bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pyochelin Potentiates the Inhibitory Activity of Gallium on Pseudomonas aeruginosa
Authors: Frangipani Emanuela , Bonchi Carlo , Minandri Fabrizia , Imperi Francesco , Visca Paolo 
Published: June 2014

ABSTRACT

Gallium (Ga) is an iron mimetic that has successfully been repurposed for antibacterial chemotherapy. To improve the antibacterial potency of Ga on
Pseudomonas aeruginosa
, the effect of complexation with a variety of siderophores and synthetic chelators was tested. Ga complexed with the pyochelin siderophore (at a 1:2 ratio) was more efficient than Ga(NO
3
)
3
in inhibiting
P. aeruginosa
growth, and its activity was dependent on increased Ga entrance into the cell through the pyochelin translocon.
1,4-Azaindole, a Potential Drug Candidate for Treatment of Tuberculosis
Authors: Chatterji Monalisa , Shandil Radha , Manjunatha M. R. , Solapure Suresh , Ramachandran Vasanthi , Kumar Naveen , Saralaya Ramanatha , Panduga Vijender , Reddy Jitendar , KR Prabhakar , Sharma Sreevalli , Sadler Claire , Cooper Christopher B. , Mdluli Khisi , Iyer Pravin S. , Narayanan Shridhar , Shirude Pravin S. 
Published: June 2014

ABSTRACT

New therapeutic strategies against multidrug-resistant (MDR) and extensively drug-resistant (XDR)
Mycobacterium tuberculosis
are urgently required to combat the global tuberculosis (TB) threat. Toward this end, we previously reported the identification of 1,4-azaindoles, a promising class of compounds with potent antitubercular activity through noncovalent inhibition of decaprenylphosphoryl-β-
d
-ribose 2′-epimerase (DprE1). Further, this series was optimized to improve its physicochemical properties and pharmacokinetics in mice. Here, we describe the short-listing of a potential clinical candidate, compound 2, that has potent cellular activity, drug-like properties, efficacy in mouse and rat chronic TB infection models, and minimal
in vitro
safety risks. We also demonstrate that the compounds, including compound 2, have no antagonistic activity with other anti-TB drugs. Moreover, compound 2 shows synergy with PA824 and TMC207
in vitro
, and the synergy effect is translated
in vivo
with TMC207. The series is predicted to have a low clearance in humans, and the predicted human dose for compound 2 is ≤1 g/day. Altogether, our data suggest that a 1,4-azaindole (compound 2) is a promising candidate for the development of a novel anti-TB drug.
Characterization of Drug-Resistant Influenza Virus A(H1N1) and A(H3N2) Variants SelectedIn Vitrowith Laninamivir
Authors: Samson Mélanie , Abed Yacine , Desrochers François-Marc , Hamilton Stephanie , Luttick Angela , Tucker Simon P. , Pryor Melinda J. , Boivin Guy 
Published: June 2014

ABSTRACTNeuraminidase inhibitors (NAIs) play a major role for managing influenza virus infections. The widespread oseltamivir resistance among 2007-2008 seasonal A(H1N1) viruses and community outbreaks of oseltamivir-resistant A(H1N1)pdm09 strains highlights the need for additional anti-influenza virus agents. Laninamivir is a novel long-lasting NAI that has demonstratedin vitroactivity against influenza A and B viruses, and its prodrug (laninamivir octanoate) is in phase II clinical trials in the United States and other countries. Currently, little information is available on the mechanisms of resistance to laninamivir. In this study, we first performed neuraminidase (NA) inhibition assays to determine the activity of laninamivir against a set of influenza A viruses containing NA mutations conferring resistance to one or many other NAIs. We also generated drug-resistant A(H1N1) and A(H3N2) viruses underin vitrolaninamivir pressure. Laninamivir demonstrated a profile of susceptibility that was similar to that of zanamivir. More specifically, it retained activity against oseltamivir-resistant H275Y and N295S A(H1N1) variants and the E119V A(H3N2) variant.In vitro, laninamivir pressure selected the E119A NA substitution in the A/Solomon Islands/3/2006 A(H1N1) background, whereas E119K and G147E NA changes along with a K133E hemagglutinin (HA) substitution were selected in the A/Quebec/144147/2009 A(H1N1)pdm09 strain. In the A/Brisbane/10/2007 A(H3N2) background, a large NA deletion accompanied by S138A/P194L HA substitutions was selected. This H3N2 variant had altered receptor-binding properties and was highly resistant to laninamivir in plaque reduction assays. Overall, we confirmed the similarity between zanamivir and laninamivir susceptibility profiles and demonstrated that both NA and HA changes can contribute to laninamivir resistancein vitro.
Phase I Safety, Pharmacokinetics, and Pharmacogenetics Study of the Antituberculosis Drug PA-824 with Concomitant Lopinavir-Ritonavir, Efavirenz, or Rifampin
Authors: Dooley Kelly E. , Luetkemeyer Anne F. , Park Jeong-Gun , Allen Reena , Cramer Yoninah , Murray Stephen , Sutherland Deborah , Aweeka Francesca , Koletar Susan L. , Marzan Florence , Bao Jing , Savic Rada , Haas David W. 
Published: June 2014

ABSTRACT

There is an urgent need for new antituberculosis (anti-TB) drugs, including agents that are safe and effective with concomitant antiretrovirals (ARV) and first-line TB drugs. PA-824 is a novel antituberculosis nitroimidazole in late-phase clinical development. Cytochrome P450 (CYP) 3A, which can be induced or inhibited by ARV and antituberculosis drugs, is a minor (∼20%) metabolic pathway for PA-824. In a phase I clinical trial, we characterized interactions between PA-824 and efavirenz (arm 1), lopinavir/ritonavir (arm 2), and rifampin (arm 3) in healthy, HIV-uninfected volunteers without TB disease. Participants in arms 1 and 2 were randomized to receive drugs via sequence 1 (PA-824 alone, washout, ARV, and ARV plus PA-824) or sequence 2 (ARV, ARV with PA-824, washout, and PA-824 alone). In arm 3, participants received PA-824 and then rifampin and then both. Pharmacokinetic sampling occurred at the end of each dosing period. Fifty-two individuals participated. Compared to PA-824 alone, plasma PA-824 values (based on geometric mean ratios) for maximum concentration (
C
max
), area under the concentration-time curve from 0 to 24 h (AUC
0–24
), and trough concentration (
C
min
) were reduced 28%, 35%, and 46% with efavirenz, 13%, 17%, and 21% with lopinavir-ritonavir (lopinavir/r) and 53%, 66%, and 85% with rifampin, respectively. Medications were well tolerated. In conclusion, lopinavir/r had minimal effect on PA-824 exposures, supporting PA-824 use with lopinavir/r without dose adjustment. PA-824 exposures, though, were reduced more than expected when given with efavirenz or rifampin. The clinical implications of these reductions will depend upon data from current clinical trials defining PA-824 concentration-effect relationships. (This study has been registered at ClinicalTrials.gov under registration no. NCT01571414.)
Identification of Novel Coxiella burnetii Icm/Dot Effectors and Genetic Analysis of Their Involvement in Modulating a Mitogen-Activated Protein Kinase Pathway
Authors: Lifshitz Ziv , Burstein David , Schwartz Kierstyn , Shuman Howard A. , Pupko Tal , Segal Gil 
Published: June 2014

ABSTRACT

Coxiella burnetii
, the causative agent of Q fever, is a human intracellular pathogen that utilizes the Icm/Dot type IVB secretion system to translocate effector proteins into host cells. To identify novel
C. burnetii
effectors, we applied a machine-learning approach to predict
C. burnetii
effectors, and examination of 20 such proteins resulted in the identification of 13 novel effectors. To determine whether these effectors, as well as several previously identified effectors, modulate conserved eukaryotic pathways, they were expressed in
Saccharomyces cerevisiae
. The effects on yeast growth were examined under regular growth conditions and in the presence of caffeine, a known modulator of the yeast cell wall integrity (CWI) mitogen-activated protein (MAP) kinase pathway. In the presence of caffeine, expression of the effectors CBU0885 and CBU1676 caused an enhanced inhibition of yeast growth, and the growth inhibition of CBU0388 was suppressed. Furthermore, analysis of synthetic lethality effects and examination of the activity of the CWI MAP kinase transcription factor Rlm1 indicated that CBU0388 enhances the activation of this MAP kinase pathway in yeast, while CBU0885 and CBU1676 abolish this activation. Additionally, coexpression of CBU1676 and CBU0388 resulted in mutual suppression of their inhibition of yeast growth. These results strongly indicate that these three effectors modulate the CWI MAP kinase pathway in yeast. Moreover, both CBU1676 and CBU0885 were found to contain a conserved haloacid dehalogenase (HAD) domain, which was found to be required for their activity. Collectively, our results demonstrate that MAP kinase pathways are most likely targeted by
C. burnetii
Icm/Dot effectors.
Protective Role of the Capsule and Impact of Serotype 4 Switching on Streptococcus mitis
Authors: Rukke Håkon V. , Kalluru Raja Sab , Repnik Urska , Gerlini Alice , José Ricardo J. , Periselneris Jimstan , Marshall Helina , Griffiths Gareth , Oggioni Marco Rinaldo , Brown Jeremy S. , Petersen Fernanda C. 
Published: June 2014

ABSTRACT

The polysaccharide capsule surrounding
Streptococcus pneumoniae
is essential for virulence. Recently,
Streptococcus mitis
, a human commensal and a close relative of
S. pneumoniae
, was also shown to have a capsule. In this study, the
S. mitis
type strain switched capsule by acquisition of the serotype 4 capsule locus of
S. pneumoniae
TIGR4, following induction of competence for natural transformation. Comparison of the wild type with the capsule-switching mutant and with a capsule deletion mutant showed that the capsule protected
S. mitis
against phagocytosis by RAW 264.7 macrophages. This effect was enhanced in the
S. mitis
strain expressing the
S. pneumoniae
capsule, which showed, in addition, increased resistance against early clearance in a mouse model of lung infection. Expression of both capsules also favored survival in human blood, and the effect was again more pronounced for the capsule-switching mutant.
S. mitis
survival in horse blood or in a mouse model of bacteremia was not significantly different between the wild type and the mutant strains. In all models,
S. pneumoniae
TIGR4 showed higher rates of survival than the
S. mitis
type strain or the capsule-switching mutant, except in the lung model, in which significant differences between
S. pneumoniae
TIGR4 and the capsule-switching mutant were not observed. Thus, we identified conditions that showed a protective function for the capsule in
S. mitis
. Under such conditions,
S. mitis
resistance to clearance could be enhanced by capsule switching to serotype 4, but it was enhanced to levels lower than those for the virulent strain
S. pneumoniae
TIGR4.
Placental Cytokine and Chemokine Profiles Reflect Pregnancy Outcomes in Women Exposed to Plasmodium falciparum Infection
Authors: Chêne Arnaud , Briand Valérie , Ibitokou Samad , Dechavanne Sébastien , Massougbodji Achille , Deloron Philippe , Luty Adrian J. F. , Gamain Benoît , Fievet Nadine 
Published: June 2014

ABSTRACTPregnancy-associated malaria (PAM) can lead to severe complications for both mother and baby. Certain placental cytokine/chemokine profiles have been shown to reflect poor pregnancy outcomes, including maternal anemia and low birth weight. In intervillous plasma samples from 400 Beninese women living in an area wherePlasmodium falciparumis endemic, we quantified 16 cytokines/chemokines. We assessed their profiles in groups with PAM, with maternal anemia, with preterm births, or with a low birth weight for gestational age. Repeated ultrasound measurements ensured that prematurity and low birth weight were highly accurate. Preliminary analyses revealed trends for lower cytokine/chemokine concentrations in placental plasma associated both with babies with low birth weight for gestational age and withP. falciparuminfection during pregnancy, while, as a function of the latter, the concentration of gamma interferon (IFN-γ)-inducible protein 10 (IP-10) was higher. Multivariate analyses showed that (i) higher placental plasma interleukin-10 (IL-10) levels were associated withP. falciparuminfections and (ii) independently ofP. falciparuminfections, lower concentrations of both IFN-γ and IL-5 were associated with low birth weight for gestational age. Our data further strengthen the idea that IL-10 and IP-10 could be useful diagnostic markers ofP. falciparuminfection during pregnancy. The concentrations of cytokines/chemokines in placental plasma may represent previously unrecognized markers of poor fetal growth.
Interplay between Two Bacterial Actin Homologs, MamK and MamK-Like, Is Required for the Alignment of Magnetosome Organelles in Magnetospirillum magneticum AMB-1
Authors: Abreu Nicole , Mannoubi Soumaya , Ozyamak Ertan , Pignol David , Ginet Nicolas , Komeili Arash 
Published: June 2014

ABSTRACT

Many bacterial species contain multiple actin-like proteins tasked with the execution of crucial cell biological functions. MamK, an actin-like protein found in magnetotactic bacteria, is important in organizing magnetosome organelles into chains that are used for navigation along geomagnetic fields. MamK and numerous other magnetosome formation factors are encoded by a genetic island termed the magnetosome island. Unlike most magnetotactic bacteria,
Magnetospirillum magneticum
AMB-1 (AMB-1) contains a second island of magnetosome-related genes that was named the magnetosome islet. A homologous copy of
mamK
,
mamK-like
, resides within this islet and encodes a protein capable of filament formation
in vitro
. Previous work had shown that
mamK-like
is expressed
in vivo
, but its function, if any, had remained unknown. Though MamK-like is highly similar to MamK, it contains a mutation that in MamK and other actins blocks ATPase activity
in vitro
and filament dynamics
in vivo
. Here, using genetic analysis, we demonstrate that
mamK-like
has an
in vivo
role in assisting organelle alignment. In addition, MamK-like forms filaments
in vivo
in a manner that is dependent on the presence of MamK and the two proteins interact in a yeast two-hybrid assay. Surprisingly, despite the ATPase active-site mutation, MamK-like is capable of ATP hydrolysis
in vitro
and promotes MamK filament turnover
in vivo
. Taken together, these experiments suggest that direct interactions between MamK and MamK-like contribute to magnetosome alignment in AMB-1.
DNA Ligase C1 Mediates the LigD-Independent Nonhomologous End-Joining Pathway of Mycobacterium smegmatis
Authors: Bhattarai Hitesh , Gupta Richa , Glickman Michael S. 
Published: June 2014

ABSTRACT

Nonhomologous end joining (NHEJ) is a recently described bacterial DNA double-strand break (DSB) repair pathway that has been best characterized for mycobacteria. NHEJ can religate transformed linear plasmids, repair ionizing radiation (IR)-induced DSBs in nonreplicating cells, and seal I-SceI-induced chromosomal DSBs. The core components of the mycobacterial NHEJ machinery are the DNA end binding protein Ku and the polyfunctional DNA ligase LigD. LigD has three autonomous enzymatic modules: ATP-dependent DNA ligase (LIG), DNA/RNA polymerase (POL), and 3′ phosphoesterase (PE). Although genetic ablation of
ku
or
ligD
abolishes NHEJ and sensitizes nonreplicating cells to ionizing radiation, selective ablation of the ligase activity of LigD
in vivo
only mildly impairs NHEJ of linearized plasmids, indicating that an additional DNA ligase can support NHEJ. Additionally, the
in vivo
role of the POL and PE domains in NHEJ is unclear. Here we define a LigD ligase-independent NHEJ pathway in
Mycobacterium smegmatis
that requires the ATP-dependent DNA ligase LigC1 and the POL domain of LigD.
Mycobacterium tuberculosis
LigC can also support this backup NHEJ pathway. We also demonstrate that, although dispensable for efficient plasmid NHEJ, the activities of the POL and PE domains are required for repair of IR-induced DSBs in nonreplicating cells. These findings define the genetic requirements for a LigD-independent NHEJ pathway in mycobacteria and demonstrate that all enzymatic functions of the LigD protein participate in NHEJ
in vivo
.
Suppression of Conformation-Compromised Mutants of Salmonella enterica Serovar Typhimurium MelB
Authors: Amin Anowarul , Ethayathulla Abdul S. , Guan Lan 
Published: June 2014

ABSTRACT

The crystal structure of the Na
+
-coupled melibiose permease of
Salmonella enterica
serovar Typhimurium (MelB
St
) demonstrates that MelB is a member of the major facilitator superfamily of transporters. Arg residues at positions 295, 141, and 363 are involved in interdomain interactions at the cytoplasmic side by governing three clusters of electrostatic/polar interactions. Insertion of (one at a time) Glu, Leu, Gln, or Cys at positions R295, R141, and R363, or Lys at position R295, inhibits active transport of melibiose to a level of 2 to 20% of the value for wild-type (WT) MelB
St
, with little effect on binding affinities for both sugar and Na
+
. Interestingly, a spontaneous suppressor, D35E (periplasmic end of helix I), was isolated from the R363Q MelB
St
mutant. Introduction of the D35E mutation in each of the mutants at R295, R141 (except R141E), or R363 rescues melibiose transport to up to 91% of the WT value. Single-site mutations for the pair of D35 and R175 (periplasmic end of helix VI) were constructed by replacing Asp with Glu, Gln, or Cys and R175 with Gln, Asn, or Cys. All mutants with mutations at R175 are active, indicating that a positive charge at R175 is not necessary. Mutant D35E shows reduced transport; D35Q and D35C are nearly inactivated. Surprisingly, the D35Q mutation partially rescues both R141C and R295Q mutations. The data support the idea that Arg at position 295 and a positive charge at positions 141 and 363 are required for melibiose transport catalyzed by MelB
St
, and their mutation inhibits conformational cycling, which is suppressed by a minor modification at the opposite side of the membrane.
Acetyl Coenzyme A Synthetase Is Acetylated on Multiple Lysine Residues by a Protein Acetyltransferase with a Single Gcn5-Type
N
-Acetyltransferase (GNAT) Domain in Saccharopolyspora erythraea
Authors: You Di , Yao Li-li , Huang Dan , Escalante-Semerena Jorge C. , Ye Bang-Ce 
Published: June 2014

ABSTRACT

Reversible lysine acetylation (RLA) is used by cells of all domains of life to modulate protein function. To date, bacterial acetylation/deacetylation systems have been studied in a few bacteria (e.g.,
Salmonella enterica
,
Bacillus subtilis
,
Escherichia coli
,
Erwinia amylovora
,
Mycobacterium tuberculosis
, and
Geobacillus kaustophilus
), but little is known about RLA in antibiotic-producing actinomycetes. Here, we identify the Gcn5-like protein acetyltransferase AcuA of
Saccharopolyspora erythraea
(
Sac
AcuA, SACE_5148) as the enzyme responsible for the acetylation of the AMP-forming acetyl coenzyme A synthetase (
Sac
AcsA, SACE_2375). Acetylated
Sac
AcsA was deacetylated by a sirtuin-type NAD
+
-dependent consuming deacetylase (
Sac
SrtN, SACE_3798).
In vitro
acetylation/deacetylation of
Sac
AcsA enzyme was studied by Western blotting, and acetylation of lysine residues Lys
237
, Lys
380
, Lys
611
, and Lys
628
was confirmed by mass spectrometry. In a strain devoid of
Sac
AcuA, none of the above-mentioned Lys residues of
Sac
AcsA was acetylated. To our knowledge, the ability of
Sac
AcuA to acetylate multiple Lys residues is unique among AcuA-type acetyltransferases. Results from site-specific mutagenesis experiments showed that the activity of
Sac
AcsA was controlled by lysine acetylation. Lastly, immunoprecipitation data showed that
in vivo
acetylation of
Sac
AcsA was influenced by glucose and acetate availability. These results suggested that reversible acetylation may also be a conserved regulatory posttranslational modification strategy in antibiotic-producing actinomycetes.
Sequence Variation in
tcdA
and
tcdB
of Clostridium difficile: ST37 with Truncated
tcdA
Is a Potential Epidemic Strain in China
Authors: Du Pengcheng , Cao Bo , Wang Jing , Li Wenge , Jia Hongbing , Zhang Wen , Lu Jinxing , Li Zhongjie , Yu Hongjie , Chen Chen , Cheng Ying 
Published: June 2014

ABSTRACT

Clostridium difficile
is a well-known nosocomial infectious pathogen. Research on
C. difficile
infection has primarily focused on strains such as the hypervirulent PCR ribotype 027 (sequence type 1 [ST1]) emerging in Europe and North America. However, other new emerging ribotypes in some countries have attracted attention, such as PCR ribotype 17 (ST37) in Asia and Latin America. We collected 70 strains and sequenced their toxin genes,
tcdA
and
tcdB
. Multilocus sequence typing (MLST) was used to study their population structure. In addition,
tcdA
and/or
tcdB
sequences of 25 other isolates were obtained from GenBank. Single nucleotide polymorphisms (SNPs) were identified and analyzed. Phylogenetic analyses were performed to study toxin gene evolution. All
tcdA
and
tcdB
sequences were divided into 1 of 16 types (denoted A01 to -16 and B01 to -16, respectively). Hypervirulent strain RT027 is A13B12, and RT078 is A14B10, whereas the newly epidemic strain RT017 is A15B13. SNP analysis suggests the possibility of recombination in
tcdB
, perhaps through horizontal gene transfer. SNPs were also found in the sequences corresponding to the PCR primers widely used for toxin detection. Our study shows that ST037 shares a few genotypic features in its
tcdA
and
tcdB
genes with some known hypervirulent strains, indicating that they fall into a unique clade. Our findings can be used to map the relationships among
C. difficile
strains more finely than can be done with less sensitive methods, such as toxinotyping or even MLST, to reveal their inherent epidemiological characteristics.
Understanding how appraisal of doctors produces its effects: a realist review protocol
Authors: Brennan Nicola , Bryce Marie , Pearson Mark , Wong Geoff , Cooper Chris , Archer Julian 
Published: June 2014

IntroductionUK doctors are now required to participate in revalidation to maintain their licence to practise. Appraisal is a fundamental component of revalidation. However, objective evidence of appraisal changing doctors’ behaviour and directly resulting in improved patient care is limited. In particular, it is not clearhowthe process of appraisal is supposed to change doctors’ behaviour and improve clinical performance. The aim of this research is to understandhow and whyappraisal of doctors is supposed to produce its effect.Methods and analysisRealist review is a theory-driven interpretive approach to evidence synthesis. It applies realist logic of inquiry to produce an explanatory analysis of an intervention that is, what works, for whom, in what circumstances, in what respects. Using a realist review approach, an initial programme theory of appraisal will be developed by consulting with key stakeholders in doctors’ appraisal in expert panels (ethical approval is not required), and by searching the literature to identify relevant existing theories. The search strategy will have a number of phases including a combination of: (1) electronic database searching, for example, EMBASE, MEDLINE, the Cochrane Library, ASSIA, (2) ‘cited by’ articles search, (3) citation searching, (4) contacting authors and (5) grey literature searching. The search for evidence will be iteratively extended and refocused as the review progresses. Studies will be included based on their ability to provide data that enable testing of the programme theory. Data extraction will be conducted, for example, by note taking and annotation at different review stages as is consistent with the realist approach. The evidence will be synthesised using realist logic to interrogate the final programme theory of the impact of appraisal on doctors’ performance. The synthesis results will be written up according to RAMESES guidelines and disseminated through peer-reviewed publication and presentations.Trial registration numberThe protocol is registered with PROSPERO 2014:CRD42014007092.