bluuebunny/crossref_metadata_2025_split huggingface dataset:
Field-Based Flow Cytometry for
Ex Vivo
Characterization of Plasmodium vivax and P. falciparum Antimalarial Sensitivity
Authors: Russell B. , Malleret B. , Suwanarusk R. , Anthony C. , Kanlaya S. , Lau Y. L. , Woodrow C. J. , Nosten F. , Renia L. 
Published: July 2013

ABSTRACT

Ex vivo
antimalarial sensitivity testing in human malaria parasites has largely depended on microscopic determination of schizont maturation. While this microscopic method is sensitive, it suffers from poor precision and is laborious. The recent development of portable, low-cost cytometers has allowed us to develop and validate a simple, field-optimized protocol using SYBR green and dihydroethidium for the accurate and objective determination of antimalarial drug sensitivity in freshly isolated
Plasmodium vivax
and
Plasmodium falciparum
.
Mutation of RNA Polymerase β-Subunit Gene Promotes Heterogeneous-to-Homogeneous Conversion of β-Lactam Resistance in Methicillin-Resistant Staphylococcus aureus
Authors: Aiba Yoshifumi , Katayama Yuki , Hishinuma Tomomi , Murakami-Kuroda Hiroko , Cui Longzhu , Hiramatsu Keiichi 
Published: July 2013

ABSTRACT

Three types of phenotypic expression of β-lactam resistance have been reported in methicillin-resistant
Staphylococcus aureus
(MRSA): heterogeneous, homogeneous, and Eagle-type resistance. Heterogeneous-to-homogeneous conversion of β-lactam resistance is postulated to be caused by a chromosomal mutation (
chr*
) in addition to the expression of the
mecA
gene. Eagle-type resistance is a unique phenotype of
chr*
occurring in pre-MRSA strain N315 whose
mecA
gene expression is strongly repressed by an intact
mecI
gene. We here report that certain mutations of the
rpoB
gene, encoding the RNA polymerase β subunit, belong to
chr*
. We studied homogeneous MRSA (homo-MRSA) strain N315ΔIP-H5 (abbreviated as ΔIP-H5), which was obtained from hetero-MRSA strain N315ΔIP by selection with 8 mg/liter imipenem. Whole-genome sequencing of ΔIP-H5 revealed the presence of a unique mutation in the
rpoB
gene,
rpoB
(N967I), causing the amino acid replacement of Asn by Ile at position 967 of RpoB. The effect of the
rpoB
(N967I) mutation was confirmed by constructing a revertant H5
rpoB
(I967N) strain as well as an N315-derived mutant, N315
rpoB
(N967I). H5
rpoB
(I967N) regained the hetero-resistance phenotype, and the N315
rpoB
(N967I) strain showed an Eagle-type phenotype similar to that of the typical Eagle-type MRSA strain N315h4. Furthermore, subsequent whole-genome sequencing revealed that N315h4 also had a missense mutation of
rpoB
(R644H). Introduction of the
rpoB
(N967I) mutation was accompanied by decreased autolysis, prolonged doubling time, and tolerance to bactericidal concentrations of methicillin. We consider that
rpoB
mutations are the major cause for heterogeneous-to-homogeneous phenotypic conversion of β-lactam resistance in MRSA strain N315 and its derived strains.
Head-to-Head Comparison of Inhibitory and Fungicidal Activities of Fluconazole, Itraconazole, Voriconazole, Posaconazole, and Isavuconazole against Clinical Isolates of Trichosporon asahii
Authors: Hazirolan Gulsen , Canton Emilia , Sahin Selma , Arikan-Akdagli Sevtap 
Published: July 2013

ABSTRACT

Treatment of disseminated
Trichosporon
infections still remains difficult. Amphotericin B frequently displays inadequate fungicidal activity and echinocandins have no meaningful antifungal effect against this genus. Triazoles are currently the drugs of choice for the treatment of
Trichosporon
infections. This study evaluates the inhibitory and fungicidal activities of five triazoles against 90 clinical isolates of
Trichosporon asahii
. MICs (μg/ml) were determined according to Clinical and Laboratory Standards Institute microdilution method M27-A3 at 24 and 48 h using two endpoints, MIC-2 and MIC-0 (the lowest concentrations that inhibited ∼50 and 100% of growth, respectively). Minimum fungicidal concentrations (MFCs; μg/ml) were determined by seeding 100 μl of all clear MIC wells (using an inoculum of 10
4
CFU/ml) onto Sabouraud dextrose agar. Time-kill curves were assayed against four clinical
T. asahii
isolates and the
T. asahii
ATCC 201110 strain. The MIC-2 (∼50% reduction in turbidity compared to the growth control well)/MIC-0 (complete inhibition of growth)/MFC values that inhibited 90% of isolates at 48 h were, respectively, 8/32/64 μg/ml for fluconazole, 1/2/8 μg/ml for itraconazole, 0.12/0.5/2 μg/ml for voriconazole, 0.5/2/4 μg/ml for posaconazole, and 0.25/1/4 μg/ml for isavuconazole. The MIC-0 endpoints yielded more consistent MIC results, which remained mostly unchanged when extending the incubation to 48 h (98 to 100% agreement with 24-h values) and are easier to interpret. Based on the time-kill experiments, none of the drugs reached the fungicidal endpoint (99.9% killing), killing activity being shown but at concentrations not reached in serum. Statistical analysis revealed that killing rates are dose and antifungal dependent. The lowest concentration at which killing activity begins was for voriconazole, and the highest was for fluconazole. These results suggest that azoles display fungistatic activity and lack fungicidal effect against
T. asahii
. By rank order, the most active triazole is voriconazole, followed by itraconazole ∼ posaconazole ∼ isavuconazole > fluconazole.
ComparativeIn VitroActivities of SMT19969, a New Antimicrobial Agent, against Clostridium difficile and 350 Gram-Positive and Gram-Negative Aerobic and Anaerobic Intestinal Flora Isolates
Authors: Goldstein Ellie J. C. , Citron Diane M. , Tyrrell Kerin L. , Merriam C. Vreni 
Published: July 2013

ABSTRACTThe comparativein vitroactivity of SMT19969, a novel, narrow-spectrum, nonabsorbable agent, was studied against 50 ribotype-definedClostridium difficilestrains, 174 Gram-positive and 136 Gram-negative intestinal anaerobes, and 40 Gram-positive aerobes. SMT19969 was one dilution more active againstC. difficileisolates (MIC range, 0.125 to 0.5 μg/ml; MIC90, 0.25 μg/ml), including ribotype 027 strains, than fidaxomicin (range, 0.06 to 1 μg/ml; MIC90, 0.5 μg/ml) and two to six dilutions lower than either vancomycin or metronidazole. SMT19969 and fidaxomicin were generally less active against Gram-negative anaerobes, especially theBacteroides fragilisgroup species, than vancomycin and metronidazole, suggesting that SMT19969 has a lesser impact on the normal intestinal microbiota that maintain colonization resistance. SMT19969 showed limited activity against other Gram-positive anaerobes, includingBifidobacteriaspecies,Eggerthella lenta,Finegoldia magna, andPeptostreptococcus anaerobius, with MIC90s of >512, >512, 64, and 64 μg/ml, respectively.Clostridiumspecies showed various levels of susceptibility, withC. innocuumbeing susceptible (MIC90, 1 μg/ml) andC. ramosumandC. perfringensbeing nonsusceptible (MIC90, >512 μg/ml). Activity againstLactobacillusspp. (range, 0.06 to >512 μg/ml; MIC90, >512 μg/ml) was comparable to that of fidaxomicin and varied by species and strain. Gram-positive aerobic cocci (Staphylococcus aureus,Enterococcus faecalis,E. faecium, and streptococci) showed high SMT19969 MIC90values (128 to >512 μg/ml).
Effect of Nitroxides on Swarming Motility and Biofilm Formation, Multicellular Behaviors in Pseudomonas aeruginosa
Authors: de la Fuente-Núñez César , Reffuveille Fany , Fairfull-Smith Kathryn E. , Hancock Robert E. W. 
Published: July 2013

ABSTRACT

The ability of nitric oxide (NO) to induce biofilm dispersion has been well established. Here, we investigated the effect of nitroxides (sterically hindered nitric oxide analogues) on biofilm formation and swarming motility in
Pseudomonas aeruginosa
. A transposon mutant unable to produce nitric oxide endogenously (
nirS
) was deficient in swarming motility relative to the wild type and the complemented strain. Moreover, expression of the
nirS
gene was upregulated by 9.65-fold in wild-type swarming cells compared to planktonic cells. Wild-type swarming levels were substantially restored upon the exogenous addition of nitroxide containing compounds, a finding consistent with the hypothesis that NO is necessary for swarming motility. Here, we showed that nitroxides not only mimicked the dispersal activity of NO but also prevented biofilms from forming in flow cell chambers. In addition, a
nirS
transposon mutant was deficient in biofilm formation relative to the wild type and the complemented strain, thus implicating NO in the formation of biofilms. Intriguingly, despite its stand-alone action in inhibiting biofilm formation and promoting dispersal, a nitroxide partially restored the ability of a
nirS
mutant to form biofilms.
Neisseria Prophage Repressor Implicated in Gonococcal Pathogenesis
Authors: Daou Nadine , Yu Chunxiao , Mcclure Ryan , Gudino Cynthia , Reed George W. , Genco Caroline A. 
Published: July 2013

ABSTRACT

Neisseria gonorrhoeae
, the causative agent of the sexually transmitted disease gonorrhea, can infect and colonize multiple mucosal sites in both men and women. The ability to cope with different environmental conditions requires tight regulation of gene expression. In this study, we identified and characterized a gonococcal transcriptional regulatory protein (Neisseria phage repressor [Npr]) that was previously annotated as a putative gonococcal phage repressor protein. Npr was found to repress transcription of NGNG_00460 to NGNG_00463 (NGNG_00460-00463), an operon present within the phage locus NgoΦ4. Npr binding sites within the NGNG_00460-00463 promoter region were found to overlap the −10 and −35 promoter motifs. A gonococcal
npr
mutant demonstrated increased adherence to and invasion of human endocervical epithelial cells compared to a wild-type gonococcal strain. Likewise, the gonococcal
npr
mutant exhibited enhanced colonization in a gonococcal mouse model of mucosal infection. Analysis of the gonococcal
npr
mutant using RNA sequence (RNA-seq) analysis demonstrated that the Npr regulon is limited to the operon present within the phage locus. Collectively, our studies have defined a new gonococcal phage repressor protein that controls the transcription of genes implicated in gonococcal pathogenesis.
Inflammation-Induced Acid Tolerance Genes
gadAB
in Luminal Commensal Escherichia coli Attenuate Experimental Colitis
Authors: Tchaptchet Sandrine , Fan Ting-Jia , Goeser Laura , Schoenborn Alexi , Gulati Ajay S. , Sartor R. Balfour , Hansen Jonathan J. 
Published: July 2013

ABSTRACT

Dysregulated immune responses to commensal intestinal bacteria, including
Escherichia coli
, contribute to the development of inflammatory bowel diseases (IBDs) and experimental colitis. Reciprocally,
E. coli
responds to chronic intestinal inflammation by upregulating expression of stress response genes, including
gadA
and
gadB
. GadAB encode glutamate decarboxylase and protect
E. coli
from the toxic effects of low pH and fermentation acids, factors present in the intestinal lumen in patients with active IBDs. We hypothesized that
E. coli
upregulates
gadAB
during inflammation to enhance its survival and virulence. Using real-time PCR, we determined
gadAB
expression in luminal
E. coli
from ex-germfree wild-type (WT) and interleukin-10 (IL-10) knockout (KO) (IL-10
−/−
) mice selectively colonized with a commensal
E. coli
isolate (NC101) that causes colitis in KO mice in isolation or in combination with 7 other commensal intestinal bacterial strains.
E. coli
survival and host inflammatory responses were measured in WT and KO mice colonized with NC101 or a mutant lacking the
gadAB
genes (NC101Δ
gadAB
). The susceptibility of NC101 and NC101Δ
gadAB
to killing by host antimicrobial peptides and their translocation across intestinal epithelial cells were evaluated using bacterial killing assays and transwell experiments, respectively. We show that expression of
gadAB
in luminal
E. coli
increases proportionately with intestinal inflammation in KO mice and enhances the susceptibility of NC101 to killing by the host antimicrobial peptide cryptdin-4 but decreases bacterial transmigration across intestinal epithelial cells, colonic inflammation, and mucosal immune responses. Chronic intestinal inflammation upregulates acid tolerance pathways in commensal
E. coli
isolates, which, contrary to our original hypothesis, limits their survival and colitogenic potential. Further investigation of microbial adaptation to immune-mediated inflammation may provide novel insights into the pathogenesis and treatment of IBDs.
Emetic Potentials of Newly Identified Staphylococcal Enterotoxin-Like Toxins
Authors: Omoe Katsuhiko , Hu Dong-Liang , Ono Hisaya K. , Shimizu Satoru , Takahashi-Omoe Hiromi , Nakane Akio , Uchiyama Takehiko , Shinagawa Kunihiro , Imanishi Ken'ichi 
Published: July 2013

ABSTRACT
Staphylococcal enterotoxins (SEs) are a common causative agent of food poisoning. Recently, many new SE-like (SEl) toxins have been reported, although the role of SEls in food poisoning remains unclear. In this study, the emetic potentials of SElK, SElL, SElM, SElN, SElO, SElP, and SElQ were assessed using a monkey-feeding assay. All the SEls that were tested induced emetic reactions in monkeys at a dose of 100 μg/kg, although the numbers of affected monkeys were significantly smaller than the numbers that were affected after consuming SEA or SEB. This result suggests that these new SEs may play some role in staphylococcal food poisoning.
Virulent Shigella flexneri Affects Secretion, Expression, and Glycosylation of Gel-Forming Mucins in Mucus-Producing Cells
Authors: Sperandio Brice , Fischer Natalie , Chevalier-Curt Marie Joncquel , Rossez Yannick , Roux Pascal , Robbe Masselot Catherine , Sansonetti Philippe J. 
Published: July 2013

ABSTRACT

Mucin glycoproteins are secreted in large amounts by the intestinal epithelium and constitute an efficient component of innate immune defenses to promote homeostasis and protect against enteric pathogens. In this study, our objective was to investigate how the bacterial enteropathogen
Shigella flexneri
, which causes bacillary dysentery, copes with the mucin defense barrier. We report that upon
in vitro
infection of mucin-producing polarized human intestinal epithelial cells, virulent
S. flexneri
manipulates the secretion of gel-forming mucins. This phenomenon, which is triggered only by virulent strains, results in accumulation of mucins at the cell apical surface, leading to the appearance of a gel-like structure that favors access of bacteria to the cell surface and the subsequent invasion process. We identify MUC5AC, a gel-forming mucin, as a component of this structure. Formation of this gel does not depend on modifications of electrolyte concentrations, induction of trefoil factor expression, endoplasmic reticulum stress, or response to unfolded proteins. In addition, transcriptional and biochemical analyses of infected cells reveal modulations of mucin gene expression and modifications of mucin glycosylation patterns, both of which are induced by virulent bacteria in a type III secretion system-dependent manner. Thus,
S. flexneri
has developed a dedicated strategy to alter the mucus barrier by targeting key elements of the gel-forming capacity of mucins: gene transcription, protein glycosylation, and secretion.
The p38 MAPK and JNK Pathways Protect Host Cells against Clostridium perfringens Beta-Toxin
Authors: Nagahama Masahiro , Shibutani Masahiro , Seike Soshi , Yonezaki Mami , Takagishi Teruhisa , Oda Masataka , Kobayashi Keiko , Sakurai Jun 
Published: July 2013

ABSTRACT

Clostridium perfringens
beta-toxin is an important agent of necrotic enteritis and enterotoxemia. Beta-toxin is a pore-forming toxin (PFT) that causes cytotoxicity. Two mitogen-activated protein kinase (MAPK) pathways (p38 and c-Jun N-terminal kinase [JNK]-like) provide cellular defense against various stresses. To investigate the role of the MAPK pathways in the toxic effect of beta-toxin, we examined cytotoxicity in five cell lines. Beta-toxin induced cytotoxicity in cells in the following order: THP-1 = U937 > HL-60 > BALL-1 = MOLT-4. In THP-1 cells, beta-toxin formed oligomers on lipid rafts in membranes and induced the efflux of K
+
from THP-1 cells in a dose- and time-dependent manner. The phosphorylation of p38 MAPK and JNK occurred in response to an attack by beta-toxin. p38 MAPK (SB203580) and JNK (SP600125) inhibitors enhanced toxin-induced cell death. Incubation in K
+
-free medium intensified p38 MAPK activation and cell death induced by the toxin, while incubation in K
+
-high medium prevented those effects. While streptolysin O (SLO) reportedly activates p38 MAPK via reactive oxygen species (ROS), we showed that this pathway did not play a major role in p38 phosphorylation in beta-toxin-treated cells. Therefore, we propose that beta-toxin induces activation of the MAPK pathway to promote host cell survival.
Heme Uptake Mediated by LHR1 Is Essential for Leishmania amazonensis Virulence
Authors: Miguel Danilo C. , Flannery Andrew R. , Mittra Bidyottam , Andrews Norma W. 
Published: July 2013

ABSTRACT

The protozoan parasite
Leishmania amazonensis
is a heme auxotroph and must acquire this essential factor from the environment. Previous studies showed that
L. amazonensis
incorporates heme through the transmembrane protein LHR1 (L
eishmania H
eme
R
esponse 1).
LHR1
-null promastigotes were not viable, suggesting that the transporter is essential for survival. Here, we compared the growth, differentiation, and infectivity for macrophages and mice of wild-type,
LHR1
-single-knockout (
LHR1/
Δ
lhr1
), and
LHR1
-complemented (
LHR1/
Δ
lhr1
plus
LHR1
)
L. amazonensis
strains.
LHR1/
Δ
lhr1
promastigotes replicated poorly in heme-deficient media and had lower intracellular heme content than wild-type parasites.
LHR1/
Δ
lhr1
promastigotes were also less effective in reducing ferric iron to ferrous iron, a reaction mediated by the heme-containing parasite enzyme LFR1 (
Leishmania Ferric Reductase
1).
LHR1/
Δ
lhr1
parasites differentiated normally into aflagellated forms expressing amastigote-specific markers but were not able to replicate intracellularly after infecting macrophages. Importantly, the intracellular growth of
LHR1/
Δ
lhr1
amastigotes was fully restored when macrophages were allowed to phagocytose red blood cells prior to infection.
LHR1/
Δ
lhr1
parasites were also severely defective in the development of cutaneous lesions in mice. All phenotypes observed in
LHR1/
Δ
lhr1
L. amazonensis
were rescued by expression of episomal
LHR1
. Our results reveal the importance of efficient heme uptake for
L. amazonensis
replication and vertebrate host infectivity, reinforcing the potential usefulness of LHR1 as a target for new antileishmanial drugs.
Toxin Inhibition of Antimicrobial Factors Induced by Bacillus anthracis Peptidoglycan in Human Blood
Authors: Barua Soumitra , Iyer Janaki K. , Larabee Jason L. , Raisley Brent , Hughes Molly A. , Coggeshall K. Mark , Ballard Jimmy D. 
Published: July 2013

ABSTRACT

Here, we describe the capacity of
Bacillus anthracis
peptidoglycan (BaPGN) to trigger an antimicrobial response in human white blood cells (WBCs). Analysis of freshly isolated human blood cells found that monocytes and neutrophils, but not B and T cells, were highly responsive to BaPGN and produced a variety of cytokines and chemokines. This BaPGN-induced response was suppressed by anthrax lethal toxin (LT) and edema toxin (ET), with the most pronounced effect on human monocytes, and this corresponded with the higher levels of anthrax toxin receptor 1 (ANTXR1) in these cells than in neutrophils. The supernatant from BaPGN-treated cells altered the growth of
B. anthracis
Sterne, and this effect was blocked by LT, but not by ET. An FtsX mutant of
B. anthracis
known to be resistant to the antimicrobial effects of interferon-inducible Glu-Leu-Arg (ELR)-negative CXC chemokines was not affected by the BaPGN-induced antimicrobial effects. Collectively, these findings describe a system in which BaPGN triggers expression of antimicrobial factors in human WBCs and reveal a distinctive role, not shared with ET, in LT's capacity to suppress this response.
Association between childhood adversities and adulthood depressive symptoms in South Korea: results from a nationally representative longitudinal study
Authors: Kim Seung-Sup , Jang Hyobum , Chang Hyoung Yoon , Park Young Su , Lee Dong-Woo 
Published: July 2013

ObjectiveTo examine how childhood adversity (ie, parental death, parental divorce, suspension of school education due to financial strain or being raised in a relative's house due to financial strain) is associated with prevalence and incidence of adulthood depressive symptoms and whether this association differs by gender and by age in South Korea.DesignProspective cohort design.SettingNationally representative longitudinal survey in South Korea.Participants11 526 participants in South Korea.Outcome measurePrevalence and incidence of adulthood depressive symptoms were assessed as a dichotomous variable using the Centers for Epidemiologic Studies Depression (CES-D) Scale in 2006 and 2007.ResultsIn the prevalence analysis, each of the four childhood adversities was significantly associated with a higher prevalence of adulthood depressive symptoms. The higher incidence of depressive symptoms was associated with suspension of school education (OR 1.55, 95% CI 1.32 to 1.82) and parental divorce (OR 1.65, 95% CI 1.00 to 2.71). In the age-stratified analyses, prevalence of depressive symptoms was associated with all CAs across different adulthoods, except for parental divorce and late adulthood depressive symptoms. After being stratified by gender, the association was significant for parental divorce (OR 3.76, 95% CI 2.34 to 6.03) in the prevalence analysis and for being raised in a relative’s house (OR 1.89, 95% CI 1.21 to 2.94) in the incidence analysis only among women.ConclusionsThis study suggests that childhood adversity may increase prevalence and incidence of adulthood depressive symptoms, and the impact of parental divorce or being raised in a relative's house due to financial strain on adulthood depressive symptoms may differ by gender.