bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probing the Differential Interactions of Quinazolinedione PD 0305970 and Quinolones with Gyrase and Topoisomerase IV
Authors: Pan Xiao-Su , Gould Katherine A. , Fisher L. Mark 
Published: June 2009

ABSTRACT

Quinazoline-2,4-diones, such as PD 0305970, are new DNA gyrase and topoisomerase IV (topo IV) inhibitors with potent activity against gram-positive pathogens, including quinolone-resistant isolates. The mechanistic basis of dione activity vis-à-vis quinolones is not understood. We present evidence for
Streptococcus pneumoniae
gyrase and topo IV that PD 0305970 and quinolones interact differently with the enzyme breakage-reunion and Toprim domains, DNA, and Mg
2+
-four components that are juxtaposed in the topoisomerase cleavage complex to effect DNA scission. First, PD 0305970 targets primarily gyrase in
Streptococcus pneumoniae
. However, unlike quinolones, which select predominantly for
gyrA
(or topo IV
parC
) mutations in the breakage-reunion domain, unusually the dione selected for novel mutants with alterations that map to a region of the Toprim domain of GyrB (R456H and E474A or E474D) or ParE (D435H and E475A). This “dione resistance-determining region” overlaps the GyrB quinolone resistance-determining region and the region that binds essential Mg
2+
ions, each function involving conserved EGDSA and PLRGK motifs. Second, dione-resistant gyrase and topo IV were inhibited by ciprofloxacin, whereas quinolone-resistant enzymes (GyrA S81F and ParC S79F) remained susceptible to PD 0305970. Third, dione-promoted DNA cleavage by gyrase occurred at a distinct repertoire of sites, implying that structural differences with quinolones are sensed at the DNA level. Fourth, unlike the situation with quinolones, the Mg
2+
chelator EDTA did not reverse dione-induced gyrase cleavage nor did the dione promote Mg
2+
-dependent DNA unwinding. It appears that PD 0305970 interacts uniquely to stabilize the cleavage complex of gyrase/topo IV perhaps via an altered orientation directed by the bidentate 3-amino-2,4-dione moiety.
Antiprotozoal Activity of 1-Phenethyl-4-Aminopiperidine Derivatives
Authors: Dardonville Christophe , Fernández-Fernández Cristina , Gibbons Sarah-Louise , Jagerovic Nadine , Nieto Lidia , Ryan Gary , Kaiser Marcel , Brun Reto 
Published: June 2009

ABSTRACT

A series of 44 4-aminopiperidine derivatives was screened in vitro against four protozoan parasites (
Trypanosoma brucei rhodesiense
,
Trypanosoma cruzi
,
Leishmania donovani
, and
Plasmodium falciparum
). This screening identified 29 molecules selectively active against bloodstream-form
T. b. rhodesiense
trypomastigotes, with 50% inhibitory concentrations (IC
50
) ranging from 0.12 to 10 μM, and 33 compounds active against the chloroquine- and pyrimethamine-resistant K1 strain of
P. falciparum
(IC
50
range, 0.17 to 5 μM). In addition, seven compounds displayed activity against intracellular
T. cruzi
amastigotes in the same range as the reference drug benznidazole (IC
50
, 1.97 μM) but were also cytotoxic to L-6 cells, showing little selectivity for
T. cruzi
. None of the molecules tested showed interesting antileishmanial activity against axenic amastigotes of
L. donovani
. To our knowledge, this is the first report of the antitrypanosomal activity of molecules bearing the 4-aminopiperidine skeleton.
Cellular Accumulation and Pharmacodynamic Evaluation of the Intracellular Activity of CEM-101, a Novel Fluoroketolide, againstStaphylococcus aureus,Listeria monocytogenes, andLegionella pneumophilain Human THP-1 Macrophages
Authors: Lemaire Sandrine , Van Bambeke Françoise , Tulkens Paul M. 
Published: June 2009

ABSTRACTCEM-101 is a novel fluoroketolide with lower MICs than those of telithromycin and macrolides. Our aim was to assess the cellular accumulation and intracellular activity of CEM-101 using models developed for analyzing the pharmacokinetics and pharmacological properties of antibiotics against phagocytized bacteria. We used THP-1 macrophages andStaphylococcus aureus(ATCC 25923 [methicillin (meticillin) sensitive]),Listeria monocytogenes(strain EGD), andLegionella pneumophila(ATCC 33153). CEM-101 reached cellular-to-extracellular-concentration ratios of about 350 within 24 h (versus approximately 20, 30, and 160 for telithromycin, clarithromycin, and azithromycin, respectively). This intracellular accumulation was suppressed by incubation at a pH of ≤6 and by monensin (proton ionophore) and was unaffected by verapamil (P-glycoprotein inhibitor; twofold accumulation increase for azithromycin) or gemfibrozil. While keeping with the general properties of the macrolide antibiotics in terms of maximal efficacy (Emax; approximately 1-log10-CFU decrease compared to the postphagocytosis inoculum after a 24-h incubation), CEM-101 showed significantly greater potency against phagocytizedS. aureusthan telithromycin, clarithromycin, and azithromycin (for which the 50% effective concentration [EC50] and static concentrations were about 3-, 6-, and 15-fold lower, respectively). CEM-101 was also about 50-fold and 100-fold more potent than azithromycin against phagocytizedL. monocytogenesandL. pneumophila, respectively. These differences in EC50s and static concentrations between drugs were minimized when data were expressed as multiples of the MIC, demonstrating the critical role of intrinsic drug activity (MIC) in eliciting the antibacterial intracellular effects, whereas accumulation per se was unimportant. CEM-101 should show enhanced in vivo potency if used at doses similar to those of the comparators tested here.
Effect of Hemagglutinin-Neuraminidase Inhibitors BCX 2798 and BCX 2855 on Growth and Pathogenicity of Sendai/Human Parainfluenza Type 3 Chimera Virus in Mice
Authors: Watanabe Makiko , Mishin Vasiliy P. , Brown Scott A. , Russell Charles J. , Boyd Kelli , Babu Y. Sudhakara , Taylor Garry , Xiong Xiaoping , Yan Xiaowei , Portner Allen , Alymova Irina V. 
Published: June 2009

ABSTRACTHuman parainfluenza virus type 3 (hPIV-3) is a major respiratory tract pathogen that affects young children, but no vaccines or antiviral drugs against it have yet been developed. We developed a mouse model to evaluate the efficacies of the novel parainfluenza virus hemagglutinin-neuraminidase (HN) inhibitors BCX 2798 and BCX 2855 against a recombinant Sendai virus (rSeV) in which the fusion (F) and HN surface glycoproteins (FHN) were replaced by those of hPIV-3 [rSeV(hPIV-3FHN)]. In the prophylaxis model, 129X1/SvJ mice were infected with a 90% or 20% lethal dose of the virus and were treated intranasally for 5 days with 10 mg/kg of body weight/day of either compound starting 4 h before infection. Prophylactic treatment of the mice with either compound did not prevent their death in a 90% lethality model of rSeV(hPIV-3FHN) infection. However, it significantly reduced the lung virus titers, the amount of weight lost, and the rate of mortality in mice infected with a 20% lethal virus dose. In the therapy model, mice were infected with a nonlethal dose of the virus (100 PFU/mouse) and were treated intranasally with 1 or 10 mg/kg/day of either compound for 5 days starting at 24 or 48 h postinfection. Treatment of the mice with either compound significantly reduced the virus titer in the lungs, subsequently causing a reduction in the number of immune cells and the levels of cytokines in the bronchoalveolar lavage fluid and histopathologic changes in the airways. Our results indicate that BCX 2798 and BCX 2855 are effective inhibitors of hPIV-3 HN in our mouse model and may be promising candidates for the prophylaxis and treatment of hPIV-3 infection in humans.
Profound Antiviral Effect of Oral Administration of MIV-210 on Chronic Hepadnaviral Infection in a Woodchuck Model of Hepatitis B
Authors: Michalak Tomasz I. , Zhang Hong , Churchill Norma D. , Larsson Torbjörn , Johansson Nils-Gunnar , Öberg Bo 
Published: June 2009

ABSTRACTMIV-210 is a prodrug of 3′-fluoro-2′,3′-dideoxyguanosine with high oral bioavailability in humans and potent activity against hepatitis B virus (HBV). Woodchucks infected with woodchuck hepatitis virus (WHV) represent an accurate model of HBV infection that is utilized for evaluation of the efficacy and safety of novel anti-HBV agents. Oral administration of MIV-210 at 20 or 60 mg/kg of body weight/day induced a rapid virological response in chronically infected woodchucks, reducing serum WHV DNA levels by 4.75 log10and 5.72 log10, respectively, in 2 weeks. A progressive decline in WHV viremia occurred throughout the 10-week therapy, giving final reductions of 7.23 log10and 7.68 log10in the 20- and 60-mg/kg/day groups, respectively. Further, a daily dose of 10 mg/kg decreased the serum WHV load 400-fold after 4 weeks of treatment, and a dose of 5 mg/kg/day was sufficient to maintain this antiviral effect during the following 6-week period. MIV-210 at 20 or 60 mg/kg/day reduced the liver WHV DNA load 200- to 2,500-fold from pretreatment levels and, importantly, led to a 2.0 log10drop in the hepatic content of WHV covalently closed circular DNA. The treatment with 60 mg/kg/day was well tolerated. Liver biopsy specimens obtained after the 10-week treatment with 20 or 60 mg/kg/day and after the 10-week follow-up showed hepatocyte and mitochondrial ultrastructures comparable to those in the placebo-treated group. It was concluded that MIV-210 is highly effective against chronic WHV infection. These findings, together with the previously demonstrated inhibitory activity of MIV-210 against lamivudine-, adefovir-, and entecavir-resistant HBV variants, make MIV-210 a highly valuable candidate for further testing as an agent against chronic hepatitis B.
Efficacy of Iclaprim against Wild-Type and Thymidine Kinase-Deficient Methicillin-Resistant
Staphylococcus aureus
Isolates in an In Vitro Fibrin Clot Model
Authors: Entenza José M. , Haldimann Andreas , Giddey Marlyse , Lociuro Sergio , Hawser Stephen , Moreillon Philippe 
Published: June 2009

ABSTRACT

Iclaprim is a novel diaminopyrimidine antibiotic that is active against methicillin-resistant
Staphylococcus aureus
(MRSA). However, it is known that the activity of diaminopyrimidines against
S. aureus
is antagonized by thymidine through uptake and conversion to thymidylate by thymidine kinase. Unlike with humans, for whom thymidine levels are low, thymidine levels in rodents are high, thus precluding the accurate evaluation of iclaprim efficacy in animal models. We have studied the bactericidal activity of iclaprim against an isogenic pair of MRSA isolates, the wild-type parent AW6 and its thymidine kinase-deficient mutant AH1252, in an in vitro fibrin clot model. Clots, which were aimed at mimicking vegetation structure, were made from human or rat plasma containing either the parent AW6 or the mutant AH1252, and they were exposed to homologous serum supplemented with iclaprim (3.5 μg/ml), trimethoprim-sulfamethoxazole (TMP-SMX; 8/40 μg/ml), vancomycin (40 μg/ml), or saline, each of which was added one time for 48 h. In rat clots, iclaprim and TMP-SMX were bacteriostatic against the parent, AW6. In contrast, they were bactericidal (≥3 log
10
CFU/clot killing of the original inoculum) against the mutant AH1252. Vancomycin was the most active drug against AW6 (
P
< 0.05), but it showed an activity similar those of iclaprim and TMP-SMX against AH1252. In human clots, iclaprim was bactericidal against both AW6 and AH1252 strains and was as effective as TMP-SMX and vancomycin (
P
> 0.05). Future studies of animals using simulated human kinetics of iclaprim and thymidine kinase-deficient MRSA, which eliminate the thymidine-induced confounding effect, are warranted to support the use of iclaprim in the treatment of severe MRSA infections in humans.
Population Pharmacokinetics of Linezolid in Adults with Pulmonary Tuberculosis
Authors: McGee Bryan , Dietze Reynaldo , Hadad David Jamil , Molino Lucilia Pereira Dutra , Maciel Ethel Leonor Noia , Boom W. Henry , Palaci Moises , Johnson John L. , Peloquin Charles A. 
Published: June 2009

ABSTRACT

Nineteen adults with pulmonary tuberculosis received linezolid (600 mg) once or twice daily in an early bactericidal activity trial. A one-compartment population model produced median values for the absorption rate constant, volume of distribution, and elimination rate constant of 1.5 h
−1
, 29.6 liters, and 0.25 h
−1
(once daily) and 2.7 h
−1
, 32.1 liters, and 0.15 h
−1
(twice daily). Linezolid administered twice daily produced higher values for free drug area under the concentration-time curve (AUC)/MIC and time above MIC. Both regimens achieved free AUC/MIC ratios > 100. Median times above the MIC for free drug were 100% (twice daily) and 63% (once daily).
Analysis of the Genome of theEscherichia coliO157:H7 2006 Spinach-Associated Outbreak Isolate Indicates Candidate Genes That May Enhance Virulence
Authors: Kulasekara Bridget R. , Jacobs Michael , Zhou Yang , Wu Zaining , Sims Elizabeth , Saenphimmachak Channakhone , Rohmer Laurence , Ritchie Jennifer M. , Radey Matthew , McKevitt Matthew , Freeman Theodore Larson , Hayden Hillary , Haugen Eric , Gillett Will , Fong Christine , Chang Jean , Beskhlebnaya Viktoriya , Waldor Matthew K. , Samadpour Mansour , Whittam Thomas S. , Kaul Rajinder , Brittnacher Mitchell , Miller Samuel I. 
Published: June 2009

ABSTRACTIn addition to causing diarrhea,Escherichia coliO157:H7 infection can lead to hemolytic-uremic syndrome (HUS), a severe disease characterized by hemolysis and renal failure. Differences in HUS frequency amongE. coliO157:H7 outbreaks have been noted, but our understanding of bacterial factors that promote HUS is incomplete. In 2006, in an outbreak ofE. coliO157:H7 caused by consumption of contaminated spinach, there was a notably high frequency of HUS. We sequenced the genome of the strain responsible (TW14359) with the goal of identifying candidate genetic factors that contribute to an enhanced ability to cause HUS. The TW14359 genome contains 70 kb of DNA segments not present in either of the two reference O157:H7 genomes. We identified seven putative virulence determinants, including two putative type III secretion system effector proteins, candidate genes that could result in increased pathogenicity or, alternatively, adaptation to plants, and an intact anaerobic nitric oxide reductase gene,norV. We surveyed 100 O157:H7 isolates for the presence of these putative virulence determinants. AnorVdeletion was found in over one-half of the strains surveyed and correlated strikingly with the absence ofstx1. The other putative virulence factors were found in 8 to 35% of the O157:H7 isolates surveyed, and their presence also correlated with the presence ofnorVand the absence ofstx1, indicating that the presence ofnorVmay serve as a marker of a greater propensity for HUS, similar to the correlation between the absence ofstx1and a propensity for HUS.
The NanA Neuraminidase of
Streptococcus pneumoniae
Is Involved in Biofilm Formation
Authors: Parker Dane , Soong Grace , Planet Paul , Brower Jonathan , Ratner Adam J. , Prince Alice 
Published: June 2009

ABSTRACT

Streptococcus pneumoniae
remains a major cause of bacteremia, pneumonia, and otitis media despite vaccines and effective antibiotics. The neuraminidase of
S. pneumoniae
, which catalyzes the release of terminal sialic acid residues from glycoconjugates, is involved in host colonization in animal models of infection and may provide a novel target for preventing pneumococcal infection. We demonstrate that the
S. pneumoniae
neuraminidase (NanA) cleaves sialic acid and show that it is involved in biofilm formation, suggesting an additional role in pathogenesis, and that it shares this property with the neuraminidase of
Pseudomonas aeruginosa
even though we show that the two enzymes are phylogenetically divergent. Using an in vitro model of biofilm formation incorporating human airway epithelial cells, we demonstrate that small-molecule inhibitors of NanA block biofilm formation and may provide a novel target for preventative therapy. This work highlights the role played by the neuraminidase in pathogenesis and represents an important step in drug development for prevention of colonization of the respiratory tract by this important pathogen.
Sialic Acid Catabolism Confers a Competitive Advantage to Pathogenic
Vibrio cholerae
in the Mouse Intestine
Authors: Almagro-Moreno Salvador , Boyd E. Fidelma 
Published: June 2009

ABSTRACT

Sialic acids comprise a family of nine-carbon ketosugars that are ubiquitous on mammalian mucous membranes. However, sialic acids have a limited distribution among
Bacteria
and are confined mainly to pathogenic and commensal species.
Vibrio
pathogenicity island 2 (VPI-2), a 57-kb region found exclusively among pathogenic strains of
Vibrio cholerae
, contains a cluster of genes (
nan-nag
) putatively involved in the scavenging (
nanH
), transport (
dctPQM
), and catabolism (
nanA
,
nanE
,
nanK
, and
nagA
) of sialic acid. The capacity to utilize sialic acid as a carbon and energy source might confer an advantage to
V. cholerae
in the mucus-rich environment of the gut, where sialic acid availability is extensive. In this study, we show that
V. cholerae
can utilize sialic acid as a sole carbon source. We demonstrate that the genes involved in the utilization of sialic acid are located within the
nan-nag
region of VPI-2 by complementation of
E
scherichia coli
mutants and gene knockouts in
V. cholerae
N16961. We show that
nanH
,
dctP
,
nanA
, and
nanK
are highly expressed in
V. cholerae
grown on sialic acid. By using the infant mouse model of infection, we show that
V. cholerae
Δ
nanA
strain SAM1776 is defective in early intestinal colonization stages. In addition, SAM1776 shows a decrease in the competitive index in colonization-competition assays comparing the mutant strain with both O1 El Tor and classical strains. Our data indicate an important relationship between the catabolism of sialic acid and bacterial pathogenesis, stressing the relevance of the utilization of the resources found in the host's environment.
Aggregatibacter actinomycetemcomitans
Builds Mutualistic Biofilm Communities with
Fusobacterium nucleatum
and
Veillonella
Species in Saliva
Authors: Periasamy Saravanan , Kolenbrander Paul E. 
Published: June 2009

ABSTRACT

Human oral bacterial pathogens grow in attached multispecies biofilm communities. Unattached cells are quickly removed by swallowing. Therefore, surface attachment is essential for growth, and we investigated multispecies community interactions resulting in mutualistic growth on saliva as the sole nutritional source. We used two model systems, saliva-coated transferable solid-phase polystyrene pegs (peg biofilms) and flow cells with saliva-coated glass surfaces. Fluorescent antibody staining and image analysis were used to quantify the biomass in flow cells, and quantitative real-time PCR with species-specific primers was used to quantify the biomass in peg biofilms.
Veillonella
sp. strain PK1910,
Aggregatibacter actinomycetemcomitans
JP2, and
Fusobacterium nucleatum
ATCC 10953 were unable to grow as single species in flow cells. Only
A. actinomycetemcomitans
grew after 36 h when peg biofilms remained submerged in saliva from the time of inoculation. Mixed-species coaggregates were used for two- and three-species inoculation. The biomass in two-species biofilms increased in both systems when
Veillonella
sp. strain PK1910 was present as one of the partners. Enhanced growth of all strains was observed in three-species biofilms in flow cells. Interestingly, in flow cells
F. nucleatum
and
A. actinomycetemcomitans
exhibited mutualism, and, although
F. nucleatum
was unable to grow with either of the other species in the peg system,
F. nucleatum
stimulated the growth of
Veillonella
sp. and together these two organisms increased the total biomass of
A. actinomycetemcomitans
in three-species peg biofilms. We propose that mutualistic two-species and multispecies oral biofilm communities form in vivo and that mutualism between commensal veillonellae and late colonizing pathogens, such as aggregatibacteria, contributes to the development of periodontal disease.
CD4+CD25+Foxp3−T-Regulatory Cells Produce both Gamma Interferon and Interleukin-10 during Acute Severe Murine Spotted Fever Rickettsiosis
Authors: Fang Rong , Ismail Nahed , Shelite Thomas , Walker David H. 
Published: June 2009

ABSTRACTSpotted fever group rickettsiae cause life-threatening human infections worldwide. Until now, the immune regulatory mechanisms involved in fatal rickettsial infection have been unknown. C3H/HeN mice infected with 3 × 105PFU ofRickettsia conoriideveloped an acute progressive disease, and all mice succumbed to this infection. A sublethal infection induced protective immunity, and mice survived. Compared to splenic T cells from sublethally infected mice, splenic T cells from lethally infected mice produced significantly lower levels of interleukin-2 (IL-2) and gamma interferon (IFN-γ) and a higher level of IL-10, but not of IL-4 or transforming growth factor β, and there was markedly suppressed CD4+T-cell proliferation in response to antigen-specific stimulation withR. conorii. Furthermore, lethal infection induced significant expansion of CD4+CD25+Foxp3−T cells in infected organs compared to the levels in naïve and sublethally infected mice. In a lethal infection, splenic CD4+CD25+Foxp3−T cells, which were CTLA-4highT-bet+and secreted both IFN-γ and IL-10, suppressed the proliferation of and IL-2 production by splenic CD4+CD25−Foxp3−T cells in vitro. Interestingly, depletion of CD25+T cells in vivo did not change the disease progression, but it increased the bacterial load in the lung and liver, significantly reduced the number of IFN-γ-producing Th1 cells in the spleen, and increased the serum levels of IFN-γ. These results suggested that CD4+CD25+T cells generated in acute murine spotted fever rickettsiosis are Th1-cell-related adaptive T-regulatory cells, which substantially contribute to suppressing the systemic immune response, possibly by a mechanism involving IL-10 and/or cytotoxic T-lymphocyte antigen 4.
Toxoplasma gondiiCyclophilin 18-Mediated Production of Nitric Oxide Induces Bradyzoite Conversion in a CCR5-Dependent Manner
Authors: Ibrahim Hany M. , Bannai Hiroshi , Xuan Xuenan , Nishikawa Yoshifumi 
Published: June 2009

ABSTRACTToxoplasma gondiimodulates pro- and anti-inflammatory responses to regulate parasite multiplication and host survival. Pressure from the immune response causes the conversion of tachyzoites into slowly dividing bradyzoites. The regulatory mechanisms involved in this switch are poorly understood. The aim of this study was to investigate the immunomodulatory role ofT. gondiicyclophilin 18 (TgCyp18) in macrophages and the consequences of the cellular responses on the conversion machinery. Recombinant TgCyp18 induced the production of nitric oxide (NO), interleukin-12 (IL-12), and tumor necrosis factor alpha through its binding with cysteine-cysteine chemokine receptor 5 (CCR5) and the production of gamma interferon and IL-6 in a CCR5-independent manner. Interestingly, the treatment of macrophages with TgCyp18 resulted in the inhibition of parasite growth and an enhancement of the conversion into bradyzoites via NO in a CCR5-dependent manner. In conclusion,T. gondiipossesses sophisticated mechanisms to manipulate host cell responses in a TgCyp18-mediated process.