bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of Efflux Pump Expression and Drug Resistance by the Transcription Factors Mrr1, Upc2, and Cap1 in Candida albicans
Authors: Schubert Sabrina , Barker Katherine S. , Znaidi Sadri , Schneider Sabrina , Dierolf Franziska , Dunkel Nico , Aïd Malika , Boucher Geneviève , Rogers P. David , Raymond Martine , Morschhäuser Joachim 
Published: March 2011

ABSTRACT

Constitutive overexpression of the Mdr1 efflux pump is an important mechanism of acquired drug resistance in the yeast
Candida albicans
. The zinc cluster transcription factor Mrr1 is a central regulator of
MDR1
expression, but other transcription factors have also been implicated in
MDR1
regulation. To better understand how
MDR1
-mediated drug resistance is achieved in this fungal pathogen, we studied the interdependence of Mrr1 and two other
MDR1
regulators, Upc2 and Cap1, in the control of
MDR1
expression. A mutated, constitutively active Mrr1 could upregulate
MDR1
and confer drug resistance in the absence of Upc2 or Cap1. On the other hand, Upc2 containing a gain-of-function mutation only slightly activated the
MDR1
promoter, and this activation depended on the presence of a functional
MRR1
gene. In contrast, a C-terminally truncated, activated form of Cap1 could upregulate
MDR1
in a partially Mrr1-independent fashion. The induction of
MDR1
expression by toxic chemicals occurred independently of Upc2 but required the presence of Mrr1 and also partially depended on Cap1. Transcriptional profiling and
in vivo
DNA binding studies showed that a constitutively active Mrr1 binds to and upregulates most of its direct target genes in the presence or absence of Cap1. Therefore, Mrr1 and Cap1 cooperate in the environmental induction of
MDR1
expression in wild-type
C. albicans
, but gain-of-function mutations in either of the two transcription factors can independently mediate efflux pump overexpression and drug resistance.
A New Small Molecule Specifically Inhibits the Cariogenic Bacterium Streptococcus mutans in Multispecies Biofilms
Authors: Liu Chang , Worthington Roberta J. , Melander Christian , Wu Hui 
Published: March 2011

ABSTRACT

Streptococcus mutans
is a major cariogenic bacterium. It has adapted to the biofilm lifestyle, which is essential for pathogenesis of dental caries. We aimed to identify small molecules that can inhibit cariogenic
S. mutans
and to discover lead structures that could give rise to therapeutics for dental caries. In this study, we screened a focused small-molecule library of 506 compounds. Eight small molecules which inhibited
S. mutans
at a concentration of 4 μM or less but did not affect cell growth or biofilm formation of commensal bacteria, represented by
Streptococcus sanguinis
and
Streptococcus gordonii
, in monospecies biofilms were identified. The active compounds share similar structural properties, which are characterized by a 2-aminoimidazole (2-AI) or 2-aminobenzimidazole (2-ABI) subunit. In multispecies biofilm models, the most active compound also inhibited cell survival and biofilm formation of
S. mutans
but did not affect commensal streptococci. This inhibitor downregulated the expression of six biofilm-associated genes,
ftf
,
pac
,
relA
,
comDE
,
gbpB
, and
gtfB
, in planktonic
S. mutans
cells, while it downregulated the expression of only
ftf
,
pac
, and
relA
in the biofilm cells of
S. mutans
. The most potent compound also inhibited production of two key adhesins of
S. mutans
, antigen I/II and glucosyltransferase (GTF). However, the compound did not alter the expression of the corresponding genes in both
S. sanguinis
and
S. gordonii
, indicating that it possesses a selective inhibitory activity against
S. mutans
.
Structure-Activity Studies and Therapeutic Potential of Host Defense Peptides of Human Thrombin
Authors: Kasetty Gopinath , Papareddy Praveen , Kalle Martina , Rydengård Victoria , Mörgelin Matthias , Albiger Barbara , Malmsten Martin , Schmidtchen Artur 
Published: March 2011

ABSTRACT

Peptides of the C-terminal region of human thrombin are released upon proteolysis and identified in human wounds. In this study, we wanted to investigate minimal determinants, as well as structural features, governing the antimicrobial and immunomodulating activity of this peptide region. Sequential amino acid deletions of the peptide GKYGFYTHVFRLKKWIQKVIDQFGE (GKY25), as well as substitutions at strategic and structurally relevant positions, were followed by analyses of antimicrobial activity against the Gram-negative bacteria
Escherichia coli
and
Pseudomonas aeruginosa
, the Gram-positive bacterium
Staphylococcus aureus
, and the fungus
Candida albicans
. Furthermore, peptide effects on lipopolysaccharide (LPS)-, lipoteichoic acid-, or zymosan-induced macrophage activation were studied. The thrombin-derived peptides displayed length- and sequence-dependent antimicrobial as well as immunomodulating effects. A peptide length of at least 20 amino acids was required for effective anti-inflammatory effects in macrophage models, as well as optimal antimicrobial activity as judged by MIC assays. However, shorter (>12 amino acids) variants also displayed significant antimicrobial effects. A central K14 residue was important for optimal antimicrobial activity. Finally, one peptide variant, GKYGFYTHVFRLKKWIQKVI (GKY20) exhibiting improved selectivity, i.e., low toxicity and a preserved antimicrobial as well as anti-inflammatory effect, showed efficiency in mouse models of LPS shock and
P. aeruginosa
sepsis. The work defines structure-activity relationships of C-terminal host defense peptides of thrombin and delineates a strategy for selecting peptide epitopes of therapeutic interest.
Evolution and Spread of a Multidrug-Resistant Proteus mirabilis Clone with Chromosomal AmpC-Type Cephalosporinases in Europe
Authors: D'Andrea M. M. , Literacka E. , Zioga A. , Giani T. , Baraniak A. , Fiett J. , Sadowy E. , Tassios P. T. , Rossolini G. M. , Gniadkowski M. , Miriagou V. 
Published: March 2011

ABSTRACT

Proteus mirabilis
isolates obtained in 1999 to 2008 from three European countries were analyzed; all carried chromosomal AmpC-type cephalosporinase
bla
CMY
genes from a
Citrobacter freundii
origin (
bla
CMY-2
-like genes). Isolates from Poland harbored several
bla
CMY
genes (
bla
CMY-4
,
bla
CMY-12
,
bla
CMY-14
,
bla
CMY-15
, and
bla
CMY-38
and the new gene
bla
CMY-45
), while isolates from Italy and Greece harbored
bla
CMY-16
only. Earlier isolates with
bla
CMY-4
or
bla
CMY-12
, recovered in France from Greek and Algerian patients, were also studied. All isolates showed striking similarities. Their
bla
CMY
genes resided within IS
Ecp1
transposition modules, named Tn
6093
, characterized by a 110-bp distance between IS
Ecp1
and
bla
CMY
, and identical fragments of both
C. freundii
DNA and a ColE1-type plasmid backbone. Moreover, these modules were inserted into the same chromosomal site, within the
pepQ
gene. Since ColE1 plasmids carrying IS
Ecp1
with similar
C. freundii
DNA fragments (Tn
6114
) had been identified earlier, it is likely that a similar molecule had mediated at some stage this DNA transfer between
C. freundii
and
P. mirabilis
. In addition, isolates with
bla
CMY-12
,
bla
CMY-15
, and
bla
CMY-38
genes harbored a second
bla
CMY
copy within a shorter IS
Ecp1
module (Tn
6113
), always inserted downstream of the
ppiD
gene. Sequence analysis of all mobile
bla
CMY-2
-like genes indicated that those integrated in the
P. mirabilis
chromosome form a distinct cluster that may have evolved by the stepwise accumulation of mutations. All of these observations, coupled to strain typing data, suggest that the
bla
CMY
genes studied here may have originated from a single IS
Ecp1
-mediated mobilization-transfer-integration process, followed by the spread and evolution of a
P. mirabilis
clone over time and a large geographic area.
Staphylococcus aureus Transporters Hts, Sir, and Sst Capture Iron Liberated from Human Transferrin by Staphyloferrin A, Staphyloferrin B, and Catecholamine Stress Hormones, Respectively, and Contribute to Virulence
Authors: Beasley Federico C. , Marolda Cristina L. , Cheung Johnson , Buac Suzana , Heinrichs David E. 
Published: March 2011

ABSTRACT

Staphylococcus aureus
is a frequent cause of bloodstream, respiratory tract, and skin and soft tissue infections. In the bloodstream, the iron-binding glycoprotein transferrin circulates to provide iron to cells throughout the body, but its iron-binding properties make it an important component of innate immunity. It is well established that siderophores, with their high affinity for iron, in many instances can remove iron from transferrin as a means to promote proliferation of bacterial pathogens. It is also established that catecholamine hormones can interfere with the iron-binding properties of transferrin, thus allowing infectious bacteria access to this iron pool. The present study demonstrates that
S. aureus
can use either of two carboxylate-type siderophores, staphyloferrin A and staphyloferrin B, via the transporters Hts and Sir, respectively, to access the transferrin iron pool. Growth of staphyloferrin-producing
S. aureus
in serum or in the presence of holotransferrin was not enhanced in the presence of catecholamines. However, catecholamines significantly enhanced the growth of staphyloferrin-deficient
S. aureus
in human serum or in the presence of human holotransferrin. It was further demonstrated that the Sst transporter was essential for this activity as well as for the utilization of bacterial catechol siderophores. The substrate binding protein SstD was shown to interact with ferrated catecholamines and catechol siderophores, with low to submicromolar affinities. Experiments involving mice challenged intravenously with wild-type
S. aureus
and isogenic mutants demonstrated that the combination of Hts, Sir, and Sst transport systems was required for full virulence of
S. aureus
.
Joint Effects of Host Genetic Background and Mycobacterial Pathogen on Susceptibility to Infection
Authors: Di Pietrantonio Tania , Correa José A. , Orlova Marianna , Behr Marcel A. , Schurr Erwin 
Published: March 2011

ABSTRACTThe present study examined the differential contribution of host genetic background and mycobacterial pathogen variability to biological and mechanistic phenotypes of infection. For this purpose, A/J and C57BL/6J mice were infected intravenously with a low dose ofMycobacterium tuberculosisH37Rv or the Russia, Japan, and Pasteur substrains ofMycobacterium bovisbacille Calmette-Guérin (BCG). The pulmonary bacterial counts (number of CFU) and transcript levels of select cytokines (e.g.,Ifng,Il12b, andIl4) at 1, 3, and 6 weeks postinfection were measured as biological and mechanistic phenotypes, respectively. The individual and combined impact of the host and mycobacteria on these phenotypes was assessed using three-way analysis of variance (ANOVA), which partitions phenotypic variation into host, pathogen, time, and interaction effects. All phenotypes, except pulmonaryIl4transcript levels, displayed evidence for host-mycobacterium specificity by means of significant interaction terms. Pulmonary expression profiles of 34 chemokines and chemokine-related genes were compared across the hosts and mycobacteria. The differences in induction of these immune messenger genes between A/J and C57BL/6J mice were modest and generally failed to reach significance. In contrast, the mycobacteria induced significant variance in a subset of the immune messenger genes, which was more evident in A/J mice relative to that in C57BL/6J mice. Overall, the results demonstrated the importance of considering the joint effects of the mycobacterial and host genetic backgrounds on susceptibility to mycobacterial infections.
Cross-Reactive Protection against Enterohemorrhagic Escherichia coli Infection by Enteropathogenic E. coli in a Mouse Model
Authors: Calderon Toledo Carla , Arvidsson Ida , Karpman Diana 
Published: March 2011

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) and enterohemorrhagic
E. coli
(EHEC) are related attaching and effacing (A/E) pathogens. The genes responsible for the A/E pathology are carried on a chromosomal pathogenicity island termed the locus of enterocyte effacement (LEE). Both pathogens share a high degree of homology in the LEE and additional O islands. EHEC prevalence is much lower in areas where EPEC is endemic. This may be due to the development of antibodies against common EPEC and EHEC antigens. This study investigated the hypothesis that EPEC infections may protect against EHEC infections. We used a mouse model to inoculate BALB/c mice intragastrically, first with EPEC and then with EHEC (
E. coli
O157:H7). Four control groups received either a nonpathogenic
E. coli
(NPEC) strain followed by EHEC (NPEC/EHEC), phosphate-buffered saline (PBS) followed by EHEC (PBS/EHEC), EPEC/PBS, or PBS/PBS. Mice were monitored for weight loss and symptoms. EPEC colonized the intestine after challenge, and mice developed serum antibodies to intimin and
E. coli
secreted protein B (encoded in the LEE). Prechallenge with an EPEC strain had a protective effect after EHEC infection, as only a few mice developed mild symptoms, from which they recovered. These mice had an increase in body weight similar to that in control animals, and tissue morphology exhibited mild intestinal changes and normal renal histology. All mice that were not prechallenged with the EPEC strain developed mild to severe symptoms after EHEC infection, with weight loss as well as intestinal and renal histopathological changes. These data suggest that EPEC may protect against EHEC infection in this mouse model.
Type I Interferons Increase Host Susceptibility to Trypanosoma cruzi Infection
Authors: Chessler Anne-Danielle C. , Caradonna Kacey L. , Da'dara Akram , Burleigh Barbara A. 
Published: March 2011

ABSTRACTTrypanosoma cruzi, the protozoan parasite that causes human Chagas' disease, induces a type I interferon (IFN) (IFN-α/β) response during acute experimental infection in mice and in isolated primary cell types. To examine the potential impact of the type I IFN response in shaping outcomes in experimentalT. cruziinfection, groups of wild-type (WT) and type I IFN receptor-deficient (IFNAR−/−) 129sv/ev mice were infected with two differentT. cruzistrains under lethal and sublethal conditions and several parameters were measured during the acute stage of infection. The results demonstrate that type I IFNs are not required for early host protection againstT. cruzi. In contrast, under conditions of lethalT. cruzichallenge, WT mice succumbed to infection whereas IFNAR−/−mice were ultimately able to control parasite growth and survive.T. cruziclearance in and survival of IFNAR−/−mice were accompanied by higher levels of IFN-γ production by isolated splenocytes in response to parasite antigen. The suppression of IFN-γ in splenocytes from WT mice was independent of IL-10 levels. While the impact of type I IFNs on the production of IFN-γ and other cytokines/chemokines remains to be fully determined in the context ofT. cruziinfection, our data suggest that, under conditions of high parasite burden, type I IFNs negatively impact IFN-γ production, initiating a detrimental cycle that contributes to the ultimate failure to control infection. These findings are consistent with a growing theme in the microbial pathogenesis field in which type I IFNs can be detrimental to the host in a variety of nonviral pathogen infection models.
Dictyostelium discoideum as a Model System for Identification of Burkholderia pseudomallei Virulence Factors
Authors: Hasselbring Benjamin M. , Patel Maharsh K. , Schell Mark A. 
Published: March 2011

ABSTRACT

Burkholderia pseudomallei
is an emerging bacterial pathogen and category B biothreat. Human infections with
B. pseudomallei
(called melioidosis) present as a range of manifestations, including acute septicemia and pneumonia. Although melioidosis can be fatal, little is known about the molecular basis of
B. pseudomallei
pathogenicity, in part because of the lack of simple, genetically tractable eukaryotic models to facilitate
en masse
identification of virulence determinants or explore host-pathogen interactions. Two assays, one high-throughput and one quantitative, were developed to monitor levels of resistance of
B. pseudomallei
and the closely related nearly avirulent species
Burkholderia thailandensis
to predation by the phagocytic amoeba
Dictyostelium discoideum
. The quantitative assay showed that levels of resistance to, and survival within, amoeba by these bacteria and their known virulence mutants correlate well with their published levels of virulence in animals. Using the high-throughput assay, we screened a 1,500-member
B. thailandensis
transposon mutant library and identified 13 genes involved in resistance to predation by
D. discoideum
. Orthologs of these genes were disrupted in
B. pseudomallei
, and nearly all mutants had similarly decreased resistance to predation by
D. discoideum
. For some mutants, decreased resistance also correlated with reduced survival in and cytotoxicity toward macrophages, as well as attenuated virulence in mice. These observations suggest that some factors required by
B. pseudomallei
for resistance to environmental phagocytes also aid in resistance to phagocytic immune cells and contribute to disease in animals. Thus,
D. discoideum
provides a novel, high-throughput model system for facilitating inquiry into
B. pseudomallei
virulence.
Longitudinal Analysis of the Prevalence, Maintenance, and IgA Response to Species of the Order Bacteroidales in the Human Gut
Authors: Zitomersky Naamah Levy , Coyne Michael J. , Comstock Laurie E. 
Published: March 2011

ABSTRACT

Bacteroidales
species are the most abundant Gram-negative bacteria of the human intestinal microbiota. These bacteria evolved to synthesize numerous capsular polysaccharides (PS) that are subject to phase variation. In
Bacteroides fragilis
, PS synthesis is regulated so that only one of the eight PS biosynthesis loci is transcribed at a time in each bacterium. To determine if the bacteria evolved this unusual property to evade a host IgA response, we directly studied the human fecal ecosystem. We performed a longitudinal analysis of the abundant
Bacteroidales
species from 15 healthy adults at four intervals over a year. For this study, we used bacterial culture to perform analyses not accurate with DNA-based methods, including quantification of total viable
Bacteroidales
bacteria, strain maintenance, and IgA responses. Abundant
Bacteroidales
isolates were identified to the species level using multiplex PCR and 16S rRNA gene sequencing. Arbitrarily primed PCR was used for strain typing. IgA responses to endogenous strains carried over the year were analyzed, and the orientations of the invertible PS locus promoters from the ecosystem were quantified. Subjects consistently harbored from 5 × 10
8
to 8 × 10
10
Bacteroidales
bacteria/g of feces. Within the cohort, 20 different
Bacteroidales
species were detected at high concentrations.
Bacteroides uniformis
was the most prevalent; however, abundant
Bacteroidales
species varied between subjects. Strains could be maintained over the year within the ecosystem at high density. IgA responses were often not induced and did not correlate with the elimination of a strain or major changes in the orientations of the capsular PS locus promoters.
Complex Cellular Responses of Helicobacter pylori-Colonized Gastric Adenocarcinoma Cells
Authors: Schneider Sabine , Carra Gert , Sahin Ugur , Hoy Benjamin , Rieder Gabriele , Wessler Silja 
Published: March 2011

ABSTRACT

Helicobacter pylori
is an important class I carcinogen that persistently infects the human gastric mucosa to induce gastritis, gastric ulceration, and gastric cancer.
H. pylori
pathogenesis strongly depends on pathogenic factors, such as VacA (vacuolating cytotoxin A) or a specialized type IV secretion system (T4SS), which injects the oncoprotein CagA (cytotoxin-associated gene A product) into the host cell. Since access to primary gastric epithelial cells is limited, many studies on the complex cellular and molecular mechanisms of
H. pylori
were performed in immortalized epithelial cells originating from individual human adenocarcinomas. The aim of our study was a comparative analysis of 14 different human gastric epithelial cell lines after colonization with
H. pylori
. We found remarkable differences in host cell morphology, extent of CagA tyrosine phosphorylation, adhesion to host cells, vacuolization, and interleukin-8 (IL-8) secretion. These data might help in the selection of suitable cell lines to study host cell responses to
H. pylori
in vitro
, and they imply that different host cell factors are involved in the determination of
H. pylori
pathogenesis. A better understanding of
H. pylori
-directed cellular responses can provide novel and more balanced insights into the molecular mechanisms of
H. pylori
-dependent pathogenesis
in vivo
and may lead to new therapeutic approaches.
Double Blinding with a New Placebo Needle: A Validation Study on Participant Blinding
Authors: Takakura Nobuari , Takayama Miho , Kawase Akiko , Yajima Hiroyoshi 
Published: March 2011

Background A no-touch control needle in which the needle tip cannot reach the skin has been designed, and has been validated for practitioner blinding in a previous study but not for participant blinding. Objective To test whether the no-touch control needle can effectively blind subjects. Methods An acupuncturist applied, in turn, a no-touch control, skin-touch placebo and penetrating needle in one forearm of 80 healthy subjects. After removing each needle, the subjects were asked to judge the type of needle and rate the sensation of skin penetration/penetration-like or skin pressure/pressure-like pain on a 100 mm visual analogue scale. Results The subjects correctly identified 67% of needles overall. 17 of the 80 no-touch control needles were judged as skin-touch, and one as penetrating. In addition, six skin-touch placebo needles, and no penetrating needles, were judged as no-touch. Half of the 80 skin-touch placebo needles and 65 of the 80 penetrating needles and two no-touch control needles elicited pain. Of 240 needles, the practitioner identified 120 correctly that did not fit the probability of 1/3 (χ2=30.00, p<0.01). Conclusions The no-touch control needles may be used as a blind control for the acupuncture procedure, or to test the physiological effect of the skin-touch needles, but are not suitable for double-blind testing of the needle effect.