bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lipoprotein PsaA in Virulence ofStreptococcus pneumoniae: Surface Accessibility and Role in Protection from Superoxide
Authors: Johnston Jason W. , Myers Lisa E. , Ochs Martina M. , Benjamin William H. , Briles David E. , Hollingshead Susan K. 
Published: September 2004

ABSTRACTPsaA ofStreptococcus pneumoniae, originally believed to be an adhesin, is the lipoprotein component of an Mn2+transporter. Mutations inpsaAcause deficiencies in growth, virulence, adherence, and the oxidative stress response. Immunofluorescence microscopy shows that PsaA is hidden beneath the cell wall and the polysaccharide capsule and only exposed to antibodies upon cell wall removal. ApsaBCdeletion mutant, expressing PsaA normally, was as deficient in adherence to Detroit 562 cells as were strains lacking PsaA. Thus, PsaA does not appear to act directly as an adhesin, but rather,psaAmutations indirectly affect this process through the disruption of Mn2+transport. The deficiency in Mn2+transport also causes hypersensitivity to oxidative stress from H2O2and superoxide. In a chemically defined medium, growth of the wild-type strain was possible in the absence of Fe2+and Mn2+cations after a lag of about 15 h. Addition of Mn2+alone or together with Fe2+allowed prompt and rapid growth. In the absence of Mn2+, the addition of Fe2+alone extended the 15-h lag phase to 25 h. Thus, while Fe2+adversely affects the transition from lag phase to log phase, perhaps through increasing oxidative stress, this effect is relieved by the presence of Mn2+. A scavenger specific for superoxides but not those specific for hydroxyl radicals or H2O2was able to eliminate the inhibition of growth caused by iron supplementation in the absence of Mn2+. This implies that superoxides are a key player in oxidative stress generated in the presence of iron.
Tissue-Specific Adherent
Enterococcus faecalis
Strains That Show Highly Efficient Adhesion to Human Bladder Carcinoma T24 Cells Also Adhere to Extracellular Matrix Proteins
Authors: Tomita Haruyoshi , Ike Yasuyoshi 
Published: September 2004

ABSTRACT

The ability of
Enterococcus faecalis
clinical isolates to adhere to immobilized extracellular matrixes (ECMs) coating the walls of microtiter plates was examined by microscopy. The ECMs consisted of fibronectin, laminin, collagen types I, II, IV, and V, fibrinogen, and lactoferrin. With the exception of fibrinogen, each isolate showed a different level of adherence to each of the ECMs. No significant level of adherence to fibrinogen was observed for any isolate. The tissue-specific adhesive strains AS11, AS12, AS14, AS15, HT11, and HT12, which showed highly efficient adherence to human bladder carcinoma T24 cells and human bladder epithelial cells, showed strong adherence to fibronectin, laminin, and collagen type I, II, IV, and V ECMs, and the levels were greater than 10
4
cells/mm
2
of well surface coated by ECM. None of the isolates that showed little adherence to human bladder carcinoma T24 cells showed efficient adherence to all the ECMs. The levels of adherence of gelatinase-producing isolates to the collagens were lower than the levels of adherence of gelatinase-negative isolates. When tissue-specific adhesive strains that adhered strongly to each ECM were preincubated with fibronectin, the adherence of the strains to fibronectin was inhibited, but the adherence of the strains to collagen type IV was not inhibited. Likewise, preincubation with collagen type IV inhibited adherence to collagen type IV but not adherence to fibronectin. All of the
E. faecalis
isolates were shown to carry the
ace
gene by PCR analysis performed with specific primers for collagen binding domain A of
ace
. The
ace
gene encodes Ace (adhesin of collagen from enterococci). The
prtF
gene of group A streptococci, which encodes the fibronectin binding protein of group A streptococci, was not detected in the tissue-specific adhesive strains by Southern analysis performed with the
prtF
probe of the
Streptococcus pyogenes
JRS4 strain. Mutants with altered collagen binding were isolated by insertion of Tn
916
into the chromosome of tissue-specific adhesive strain AS14. The number of mutant adhesive bacterial cells that adhered to collagen and also to laminin was 1 or 2 orders lower than the number observed for the wild-type strain, but the level of adherence to fibronectin remained the same as that of the wild-type strain.
Invasion Profiles of Brazilian Field Isolates of
Plasmodium falciparum
: Phenotypic and Genotypic Analyses
Authors: Lobo Cheryl-Ann , de Frazao Karla , Rodriguez Marilis , Reid Marion , Zalis Mariano , Lustigman Sara 
Published: September 2004

ABSTRACT

The invasion of red blood cells (RBCs) by
Plasmodium falciparum
is dependent on multiple molecular interactions between erythrocyte receptors and parasite ligands. Invasion studies using culture-adapted parasite strains have indicated significant receptor heterogeneity. It is not known whether this heterogeneity reflects the parasite invasion arsenal in the field. We have studied the invasion phenotypes of 14 distinct field isolates from the Legal Amazon areas of Brazil by using erythrocyte invasion assays to investigate invasion into normal, enzyme-treated, and clinical-mutant RBCs. Analysis of these isolates revealed four distinct invasion profiles. Using En(a−) cells to get an unequivocal estimate of the use of glycophorin A (GPA) as a receptor, we found that the 175-kDa erythrocyte-binding antigen (EBA-175)/GPA pathway was used by a minority of the parasite isolates studied. Although polymorphism of region II domains at specific amino acid positions in both EBA-140 and EBA-181 was found in these field isolates, this did not correlate with invasion profiles and thus receptor selectivity. These studies have further confirmed the existence of a significant diversity of invasion pathways in nature and suggest that additional parasite ligands will have to be targeted to devise global vaccines that will work in the field.
Naturally Acquired Passive Protective Activity against
Neisseria meningitidis
Group C in the Absence of Serum Bactericidal Activity
Authors: Welsch Jo Anne , Granoff Dan 
Published: September 2004

ABSTRACT

The hallmark of immunity to meningococcal disease is a bactericidal titer in serum of ≥1:4 measured with human complement, but this threshold titer may underestimate the extent of protection. We used the infant rat model of meningococcal bacteremia to measure group C passive protective activity in serum samples from 91 unimmunized adults living in California. A total of 35 sera (38.5%) had passive protective activity. Sera with complement-mediated bactericidal titers of ≥1:4 were 3.4-fold more likely to confer protection (89%) than nonbactericidal sera (26%;
P
< 0.0001). Thus, bactericidal titers of ≥1:4 are a marker of protection, but this threshold lacks sensitivity for predicting protective activity. We investigated the 73 sera with bactericidal titers of <1:4 to determine the basis of protective activity. The 19 sera with protective activity had a higher geometric mean group C anticapsular antibody concentration (0.72 μg/ml) than the 54 sera that lacked protective activity (0.16 μg/ml;
P
< 0.001). Thus, protective activity in the absence of bactericidal activity was associated with higher concentrations of anticapsular antibodies, but not all sera with anticapsular antibodies conferred protection. Of 18 nonbactericidal sera with anticapsular antibody concentrations between 0.31 and 0.99 μg/ml, the 11 sera that conferred protection had a higher mean antibody avidity constant (21.9 nM
−1
) than the 7 nonprotective sera (14.6 nM
−1
;
P
< 0.03). Thus, in sera with titers of <1:4, protective activity is associated with higher-avidity group C anticapsular antibodies, which are present in concentrations insufficient to elicit complement-mediated bacteriolysis in vitro but sufficient to confer protection in an in vivo bacteremia model.
Porphyromonas gingivalisStrain-Dependent Activation of Human Endothelial Cells
Authors: Walter Clemens , Zahlten Janine , Schmeck Bernd , Schaudinn Christoph , Hippenstiel Stefan , Frisch Eckehard , Hocke Andreas C. , Pischon Nicole , Kuramitsu Howard K. , Bernimoulin Jean-Pierre , Suttorp Norbert , Krüll Matthias 
Published: September 2004

ABSTRACTPorphyromonas gingivalisis an important bacterium involved in periodontal diseases. Colonization by periodontopathogens has been associated with severe local inflammatory reactions in the connective tissue. In this study we characterizedP. gingivalis-mediated infection and activation of human umbilical vein endothelial cells by using two strains of different virulence capacities, strains ATCC 53977 and DSMZ 20709. Both strains were able to adhere to and infect endothelial cells with an infection rate of 0.48% for ATCC 53977 and 0.007% for DSMZ 20709. The triggering of two signal transduction pathways inP. gingivalis-infected endothelial cells was demonstrated for both strains, with a rapid increase of p38 mitogen-activated protein kinase phosphorylation and a more delayed degradation of IκBα, followed by nuclear translocation of NF-κB. In addition, both strains induced enhanced expression of endothelial adhesion molecules E-selectin and intracellular adhesion molecule 1 (ICAM-1). Target cell activation was independent of bacterial fimbriae expression since thefimAknockout strain A7436 ΔfimAinduced the same level of ICAM-1 as the corresponding wild type (A7436-WT). Thus, twoP. gingivalisstrains, ATCC 53799 and DSMZ 20709, infect endothelial cells and trigger signaling cascades leading to endothelial activation, which in turn may result in or promote severe local and systemic inflammation.
Strain-Dependent Role of BrkA duringBordetella pertussisInfection of the Murine Respiratory Tract
Authors: Elder Kelly D. , Harvill Eric T. 
Published: September 2004

ABSTRACTBordetella pertussis, the causative agent of whooping cough, expresses many virulence factors believed to be involved in infection and disease progression. While these factors as a group are required for infection, deletion of individual virulence factor genes generally has limited effects on the ability ofB. pertussisto efficiently infect the respiratory tract of mice, suggesting they may perform noncritical or redundant functions. We have recently observed that aB. pertussisstrain, putatively with a mutation of a single gene,brkA, results in a severe defect in vivo. Although BrkA has been shown to be required forB. pertussisto resist complement-mediated killing in vitro, the relevance of these findings to the in vivo role of BrkA during infection has not been examined. Transducing this mutation into multiple wild-typeB. pertussisstrains allowed us to confirm the in vitro phenotype of reduced resistance to serum complement. All ΔbrkAmutants were increased in their sensitivity to complement in vitro, both in the presence and absence of antibodies. However, these strains differed substantially in their phenotypes in vivo. ΔbrkAmutants of recent clinical isolates were indistinguishable from wild-type strains in their efficient infection of respiratory organs, suggesting that the function of BrkA in these strains is noncritical or redundant. In contrast, multiple ΔbrkAstrains derived from Tohama I were severely defective during the first week postinoculation compared to their wild-type parent. This defect was present even in complement-deficient mice, revealing a complement-independent phenotype for the ΔbrkAmutant in respiratory tract infection.
Role of Cell-Cell Communication in Inhibiting Butyric Acid-Induced T-Cell Apoptosis
Authors: Kurita-Ochiai Tomoko , Seto Shintaro , Ochiai Kuniyasu 
Published: September 2004

ABSTRACT
We have previously demonstrated that human gingival fibroblasts rescue butyric acid-induced T-cell apoptosis via proinflammatory cytokines such as interleukin 6 (IL-6) and IL-11, which are produced by fibroblasts stimulated with butyric acid. In this study, we determined if T-cell adhesion to human gingival fibroblasts influenced the susceptibility of T cells to butyric acid-induced apoptosis. We have shown that the number of Jurkat T cells adherent to gingival fibroblasts (Gin-1 cells) was significantly increased by the addition of butyric acid. All Jurkat cells that adhered to Gin-1 cells remained viable, while the nonadherent Jurkat cells dropped into apoptosis. The increase in T-cell adhesion to fibroblasts was also observed when Jurkat cells, but not Gin-1 cells, were pretreated with butyric acid. The expression levels of CD44, very late antigen 2 (VLA-2) and VLA-5 but not of leukocyte function-associated antigen 1 (LFA-1) and VLA-4 on Jurkat cells were increased following treatment with butyric acid. Furthermore, pretreatment of butyric acid-sensitized Jurkat cells with monoclonal antibodies against CD44, VLA-2, and VLA-5, but not LFA-1 and VLA-4, followed by coculture with Gin-1 cells inhibited T-cell adhesion to fibroblasts and increased apoptosis of nonadherent T cells after coculture of gingival fibroblasts and Jurkat cells. These results indicate that T-cell adherence to fibroblasts is enhanced by butyric acid and that butyric acid-induced T-cell apoptosis is down-regulated by T-cell adhesion to gingival fibroblasts through an interaction with the adhesion molecules CD44, VLA-2, and VLA-5 expressed on T cells stimulated with butyric acid.
IcmF and DotU Are Required for Optimal Effector Translocation and Trafficking of the
Legionella pneumophila
Vacuole
Authors: VanRheenen Susan M. , Duménil Guillaume , Isberg Ralph R. 
Published: September 2004

ABSTRACT

The gram-negative bacterium
Legionella pneumophila
causes a severe form of pneumonia called Legionnaires' disease, characterized by bacterial replication within alveolar macrophages. Prior to intracellular replication, the vacuole harboring the bacterium must first escape trafficking to the host lysosome, a process that is dependent on the Dot/Icm type IV secretion system. To identify genes required for intracellular growth, bacterial mutants were isolated that were delayed in escape from the macrophage but which retain a minimally functional Dot/Icm machinery. The mutations were found in eight distinct genes, including three genes known to be required for optimal intracellular growth. Two of these genes,
icmF
and
dotU
, are located at one end of a cluster of genes that encode the type IV secretion system, yet both
icmF
and
dotU
lack orthologs in other type IV translocons. DotU protein is degraded in the early postexponential phase in wild-type
L. pneumophila
and at all growth phases in an
icmF
mutant. IcmF contains an extracytoplasmic domain(s) based on accessibility to a membrane-impermeant amine-reactive reagent. In the absence of either gene,
L. pneumophila
targets inappropriately to LAMP-1-positive compartments during macrophage infection, is defective in the formation of replicative vacuoles, and is impaired in the translocation of the effector protein SidC. Therefore, although IcmF and DotU do not appear to be part of the core type IV secretion system, these proteins are necessary for an efficiently functioning secretion apparatus.
Inhibition of Apoptosis byEscherichia coliK1 Is Accompanied by Increased Expression of BclXLand Blockade of Mitochondrial CytochromecRelease in Macrophages
Authors: Sukumaran Sunil K. , Selvaraj Suresh K. , Prasadarao Nemani V. 
Published: September 2004

ABSTRACTEscherichia coliK1 survival in the blood is a critical step for the onset of meningitis in neonates. Therefore, the circulating bacteria are impelled to avoid host defense mechanisms by finding a niche to survive and multiply. Our recent studies have shown thatE. coliK1 enters and survives in both monocytes and macrophages in the newborn rat model of meningitis as well as in macrophage cell lines. Here we demonstrate thatE. coliK1 not only extends the survival of human and murine infected macrophage cell lines but also renders them resistant to apoptosis induced by staurosporine. Macrophages infected with wild-typeE. coliexpressing outer membrane protein A (OmpA), but not with OmpA−E. coli, are resistant to DNA fragmentation and phosphatidylserine exposure induced by staurosporine. Infection with OmpA+E. coliinduces the expression of BclXL, an antiapoptotic protein, both at the mRNA level as assessed by gene array analysis and at the protein level as evaluated by immunoblotting. OmpA−E. coliinfection of macrophages induced the release of cytochromecfrom mitochondria into the cytosol and the activation of caspases 3, 6, and 9, events that were significantly blocked in OmpA+E. coli-infected macrophages. In addition, OmpA+E. coli-infected cells were resistant to a decrease in the transmembrane potential of mitochondria induced by staurosporine as measured by the MitoCapture fluorescence technique. Complementation of OmpA−E. coliwith a plasmid containing theompAgene restored the ability of OmpA−E. colito inhibit the apoptosis of infected macrophages, further demonstrating thatE. coliOmpA expression is critical for inducing macrophage survival and thereby finding a safe haven for its growth.
Development and Characterization of an In Vivo Central Venous Catheter
Candida albicans
Biofilm Model
Authors: Andes D. , Nett J. , Oschel P. , Albrecht R. , Marchillo K. , Pitula A. 
Published: September 2004

ABSTRACT

Biofilms represent a niche for microorganisms where they are protected from both the host immune system and antimicrobial therapies. Biofilm growth serves as an increasing source of clinical infections.
Candida
infections are difficult to manage due to their persistent nature and associated drug resistance. Observations made in biofilm research have generally been limited to in vitro models. Using a rat central venous catheter model, we characterized in vivo
Candida albicans
biofilm development. Time-course quantitative culture demonstrated a progressive increase in the burden of viable cells for the first 24 h of development. Fluorescence and scanning electron microscopy revealed a bilayered architecture. Adjacent to the catheter surface, yeast cells were densely embedded in an extracellular matrix. The layer adjacent to the catheter lumen was less dense. The outermost surface of the biofilm contained both yeast and hyphal forms, and the extracellular material in which they were embedded appeared fibrous. These architectural features were similar in many respects to those described for in vitro models. However, scanning electron microscopy also revealed host cells embedded within the biofilm matrix. Drug susceptibility was determined by using two assays and demonstrated a biofilm-associated drug resistance phenotype. The first assay demonstrated continued growth of cells in the presence of supra-MIC antifungal drug concentrations. The second assay demonstrated reduced susceptibility of biofilm-grown cells following removal from the biofilm structure. Lastly, the model provided sufficient nucleic material for study of differential gene expression associated with in vivo biofilm growth. Two fluconazole efflux pumps,
CDR1
and
CDR2
, were upregulated in the in vivo biofilm-associated cells. Most importantly, the studies described provide a model for further investigation into the molecular mechanisms of
C. albicans
biofilm biology and drug resistance. In addition, the model provides a means to study novel drug therapies and device technologies targeted to the control of biofilm-associated infections.
Enterococcal Surface Protein, Esp, Enhances Biofilm Formation by
Enterococcus faecalis
Authors: Tendolkar Preeti M. , Baghdayan Arto S. , Gilmore Michael S. , Shankar Nathan 
Published: September 2004

ABSTRACT

Enterococci play a dual role in human ecology. They serve as commensal organisms of the gastrointestinal tract and are also leading causes of multiple antibiotic-resistant hospital-acquired infection. Many nosocomial infections result from the ability of microorganisms to form biofilms. The molecular mechanisms involved in enterococcal biofilm formation are only now beginning to be understood. Enterococcal surface protein, Esp, has been reported to contribute to biofilm formation by
Enterococcus faecalis
. Recent studies have shown that enterococci form biofilms independently of Esp expression. To precisely determine what role Esp plays in
E. faecalis
biofilm formation, Esp was expressed on the cell surface of genetically well-defined, natively Esp-deficient strains, and isogenic Esp-positive and Esp-deficient strains were compared for their biofilm-forming ability. The results show that Esp expression leads to a significant increase in biofilm formation, irrespective of the strain tested. The contribution of Esp to biofilm formation was found to be most pronounced in the presence of 0.5% (wt/vol) or greater glucose. These results unambiguously define Esp as a key contributor to the ability of
E. faecalis
to form biofilms.
Bacterial Overgrowth in the Cystic Fibrosis Transmembrane Conductance Regulator Null Mouse Small Intestine
Authors: Norkina Oxana , Burnett Tim G. , De Lisle Robert C. 
Published: September 2004

ABSTRACTWe recently reported the inflammation of the cystic fibrosis (CF) mouse small intestine, and we hypothesized bacterial overgrowth as a possible cause. Quantitative PCR of bacterial 16S genomic DNA in the CF mouse small intestine revealed an increase of greater than 40-fold compared to controls. Sequencing of 16S PCR products and Gram staining showed that the majority of bacteria in the CF mouse intestine were gram negative. Bacteria were observed to colonize the mucus that accumulates in the intestinal lumen of mice with CF. Impaired Paneth cell defenses were suggested by observation of partially dispersed Paneth granules in the mucus plugs of CF mouse intestinal crypts, and this mucus was strongly immunoreactive for Paneth cell bactericidal products. The role of bacterial overgrowth in intestinal inflammation in CF was tested by treating mice with oral antibiotics (ciprofloxacin and metronidazole) for 3 weeks, which reduced bacterial load in the CF mouse small intestine over 400-fold. Antibiotic treatment decreased the expression of the inflammation-related genes mast cell protease 2, leucine-rich α2 glycoprotein/leucine-rich high endothelial venule glycoprotein, suppressor of cytokine signaling 3, hematopoietic cell transcript 1, and resistin-like molecule β/found in inflammatory zone 2, all of which were no longer expressed at levels significantly different from control levels. The reduction of intestinal bacteria also significantly improved the growth of CF mice but had no effect on the growth of wild-type mice. These data suggest that bacterial overgrowth in the CF mouse small intestine has a role in inflammation and contributes to the failure to thrive in this mouse model of CF.
TheStreptococcus pyogenesCapsule Is Required for Adhesion of Bacteria to Virus-Infected Alveolar Epithelial Cells and Lethal Bacterial-Viral Superinfection
Authors: Okamoto Shigefumi , Kawabata Shigetada , Terao Yutaka , Fujitaka Hideaki , Okuno Yoshinobu , Hamada Shigeyuki 
Published: September 2004

ABSTRACTAn apparent worldwide resurgence of invasive group AStreptococcus(GAS) infections remains unexplained. However, we recently demonstrated in mice that when an otherwise nonlethal intranasal GAS infection is preceded by a nonlethal influenza A virus (IAV) infection, induction of lethal invasive GAS infections is often the result. In the present study, we established several isogenic mutants from a GAS isolate and evaluated several virulence factors as candidates responsible for the induction of invasive GAS infections. Disruption of the synthesis of the capsule, Mga, streptolysin O, streptolysin S, or streptococcal pyrogenic exotoxin B of GAS significantly reduced mortality among mice superinfected with IAV and a mutant. In addition, the number of GAS organisms adhering to IAV-infected alveolar epithelial cells was markedly reduced with the capsule-depleted mutant, although this was not the case with the other mutants. Wild-type GAS was found to bind directly to IAV particles, whereas the nonencapsulated mutant showed much less ability to bind. These results suggest that the capsule plays a key role in the invasion of host tissues by GAS following superinfection with IAV and GAS.