bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enterococcus faecium
Low-Affinity
pbp5
Is a Transferable Determinant
Authors: Rice Louis B. , Carias Lenore L. , Rudin Susan , Laktičová Viera , Wood Aaron , Hutton-Thomas Rebecca 
Published: November 2005

ABSTRACT

Using 15 unrelated
Enterococcus faecium
isolates as donors, we demonstrated that ampicillin resistance was transferable to an
E. faecium
recipient containing a
pbp5
deletion for all but four strains. The transfers occurred at low frequencies (generally ca. 10
−9
transconjugants/recipient CFU), consistent with chromosome-to-chromosome transfer.
pbp5
transfer occurred within large genetic regions, and insertion into the recipient genome occurred most commonly into the recipient SmaI restriction fragment that had been created by the previous
pbp5
deletion. Restriction mapping of the region upstream of
pbp5
revealed a commonality of fragment sizes among the clinical isolates from the United States which differed significantly from those of three strains that were isolated from turkey feces. These data prove conclusively that
E. faecium pbp5
is a transferable determinant, even in the absence of a coresiding vancomycin resistance mobile element. They also suggest that the spread of high-level ampicillin resistance among U.S.
E. faecium
strains is due in part to the transfer of low-affinity
pbp5
between clinical isolates.
Pharmacodynamics of Caspofungin in a Murine Model of Systemic Candidiasis: Importance of Persistence of Caspofungin in Tissues to Understanding Drug Activity
Authors: Louie Arnold , Deziel Mark , Liu Weiguo , Drusano Michael F. , Gumbo Tawanda , Drusano George L. 
Published: November 2005

ABSTRACTPharmacokinetic and pharmacodynamic studies were conducted in a murine model of systemic candidiasis to determine the pharmacodynamic parameter linked with caspofungin efficacy. Additional studies defined the importance of persistent tissue drug concentrations to treatment outcome. The pharmacokinetics of caspofungin were determined in the serum and kidneys of infected mice over 96 h. Population pharmacokinetic analysis demonstrated a serum terminal half-life (t1/2) for caspofungin of 20.2 h when only serum concentrations were considered, but the terminalt1/2increased to 59.2 h when serum and kidney concentration-time data were comodeled. In dose-range studies, the dose-response effect was well described by an inhibitory sigmoid curve for the exposure-effect killing caused by the drug (r2> 0.96;P≪ 0.001). In dose-fractionation studies, fungal counts in kidneys were not statistically different for total doses given as one, two, or four equally divided doses over 96 h, indicating that the area under the concentration-time curve/MIC is the pharmacodynamic parameter that predicts caspofungin efficacy in our infection model. In a separate study, mice infected withCandida albicans24 h after serum concentrations of caspofungin fell below the MIC for the fungal isolate had significant reductions in fungal densities in their kidneys compared with the growth of fungi in the kidneys of untreated controls (P= 0.005). This in vivo biological assay demonstrates that therapeutic concentrations of caspofungin persist at the site of infection in kidney tissue well after serum concentrations fall below the MIC, underscoring the primacy of caspofungin levels in tissues on determining treatment outcome.
Population Pharmacokinetics of Amphotericin B Lipid Complex in Neonates
Authors: Würthwein Gudrun , Groll Andreas H. , Hempel Georg , Adler-Shohet Felice C. , Lieberman Jay M. , Walsh Thomas J. 
Published: November 2005

ABSTRACTThe pharmacokinetics of amphotericin B lipid complex (ABLC) were investigated in neonates with invasive candidiasis enrolled in a phase II multicenter trial. Sparse blood (153 samples; 1 to 9 per patient, 1 to 254 h after the dose) and random urine and cerebrospinal fluid (CSF) samples of 28 neonates (median weight [WT], 1.06 kg; range, 0.48 to 4.9 kg; median gestational age, 27 weeks; range, 24 to 41 weeks) were analyzed. Patients received intravenous ABLC at 2.5 (n= 15) or 5 (n= 13) mg/kg of body weight once a day over 1 or 2 h, respectively, for a median of 21 days (range, 4 to 47 days). Concentrations of amphotericin B were quantified as total drug by high-performance liquid chromatography. Blood data for time after dose (TAD) of <24 h fitted best to a one-compartment model with an additive-error model for residual variability, WT0.75(where 0.75 is an exponent) as a covariate of clearance (CL), and WT as a covariate of volume of distribution (V). Prior amphotericin B, postnatal age, and gestational age did not further improve the model. The final model equations were CL (liters/h) = 0.399 × WT0.75(interindividual variability, 35%) andV(liters) = 10.5 × WT (interindividual variability, 43%). Noncompartmental analysis of pooled data with a TAD of >24 h revealed a terminal half-life of 395 h. Mean concentrations in the urine after 1, 2, and 3 weeks ranged from 0.082 to 0.430 μg/ml, and those in CSF ranged from undetectable to 0.074 μg/ml. The disposition of ABLC in neonates was similar to that observed in other age groups: weight was the only factor that influenced clearance. Based on these results and previously published safety and efficacy data, we recommend a daily dosage between 2.5 and 5.0 mg/kg for treatment of invasiveCandidainfections in neonates.
A Cysteine Protease Inhibitor Protects Dogs from Cardiac Damage during Infection byTrypanosoma cruzi
Authors: Barr S. C. , Warner K. L. , Kornreic B. G. , Piscitelli J. , Wolfe A. , Benet L. , McKerrow J. H. 
Published: November 2005

ABSTRACTCruzain is an essential cysteine protease ofTrypanosoma cruziand a therapeutic target for Chagas' disease. Eight dogs were infected withT. cruzi; three were treated with an inhibitor of cruzain, K777, for 14 days. Treatment with K777 abrogated myocardial damage byT. cruzi, as documented by histopathological lesion scores and serum troponin I levels.
Host Restriction ofSalmonella entericaSerotype Typhi Is Not Caused by Functional Alteration of SipA, SopB, or SopD
Authors: Raffatellu Manuela , Sun Yao-Hui , Wilson R. Paul , Tran Quynh T. , Chessa Daniela , Andrews-Polymenis Helene L. , Lawhon Sara D. , Figueiredo Josely F. , Tsolis Renée M. , Adams L. Garry , Bäumler Andreas J. 
Published: November 2005

ABSTRACTSalmonella entericaserotype Typhi is a strictly human adapted pathogen that does not cause disease in nonprimate vertebrate hosts, whileSalmonella entericaserotype Typhimurium is a broad-host-range pathogen. Serotype Typhi lacks some of the proteins (effectors) exported by the invasion-associated type III secretion system that are required by serotype Typhimurium for eliciting fluid secretion and inflammation in bovine ligated ileal loops. We investigated whether the remaining serotype Typhi effectors implicated in enteropathogenicity (SipA, SopB, and SopD) are functionally exchangeable with their serotype Typhimurium homologues. Serotype Typhi elicited fluid accumulation in bovine ligated ileal loops at levels similar to those elicited by a noninvasive serotype Typhimurium strain (thesipA sopABDE2mutant) or by sterile culture medium. However, introduction of the cloned serotype TyphisipA,sopB, andsopDgenes complemented the ability of a serotype TyphimuriumsipA sopABDE2mutant to elicit fluid secretion in bovine ligated ileal loops. Introduction of the cloned serotype TyphisipA,sopB, andsopDgenes increased the invasiveness of a serotype TyphimuriumsipA sopABDE2mutant for human colon carcinoma epithelial (HT-29 and T84) cells and bovine kidney (MDBK) cells. Translational fusions between the mature TEM-1 β-lactamase reporter and SipA or SopD demonstrated that serotype Typhi translocates these effectors into host cells. We conclude that the inability of serotype Typhi to cause fluid accumulation in bovine ligated ileal loops is not caused by a functional alteration of its SipA, SopB, and SopD effector proteins with respect to their serotype Typhimurium homologues.
β-Arrestin 1 Participates in Platelet-Activating Factor Receptor-Mediated Endocytosis of
Streptococcus pneumoniae
Authors: Radin Jana N. , Orihuela Carlos J. , Murti Gopal , Guglielmo Christopher , Murray Peter J. , Tuomanen Elaine I. 
Published: November 2005

ABSTRACT

Pneumococci traverse eukaryotic cells within vacuoles without intracytoplasmic multiplication. The platelet-activating factor receptor (PAFr) has been suggested as a portal of entry. Pneumococci colocalized with PAFr on endothelial cells and PAFr
−/−
mice showed a substantially impaired ability to support bacterial translocation, particularly from blood to brain. Pneumococci-induced colocalization of PAFr and β-arrestin 1 at the plasma membrane of endothelial cells and PAFr-mediated pneumococcal uptake in transfected COS cells were greatly increased by cotransfection with the scaffold/adapter protein β-arrestin 1. Activation of extracellular signal-regulated kinase kinases was required for uptake and was limited to the cytoplasmic compartment, consistent with activation by β-arrestin rather than PAFr. Uptake of the pneumococcal vacuole involved clathrin, and half the bacteria proceeded into vacuoles marked by Rab5 and later Rab7, the classical route to the lysosome. Overexpression of β-arrestin in endothelial cells decreased colocalization with Rab7. We conclude that the association of β-arrestin with the PAFr contributes to successful translocation of pneumococci.
Helicobacter pylori
Activates Myosin Light-Chain Kinase To Disrupt Claudin-4 and Claudin-5 and Increase Epithelial Permeability
Authors: Fedwick Jason P. , Lapointe Tamia K. , Meddings Jonathan B. , Sherman Philip M. , Buret Andre G. 
Published: November 2005

ABSTRACT

Helicobacter pylori
is a spiral, gram-negative bacterium that specifically and persistently infects the human stomach. In some individuals,
H. pylori
-induced chronic gastritis may progress to gastroduodenal ulcers and gastric cancer. Currently, the host-microbe interactions that determine the clinical outcome of infection are not well defined.
H. pylori
strains capable of disrupting the gastric epithelial barrier may increase the likelihood of developing serious disease. In this study,
H. pylori
strain SS1 increased gastric, but not small intestinal, permeability in C57BL/6 mice.
H. pylori
strain SS1 was able to directly increase paracellular permeability, in the absence of host inflammatory cells, by disrupting the tight-junctional proteins occludin, claudin-4, and claudin-5 in confluent nontransformed epithelial cells.
H. pylori
SS1 also reduced claudin-4 protein levels in human gastric AGS cells. The ability of
H. pylori
SS1 to increase permeability appeared to be independent of the well-characterized virulence factors vacuolating cytotoxin and CagA protein.
H. pylori
activated myosin light-chain kinase in epithelial cells to phosphorylate myosin light chain and increase permeability by disrupting claudin-4 and claudin-5. The bacterial factor responsible for increasing epithelial permeability was heat sensitive, membrane bound, and required apical contact with monolayers. In conclusion, disruptions of the tight junctions observed in this study implicate host cell signaling pathways, including the phosphorylation of myosin light chain and the regulation of tight-junctional proteins claudin-4 and claudin-5, in the pathogenesis of
H. pylori
infection.
Structure, Cellular Distribution, Antigenicity, and Biological Functions of
Fonsecaea pedrosoi
Ceramide Monohexosides
Authors: Nimrichter Leonardo , Cerqueira Mariana D. , Leitão Eduardo A. , Miranda Kildare , Nakayasu Ernesto S. , Almeida Sandro R. , Almeida Igor C. , Alviano Celuta S. , Barreto-Bergter Eliana , Rodrigues Marcio L. 
Published: November 2005

ABSTRACT

Monohexosylceramides (CMHs, or cerebrosides) have been reported as membrane and cell wall constituents of both pathogenic and nonpathogenic fungi, presenting remarkable differences in their ceramide moiety compared to mammalian CMHs. Current evidence suggests that CMHs are involved in fungal differentiation and growth and contribute to host immune response. Here we describe a structural diversity between cerebrosides obtained from different forms of the human pathogen
Fonsecaea pedrosoi
. The major CMH species produced by conidial forms displayed the same structure previously demonstrated by our group for mycelia, an
N
-2′-hydroxyhexadecanoyl-1-β-
d
-glucopyranosyl-9-methyl-4,8-sphingadienine. However, the major cerebroside species purified from sclerotic cells carries an additional hydroxyl group, bound to its long-chain base. The structural difference between cerebrosides from mycelial and sclerotic cells was apparently not relevant for their antigenicity, since they were both recognized at similar levels by sera from individuals with chromoblastomycosis and a monoclonal antibody to a conserved cerebroside structure. Preincubation of fungal cells with anti-CMH monoclonal antibodies had no effect on the interaction of
F. pedrosoi
sclerotic cells with murine macrophages. In contrast to what has been described for other fungal species, sclerotic bodies are resistant to the antifungal action of anti-CMH antibodies. Immunofluorescence analysis showed that recognition of sclerotic cells by these antibodies only occurs at cell wall regions in which melanization is not evident. Accordingly, melanin removal with alkali results in an increased reaction of fungal cells with anti-CMH antibodies. Our results indicate that cerebroside expression in
F. pedrosoi
cells is associated with dimorphism and melanin assembly on the fungal cell wall.
Demonstration of OspC Type Diversity in Invasive Human Lyme Disease Isolates and Identification of Previously Uncharacterized Epitopes That Define the Specificity of the OspC Murine Antibody Response
Authors: Earnhart Christopher G. , Buckles Eric L. , Dumler John Stephen , Marconi Richard T. 
Published: November 2005

ABSTRACT
Outer surface protein C (OspC) of the Lyme disease spirochetes is an important virulence factor that has potential utility for vaccine development. Of the 21 OspC types that have been identified, it has been postulated that types A, B, I, and K are specifically associated with invasive infections. Through an analysis of isolates collected from patients in Maryland we found that OspC types C, D, and N are also associated with invasive infections. This observation suggests that there is greater diversity in the group of OspC types associated with invasive infection than has been previously suggested. Detailed knowledge of the antigenic structure of OspC is essential for vaccine development. To determine if the antibody response to OspC is type specific, recombinant proteins of several different OspC types were immunoblotted and screened with sera from mice infected with isolates having known OspC types. These analyses revealed a high degree of specificity in the antibody response and suggested that the immunodominant epitopes of OspC reside in the variable domains of the protein. To localize these epitopes, OspC fragments were generated and screened with serum collected from infected mice. These analyses led to identification of previously uncharacterized epitopes that define the type specificity of the OspC antibody response. These analyses provide important insight into the antigenic structure of OspC and also provide a basis for understanding the variable nature of the antibody response to this important virulence factor of the Lyme disease spirochetes.
Carbohydrate Moieties of Microsporidian Polar Tube Proteins Are Targeted by Immunoglobulin G in Immunocompetent Individuals
Authors: Peek Ron , Delbac Frédéric , Speijer Dave , Polonais Valérie , Greve Sophie , Wentink-Bonnema Ellen , Ringrose Jeffrey , van Gool Tom 
Published: November 2005

ABSTRACT

Microsporidia of the
Encephalitozoon
species are frequently found as opportunistic pathogens of immunocompromised patients, but very little is known about the prevalence and significance of
Encephalitozoon
infection in immunocompetent individuals. It was reported previously that 8% of Dutch blood donors and 5% of pregnant French women had an immunoglobulin G (IgG) immune response against specific organelles of
Encephalitozoon intestinalis.
These organelles, the so-called polar tube and anchoring disk, are used to penetrate membranes of host cells during infection. The unexpectedly high percentage of immunocompetent individuals with IgG against these organelles suggested that infection of humans with microsporidia might be more common than previously recognized. In the present study, we analyzed this anti-
Encephalitozoon
IgG response by using indirect immunofluorescence, Western blotting, two-dimensional gel electrophoresis, and chemical deglycosylation. Our results show that the antibody response is directed against the posttranslational carbohydrate modification of the major polar tube protein (polar tube protein 1) and carbohydrate moieties of proteins in the anchoring region of the polar tube of
Encephalitozoon
. In addition, the antibodies were found to decrease the infectivity of
E. intestinalis
in vitro. The significance and possible origin of these prevalent antibodies are discussed.
Influence of Pilin Glycosylation on
Pseudomonas aeruginosa
1244 Pilus Function
Authors: Smedley James G. , Jewell Erica , Roguskie Jennifer , Horzempa Joseph , Syboldt Andrew , Stolz Donna Beer , Castric Peter 
Published: November 2005

ABSTRACT

The opportunistic pathogen
Pseudomonas aeruginosa
is a leading cause of nosocomial pneumonia. Among its virulence factors, the type IV pili of
P. aeruginosa
strain 1244 contain a covalently linked, three-sugar glycan of previously unknown significance. The work described in this paper was carried out to determine the influence of the
P. aeruginosa
1244 pilin glycan on pilus function, as well as a possible role in pathogenesis. To accomplish this, a deletion was introduced into the
pilO
gene of this organism. The isogenic knockout strain produced, 1244G7, was unable to glycosylate pilin but could produce pili normal in appearance and quantity. In addition, this strain had somewhat reduced twitching motility, was sensitive to pilus-specific bacteriophages, and could form a normal biofilm. Analysis of whole cells and isolated pili from wild-type
P. aeruginosa
strain 1244 by transmission electron microscopy with a glycan-specific immunogold label showed that this saccharide was distributed evenly over the fiber surface. The presence of the pilin glycan reduced the hydrophobicity of purified pili as well as whole cells. With regard to pathogenicity,
P. aeruginosa
strains producing glycosylated pili were commonly found among clinical isolates and particularly among those strains isolated from sputum. Competition index analysis using a mouse respiratory model comparing strains 1244 and 1244G7 indicated that the presence of the pilin glycan allowed for significantly greater survival in the lung environment. These results collectively suggest that the pilin glycan is a significant virulence factor and may aid in the establishment of infection.
Capsule-Negative
Staphylococcus aureus
Induces Chronic Experimental Mastitis in Mice
Authors: Tuchscherr Lorena P. N. , Buzzola Fernanda R. , Alvarez Lucía P. , Caccuri Roberto L. , Lee Jean C. , Sordelli Daniel O. 
Published: November 2005

ABSTRACT

Staphylococcus aureus
capsular polysaccharides (CP) have been shown to enhance staphylococcal virulence in numerous animal models of infection. Although serotype 5 CP (CP5) and CP8 predominate among
S. aureus
isolates from humans, most staphylococcal isolates from bovines with mastitis in Argentina are capsule negative. This study was designed to evaluate the effects of CP5 and CP8 expression on the pathogenesis of experimental murine mastitis. Lactating mice were challenged by the intramammary route with one of three isogenic
S. aureus
strains producing CP5, CP8, or no capsule. Significantly greater numbers of acapsular mutant cells were recovered from the infected glands 12 days after bacterial challenge compared with the encapsulated strains. Histopathological analyses revealed greater polymorphonuclear and mononuclear leukocyte infiltration and congestion in the mammary glands of mice infected with the encapsulated strains compared with the acapsular mutant, and the serotype 5 strain elicited more inflammation than the serotype 8 strain. In vitro experiments revealed that the acapsular
S. aureus
strain was internalized by MAC-T bovine epithelial cells in significantly greater numbers than the CP5- or CP8-producing strain. Taken together, the results suggest that
S. aureus
lacking a capsule was able to persist in the murine mammary gland, whereas encapsulated strains elicited more inflammation and were eliminated faster. Loss of CP5 or CP8 expression may enhance the persistence of staphylococci in the mammary glands of chronically infected hosts.
A Leucine-Rich Motif Targets
Pseudomonas aeruginosa
ExoS within Mammalian Cells
Authors: Zhang Yue , Barbieri Joseph T. 
Published: November 2005

ABSTRACT

Type III cytotoxins contribute to the ability of bacterial pathogens to subvert the host innate immune system. ExoS (453 amino acids) is a bifunctional type III cytotoxin produced by
Pseudomonas aeruginosa
. Residues 96 to 232 comprise a Rho GTPase activating protein domain, while residues 233 to 453 comprise a 14-3-3-dependent ADP-ribosyltransferase domain. An N-terminal domain (termed the membrane localization domain [MLD]) targets ExoS to the Golgi-endoplasmic reticulum (Golgi-ER) of mammalian cells. This study identifies an amino acid motif that is responsible for the membrane binding properties of the MLD. Deletion mapping showed that the MLD included a symmetrical leucine-rich motif within residues 51 to 77 of ExoS. The terminal dileucines and internal leucines and an isoleucine within the MLD, but not charged or other hydrophobic residues, targeted a reporter protein to the Golgi-ER region of HeLa cells. Mutations of the leucines within the MLD did not affect type III secretion or translocation into HeLa cells but limited the ability of ExoS to ADP-ribosylate Ras GTPases. Mutations of charged residues within the MLD did not affect type III secretion, delivery into HeLa cells, or the ability of ExoS to ADP-ribosylate Ras GTPases. The organization of the leucines within the MLD of ExoS is different from that of previously described leucine-rich motifs but is present in several other bacterial proteins. This implies a role for intracellular targeting in the efficient targeting of mammalian cells by type III cytotoxins.