bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aspergillus
Section
Fumigati
: Antifungal Susceptibility Patterns and Sequence-Based Identification
Authors: Alcazar-Fuoli Laura , Mellado Emilia , Alastruey-Izquierdo Ana , Cuenca-Estrella Manuel , Rodriguez-Tudela Juan L. 
Published: January 2008

ABSTRACT

This study analyzed 28
Aspergillus
strains belonging to the section
Fumigati
that were isolated from clinical samples in Spain. All isolates sporulated slowly and were unable to grow at 48°C. Phylogenetic analysis based on sequencing of partial sequences of the β-tubulin and rodlet A genes was used to classify the 28 strains into six different clades (
Neosartorya hiratsukae
,
Neosartorya pseudofischeri
,
Aspergillus viridinutans
,
Aspergillus lentulus
,
Aspergillus fumigatiaffinis
, and
Aspergillus fumisynnematus
). Antifungal susceptibility testing showed heterogeneous patterns and grouped the strains together by species. Most
A. lentulus
and
A. fumigatiaffinis
isolates showed high MICs of amphotericin B (geometric mean [GM] MICs, ≥4.5 μg/ml), itraconazole (GM MICs, ≥6 μg/ml), voriconazole (GM MICs, ≥3 μg/ml), and ravuconazole (GM MICs, ≥3 μg/ml);
N pseudofischeri
and
A. viridinutans
showed high MICs of itraconazole (GM MICs, ≥8 μg/ml), voriconazole (GM MICs, ≥3.33 μg/ml), and ravuconazole (GM MICs, ≥2 μg/ml); and
N. hiratsukae
and
A. fumisynnematus
were susceptible to all the antifungals tested. In conclusion, a number of different species whose morphological features resemble those of
Aspergillus fumigatus
could succeed in producing invasive infections in the susceptible host. In addition, some of them showed high MICs for most of the antifungals available for the treatment of patients infected with these organisms. The epidemiology and clinical relevance of these species should therefore be addressed.
Convergent In Vivo and In Vitro Selection of Ceftazidime Resistance Mutations at Position 167 of CTX-M-3 β-Lactamase in Hypermutable
Escherichia coli
Strains
Authors: Stepanova Marina N. , Pimkin Maxim , Nikulin Anatoly A. , Kozyreva Varvara K. , Agapova Elena D. , Edelstein Mikhail V. 
Published: January 2008

ABSTRACT

We report on a novel CTX-M extended-spectrum β-lactamase (ESBL), designated CTX-M-42, with enhanced activity toward ceftazidime. CTX-M-42 was identified in a hypermutable
Escherichia coli
nosocomial isolate (isolate Irk2320) and is a Pro167Thr amino acid substitution variant of CTX-M-3. By molecular typing of ESBL-producing
E. coli
strains previously isolated in the same hospital ward, we were able to identify a putative progenitor (strain Irk1224) of Irk2320, which had a mutator phenotype and harbored the CTX-M-3 β-lactamase. To reproduce the natural evolution of CTX-M-3, we selected for ceftazidime resistance mutations in
bla
CTX-M-3
gene in vitro both in clinical isolate Irk1224 and in laboratory-derived hypermutable (
mutD5
) strain GM2995. These experiments yielded CTX-M-3
Pro167Ser
and CTX-M-3
Asn136Lys
mutants which conferred higher levels of resistance to ceftazidime than to cefotaxime. CTX-M-3
Asn136Lys
had a level of low activity toward ampicillin, which may explain its absence from clinical isolates. We conclude that the selection of CTX-M-42 could have occurred in vivo following treatment with ceftazidime and was likely facilitated by the hypermutable background.
Characterization of a Novel Human Immunodeficiency Virus Type 1 Protease Inhibitor, A-790742
Authors: Dekhtyar Tatyana , Ng Teresa I. , Lu Liangjun , Masse Sherie , DeGoey David A. , Flosi William J. , Grampovnik David J. , Klein Larry L. , Kempf Dale J. , Molla Akhteruzzaman 
Published: January 2008

ABSTRACTA-790742 is a potent human immunodeficiency virus type 1 (HIV-1) protease inhibitor, with 50% effective concentrations ranging from 2 to 7 nM against wild-type HIV-1. The activity of this compound is lowered by approximately sevenfold in the presence of 50% human serum. A-790742 maintained potent antiviral activity against lopinavir-resistant variants generated in vitro as well as against a panel of molecular clones containing proteases derived from HIV-1 patient isolates with multiple protease mutations. During in vitro selection, A-790742 selected two primary mutations (V82L and I84V) along with L23I, L33F, K45I, A71V/A, and V77I in the pNL4-3 background and two other mutations (A71V and V82G) accompanied by M46I and L63P in the HIV-1 RF background. HIV-1 pNL4-3 clones with a single V82L or I84V mutation were phenotypically resistant to A-790742 and ritonavir. Taking these results together, A-790742 displays a favorable anti-HIV-1 profile against both the wild type and a large number of mutants resistant to other protease inhibitors. The selection of the uncommon V82L and V82G mutations in protease by A-790742 suggests the potential for an advantageous resistance profile with this protease inhibitor.
Spontaneous Deletion of the Methicillin Resistance Determinant,
mecA
, Partially Compensates for the Fitness Cost Associated with High-Level Vancomycin Resistance in
Staphylococcus aureus
Authors: Noto Michael J. , Fox Paige M. , Archer Gordon L. 
Published: January 2008

ABSTRACT

Treatment of infections caused by
Staphylococcus aureus
is often confounded by the bacterium's ability to develop resistance to chemotherapeutic agents. Methicillin-resistant
S. aureus
(MRSA) arises through the acquisition of staphylococcal chromosomal cassette
mec
(SCC
mec
), a genomic island containing the methicillin resistance determinant,
mecA
. In contrast, resistance to vancomycin can result from exposure to the drug, a mechanism that is not dependent upon a gene acquisition event. Here we describe three MRSA strains that became resistant to vancomycin during passage in the presence of increasing concentrations of the drug. In each case two derivative strains were isolated, one that had lost
mecA
and one that retained
mecA
during passage. Strain 5836VR lost
mecA
by the site-specific chromosomal excision of SCC
mec
, while the other two strains (strains 3130VR and VP32) deleted portions of their SCC
mec
elements in a manner that appeared to involve IS
431
. Conversion to vancomycin resistance caused a decrease in the growth rate that was partially compensated for by the deletion of
mecA
. In mixed-culture competition experiments, vancomycin-resistant strains that lacked
mecA
readily outcompeted their
mecA
-containing counterparts, suggesting that the loss of
mecA
during conversion to vancomycin resistance was advantageous to the organism.
Inhibition of Human Immunodeficiency Virus Type 1 Replication in Human Cells by Debio-025, a Novel Cyclophilin Binding Agent
Authors: Ptak Roger G. , Gallay Philippe A. , Jochmans Dirk , Halestrap Andrew P. , Ruegg Urs T. , Pallansch Luke A. , Bobardt Michael D. , de Béthune Marie-Pierre , Neyts Johan , De Clercq Erik , Dumont Jean-Maurice , Scalfaro Pietro , Besseghir Kamel , Wenger Roland M. , Rosenwirth Brigitte 
Published: January 2008

ABSTRACTDebio-025 is a synthetic cyclosporine with no immunosuppressive capacity but a high inhibitory potency against cyclophilin A (CypA)-associatedcis-transprolyl isomerase (PPIase) activity. A lack of immunosuppressive effects compared to that of cyclosporine was demonstrated both in vitro and in vivo. For three cyclosporines, the inhibitory potential against PPIase activity was quantitatively correlated with that against human immunodeficiency virus type 1 (HIV-1) replication. Debio-025 selectively inhibited the replication of HIV-1 in a CD4+cell line and in peripheral blood mononuclear cells: potent activity was demonstrated against clinical isolates of various HIV-1 subtypes, including isolates with multidrug resistance to reverse transcriptase and protease inhibitors. Simian immunodeficiency virus and HIV-2 strains were generally resistant to inhibition by Debio-025; however, some notable exceptions of sensitive HIV-2 clinical isolates were detected. In two-drug combination studies, additive inhibitory effects were found between Debio-025 and 19 clinically used drugs of different classes. Clinical HIV-1 isolates that are naturally resistant to Debio-025 and that do not depend on CypA for infection were identified. Comparison of the amino acid sequences of the CypA binding domain of the capsid (CA) protein from Debio-025-sensitive and -resistant HIV-1 isolates indicated that resistance was mostly associated with an H87Q/P exchange. Mechanistically, cyclosporines competitively inhibit the binding of CypA to the HIV-1 CA protein, which is an essential interaction required for early steps in HIV-1 replication. By real-time PCR we demonstrated that early reverse transcription is reduced in the presence of Debio-025 and that late reverse transcription is almost completely blocked. Thus, Debio-025 seems to interfere with the function of CypA during the progression/completion of HIV-1 reverse transcription.
Outer Membrane Protein DsrA Is the Major Fibronectin-Binding Determinant of
Haemophilus ducreyi
Authors: Leduc Isabelle , White C. Dinitra , Nepluev Igor , Throm Robert E. , Spinola Stanley M. , Elkins Christopher 
Published: January 2008

ABSTRACT

The ability to bind extracellular matrix proteins is a critical virulence determinant for skin pathogens.
Haemophilus ducreyi
, the etiological agent of the genital ulcer disease chancroid, binds extracellular matrix components, including fibronectin (FN). We investigated
H. ducreyi
FN binding and report several important findings about this interaction. First, FN binding by
H. ducreyi
was greatly increased in bacteria grown on heme and almost completely inhibited by hemoglobin. Second, wild-type strain 35000HP bound significantly more FN than did a
dsrA
mutant in two different FN binding assays. Third, the expression of
dsrA
in the
dsrA
mutant restored FN binding and conferred the ability to bind FN to a non-FN-binding
Haemophilus influenzae
strain. Fourth, an anti-DsrA monoclonal antibody partially blocked FN binding by
H. ducreyi
. The hemoglobin receptor, the collagen-binding protein, the
H. ducreyi
lectin, the fine-tangle pili, and the outer membrane protein OmpA2 were not involved in
H. ducreyi
FN binding, since single mutants bound FN as well as the parent strain did. However, the major outer membrane protein may have a minor role in FN binding by
H. ducreyi
, since a double
dsrA momp
mutant bound less FN than did the single
dsrA
mutant. Finally, despite major sequence differences, DsrA proteins from both class I and class II
H. ducreyi
strains mediated FN and vitronectin binding. We concluded that DsrA is the major factor involved in FN binding by both classes of
H. ducreyi
strains.
Regulatory Roles of CD1d-Restricted NKT Cells in the Induction of Toxic Shock-Like Syndrome in an Animal Model of Fatal Ehrlichiosis
Authors: Stevenson H. L. , Crossley E. C. , Thirumalapura N. , Walker D. H. , Ismail N. 
Published: January 2008

ABSTRACTCD1d-restricted NKT cells are key players in host defense against various microbial infections. Using a murine model of fatal ehrlichiosis, we investigated the role of CD1d-restricted NKT cells in induction of toxic shock-like syndrome caused by gram-negative, lipopolysaccharide-lacking, monocytotropicEhrlichia. Our previous studies showed that intraperitoneal infection of wild-type (WT) mice with virulentEhrlichia(Ixodes ovatus Ehrlichia[IOE]) results in CD8+T-cell-mediated fatal toxic shock-like syndrome marked by apoptosis of CD4+T cells, a weak CD4+Th1 response, overproduction of tumor necrosis factor alpha and interleukin-10, and severe liver injury. Although CD1d−/−mice succumbed to high-dose IOE infection similar to WT mice, they did not develop signs of toxic shock, as shown by elevated bacterial burdens, low serum levels of tumor necrosis factor, normal serum levels of liver enzymes, and the presence of few apoptotic hepatic cells. An absence of NKT cells restored the percentages and absolute numbers of CD4+and CD8+T cells and CD11b+cells in the spleen compared to WT mice and was also associated with decreased expression of Fas on splenic CD4+lymphocytes and granzyme B in hepatic CD8+lymphocytes. Furthermore, our data show that NKT cells promote apoptosis of macrophages and up-regulation of the costimulatory molecule CD40 on antigen-presenting cells, including dendritic cells, B cells, and macrophages, which may contribute to the induction of pathogenic T-cell responses. In conclusion, our data suggest that NKT cells mediateEhrlichia-induced T-cell-mediated toxic shock-like syndrome, most likely via cognate and noncognate interactions with antigen-presenting cells.
Fibronectin Binding and Proteolytic Degradation byLeishmaniaand Effects on Macrophage Activation
Authors: Kulkarni Manjusha M. , Jones Eric A. , McMaster W. Robert , McGwire Bradford S. 
Published: January 2008

ABSTRACTInfection by vector-borne protozoa of the genusLeishmaniaoccurs by the deposition of parasites within the skin of the mammalian host, where they eventually bind to and are phagocytized by Mφs. Our previous work supported the idea that parasites can interact with extracellular matrix and basement membrane proteins, such as fibronectin (FN), within the skin, leading to enhanced invasion. In this report, we extend these findings and show that both promastigotes and amastigotes ofLeishmaniaspecies can bind directly to soluble FN and laminin (LM) and that promastigotes express a distinct surface protein of ∼60 kDa that binds both FN and LM. Promastigotes of multipleLeishmaniaspecies can rapidly degrade FN by using surface-localized and secreted metalloprotease (leishmanolysin). FN degradation at the surfaces of amastigotes is leishmanolysin dependent, whereas both secreted leishmanolysin and cysteine protease B contribute to extracellular FN degradation.Leishmania-degraded FN decreased the production of reactive oxygen intermediates by parasite-infected macrophages and affected the accumulation of intracellular parasites. These findings show that both parasite stages ofLeishmaniaspecies bind to and proteolytically degrade FN at the parasite surface and distantly through secreted proteases and that degraded forms of FN can influence the activation state of parasite-infected macrophages.
Attenuated Endocytosis and Toxicity of a Mutant Cholera Toxin with Decreased Ability To Cluster Ganglioside GM
1
Molecules
Authors: Wolf Anne A. , Jobling Michael G. , Saslowsky David E. , Kern Eli , Drake Kimberly R. , Kenworthy Anne K. , Holmes Randall K. , Lencer Wayne I. 
Published: January 2008

ABSTRACT

Cholera toxin (CT) moves from the plasma membrane (PM) of host cells to the endoplasmic reticulum (ER) by binding to the lipid raft ganglioside GM
1
. The homopentomeric B-subunit of the toxin can bind up to five GM
1
molecules at once. Here, we examined the role of polyvalent binding of GM
1
in CT action by producing chimeric CTs that had B-subunits with only one or two normal binding pockets for GM
1
. The chimeric toxins had attenuated affinity for binding to host cell PM, as expected. Nevertheless, like wild-type (wt) CT, the CT chimeras induced toxicity, fractionated with detergent-resistant membranes extracted from toxin-treated cells, displayed restricted diffusion in the plane of the PM in intact cells, and remained bound to GM
1
when they were immunoprecipitated. Thus, binding normally to two or perhaps only one GM
1
molecule is sufficient for association with lipid rafts in the PM and toxin action. The chimeric toxins, however, were much less potent than wt toxin, and they entered the cell by endocytosis more slowly, suggesting that clustering of GM
1
molecules by the B-subunit enhances the efficiency of toxin uptake and perhaps also trafficking to the ER.
Further Characterization of
Vibrio vulnificus
Rugose Variants and Identification of a Capsular and Rugose Exopolysaccharide Gene Cluster
Authors: Grau Brenda L. , Henk Margaret C. , Garrison Katherine L. , Olivier Brett J. , Schulz Randall M. , O'Reilly Kathy L. , Pettis Gregg S. 
Published: January 2008

ABSTRACT

Capsular polysaccharide (CPS) is a major virulence factor in
Vibrio vulnificus
, and encapsulated strains have an opaque, smooth (OpS) colony morphology, while nonencapsulated strains have a translucent, smooth (TrS) colony morphology. Previously, we showed that OpS and TrS parental strains can yield a third colony type, rugose (R), and that the resulting strains, with the OpR and TrR phenotypes, respectively, form copious biofilms. Here we show that while OpR and TrR strains both produce three-dimensional biofilm structures that are indicative of rugose extracellular polysaccharide (rEPS) production, OpR strains also retain expression of CPS and are virulent in an iron-supplemented mouse model, while TrR strains lack CPS and are avirulent. Chlorine resistance assays further distinguished OpR and TrR isolates as exposure to 3 μg/ml NaOCl eradicated both OpS and OpR strains, while both TrS and TrR strains survived, but at rates which were significantly different from one another. Taken together, these results further emphasize the importance of CPS for virulence of
V. vulnificus
and establish a correlation between CPS expression and chlorine sensitivity in this organism. Using reverse transcriptase PCR, we also identified a nine-gene cluster associated with both CPS and rEPS expression in
V. vulnificus
, designated the
wcr
(
c
apsular and
r
ugose polysaccharide) locus, with expression occurring primarily in R variants. The latter results set the stage for characterization of functional determinants which individually or collectively contribute to expression of multiple EPS forms in this pathogen.
In Vitro Analysis of Tobramycin-Treated
Pseudomonas aeruginosa
Biofilms on Cystic Fibrosis-Derived Airway Epithelial Cells
Authors: Anderson Gregory G. , Moreau-Marquis Sophie , Stanton Bruce A. , O'Toole George A. 
Published: January 2008

ABSTRACT

P. aeruginosa
forms biofilms in the lungs of individuals with cystic fibrosis (CF); however, there have been no effective model systems for studying biofilm formation in the CF lung. We have developed a tissue culture system for growth of
P. aeruginosa
biofilms on CF-derived human airway cells that promotes the formation of highly antibiotic-resistant microcolonies, which produce an extracellular polysaccharide matrix and require the known abiotic biofilm formation genes
flgK
and
pilB
. Treatment of
P. aeruginosa
biofilms with tobramycin reduced the virulence of the biofilms both by reducing bacterial numbers and by altering virulence gene expression. We performed microarray analysis of these biofilms on epithelial cells after treatment with tobramycin, and we compared these results with gene expression of (i) tobramycin-treated planktonic
P. aeruginosa
and (ii) tobramycin-treated
P. aeruginosa
biofilms on an abiotic surface. Despite the conservation in functions required to form a biofilm, our results show that the responses to tobramycin treatment of biofilms grown on biotic versus abiotic surfaces are different, as exemplified by downregulation of genes involved in
Pseudomonas
quinolone signal biosynthesis specifically in epithelial cell-grown biofilms versus plastic-grown biofilms. We also identified the gene PA0913, which is upregulated by tobramycin specifically in biofilms grown on CF airway cells and codes for a probable magnesium transporter, MgtE. Mutation of the PA0913 gene increased the bacterial virulence of biofilms on the epithelial cells, consistent with a role for the gene in the suppression of bacterial virulence. Taken together, our data show that analysis of biofilms on airway cells provides new insights into the interaction of these microbial communities with the host.
The Periplasmic Disulfide Oxidoreductase DsbA Contributes to
Haemophilus influenzae
Pathogenesis
Authors: Rosadini Charles V. , Wong Sandy M. S. , Akerley Brian J. 
Published: January 2008

ABSTRACT

Haemophilus influenzae
is an obligate human pathogen that persistently colonizes the nasopharynx and causes disease when it invades the bloodstream, lungs, or middle ear. Proteins that mediate critical interactions with the host during invasive disease are likely to be secreted. Many secreted proteins require addition of disulfide bonds by the DsbA disulfide oxidoreductase for activity or stability. In this study, we evaluated the role in
H. influenzae
pathogenesis of DsbA, as well as HbpA, a substrate of DsbA. Mutants of
H. influenzae
Rd and type b strain Eagan having nonpolar deletions of
dsbA
were attenuated for bacteremia in animal models, and complemented strains exhibited virulence equivalent to that of the parental strains. Comparison of predicted secreted proteins in
H. influenzae
to known DsbA substrates in other species revealed several proteins that could contribute to the role of
dsbA
in virulence. One candidate, the heme transport protein, HbpA, was examined because of the importance of exogenous heme for aerobic growth of
H. influenzae
. The presence of a
dsbA
-dependent disulfide bond in HbpA was verified by an alkylation protection assay, and HbpA was less abundant in a
dsbA
mutant. The
hbpA
mutant exhibited reduced bacteremia in the mouse model, and complementation restored its in vivo phenotype to that of the parental strain. These results indicate that
dsbA
is required in vivo and that HbpA and additional DsbA-dependent factors are likely to participate in
H. influenzae
pathogenesis.
Impact of Recombinant Adenovirus Serotype 35 Priming versus Boosting of aPlasmodium falciparumProtein: Characterization of T- and B-Cell Responses to Liver-Stage Antigen 1
Authors: Rodríguez Ariane , Goudsmit Jaap , Companjen Arjen , Mintardjo Ratna , Gillissen Gert , Tax Dennis , Sijtsma Jeroen , Weverling Gerrit Jan , Holterman Lennart , Lanar David E. , Havenga Menzo J. E. , Radošević Katarina 
Published: January 2008

ABSTRACTPrime-boost vaccination regimens with heterologous antigen delivery systems have indicated that redirection of the immune response is feasible. We showed earlier that T-cell responses to circumsporozoite (CS) protein improved significantly when the protein is primed with recombinant adenovirus serotype 35 coding for CS (rAd35.CS). The current study was designed to answer the question whether such an effect can be extended to liver-stage antigens (LSA) ofPlasmodium falciparumsuch as LSA-1. Studies with mice have demonstrated that the LSA-1 protein induces strong antibody response but a weak T-cell immunity. We first identified T-cell epitopes in LSA-1 by use of intracellular gamma interferon (IFN-γ) staining and confirmed these epitopes by means of enzyme-linked immunospot assay and pentamer staining. We show that a single immunization with rAd35.LSA-1 induced a strong antigen-specific IFN-γ CD8+T-cell response but no measurable antibody response. In contrast, vaccinations with the adjuvanted recombinant LSA-1 protein induced remarkably low cellular responses but strong antibody responses. Finally, both priming and boosting of the adjuvanted protein by rAd35 resulted in enhanced T-cell responses without impairing the level of antibody responses induced by the protein immunizations alone. Furthermore, the incorporation of rAd35 in the vaccination schedule led to a skewing of LSA-1-specific antibody responses toward a Th1-type immune response. Our results show the ability of rAd35 to induce potent T-cell immunity in combination with protein in a prime-boost schedule without impairing the B-cell response.