bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prevalence, Resistance Mechanisms, and Susceptibility of Multidrug-Resistant Bloodstream Isolates of
Pseudomonas aeruginosa
Authors: Tam Vincent H. , Chang Kai-Tai , Abdelraouf Kamilia , Brioso Cristina G. , Ameka Magdalene , McCaskey Laurie A. , Weston Jaye S. , Caeiro Juan-Pablo , Garey Kevin W. 
Published: January 2010

ABSTRACT

Pseudomonas aeruginosa
is an important pathogen commonly implicated in nosocomial infections. The occurrence of multidrug-resistant (MDR)
P. aeruginosa
strains is increasing worldwide and limiting our therapeutic options. The MDR phenotype can be mediated by a variety of resistance mechanisms, and the corresponding relative biofitness is not well established. We examined the prevalence, resistance mechanisms, and susceptibility of MDR
P. aeruginosa
isolates (resistant to ≥3 classes of antipseudomonal agents [penicillins/cephalosporins, carbapenems, quinolones, and aminoglycosides]) obtained from a large, university-affiliated hospital. Among 235 nonrepeat bloodstream isolates screened between 2005 and 2007, 33 isolates (from 20 unique patients) were found to be MDR (crude prevalence rate, 14%). All isolates were resistant to carbapenems and quinolones, 91% were resistant to penicillins/cephalosporins, and 21% were resistant to the aminoglycosides. By using the first available isolate for each bacteremia episode (
n
= 18), 13 distinct clones were revealed by repetitive-element-based PCR. Western blotting revealed eight isolates (44%) to have MexB overexpression. Production of a carbapenemase (VIM-2) was found in one isolate, and mutations in
gyrA
(T83I) and
parC
(S87L) were commonly found. Growth rates of most MDR isolates were similar to that of the wild type, and two isolates (11%) were found to be hypermutable. All available isolates were susceptible to polymyxin B, and only one isolate was nonsusceptible to colistin (MIC, 3 mg/liter), but all isolates were nonsusceptible to doripenem (MIC, >2 mg/liter). Understanding and continuous monitoring of the prevalence and resistance mechanisms of MDR
P. aeruginosa
would enable us to formulate rational treatment strategies to combat nosocomial infections.
Dry Powder PA-824 Aerosols for Treatment of Tuberculosis in Guinea Pigs
Authors: Garcia-Contreras Lucila , Sung Jean C. , Muttil Pavan , Padilla Danielle , Telko Martin , VerBerkmoes Jarod L. , Elbert Katharina J. , Hickey Anthony J. , Edwards David A. 
Published: January 2010

ABSTRACT
Novel treatments for multidrug-resistant tuberculosis (MDR-TB), extensively drug-resistant tuberculosis (XDR-TB), or latent TB are needed urgently. Recently, we reported the formulation and characterization of the nitroimidazo-oxazine PA-824 for efficient aerosol delivery as dry powder porous particles and the subsequent disposition in guinea pigs after pulmonary administration. The objective of the present study was to evaluate the effects of these PA-824 therapeutic aerosols on the extent of TB infection in the low-inoculum aerosol infection guinea pig model. Four weeks after infection by the pulmonary route, animals received daily treatment for 4 weeks of either a high or a low dose of PA-824 dry powder aerosol. Animals received PA-824 cyclodextrin/lecithin suspensions orally as positive controls, and those receiving placebo particles or no treatment were negative controls. The lungs and spleens of animals receiving the high dose of inhaled PA-824 particles exhibited a lower degree of inflammation (indicated by wet tissue weights), bacterial burden, and tissue damage (indicated by histopathology) than those of untreated or placebo animals. Treatment with oral PA-824 cyclodextrin/lecithin suspension resulted in a more significant reduction in the bacterial burden of lungs and spleen, consistent with a dose that was larger than inhaled doses (eight times the inhaled low dose and four times the inhaled high dose). However, histopathological analysis revealed that the extent of tissue damage was comparable in groups receiving the oral or either inhaled dose. The present studies indicate the potential use of PA-824 dry powder aerosols in the treatment of TB.
The Extreme C Terminus of
Shigella flexneri
IpaB Is Required for Regulation of Type III Secretion, Needle Tip Composition, and Binding
Authors: Roehrich A. Dorothea , Martinez-Argudo Isabel , Johnson Steven , Blocker Ariel J. , Veenendaal Andreas K. J. 
Published: January 2010

ABSTRACT

Type III secretion systems (T3SSs) are widely distributed virulence determinants of Gram-negative bacteria. They translocate bacterial proteins into host cells to manipulate them during infection. The
Shigella
T3SS consists of a cytoplasmic bulb, a transmembrane region, and a hollow needle protruding from the bacterial surface. The distal tip of mature, quiescent needles is composed of IpaD, which is topped by IpaB. Physical contact with host cells initiates secretion and leads to assembly of a pore, formed by IpaB and IpaC, in the host cell membrane, through which other virulence effector proteins may be translocated. IpaB is required for regulation of secretion and may be the host cell sensor. However, its mode of needle association is unknown. Here, we show that deletion of 3 or 9 residues at the C terminus of IpaB leads to fast constitutive secretion of late effectors, as observed in a Δ
ipaB
strain. Like the Δ
ipaB
mutant, mutants with C-terminal mutations also display hyperadhesion. However, unlike the Δ
ipaB
mutant, they are still invasive and able to lyse the internalization vacuole with nearly wild-type efficiency. Finally, the mutant proteins show decreased association with needles and increased recruitment of IpaC. Taken together, these data support the notion that the state of the tip complex regulates secretion. We propose a model where the quiescent needle tip has an “off” conformation that turns “on” upon host cell contact. Our mutants may adopt a partially “on” conformation that activates secretion and is capable of recruiting some IpaC to insert pores into host cell membranes and allow invasion.
Burkholderia cenocepaciaCreates an Intramacrophage Replication Niche in Zebrafish Embryos, Followed by Bacterial Dissemination and Establishment of Systemic Infection
Authors: Vergunst Annette C. , Meijer Annemarie H. , Renshaw Stephen A. , O'Callaghan David 
Published: January 2010

ABSTRACTBacteria belonging to the “Burkholderia cepaciacomplex” (Bcc) often cause fatal pulmonary infections in cystic fibrosis patients, yet little is know about the underlying molecular mechanisms. These Gram-negative bacteria can adopt an intracellular lifestyle, although their ability to replicate intracellularly has been difficult to demonstrate. Here we show that Bcc bacteria survive and multiply in macrophages of zebrafish embryos. Local dissemination by nonlytic release from infected cells was followed by bacteremia and extracellular replication.Burkholderia cenocepaciaisolates belonging to the epidemic electrophoretic type 12 (ET12) lineage were highly virulent for the embryos; intravenous injection of <10 bacteria of strain K56-2 killed embryos within 3 days. However, small but significant differences between the clonal ET12 isolates K56-2, J2315, and BC7 were evident. In addition, the innate immune response in young embryos was sufficiently developed to control infection with other less virulent Bcc strains, such asBurkholderia vietnamiensisFC441 andBurkholderia stabilisLMG14294. A K56-2cepRquorum-sensing regulator mutant was highly attenuated, and its ability to replicate and spread to neighboring cells was greatly reduced. Our data indicate that the zebrafish embryo is an excellent vertebrate model to dissect the molecular basis of intracellular replication and the early innate immune responses in this intricate host-pathogen interaction.
Polysaccharide Capsule and Sialic Acid-Mediated Regulation Promote Biofilm-Like Intracellular Bacterial Communities during Cystitis
Authors: Anderson Gregory G. , Goller Carlos C. , Justice Sheryl , Hultgren Scott J. , Seed Patrick C. 
Published: January 2010

ABSTRACTUropathogenicEscherichia coli(UPEC) is the leading cause of urinary tract infections (UTIs). A murine UTI model has revealed an infection cascade whereby UPEC undergoes cycles of invasion of the bladder epithelium, intracellular proliferation in polysaccharide-containing biofilm-like masses called intracellular bacterial communities (IBC), and then dispersal into the bladder lumen to initiate further rounds of epithelial colonization and invasion. We predicted that the UPEC K1 polysaccharide capsule is a key constituent of the IBC matrix. Compared to prototypicE. coliK1 strain UTI89, a capsule assembly mutant had a fitness defect in functionally TLR4+and TLR4−mice, suggesting a protective role of capsule in inflamed and noninflamed hosts. K1 capsule assembly and synthesis mutants had dramatically reduced IBC formation, demonstrating the common requirement for K1 polysaccharide in IBC development. The capsule assembly mutant appeared dispersed in the cytoplasm of the bladder epithelial cells and failed to undergo high-density intracellular replication during later stages of infection, when the wild-type strain continued to form serial generations of IBC. Deletion of the sialic acid regulator genenanRpartially restored IBC formation in the capsule assembly mutant. These data suggest that capsule is necessary for efficient IBC formation and that aberrant sialic acid accumulation, resulting from disruption of K1 capsule assembly, produces a NanR-mediated defect in intracellular proliferation and IBC development. Together, these data demonstrate the complex but important roles of UPEC polysaccharide encapsulation and sialic acid signaling in multiple stages of UTI pathogenesis.
Haemophilus ducreyiSapA Contributes to Cathelicidin Resistance and Virulence in Humans
Authors: Mount Kristy L. B. , Townsend Carisa A. , Rinker Sherri D. , Gu Xiaoping , Fortney Kate R. , Zwickl Beth W. , Janowicz Diane M. , Spinola Stanley M. , Katz Barry P. , Bauer Margaret E. 
Published: January 2010

ABSTRACTHaemophilus ducreyiis an extracellular pathogen of human epithelial surfaces that resists human antimicrobial peptides (APs). The organism's genome contains homologs of genessensitive toantimicrobialpeptides (sapoperon) in nontypeableHaemophilus influenzae. In this study, we characterized thesap-containing loci ofH. ducreyi35000HP and demonstrated thatsapAis expressed in broth cultures andH. ducreyi-infected tissue;sapAis also conserved among both class I and class IIH. ducreyistrains. We constructed a nonpolarsapAmutant ofH. ducreyi35000HP, designated 35000HPsapA, and compared the percent survival of wild-type 35000HP and 35000HPsapAexposed to several human APs, including α-defensins, β-defensins, and the cathelicidin LL-37. Unlike anH. influenzae sapAmutant, strain 35000HPsapAwas not more susceptible to defensins than strain 35000HP was. However, we observed a significant decrease in the survival of strain 35000HPsapAafter exposure to LL-37, which was complemented by introducingsapAintrans. Thus, the Sap transporter plays a role in resistance ofH. ducreyito LL-37. We next compared mutant strain 35000HPsapAwith strain 35000HP for their ability to cause disease in human volunteers. Although both strains caused papules to form at similar rates, the pustule formation rate at sites inoculated with 35000HPsapAwas significantly lower than that of sites inoculated with 35000HP (33.3% versus 66.7%;P= 0.007). Together, these data establish that SapA acts as a virulence factor and as one mechanism forH. ducreyito resist killing by antimicrobial peptides. To our knowledge, this is the first demonstration that an antimicrobial peptide resistance mechanism contributes to bacterial virulence in humans.
Assessment of the Duration of Protection in
Campylobacter jejuni
Experimental Infection in Humans
Authors: Tribble David R. , Baqar Shahida , Scott Daniel A. , Oplinger Michael L. , Trespalacios Fernando , Rollins David , Walker Richard I. , Clements John D. , Walz Steven , Gibbs Paul , Burg Edward F. , Moran Anthony P. , Applebee Lisa , Bourgeois A. Louis 
Published: January 2010

ABSTRACT

A human
Campylobacter jejuni
infection model provided controlled exposure to assess vaccine efficacy and investigate protective immunity for this important diarrheal pathogen. A well-characterized outbreak strain,
C. jejuni
81-176, was investigated using a volunteer experimental infection model to evaluate the dose range and duration of protection. Healthy
Campylobacter
-seronegative adults received
C. jejuni
strain 81-176 via oral inoculation of 10
5
, 10
7
, or 10
9
CFU (5 adults/dose), which was followed by clinical and immunological monitoring. Based on dose range clinical outcomes, the 10
9
-CFU dose (
n
= 31) was used to assess homologous protection at 28 to 49 days (short-term veterans [STV];
n
= 8) or 1 year (long-term veterans [LTV];
n
= 7) after primary infection. An illness dose effect was observed for naïve subjects (with lower doses, 40 to 60% of the subjects were ill; with the 10
9
-CFU dose, 92% of the subjects were ill) along with complete protection for the STV group and attenuated illness for the LTV group (57%). Partial resistance to colonization was seen in STV (25% of the subjects were not infected; 3-log-lower maximum excretion level). Systemic and mucosal immune responses were robust in naïve subjects irrespective of the dose or the severity of illness. In contrast, in STV there was a lack of circulating antibody-secreting cells (ASC), reflecting the local mucosal effector responses. LTV exhibited comparable ASC responses to primary infection, and anamnestic fecal IgA responses likely contributed to self-resolving illness prior to antibiotic treatment.
Campylobacter
antigen-dependent production of gamma interferon by peripheral blood mononuclear cells was strongly associated with protection from illness, supporting the hypothesis that TH1 polarization has a primary role in acquired immunity to
C. jejuni
. This study revealed a
C. jejuni
dose-related increase in campylobacteriosis rates, evidence of complete short-term protection that waned with time, and immune response patterns associated with protection.
Screening of Predicted Secreted Antigens fromMycobacterium bovisReveals the Immunodominance of the ESAT-6 Protein Family
Authors: Jones Gareth J. , Gordon Stephen V. , Hewinson R. Glyn , Vordermeier H. Martin 
Published: January 2010

ABSTRACTResults of previous studies utilizing bioinformatic approaches in antigen-mining experiments revealed that secreted proteins are among the most frequently recognized antigens fromMycobacterium bovis. Thus, we hypothesized that the analysis of secreted proteins is likely to reveal additional immunogenic antigens that can be used to increase the specificity of diagnostic tests or be suitable vaccination candidates for mycobacterial infections. To test this hypothesis, 382 pools of overlapping peptides spanning 119M. bovissecreted and potentially secreted proteins were screened for the ability to stimulate a gamma interferon responsein vitrousing whole blood from tuberculin-positive reactor (TB reactor) cattle. Of the 119 proteins screened, 70 (59%) induced positive responses in the TB reactor animals to various degrees. Strikingly, all but one of the 15 ESAT-6 proteins tested were recognized by at least 30% of the TB reactor animals, with 12 of the 22 most commonly recognized antigens belonging to this protein family. Further analysis of these data demonstrated that there was no significant difference in immunogenicity between the ESAT-6 proteins that were components of potentially intact ESX secretory systems and those corresponding to additional partialesxloci. Importantly for vaccine design, antigenic epitopes in some highly conserved regions shared by numerous ESAT-6 proteins were identified. However, despite this considerable homology, peptide-mapping experiments also revealed that immunodominant peptides were located in regions of amino acid variability.
Interleukin-15 and Its Receptor Augment Dendritic Cell Vaccination against theneuOncogene through the Induction of Antibodies Partially Independent of CD4 Help
Authors: Steel Jason C. , Ramlogan Charmaine A. , Yu Ping , Sakai Yoshio , Forni Guido , Waldmann Thomas A. , Morris John C. 
Published: January 2010

AbstractInterleukin-15 (IL-15) stimulates the diffrentiation and proliferation of T, B, and natural killer cells; enhances CD8+ cytolytic T-ceII activity; helps maintain CD44hiCD8+ memory T cells; and stimulates immunoglobulin synthesis by B cells. IL-15 is trans-presented to effector cells by its receptor, IL-15Rα, expressed on dendritic cells (DC) and monocytes. We examined the antitumor effect of adenoviral-mediated gene transfer of IL-15 and IL-15Rα to augment a DC vaccine directed against the NEU (ErbB2) oncoprotein. Transgenic BALB-neuT mice vaccinated in late-stage tumor development with a DC vaccine expressing a truncated NEU antigen, IL-I5, and its receptor (DCAd.Neu+Ad_mIL-15+Ad.mlL-15Rα) were protected from mammary carcinomas, with 70% of animals tumor-free at 30 weeks compared with none of the animals vaccinated with NEU alone (DCAd.Neu). The combination of neu, IL-15, and IL-15Rα gene transfer leads to a significaintly greater anti-NEU antibody response compared with mice treated with DCAd.Neu or DCAd.Neu combined with either IL-15 (DCAd.Neu+Ad.mlL-15) or lL-15Rα (DCAd.Neu+Ad.mlL-15Rα). The antitumor effect was antibody mediated and involved modulation of NEU expression and signaIing. Depletion of CD4+ cells did not abrogate the antitumor effect of the vaccine, nor did it inhibit the induction of anti-NEU aritibodies. Coexpression of IL-15 and IL-15Rα in an anticancer vaccine enhanced immune responses against the NEU antigen and may overcome impaired CD4+ T-helper function. Cancer Res; 70(3); 1072–81
The EphB6 Receptor Cooperates with c-Cbl to Regulate the Behavior of Breast Cancer Cells
Authors: Truitt Luke , Freywald Tanya , DeCoteau John , Sharfe Nigel , Freywald Andrew 
Published: January 2010

Abstract
Cancer invasiveness plays a major role in the mortality of patients with solid tumors, and deregulated cell adhesion and migration are suspected to drive invasive behavior. Since Eph receptor tyrosine kinases control both cell attachment and migration, they may act to define the level of cancer invasiveness. EphB6 is an unusual Eph receptor, lacking catalytic capacity due to alterations in its kinase domain. Interestingly, increased metastatic activity is associated with reduced EphB6 receptor expression in several tumor types, including breast cancer. This emphasizes the potential of EphB6 to act as a suppressor of cancer aggressiveness; however, the mechanism of its action is not well understood. We show that restoration of EphB6 expression in invasive breast cancer cells supports actin-dependent spreading and attachment and blocks invasiveness. EphB6 stimulation induces its tyrosine phosphorylation, which is crucial for its function and is mediated by the EphB4 receptor. This is accompanied by EphB6–c-Cbl interaction and phosphorylation of c-Cbl partner, the Abl kinase. Cbl silencing suppresses Abl phosphorylation, cell adhesion, and morphologic changes and blocks the ability of EphB6 to inhibit invasiveness, confirming its importance for EphB6 activity. Despite its crucial role in EphB6 responses, EphB4 also acts in an EphB6-independent manner to enhance invasive activity, suggesting that cancer invasiveness may be defined by the balance in the EphB6-EphB4 system. Overall, our observations suggest a new role for EphB6 in suppressing cancer invasiveness through c-Cbl–dependent signaling, morphologic changes, and cell attachment and indicate that EphB6 may represent a useful prognostic marker and a promising target for therapeutic approaches. Cancer Res; 70(3); 1141–53
Smad Signaling Is Required to Maintain Epigenetic Silencing during Breast Cancer Progression
Authors: Papageorgis Panagiotis , Lambert Arthur W. , Ozturk Sait , Gao Fangming , Pan Hongjie , Manne Upender , Alekseyev Yuriy O. , Thiagalingam Arunthathi , Abdolmaleky Hamid M. , Lenburg Marc , Thiagalingam Sam 
Published: January 2010

Abstract
Breast cancer progression is associated with aberrant DNA methylation and expression of genes that control the epithelial-mesenchymal transition (EMT), a critical step in malignant conversion. Although the genes affected have been studied, there is little understanding of how aberrant activation of the DNA methylation machinery itself occurs. Using a breast cancer cell–based model system, we found that cells that underwent EMT exhibited overactive transforming growth factor β (TGFβ) signaling and loss of expression of the CDH1, CGN, CLDN4, and KLK10 genes as a result of hypermethylation of their corresponding promoter regions. Based on these observations, we hypothesized that activated TGFβ-Smad signaling provides an “epigenetic memory” to maintain silencing of critical genes. In support of this hypothesis, disrupting Smad signaling in mesenchymal breast cancer cells resulted in DNA demethylation and reexpression of the genes identified. This epigenetic reversal was accompanied by an acquisition of epithelial morphology and a suppression of invasive properties. Notably, disrupting TGFβ signaling decreased the DNA binding activity of DNA methyltransferase DNMT1, suggesting that failure to maintain methylation of newly synthesized DNA was the likely cause of DNA demethylation. Together, our findings reveal a hyperactive TGFβ-TGFβR-Smad2 signaling axis needed to maintain epigenetic silencing of critical EMT genes and breast cancer progression. Cancer Res; 70(3); 968–78
The G Protein–Coupled Receptor GPR30 Inhibits Proliferation of Estrogen Receptor–Positive Breast Cancer Cells
Authors: Ariazi Eric A. , Brailoiu Eugen , Yerrum Smitha , Shupp Heather A. , Slifker Michael J. , Cunliffe Heather E. , Black Michael A. , Donato Anne L. , Arterburn Jeffrey B. , Oprea Tudor I. , Prossnitz Eric R. , Dun Nae J. , Jordan V. Craig 
Published: January 2010

Abstract
The G protein–coupled receptor GPR30 binds 17β-estradiol (E2) yet differs from classic estrogen receptors (ERα and ERβ). GPR30 can mediate E2-induced nongenomic signaling, but its role in ERα-positive breast cancer remains unclear. Gene expression microarray data from five cohorts comprising 1,250 breast carcinomas showed an association between increased GPR30 expression and ERα-positive status. We therefore examined GPR30 in estrogenic activities in ER-positive MCF-7 breast cancer cells using G-1 and diethylstilbestrol (DES), ligands that selectively activate GPR30 and ER, respectively, and small interfering RNAs. In expression studies, E2 and DES, but not G-1, transiently downregulated both ER and GPR30, indicating that this was ER mediated. In Ca2+ mobilization studies, GPR30, but not ERα, mediated E2-induced Ca2+ responses because E2, 4-hydroxytamoxifen (activates GPR30), and G-1, but not DES, elicited cytosolic Ca2+ increases not only in MCF-7 cells but also in ER-negative SKBr3 cells. Additionally, in MCF-7 cells, GPR30 depletion blocked E2-induced and G-1–induced Ca2+ mobilization, but ERα depletion did not. Interestingly, GPR30-coupled Ca2+ responses were sustained and inositol triphosphate receptor mediated in ER-positive MCF-7 cells but transitory and ryanodine receptor mediated in ER-negative SKBr3 cells. Proliferation studies involving GPR30 depletion indicated that the role of GPR30 was to promote SKBr3 cell growth but reduce MCF-7 cell growth. Supporting this, G-1 profoundly inhibited MCF-7 cell growth, potentially via p53 and p21 induction. Further, flow cytometry showed that G-1 blocked MCF-7 cell cycle progression at the G1 phase. Thus, GPR30 antagonizes growth of ERα-positive breast cancer and may represent a new target to combat this disease. Cancer Res; 70(3); 1184–94