT

Intestinal M cells bear a receptor for secretory immunoglobulin A (IgA) (sIgA) facing the lumen of the epithelial surfaces. Cells bearing this receptor are also found throughout an experimental monolayer consisting of polarized Caco-2 cells, a colon adenocarcinoma cell line. The presence of antibodies (mainly sIgA) in the lumen of the small intestine led us to explore the participation of the sIgA receptor and antibodies in the interaction of Caco-2-associated M-like cells with the mucosal pathogen
Vibrio cholerae
. Here, we demonstrate that sIgA antibodies isolated from pooled healthy human colostrums, as well as IgG from pooled healthy human serum, can recognize
V. cholerae
. Furthermore, opsonization enhances M-like-cell transcytosis of
V. cholerae
strains. We also show that the cholera toxin (CT) receptor ganglioside GM
1
colocalizes with the sIgA receptor in cells of the epithelial monolayer. Both sIgA and IgG antibodies compete for the attachment of soluble CT subunit B to immobilized GM
1
. Our results indicate that in this in vitro model system of intestinal epithelia, human sIgA and IgG contribute to the uptake of
V. cholerae
by M-like cells, probably through an interaction with GM
1
. Our results support previous findings of others showing that sIgA can act as an endogenous adjuvant and that sIgA is important for the antigen-sampling function of M cells.
Early Neutrophil Recruitment and Aggregation in the Murine Lung Inhibit Germination ofAspergillus fumigatusConidia
Authors: Bonnett Colin R. , Cornish E. Jean , Harmsen Allen G. , Burritt James B. 
Published: November 2006

ABSTRACTSeveral types of polymorphonuclear neutrophil (PMN) deficiency are a predisposing condition for fatalAspergillus fumigatusinfection. In order to study the defensive role of PMNs in the lungs, with particular reference to PMN recruitment and antimicrobial oxidant activity, responses to pulmonary instillation ofA. fumigatusconidia were examined. Responses in BALB/c and C57BL/6 mice were compared with those in CXCR2−/−and gp91phox−/−mice, which are known to have delayed recruitment of PMN to the lungs in response to inflammatory stimuli and inactive NADPH oxidase, respectively. In BALB/c mice, PMNs were recruited to the lungs and formed oxidase-active aggregates with conidia, which inhibited germination. In C57BL/6, gp91phox−/−, and CXCR2−/−mice, PMN recruitment was slower and there was increased germination compared to that in BALB/c mice at 6 and 12 h. In gp91phox−/−mice, germination was extensive in PMN aggregates but negligible in alveolar macrophages (AM). Lung sections taken at 6 and 48 h from BALB/c mice showed PMN accumulation at peribronchiolar sites but no germinating conidia. Those from C57BL/6 and CXCR2−/−mice showed germinating conidia at 6 h but not at 48 h and few inflammatory cells. In contrast, those from gp91phox−/−mice showed germination at 6 h with more-extensive hyphal proliferation and tissue invasion at 48 h. These results indicate that when the lungs are exposed to large numbers of conidia, in addition to the phagocytic activity of AM, early PMN recruitment and formation of oxidative-active aggregates are essential in preventing germination ofA. fumigatusconidia.
Caveolin-1-Deficient Mice Show Defects in Innate Immunity and Inflammatory Immune Response during
Salmonella enterica
Serovar Typhimurium Infection
Authors: Medina Freddy A. , de Almeida Cecilia J. , Dew Elliott , Li Jiangwei , Bonuccelli Gloria , Williams Terence M. , Cohen Alex W. , Pestell Richard G. , Frank Philippe G. , Tanowitz Herbert B. , Lisanti Michael P. 
Published: November 2006

ABSTRACT

A number of studies have shown an association of pathogens with caveolae. To this date, however, there are no studies showing a role for caveolin-1 in modulating immune responses against pathogens. Interestingly, expression of caveolin-1 has been shown to occur in a regulated manner in immune cells in response to lipopolysaccharide (LPS). Here, we sought to determine the role of caveolin-1 (Cav-1) expression in
Salmonella
pathogenesis. Cav-1
−/−
mice displayed a significant decrease in survival when challenged with
Salmonella enterica
serovar Typhimurium. Spleen and tissue burdens were significantly higher in Cav-1
−/−
mice. However, infection of Cav-1
−/−
macrophages with serovar Typhimurium did not result in differences in bacterial invasion. In addition, Cav-1
−/−
mice displayed increased production of inflammatory cytokines, chemokines, and nitric oxide. Regardless of this, Cav-1
−/−
mice were unable to control the systemic infection of
Salmonella
. The increased chemokine production in Cav-1
−/−
mice resulted in greater infiltration of neutrophils into granulomas but did not alter the number of granulomas present. This was accompanied by increased necrosis in the liver. However, Cav-1
−/−
macrophages displayed increased inflammatory responses and increased nitric oxide production in vitro in response to
Salmonella
LPS. These results show that caveolin-1 plays a key role in regulating anti-inflammatory responses in macrophages. Taken together, these data suggest that the increased production of toxic mediators from macrophages lacking caveolin-1 is likely to be responsible for the marked susceptibility of caveolin-1-deficient mice to
S. enterica
serovar Typhimurium.
Monocyte Chemoattractant Protein 1 Does Not Contribute to Protective Immunity against Pneumococcal Pneumonia
Authors: Dessing Mark C. , de Vos Alex F. , Florquin Sandrine , van der Poll Tom 
Published: November 2006

ABSTRACTTo determine the role of monocyte chemoattractant protein 1 (MCP-1) during pneumococcal pneumonia, MCP-1 knockout and wild-type mice were infected withStreptococcus pneumoniae. Pulmonary MCP-1 levels were strongly correlated to bacterial loads in wild-type mice. However, MCP-1 knockout and wild-type mice were indistinguishable with respect to bacterial growth, inflammatory responses, and lethality.
Dual Roles of
Helicobacter pylori
NapA in Inducing and Combating Oxidative Stress
Authors: Wang Ge , Hong Yang , Olczak Adriana , Maier Susan E. , Maier Robert J. 
Published: November 2006

ABSTRACT

Neutrophil-activating protein (NapA) has been well documented to play roles in human neutrophil recruitment and in stimulating host cell production of reactive oxygen intermediates (ROI). A separate role for NapA in combating oxidative stress within
H. pylori
was implied by studies of various
H. pylori
mutant strains. Here, physiological analysis of a
napA
strain was the approach used to assess the iron-sequestering and stress resistance roles of NapA, its role in preventing oxidative DNA damage, and its importance to mouse colonization. The
napA
strain was more sensitive to oxidative stress reagents and to oxygen, and it contained fourfold more intracellular free iron and more damaged DNA than the parent strain. Pure, iron-loaded NapA bound to DNA, but native NapA did not, presumably linking iron levels sensed by NapA to DNA damage protection. Despite its in vitro phenotype of sensitivity to oxidative stress, the
napA
strain showed normal (like that of the wild type) mouse colonization efficiency in the conventional in vivo assay. By use of a modified mouse inoculation protocol whereby nonviable
H. pylori
is first inoculated into mice, followed by (live) bacterial strain administration, an in vivo role for NapA in colonization efficiency could be demonstrated. NapA is the critical component responsible for inducing host-mediated ROI production, thus inhibiting colonization by the
napA
strain. An animal colonization experiment with a mixed-strain infection protocol further demonstrated that the
napA
strain has significantly decreased ability to survive when competing with the wild type.
H. pylori
NapA has unique and separate roles in gastric pathogenesis.
Identification of Potential Virulence Determinants by
Himar1
Transposition of Infectious
Borrelia burgdorferi
B31
Authors: Botkin Douglas J. , Abbott April N. , Stewart Philip E. , Rosa Patricia A. , Kawabata Hiroki , Watanabe Haruo , Norris Steven J. 
Published: November 2006

ABSTRACT

Lyme disease
Borrelia
organisms are highly invasive spirochetes that alternate between vertebrate and arthropod hosts and that establish chronic infections and elicit inflammatory reactions in mammals. Although progress has been made in the targeted mutagenesis of individual genes in infectious
Borrelia burgdorferi
, the roles of the vast majority of gene products in pathogenesis remain unresolved. In this study, we examined the feasibility of using transposon mutagenesis to identify infectivity-related factors in
B. burgdorferi
. The transformable, infectious strain 5A18 NP1 was transformed with the spirochete-adapted
Himar1
transposon delivery vector pMarGent to create a small library of 33 insertion mutants. Single mouse inoculations followed by culture of four tissue sites and serology were used to screen the mutants for infectivity phenotypes. Mutants that appeared attenuated (culture positive at some sites) or noninfectious (negative at all sites) and contained the virulence-associated plasmids lp25 and lp28-1 were examined in more extensive animal studies. Three of these mutants (including those with insertions in the putative
fliG-1-
encoded flagellar motor switch protein and the
guaB-
encoded IMP dehydrogenase) were noninfectious, whereas four clones appeared to exhibit reduced infectivity. Serological reactivity in VlsE enzyme-linked immunosorbent assays correlated with the assignment of mutants to the noninfectious or attenuated-infectivity groups. The results of this study indicate that random transposon mutagenesis of infectious
B. burgdorferi
is feasible and will be of value in studying the pathogenesis of Lyme disease
Borrelia
.
Potential Source of
Francisella tularensis
Live Vaccine Strain Attenuation Determined by Genome Comparison
Authors: Rohmer Laurence , Brittnacher Mitchell , Svensson Kerstin , Buckley Danielle , Haugen Eric , Zhou Yang , Chang Jean , Levy Ruth , Hayden Hillary , Forsman Mats , Olson Maynard , Johansson Anders , Kaul Rajinder , Miller Samuel I. 
Published: November 2006

ABSTRACT

Francisella tularensis
is a bacterial pathogen that causes the zoonotic disease tularemia and is important to biodefense. Currently, the only vaccine known to confer protection against tularemia is a specific live vaccine strain (designated LVS) derived from a virulent isolate of
Francisella tularensis
subsp.
holarctica
. The origin and source of attenuation of this strain are not known. To assist with the design of a defined live vaccine strain, we sought to determine the genetic basis of the attenuation of LVS. This analysis relied primarily on the comparison between the genome of LVS and
Francisella tularensis holarctica
strain FSC200, which differ by only 0.08% of their nucleotide sequences. Under the assumption that the attenuation was due to a loss of function(s), only coding regions were examined in this comparison. To complement this analysis, the coding regions of two slightly more distantly related
Francisella tularensis
strains were also compared against the LVS coding regions. Thirty-five genes show unique sequence variations predicted to alter the protein sequence in LVS compared to the other
Francisella tularensis
strains. Due to these polymorphisms, the functions of 15 of these genes are very likely lost or impaired. Seven of these genes were demonstrated to be under stronger selective constraints, suggesting that they are the most probable to be the source of LVS attenuation and useful for a newly defined vaccine.
Borrelia burgdorferiComplement Regulator-Acquiring Surface Protein 1 of the Lyme Disease Spirochetes Is Expressed in Humans and Induces Antibody Responses Restricted to Nondenatured Structural Determinants
Authors: Rossmann Evelyn , Kitiratschky Veronique , Hofmann Heidelore , Kraiczy Peter , Simon Markus M. , Wallich Reinhard 
Published: November 2006

ABSTRACTBorrelia burgdorfericomplement regulator-acquiring surface protein 1 (CRASP-1), the dominant factor H and FHL-1-binding protein of the Lyme disease spirocheteB. burgdorferi, is implicated in pathogen persistence and was recently reported to be nonimmunogenic in humans. Here we show that serum samples from Lyme disease patients contain antibodies with exclusive specificity for nondenatured structural determinants of CRASP-1.
Prebiotic Galactooligosaccharides Reduce Adherence of EnteropathogenicEscherichia colito Tissue Culture Cells
Authors: Shoaf Kari , Mulvey George L. , Armstrong Glen D. , Hutkins Robert W. 
Published: November 2006

ABSTRACTPrebiotic oligosaccharides are thought to provide beneficial effects in the gastrointestinal tract of humans and animals by stimulating growth of selected members of the intestinal microflora. Another means by which prebiotic oligosaccharides may confer health benefits is via their antiadhesive activity. Specifically, these oligosaccharides may directly inhibit infections by enteric pathogens due to their ability to act as structural mimics of the pathogen binding sites that coat the surface of gastrointestinal epithelial cells. In this study, the ability of commercial prebiotics to inhibit attachment of microcolony-forming enteropathogenicEscherichia coli(EPEC) was investigated. The adherence of EPEC strain E2348/69 on HEp-2 and Caco-2 cells, in the presence of fructooligosaccharides, inulin, galactooligosaccharides (GOS), lactulose, and raffinose was determined by cultural enumeration and microscopy. Purified GOS exhibited the greatest adherence inhibition on both HEp-2 and Caco-2 cells, reducing the adherence of EPEC by 65 and 70%, respectively. In addition, the average number of bacteria per microcolony was significantly reduced from 14 to 4 when GOS was present. Adherence inhibition by GOS was dose dependent, reaching a maximum at 16 mg/ml. When GOS was added to adhered EPEC cells, no displacement was observed. The expression of BfpA, a bundle-forming-pilus protein involved in localized adherence, was not affected by GOS, indicating that adherence inhibition was not due to the absence of this adherence factor. In addition, GOS did not affect autoaggregation. These observations suggest that some prebiotic oligosaccharides may have antiadhesive activity and directly inhibit the adherence of pathogens to the host epithelial cell surface.