bluuebunny/crossref_metadata_2025 huggingface dataset:
Telavancin Pharmacokinetics and Pharmacodynamics in Patients with Complicated Skin and Skin Structure Infections and Various Degrees of Renal Function
Authors: Lodise T. P. , Butterfield J. M. , Hegde S. S. , Samara E. , Barriere S. L.
Published: January 2012

This study characterized the pharmacokinetic/pharmacodynamic profiles of the Food and Drug Administration (FDA)-approved telavancin renal dose adjustment schemes. A previously published two-compartment open model with first-order elimination and a combined additive and proportional residual error model derived from 749 adult subjects in 11 clinical trials was used to simulate the individual concentration-time profiles for 10,260 subjects (NONMEM). The dosing regimens simulated were 10 mg/kg of body weight once daily for individuals with creatinine clearances (CL
CR
s) of >50 ml/min, 7.5 mg/kg once daily for individuals with CL
CR
s of 30 to 50 ml/min, and 10 mg/kg every 2 days for those with CL
CR
s of <30 ml/min. The area under the concentration-time curve (AUC) under one dosing interval (AUC
τ
) was computed as dose/CL. The probability of achieving an AUC
τ
/MIC ratio of ≥219 was evaluated separately for each renal dosing scheme. Evaluation of the dosing regimens demonstrated similar AUC values across the different renal function groups. For all renal dosing strata, >90% of the simulated subjects achieved an AUC
τ
/MIC ratio of ≥219 for MIC values as high as 2 mg/liter. For patients with CL
CR
s of <30 ml/min, the probability of target attainment (PTA) exceeded 90% for both the AUC
0–24
(AUC from 0 to 24 h) and AUC
24–48
intervals for MICs of ≤1 mg/liter. At a MIC of 2 mg/liter, the PTAs were 89.3% and 23.6% for the AUC
0–24
and AUC
24–48
intervals, respectively. The comparable PTA profiles for the three dosing regimens across their respective dosing intervals indicate that the dose adjustments employed in phase III trials for complicated skin and skin structure infections were appropriate.
Ketoamide Resistance and Hepatitis C Virus Fitness in Val55 Variants of the NS3 Serine Protease
Authors: Welsch Christoph , Schweizer Sabine , Shimakami Tetsuro , Domingues Francisco S. , Kim Seungtaek , Lemon Stanley M. , Antes Iris
Published: January 2012

Drug-resistant viral variants are a major issue in the use of direct-acting antiviral agents in chronic hepatitis C. Ketoamides are potent inhibitors of the NS3 protease, with V55A identified as mutation associated with resistance to boceprevir. Underlying molecular mechanisms are only partially understood. We applied a comprehensive sequence analysis to characterize the natural variability at Val55 within dominant worldwide patient strains. A residue-interaction network and molecular dynamics simulation were applied to identify mechanisms for ketoamide resistance and viral fitness in Val55 variants. An infectious H77S.3 cell culture system was used for variant phenotype characterization. We measured antiviral 50% effective concentration (EC
50
) and fold changes, as well as RNA replication and infectious virus yields from viral RNAs containing variants. Val55 was found highly conserved throughout all hepatitis C virus (HCV) genotypes. The conservative V55A and V55I variants were identified from HCV genotype 1a strains with no variants in genotype 1b. Topology measures from a residue-interaction network of the protease structure suggest a potential Val55 key role for modulation of molecular changes in the protease ligand-binding site. Molecular dynamics showed variants with constricted binding pockets and a loss of H-bonded interactions upon boceprevir binding to the variant proteases. These effects might explain low-level boceprevir resistance in the V55A variant, as well as the Val55 variant, reduced RNA replication capacity. Higher structural flexibility was found in the wild-type protease, whereas variants showed lower flexibility. Reduced structural flexibility could impact the Val55 variant's ability to adapt for NS3 domain-domain interaction and might explain the virus yield drop observed in variant strains.
MupB, a New High-Level Mupirocin Resistance Mechanism in Staphylococcus aureus
Authors: Seah Christine , Alexander David C. , Louie Lisa , Simor Andrew , Low Donald E. , Longtin Jean , Melano Roberto G.
Published: January 2012

Mupirocin is a topical antibiotic used for the treatment of skin infections and the eradication of methicillin-resistant
Staphylococcus aureus
carriage. It inhibits bacterial protein synthesis by interfering with isoleucyl-tRNA synthetase activity. High-level mupirocin resistance (MIC of ≥512 μg/ml) is mediated by the expression of
mupA
(
ileS2
), which encodes an alternate isoleucyl-tRNA synthetase. In this study, we describe high-level mupirocin resistance mediated by a novel locus,
mupB
. The
mupB
gene (3,102 bp) shares 65.5% sequence identity with
mupA
but only 45.5% identity with
ileS
. The deduced MupB protein shares 58.1% identity (72.3% similarity) and 25.4% identity (41.8% similarity) with MupA and IleS, respectively. Despite this limited homology, MupB contains conserved motifs found in class I tRNA synthetases. Attempts to transfer high-level mupirocin resistance via conjugation or transformation (using plasmid extracts from an
mupB
-containing strain) were unsuccessful. However, by cloning the
mupB
gene into a shuttle vector, it was possible to transfer the resistance phenotype to susceptible
S. aureus
by electroporation, proving that
mupB
was responsible for the high-level mupirocin resistance. Further studies need to be done to determine the prevalence of
mupB
and to understand risk factors and outcomes associated with resistance mediated by this gene.
Attenuation-Based Dual-Fluorescent-Protein Reporter for Screening Translation Inhibitors
Authors: Osterman Ilya A. , Prokhorova Irina V. , Sysoev Vasily O. , Boykova Yulia V. , Efremenkova Olga V. , Svetlov Maxim S. , Kolb Vyacheslav A. , Bogdanov Alexey A. , Sergiev Petr V. , Dontsova Olga A.
Published: January 2012

A reporter construct was created on the basis of the transcription attenuator region of the
Escherichia coli
tryptophan operon. Dual-fluorescent-protein genes for red fluorescent protein and cerulean fluorescent protein were used as a sensor and internal control of gene expression. The sequence of the attenuator was modified to avoid tryptophan sensitivity while preserving sensitivity to ribosome stalling. Antimicrobial compounds which cause translation arrest at the stage of elongation induce the reporter both in liquid culture and on an agar plate. This reporter could be used for high-throughput screening of translation inhibitors.
In VivoImpact of Met221 Substitution in GOB Metallo-β-Lactamase
Authors: Morán-Barrio Jorgelina , Lisa María-Natalia , Vila Alejandro J.
Published: January 2012

Metallo-β-lactamases (MβLs) represent one of the main mechanisms of bacterial resistance against β-lactam antibiotics. The elucidation of their mechanism has been limited mostly by the structural diversity among their active sites. All MβLs structurally characterized so far present a Cys or a Ser residue at position 221, which is critical for catalysis. GOB lactamases stand as an exception within this picture, possessing a Met residue in this location. We studied different mutants in this position, and we show that Met221 is essential for protein stability, most likely due to its involvement in a hydrophobic core. In contrast to other known MβLs, residue 221 is not involved in metal binding or in catalysis in GOB enzymes, further highlighting the structural diversity of MβLs. We also demonstrate the usefulness of protein periplasmic profiles to assess the contribution of protein stability to antibiotic resistance.
Role of Rifampin against Propionibacterium acnes Biofilm
In Vitro
and in an Experimental Foreign-Body Infection Model
Authors: Furustrand Tafin Ulrika , Corvec Stéphane , Betrisey Bertrand , Zimmerli Werner , Trampuz Andrej
Published: January 2012

Propionibacterium acnes
is an important cause of orthopedic-implant-associated infections, for which the optimal treatment has not yet been determined. We investigated the activity of rifampin, alone and in combination, against planktonic and biofilm
P. acnes in vitro
and in a foreign-body infection model. The MIC and the minimal bactericidal concentration (MBC) were 0.007 and 4 μg/ml for rifampin, 1 and 4 μg/ml for daptomycin, 1 and 8 μg/ml for vancomycin, 1 and 2 μg/ml for levofloxacin, 0.03 and 16 μg/ml for penicillin G, 0.125 and 512 μg/ml for clindamycin, and 0.25 and 32 μg/ml for ceftriaxone. The
P. acnes
minimal biofilm eradication concentration (MBEC) was 16 μg/ml for rifampin; 32 μg/ml for penicillin G; 64 μg/ml for daptomycin and ceftriaxone; and ≥128 μg/ml for levofloxacin, vancomycin, and clindamycin. In the animal model, implants were infected by injection of 10
9
CFU
P. acnes
in cages. Antimicrobial activity on
P. acnes
was investigated in the cage fluid (planktonic form) and on explanted cages (biofilm form). The cure rates were 4% for daptomycin, 17% for vancomycin, 0% for levofloxacin, and 36% for rifampin. Rifampin cured 63% of the infected cages in combination with daptomycin, 46% with vancomycin, and 25% with levofloxacin. While all tested antimicrobials showed good activity against planktonic
P. acnes
, for eradication of biofilms, rifampin was needed. In combination with rifampin, daptomycin showed higher cure rates than with vancomycin in this foreign-body infection model.
Prospective Observational Study Comparing Three Different Treatment Regimes in Patients with Clostridium difficile Infection
Authors: Wenisch Judith M. , Schmid Daniela , Kuo Hung-Wei , Allerberger Franz , Michl Verena , Tesik Philip , Tucek Gerhard , Laferl Hermann , Wenisch Christoph
Published: January 2012

In a hospital-based, prospective cohort study, the effects of the three standard treatment regimens for mild
Clostridium difficile
infection (CDI), oral (p.o.) metronidazole at 500 mg three times/day, intravenous (i.v.) metronidazole at 500 mg three times/day, and oral (p.o.) vancomycin at 250 mg four times/day, were compared with respect to the risk of occurrence of complications, sequelae, and all-cause death within 30 days after the date of starting treatment. Differences in the incidence of these outcomes were tested by χ
2
or Fisher's exact tests. A Poisson regression model was performed to control for possible confounding effects of sex, age, and severity of comorbidity categorized according to the Charlson comorbidity index. The highest mortality was observed in the metronidazole i.v. group, with a mortality rate 38.1% (16/42) compared to mortality rates of 7.4% (9/121) in the metronidazole p.o. group and 9.5% (4/42) in the vancomycin p.o. group (
P
< 0.001). After adjustment for possible effects of sex, age (>65 years), and severity of comorbidity, the relative risk of a 30-day fatal outcome for patients receiving metronidazole i.v. was 4.3 (95% confidence interval [CI] = 1.92 to 10;
P
< 0.0001) compared to patients treated with metronidazole p.o. and 4.0 (95% CI = 1.31 to 5.0;
P
< 0.015) compared to patients treated with vancomycin p.o. There were no significant differences in the risk of complications between the three treatment groups. This study generates the hypothesis that treatment with i.v. metronidazole is inferior to the oral alternatives metronidazole and vancomycin.
Antimicrobial and Anticoagulant Activities of
N
-Chlorotaurine,
N
,
N
-Dichloro-2,2-Dimethyltaurine, and
N
-Monochloro-2,2-Dimethyltaurine in Human Blood
Authors: Martini C. , Hammerer-Lercher A. , Zuck M. , Jekle A. , Debabov D. , Anderson M. , Nagl M.
Published: January 2012

The aim of this study was to determine the potential application of
N
-chlorotaurine (NCT),
N
,
N
-dichloro-2,2-dimethyltaurine (NVC-422), and
N
-monochloro-2,2-dimethyltaurine (NVC-612) as catheter lock solutions for the prevention of catheter blockage and catheter-related bloodstream infections by testing their anticoagulant and broad-spectrum antimicrobial activities in human blood. NCT, NVC-422, NVC-612, and control compounds were serially diluted in fresh human blood to evaluate the effects on prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, and direct thrombin inhibition. Quantitative killing assays against pathogens, including methicillin-resistant
Staphylococcus aureus
,
Escherichia coli
, and
Candida albicans
, were performed in the presence of heparin and human blood. NCT and NVC-612 (1.38 mM each) and 1.02 mM NVC-422 prolonged prothrombin time (Quick value, 17 to 30%), activated partial thromboplastin time 3- to 4-fold to 76 to 125 s, and thrombin time 2- to 4-fold to 34 to 68 s. Fibrinogen decreased from 258 to 283 mg/dl (range of controls) to <40 mg/dl. No direct thrombin inhibition was observed by NVC-422 or NVC-612. Heparin did not influence the bactericidal activity of NCT. The microbicidal activities of NCT, NVC-422, and NVC-612 were maintained in diluted human blood. NCT, NVC-612, and NVC-422 have broad-spectrum antimicrobial activity in blood and anticoagulant activity targeting both intrinsic and extrinsic pathways of the coagulation system. These properties support their application as catheter lock solutions.
Pharmacokinetics of and Short-Term Virologic Response to Low-Dose 400-Milligram Once-Daily Raltegravir Maintenance Therapy
Authors: Ananworanich Jintanat , Gorowara Meena , Avihingsanon Anchalee , Kerr Stephen J. , van Heesch Nadine , Khongpetch Chuleeporn , Uanithirat Anuntaya , Hill Andrew , Ruxrungtham Kiat , Burger David M.
Published: January 2012

Because studies showed similar viral suppression with lower raltegravir doses and because Asians usually have high antiretroviral concentrations, we explored low-dose raltegravir therapy in Thais. Nineteen adults on raltegravir at 400 mg twice daily (BID) with HIV RNA loads of <50 copies/ml were randomized to receive 400 mg once daily (QD) or 800 mg QD for 2 weeks, followed by the other dosing for 2 weeks. Intensive pharmacokinetic analyses were performed, and HIV RNA was monitored. Two patients were excluded from the 400-mg QD analysis due to inevaluable pharmacokinetic data. The mean patient weight was 58 kg. Mean pharmacokinetic values were as follows: for raltegravir given at 400 mg BID, the area under the concentration-time curve from 0 to 12 h (AUC
0-12
) was 15.6 mg/liter-h and the minimum plasma drug concentration (
C
trough
) was 0.22 mg/liter; for raltegravir given at 800 mg QD, the AUC
0-24
was 33.6 mg/liter-h and the
C
trough
was 0.06 mg/liter; and for raltegravir given at 400 mg QD, the AUC
0-24
was 18.6 mg/liter-h and the
C
trough
was 0.08 mg/liter. The HIV RNA load was <50 copies/ml at each dose level. Compared to the adjusted AUC
0-24
for Westerners on raltegravir at 400 mg BID, Thais on the same dose had double the AUC
0-24
and those on raltegravir at 400 mg QD had a similar AUC
0-24
. More patients had a
C
trough
of <0.021 mg/liter on raltegravir at 400 mg QD (9/17 patients) than on raltegravir at 800 mg QD (1/19 patients) or 400 mg BID (0/19 patients). Seventeen patients used raltegravir at 400 mg QD for a median of 35 weeks; two had confirmed HIV RNA loads between 50 and 200 copies/ml, and both had low
C
trough
values. Low-dose raltegravir could be a cost-saving option for maintenance therapy in Asians or persons with low body weight. However, raltegravir at 400 mg QD was associated with a low
C
trough
and with a risk for HIV viremia. Raltegravir at 200 or 300 mg BID should be studied, but new raltegravir formulations will be needed.
Mutation Analysis of Mycobacterial
rpoB
Genes and Rifampin Resistance Using Recombinant Mycobacterium smegmatis
Authors: Nakata Noboru , Kai Masanori , Makino Masahiko
Published: January 2012

Rifampin is a major drug used to treat leprosy and tuberculosis. The rifampin resistance of
Mycobacterium leprae
and
Mycobacterium tuberculosis
results from a mutation in the
rpoB
gene, encoding the β subunit of RNA polymerase. A method for the molecular determination of rifampin resistance in these two mycobacteria would be clinically valuable, but the relationship between the mutations and susceptibility to rifampin must be clarified before its use. Analyses of mutations responsible for rifampin resistance using clinical isolates present some limitations. Each clinical isolate has its own genetic variations in some loci other than
rpoB
, which might affect rifampin susceptibility. For this study, we constructed recombinant strains of
Mycobacterium smegmatis
carrying the
M. leprae
or
M. tuberculosis rpoB
gene with or without mutation and disrupted their own
rpoB
genes on the chromosome. The rifampin and rifabutin susceptibilities of the recombinant bacteria were measured to examine the influence of the mutations. The results confirmed that several mutations detected in clinical isolates of these two pathogenic mycobacteria can confer rifampin resistance, but they also suggested that some mutations detected in
M. leprae
isolates or rifampin-resistant
M. tuberculosis
isolates are not involved in rifampin resistance.
Population Pharmacokinetics of Telavancin in Healthy Subjects and Patients with Infections
Authors: Samara Emil , Shaw Jeng-Pyng , Barriere Steven L. , Wong Shekman L. , Worboys Philip
Published: January 2012

A population pharmacokinetic model of telavancin, a lipoglycopeptide antibiotic, was developed and used to identify sources of interindividual variability. Data were obtained from healthy subjects (seven phase 1 studies), patients with complicated skin and skin structure infections (cSSSI; two phase 2 and two phase 3 studies), and patients with hospital-acquired pneumonia (HAP; two phase 3 studies). A two-compartment open model with zero-order input best fit the telavancin data from healthy individuals and patients with cSSSI or HAP. Telavancin clearance was highly correlated with renal function and, to a lesser extent, with body weight. Other covariates were related to at least one parameter in cSSSI (gender, bacterial eradication, and surgery) or HAP (age of ≥75 years) but did not markedly affect exposure. These analyses support current dosing recommendations for telavancin based on patient weight and renal function.
Case-Control Study Comparing
De Novo
and Daptomycin-Exposed Daptomycin-Nonsusceptible Enterococcus Infections
Authors: Kelesidis Theodoros , Chow Angela L. P. , Humphries Romney , Uslan Daniel Z. , Pegues David
Published: January 2012

Understanding factors associated with
de novo
daptomycin-nonsusceptible
Enterococcus
(DNSE) infections will aid in better understanding the mechanisms of daptomycin nonsusceptibility. We conducted a case-control study to compare patients with DNSE infections who were daptomycin treatment naïve (
n
= 9) and those with DNSE infections who had exposure to daptomycin (
n
= 13). Less frequent exposure to antimicrobials, increased susceptibility to nitrofurantoin and gentamicin, and shorter duration of hospitalization were associated with
de novo
DNSE infection, suggesting a potential community reservoir.
NDM-4 Metallo-β-Lactamase with Increased Carbapenemase Activity from Escherichia coli
Authors: Nordmann Patrice , Boulanger Anne E. , Poirel Laurent
Published: January 2012

A clinical
Escherichia coli
isolate resistant to all β-lactams, including carbapenems, expressed a novel metallo-β-lactamase (MBL), NDM-4, differing from NDM-1 by a single amino acid substitution (Met154Leu). NDM-4 possessed increased hydrolytic activity toward carbapenems and several cephalosporins compared to that of NDM-1. This amino acid substitution was not located in the known active sites of NDM-1, indicating that remote amino acid substitutions might also play a role in the extended activity of this MBL.
Differential Use of CCR5 by HIV-1 Clinical Isolates Resistant to Small-Molecule CCR5 Antagonists
Authors: Henrich Timothy J. , Lewine Nicolas R. P. , Lee Sun-Hee , Rao Suhas S. P. , Berro Reem , Gulick Roy M. , Moore John P. , Tsibris Athe M. N. , Kuritzkes Daniel R.
Published: January 2012

How HIV-1 resistant to small-molecule CCR5 antagonists uses the coreceptor for entry has been studied in a limited number of isolates. We characterized dependence on the N terminus (NT) and the second extracellular loop (ECL2) of CCR5 of three vicriviroc (VCV)-resistant clinical isolates broadly cross-resistant to other CCR5 antagonists. Pseudoviruses were constructed to assess CCR5 use by VCV-sensitive and -resistant envelopes of subtype B and C viruses. We determined the extent of entry inhibition by monoclonal antibodies (MAbs) directed against the NT and ECL2 in the presence and absence of VCV and the capacity of these pseudoviruses to use CCR5 mutants that contained scanning alanine substitutions in the CCR5 NT and ECL2 domains. Sensitive and resistant viruses were completely and competitively inhibited by the ECL2-specific MAb 2D7, whereas the NT-specific MAb CTC5 led to partial noncompetitive inhibition. VCV-resistant clones showed greater sensitivity to 2D7 than VCV-sensitive clones, but in the presence of saturating VCV concentrations, the 2D7 susceptibilities of two VCV-resistant viruses were similar to that of VCV-sensitive virus. The entry of VCV-sensitive and -resistant isolates was impaired to differing degrees by alanine mutations in CCR5; substitutions in NT had the greatest effect on viral entry. HIV-1 clinical isolates broadly resistant to CCR5 antagonists demonstrated significant heterogeneity in their use of CCR5. This heterogeneity makes it difficult to draw general conclusions about the relationship between patterns of CCR5 antagonist resistance and the use of specific CCR5 domains for entry.
Treatment Outcome of Bacteremia Due to KPC-Producing Klebsiella pneumoniae: Superiority of Combination Antimicrobial Regimens
Authors: Qureshi Zubair A. , Paterson David L. , Potoski Brian A. , Kilayko Mary C. , Sandovsky Gabriel , Sordillo Emilia , Polsky Bruce , Adams-Haduch Jennifer M. , Doi Yohei
Published: January 2012

Klebsiella pneumoniae
producing
Klebsiella pneumoniae
carbapenemase (KPC) has been associated with serious infections and high mortality. The optimal antimicrobial therapy for infection due to KPC-producing
K. pneumoniae
is not well established. We conducted a retrospective cohort study to evaluate the clinical outcome of patients with bacteremia caused by KPC-producing
K. pneumoniae
. A total of 41 unique patients with blood cultures growing KPC-producing
K. pneumoniae
were identified at two medical centers in the United States. Most of the infections were hospital acquired (32; 78%), while the rest of the cases were health care associated (9; 22%). The overall 28-day crude mortality rate was 39.0% (16/41). In the multivariate analysis, definitive therapy with a combination regimen was independently associated with survival (odds ratio, 0.07 [95% confidence interval, 0.009 to 0.71],
P
= 0.02). The 28-day mortality was 13.3% in the combination therapy group compared with 57.8% in the monotherapy group (
P
= 0.01). The most commonly used combinations were colistin-polymyxin B or tigecycline combined with a carbapenem. The mortality in this group was 12.5% (1/8). Despite
in vitro
susceptibility, patients who received monotherapy with colistin-polymyxin B or tigecycline had a higher mortality of 66.7% (8/12). The use of combination therapy for definitive therapy appears to be associated with improved survival in bacteremia due to KPC-producing
K. pneumoniae
.
Infection with Anaplasma phagocytophilum Activates the Phosphatidylinositol 3-Kinase/Akt and NF-κB Survival Pathways in Neutrophil Granulocytes
Authors: Sarkar Arup , Hellberg Lars , Bhattacharyya Asima , Behnen Martina , Wang Keqing , Lord Janet M. , Möller Sonja , Kohler Maja , Solbach Werner , Laskay Tamás
Published: January 2012

Anaplasma phagocytophilum
, a Gram-negative, obligate intracellular bacterium infects primarily neutrophil granulocytes. Infection with
A. phagocytophilum
leads to inhibition of neutrophil apoptosis and consequently contributes to the longevity of the host cells. Previous studies demonstrated that the infection inhibits the executionary apoptotic machinery in neutrophils. However, little attempt has been made to explore which survival signals are modulated by the pathogen. The aim of the present study was to clarify whether the phosphatidylinositol 3-kinase (PI3K)/Akt and NF-κB signaling pathways, which are considered as important survival pathways in neutrophils, are involved in
A. phagocytophilum
-induced apoptosis delay. Our data show that infection of neutrophils with
A. phagocytophilum
activates the PI3K/Akt pathway and suggest that this pathway, which in turn maintains the expression of the antiapoptotic protein Mcl-1, contributes to the infection-induced apoptosis delay. In addition, the PI3K/Akt pathway is involved in the activation of NF-κB in
A. phagocytophilum
-infected neutrophils. Activation of NF-κB leads to the release of interleukin-8 (IL-8) from infected neutrophils, which, in an autocrine manner, delays neutrophil apoptosis. In addition, enhanced expression of the antiapoptotic protein cIAP2 was observed in
A. phagocytophilum
-infected neutrophils. Taken together, the data indicate that upstream of the apoptotic cascade, signaling via the PI3K/Akt pathway plays a major role for apoptosis delay in
A. phagocytophilum
-infected neutrophils.
Correlating Levels of Type III Secretion and Secreted Proteins with Fecal Shedding of Escherichia coli O157:H7 in Cattle
Authors: Sharma V. K. , Sacco R. E. , Kunkle R. A. , Bearson S. M. D. , Palmquist D. E.
Published: January 2012

The locus of enterocyte effacement (LEE) of
Escherichia coli
O157:H7 (O157) encodes a type III secretion system (T3SS) for secreting LEE-encoded and non-LEE-encoded virulence proteins that promote the adherence of O157 to intestinal epithelial cells and the persistence of this food-borne human pathogen in bovine intestines. In this study, we compared
hha sepB
and
hha
mutants of O157 for LEE transcription, T3SS activity, adherence to HEp-2 cells, persistence in bovine intestines, and the ability to induce changes in the expression of proinflammatory cytokines. LEE transcription was upregulated in the
hha sepB
and
hha
mutant strains compared to that in the wild-type strain, but the secretion of virulence proteins in the
hha sepB
mutant was severely compromised. This reduced secretion resulted in reduced adherence of the
hha sepB
mutant to Hep-2 cells, correlating with a significantly shorter duration and lower magnitude of fecal shedding in feces of weaned (
n
= 4 per group) calves inoculated with this mutant strain. The levels of LEE transcription, T3SS activity, and adherence to HEp-2 cells were much lower in the wild-type strain than in the
hha
mutant, but no significant differences were observed in the duration or the magnitude of fecal shedding in calves inoculated with these strains. Examination of the rectoanal junction (RAJ) tissues from three groups of calves showed no adherent O157 bacteria and similar proinflammatory cytokine gene expression, irrespective of the inoculated strain, with the exception that interleukin-1β was upregulated in calves inoculated with the
hha sepB
mutant. These results indicate that the T3SS is essential for intestinal colonization and prolonged shedding, but increased secretion of virulence proteins did not enhance the duration and magnitude of fecal shedding of O157 in cattle or have any significant impact on the cytokine gene expression in RAJ tissue compared with that in small intestinal tissue from the same calves.
Plasmodium falciparum Malaria in the Peruvian Amazon, a Region of Low Transmission, Is Associated with Immunologic Memory
Authors: Clark Eva H. , Silva Claudia J. , Weiss Greta E. , Li Shanping , Padilla Carlos , Crompton Peter D. , Hernandez Jean N. , Branch OraLee H.
Published: January 2012

The development of clinical immunity toPlasmodium falciparummalaria is thought to require years of parasite exposure, a delay often attributed to difficulties in developing protective antibody levels. In this study, we evaluated severalP. falciparumvaccine candidate antigens, including apical membrane antigen 1 (AMA-1), circumsporozoite protein (CSP), erythrocyte binding antigen 175 (EBA-175), and the 19-kDa region of merozoite surface protein 1 (MSP119). After observing a more robust antibody response to MSP119, we evaluated the magnitude and longevity of IgG responses specific to this antigen in Peruvian adults and children before, during, and afterP. falciparuminfection. In this low-transmission region, even one reported prior infection was sufficient to produce a positive anti-MSP119IgG response for >5 months in the absence of reinfection. We also observed an expansion of the total plasmablast (CD19+CD27+CD38high) population in the majority of individuals shortly after infection and detected MSP1-specific memory B cells in a subset of individuals at various postinfection time points. This evidence supports our hypothesis that effective antimalaria humoral immunity can develop in low-transmission regions.
Evaluation of Salmonella enterica Type III Secretion System Effector Proteins as Carriers for Heterologous Vaccine Antigens
Authors: Hegazy Wael Abdel Halim , Xu Xin , Metelitsa Leonid , Hensel Michael
Published: January 2012

Live attenuated strains ofSalmonella entericahave a high potential as carriers of recombinant vaccines. The type III secretion system (T3SS)-dependent translocation ofS. entericacan be deployed for delivery of heterologous antigens to antigen-presenting cells. Here we investigated the efficacy of various effector proteins of theSalmonellapathogenicity island (SPI2)-encoded T3SS for the translocation of model antigens and elicitation of immune responses. The SPI2 T3SS effector proteins SifA, SteC, SseL, SseJ, and SseF share an endosomal membrane-associated subcellular localization after translocation. We observed that all effector proteins could be used to translocate fusion proteins with the model antigens ovalbumin and listeriolysin into the cytosol of host cells. Underin vitroconditions, fusion proteins with SseJ and SteC stimulated T-cell responses that were superior to those triggered by fusion proteins with SseF. However, in mice vaccinated withSalmonellacarrier strains, only fusion proteins based on SseJ or SifA elicited potent T-cell responses. These data demonstrate that the selection of an optimal SPI2 effector protein for T3SS-mediated translocation is a critical parameter for the rational design of effectiveSalmonella-based recombinant vaccines.
Vaccination of BALB/c Mice with an Avirulent Mycoplasma pneumoniae P30 Mutant Results in Disease Exacerbation upon Challenge with a Virulent Strain
Authors: Szczepanek S. M. , Majumder S. , Sheppard E. S. , Liao X. , Rood D. , Tulman E. R. , Wyand S. , Krause D. C. , Silbart L. K. , Geary S. J.
Published: January 2012

Mycoplasma pneumoniaeis a significant human respiratory pathogen that causes high morbidity worldwide. No vaccine to preventM. pneumoniaeinfection currently exists, since the mechanisms of pathogenesis are poorly understood. To this end, we constructed a P30 cytadhesin mutant (P-130) with a drastically reduced capacity for binding to erythrocytes and an inability to glide on glass substrates. This mutant was determined to be avirulent and cannot survive in the lungs of BALB/c mice. We also ascertained that the previously identified P30 gliding motility mutant II-3R is avirulent and also cannot be recovered from the lungs of mice after infection. Mutant P130 was then assessed for its efficacy as a live attenuated vaccine candidate in mice after challenge with wild-typeM. pneumoniae. After vaccination with the P-130 P30 mutant, mice showed evidence of exacerbated disease upon subsequent challenge with the wild-type strain PI1428, which appears to be driven by a Th17 response and corresponding eosinophilia. Our results are in accordance with other reports of vaccine-induced disease exacerbation in rodents and emphasize the need to better understand the basic mechanisms ofM. pneumoniaepathogenesis.
Intestinally Secreted C-Type Lectin Reg3b Attenuates Salmonellosis but Not Listeriosis in Mice
Authors: van Ampting Marleen T. J. , Loonen Linda M. P. , Schonewille Arjan J. , Konings Irene , Vink Carolien , Iovanna Juan , Chamaillard Mathias , Dekker Jan , van der Meer Roelof , Wells Jerry M. , Bovee-Oudenhoven Ingeborg M. J.
Published: January 2012

The Reg3 protein family, including the human member designated pancreatitis-associated protein (PAP), consists of secreted proteins that contain a C-type lectin domain involved in carbohydrate binding. They are expressed by intestinal epithelial cells. Colonization of germ-free mice and intestinal infection with pathogens increase the expression of Reg3g and Reg3b in the murine ileum. Reg3g is directly bactericidal for Gram-positive bacteria, but the exact role of Reg3b in bacterial infections is unknown. To investigate the possible protective role of Reg3b in intestinal infection, Reg3b knockout (Reg3b
−/−
) mice and wild-type (WT) mice were orally infected with Gram-negative
Salmonella enteritidis
or Gram-positive
Listeria monocytogenes
. At day 2 after oral
Listeria
infection and at day 4 after oral
Salmonella
infection, mice were sacrificed to collect intestinal and other tissues for pathogen quantification. Protein expression of Reg3b and Reg3g was determined in intestinal mucosal scrapings of infected and noninfected mice. In addition,
ex vivo
binding of ileal mucosal Reg3b to
Listeria
and
Salmonella
was investigated. Whereas recovery of
Salmonella
or
Listeria
from feces of Reg3b
−/−
mice did not differ from that from feces of WT mice, significantly higher numbers of viable
Salmonella
, but not
Listeria
, bacteria were recovered from the colon, mesenteric lymph nodes, spleen, and liver of the Reg3b
−/−
mice than from those of WT mice. Mucosal Reg3b binds to both bacterial pathogens and may interfere with their mode of action. Reg3b plays a protective role against intestinal translocation of the Gram-negative bacterium
S. enteritidis
in mice but not against the Gram-positive bacterium
L. monocytogenes
.
Nonhuman Primate Model of Pertussis
Authors: Warfel Jason M. , Beren Joel , Kelly Vanessa K. , Lee Gloria , Merkel Tod J.
Published: January 2012

Pertussis is a highly contagious, acute respiratory illness caused by the bacterial pathogen
Bordetella pertussis
. Despite nearly universal vaccine coverage, pertussis rates in the United States have been rising steadily over the last 20 years. Our failure to comprehend and counteract this important public health concern is due in large part to gaps in our knowledge of the disease and the mechanisms of vaccine-mediated protection. Important questions about pertussis pathogenesis and mechanisms of vaccine effectiveness remain unanswered due to the lack of an animal model that replicates the full spectrum of human disease. Because current animal models do not meet these needs, we set out to develop a nonhuman primate model of pertussis. We inoculated rhesus macaques and olive baboons with wild-type
B. pertussis
strains and evaluated animals for clinical disease. We found that only 25% of rhesus macaques developed pertussis. In contrast, 100% of inoculated baboons developed clinical pertussis. A strong anamnestic response was observed when convalescent baboons were infected 6 months following recovery from a primary infection. Our results demonstrate that the baboon provides an excellent model of clinical pertussis that will allow researchers to investigate pertussis pathogenesis and disease progression, evaluate currently licensed vaccines, and develop improved vaccines and therapeutics.
Roles of the Nuclear Lamina in Stable Nuclear Association and Assembly of a Herpesviral Transactivator Complex on Viral Immediate-Early Genes
Authors: Silva Lindsey , Oh Hyung Suk , Chang Lynne , Yan Zhipeng , Triezenberg Steven J. , Knipe David M.
Published: January 2012

Little is known about the mechanisms of gene targeting within the nucleus and its effect on gene expression, but most studies have concluded that genes located near the nuclear periphery are silenced by heterochromatin. In contrast, we found that early herpes simplex virus (HSV) genome complexes localize near the nuclear lamina and that this localization is associated with reduced heterochromatin on the viral genome and increased viral immediate-early (IE) gene transcription. In this study, we examined the mechanism of this effect and found that input virion transactivator protein, virion protein 16 (VP16), targets sites adjacent to the nuclear lamina and is required for targeting of the HSV genome to the nuclear lamina, exclusion of heterochromatin from viral replication compartments, and reduction of heterochromatin on the viral genome. Because cells infected with the VP16 mutant virus
in
1814 showed a phenotype similar to that of lamin A/C
−/−
cells infected with wild-type virus, we hypothesized that the nuclear lamina is required for VP16 activator complex formation. In lamin A/C
−/−
mouse embryo fibroblasts, VP16 and Oct-1 showed reduced association with the viral IE gene promoters, the levels of VP16 and HCF-1 stably associated with the nucleus were lower than in wild-type cells, and the association of VP16 with HCF-1 was also greatly reduced. These results show that the nuclear lamina is required for stable nuclear localization and formation of the VP16 activator complex and provide evidence for the nuclear lamina being the site of assembly of the VP16 activator complex.

IMPORTANCE
The targeting of chromosomes in the cell nucleus is thought to be important in the regulation of expression of genes on the chromosomes. The major documented effect of intranuclear targeting has been silencing of chromosomes at sites near the nuclear periphery. In this study, we show that targeting of the herpes simplex virus DNA genome to the nuclear periphery promotes formation of transcriptional activator complexes on the viral genome, demonstrating that the nuclear periphery also has sites for activation of transcription. These results highlight the importance of the nuclear lamina, the structure that lines the inner nuclear membrane, in both transcriptional activation and repression. Future studies defining the molecular structures of these two types of nuclear sites should define new levels of gene regulation.
Anharmonic effect of the decomposition reaction of the CF3CCl2O radical
Authors: Li Qian , Xia Wenwen , Yao Li , Shao Ying
Published: January 2012

The rate constant of the unimolecular decomposition reaction of the CF3CCl2O radical was calculated by using the method proposed by Yao and Lin (YL method). Two important channels of decomposition occurring via C–C and C–Cl bond scission were investigated. The results show that C–Cl bond scission is the dominant channel during the decomposition of the CF3CCl2O radical. Especially, the reasonable anharmonic effect on the decomposition reaction was investigated. The results show that the harmonic rate constants are higher than those of the anharmonic case in both microcanonical and canonical systems. The anharmonic effect is more evident with increasing energy.
Development of a solid polymer electrolyte membrane based on sulfonated poly(ether ether)ketone and polysulfone for fuel cell applications
Authors: Guhan Srinivasan , Muruganantham Rethinasabapathy , Sangeetha Dharmalingam
Published: January 2012

Polymer electrolyte membranes made of sulfonated poly(ether ether)ketone (SPEEK) and polysulfone (PSf) (2–10 wt %) were prepared by a solution casting method. The characteristic properties of the SPEEK/PSf polymer blend membranes were investigated using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and the AC impedance method. The SPEEK/PSf blend membranes showed good thermal and mechanical properties and appreciable ionic conductivity. It was revealed that the addition of PSf into the SPEEK matrix could markedly improve the electrochemical properties of the resulting membranes, which can be accomplished by a simple blend method. As a result, the SPEEK/PSf blends appear to be good candidates for the proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) applications. These blend membranes, having various amounts of PSf (2–10 wt %), were investigated in PEMFC and DMFC. The power densities were about 400 and 50 mW/cm2 for PEMFC and DMFC, respectively. This makes PSf-based DMFC and PEMFC suitable for application in portable devices and transportation, respectively.
Facile aqueous synthesis of functionalized CdTe nanoparticles and their application as fluorescence probes for determination of adenine and guanine
Authors: Li Li , Lu Yaxiang , Ding Yaping , Zhang Fenfen , Wang Yaping
Published: January 2012

Thioglycolic acid (TGA)-capped CdTe nanoparticles (NPs) were synthesized in aqueous medium, and their application as fluorescence probes in the detection of adenine and guanine was studied. The TGA-capped CdTe NPs were characterized by transmission electron microscopy, X–ray diffraction spectrometry, spectrofluorometry, Fourier transform infrared, and ultraviolet-visible spectrometry. Based on the significant enhancement of fluorescence emission of these CdTe fluorescence probes in the presence of adenine or guanine, a quantitative analysis method for these purines was proposed. Experimental conditions that govern the extent of fluorescence enhancement were optimized. Under the optimal conditions, the relative fluorescence intensity versus adenine or guanine concentrations gave a linear response, permitting the dynamic range of 7.0 × 10−7–1.0 × 10−4 mol/L and 6.0 × 10−7–9.0 × 10−5 mol/L for adenine and guanine, respectively. The method has also been applied successfully to the detection of adenine and guanine in synthetic samples with satisfactory results.
Synthesis of 2,3,4-trisubstituted pyrroles via a facile reaction of vinyl azides and tosylmethyl isocyanide
Authors: Chen Wenteng , Shao Jiaan , Li Zhi , Giulianotti Marc A. , Yu Yongping
Published: January 2012

A facile synthesis of polysubstituted pyrroles from tosylmethyl isocyanide (TOSMIC) and readily synthesized vinyl azides was developed. The reaction proceeded under mild conditions in the presence of base. 2-Tosyl-substituted pyrroles were obtained in moderate to good isolated yields. Additionally, a base-initiated one-pot pyrrole synthesis also was developed using carboxaldehydes, ethyl 2-azidoacetate, and TOSMIC.
APPLICATION OF COMPETITIVE HOPFIELD NEURAL NETWORK TO BRAIN-COMPUTER INTERFACE SYSTEMS
Authors: HSU WEI-YEN
Published: January 2012

We propose an unsupervised recognition system for single-trial classification of motor imagery (MI) electroencephalogram (EEG) data in this study. Competitive Hopfield neural network (CHNN) clustering is used for the discrimination of left and right MI EEG data posterior to selecting active segment and extracting fractal features in multi-scale. First, we use continuous wavelet transform (CWT) and Student's two-sample t-statistics to select the active segment in the time-frequency domain. The multiresolution fractal features are then extracted from wavelet data by means of modified fractal dimension. At last, CHNN clustering is adopted to recognize extracted features. Due to the characteristic of non-supervision, it is proper for CHNN to classify non-stationary EEG signals. The results indicate that CHNN achieves 81.9% in average classification accuracy in comparison with self-organizing map (SOM) and several popular supervised classifiers on six subjects from two data sets.
NOTE ON ANALYTICAL STUDIES OF ONE-DIMENSIONAL HOLOGRAPHIC SUPERCONDUCTORS
Authors: LI RAN
Published: January 2012

We employ the variational method for the Sturm–Liouville eigenvalue problem to analytically study phase transition of one-dimensional holographic superconductors. It is shown that this method is not a very powerful method to analytically calculate the properties of holographic superconductors. From the analytical treatment of scalar operator condensate at critical temperature, we also show that the mean-field critical exponent 1/2 results from the coupling term between scalar field and vector field, which may be an universal property of holographic superconductors with a similar coupling term in their equations of motion.
EXPLORING FRAMED GAUGE THEORY AS BASIS FOR PHYSICAL MODELS
Authors: CHAN HONG-MO , TSOU SHEUNG TSUN
Published: January 2012

It is shown that by introducing as dynamical variables in the formulation of gauge theories the frame vectors (or vielbeins) in internal symmetry space, in addition to the standard gauge boson and matter fermion fields, one obtains: (i) for the su(2) ×u(1) symmetry, the standard electroweak theory with the Higgs field thrown in as part of the framed gauge theoretical structure, (ii) for the su(3) ×su(2) ×u(1) symmetry, a "framed standard model" with, apart from the Higgs field as before, a global su(3) symmetry to play the role of fermion generations, plus some other properties which are shown elsewhere to give to both quarks and leptons hierarchical mass and mixing patterns similar to those experimentally observed. Besides, the "framing" of the standard model as such has brought the particle theory closer in structure to the theory of gravity where vierbeins have long figured as dynamical variables. Although most of the results have already been reported before, time and hindsight have allowed their presentation in this review to be made more transparent and succint.
MONTE CARLO CALCULATION OF SLOW ELECTRON BEAM TRANSPORT IN SOLIDS: REFLECTION COEFFICIENT THEORY IMPLICATIONS
Authors: BENTABET A.
Published: January 2012

The reflection coefficient theory developed by Vicanek and Urbassek showed that the backscattering coefficient of light ions impinging on semi-infinite solid targets is strongly related to the range and the first transport cross-section as well. In this work and in the electron case, we show that not only the backscattering coefficient is, but also most of electron transport quantities (such as the mean penetration depth, the diffusion polar angles, the final backscattering energy, etc.), are strongly correlated to both these quantities (i.e. the range and the first transport cross-section). In addition, most of the electron transport quantities are weakly correlated to the distribution of the scattering angle and the total elastic cross-section as well. To make our study as straightforward and clear as possible, we have projected different input data of elastic cross-sections and ranges in our Monte Carlo code to study the mean penetration depth and the backscattering coefficient of slow electrons impinging on semi-infinite aluminum and gold in the energy range up to 10 keV. The possibility of extending the present study to other materials and other transport quantities using the same models is a valid process.
A NECESSARY CONDITION OF FANO SWITCHING AND WAVE TRANSMISSION THROUGH THE CHAIN-STRUCTURE WITH TWO DEFECTS
Authors: YAO JIAN-MING , WANG SHI-LAI , WANG JIAN-MING , YE CHENG-ZHI
Published: January 2012

We consider a discrete model that describes a linear chain of particles coupled to two defects. This model can be regarded as a linear generalization of the familiar Fano–Anderson model. The analytical result for the plane wave transmission coefficient is obtained. Comparing the transmission coefficient of Gaussian wave with that of plane wave, we can draw a conclusion that arising perfect reflection due to destructive interference depends on the input waveform of incident particle and a necessary switching condition of Fano resonance is the input plane wave. This interesting feature may play a guiding role in devising various particle switches in theory and experiment.
MOLECULAR MOTORS CONTROL LENGTH OF ANTIPARALLEL MICROTUBULE OVERLAPS
Authors: WANG ZIQING , ZHANG CAIHUA , WANG GUODONG
Published: January 2012

Using Monte Carlo simulation, we studied the controlling length of antiparallel microtubule overlaps by motors in the presence of PRC1. Two models for the inhibition mechanism of microtubule dynamics are developed. The comparison of the simulation results and the experimental data shows that the inhibition of microtubule dynamics is probably not due to a direct inhibition of polymerization and depolymerization of microtubule by the motor at plus end of microtubule but rather caused by global structural changes in the microtubule due to the presence of bound motor on the microtubule.