bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase 2 Randomized Trial of the Safety and Efficacy of MHAA4549A, a Broadly Neutralizing Monoclonal Antibody, in a Human Influenza A Virus Challenge Model
Authors: McBride Jacqueline M. , Lim Jeremy J. , Burgess Tracy , Deng Rong , Derby Michael A. , Maia Mauricio , Horn Priscilla , Siddiqui Omer , Sheinson Daniel , Chen-Harris Haiyin , Newton Elizabeth M. , Fillos Dimitri , Nazzal Denise , Rosenberger Carrie M. , Ohlson Maikke B. , Lambkin-Williams Rob , Fathi Hosnieh , Harris Jeffrey M. , Tavel Jorge A. 
Published: August 2017

ABSTRACTMHAA4549A, a human monoclonal antibody targeting the hemagglutinin stalk region of influenza A virus (IAV), is being developed as a therapeutic for patients hospitalized with severe IAV infection. The safety and efficacy of MHAA4549A were assessed in a randomized, double-blind, placebo-controlled, dose-ranging study in a human IAV challenge model. One hundred healthy volunteers were inoculated with A/Wisconsin/67/2005 (H3N2) IAV and, 24 to 36 h later, administered a single intravenous dose of either placebo, MHAA4549A (400, 1,200, or 3,600 mg), or a standard oral dose of oseltamivir. Subjects were assessed for safety, pharmacokinetics (PK), and immunogenicity. The intent-to-treat-infected (ITTI) population was assessed for changes in viral load, influenza symptoms, and inflammatory biomarkers. MHAA4549A was well tolerated in all IAV challenge subjects. The 3,600-mg dose of MHAA4549A significantly reduced the viral burden relative to that of the placebo as determined by the area under the curve (AUC) of nasopharyngeal virus infection, quantified using quantitative PCR (98%) and 50% tissue culture infective dose (TCID50) (100%) assays. Peak viral load, duration of viral shedding, influenza symptom scores, mucus weight, and inflammatory biomarkers were also reduced. Serum PK was linear with a half-life of ∼23 days. No MHAA4549A-treated subjects developed anti-drug antibodies. In conclusion, MHAA4549A was well tolerated and demonstrated statistically significant and substantial antiviral activity in an IAV challenge model. (This study has been registered at ClinicalTrials.gov under identifier NCT01980966.)
Activity of the β-Lactamase Inhibitor LN-1-255 against Carbapenem-Hydrolyzing Class D β-Lactamases from Acinetobacter baumannii
Authors: Vázquez-Ucha Juan Carlos , Maneiro María , Martínez-Guitián Marta , Buynak John , Bethel Christopher R. , Bonomo Robert A. , Bou Germán , Poza Margarita , González-Bello Concepción , Beceiro Alejandro 
Published: August 2017

ABSTRACT

The number of infections caused by Gram-negative pathogens carrying carbapenemases is increasing, and the group of carbapenem-hydrolyzing class D β-lactamases (CHDLs) is especially problematic. Several clinically important CHDLs have been identified in
Acinetobacter baumannii
, including OXA-23, OXA-24/40, OXA-58, OXA-143, OXA-235, and the chromosomally encoded OXA-51. The selection and dissemination of carbapenem-resistant
A. baumannii
strains constitutes a serious global threat. Carbapenems have been successfully utilized as last-resort antibiotics for the treatment of multidrug-resistant
A. baumannii
infections. However, the spread of OXA carbapenemases is compromising the continued use of these antimicrobials. In response to this clinical issue, it is necessary and urgent to design and develop new specific inhibitors with efficacy against these enzymes. The aim of this work was to characterize the inhibitory activity of LN-1-255 (a 6-alkylidene-2-substituted penicillin sulfone) and compare it to that of two established inhibitors (avibactam and tazobactam) against the most relevant enzymes of each group of class D carbapenemases in
A. baumannii
. The β-lactamase inhibitor LN-1-255 demonstrated excellent microbiological synergy and inhibition kinetics parameters against all tested CHDLs and a significantly higher activity than tazobactam and avibactam. A combination of carbapenems and LN-1-255 was effective against
A. baumannii
class D carbapenemases. Docking assays confirmed the affinity of LN-1-255 for the active site of these enzymes. LN-1-255 represents a potential new β-lactamase inhibitor that may have a significant role in eradicating infections caused by
A. baumannii
isolates carrying CHDLs.
Systematic Review and Meta-analyses of the Effect of Chemotherapy on Pulmonary Mycobacterium abscessus Outcomes and Disease Recurrence
Authors: Pasipanodya Jotam G. , Ogbonna Deborah , Ferro Beatriz E. , Magombedze Gesham , Srivastava Shashikant , Deshpande Devyani , Gumbo Tawanda 
Published: August 2017

ABSTRACT

In pharmacokinetic/pharmacodynamic models of pulmonary
Mycobacterium abscessus
complex, the recommended macrolide-containing combination therapy has poor kill rates. However, clinical outcomes are unknown. We searched the literature for studies published between 1990 and 2017 that reported microbial outcomes in patients treated for pulmonary
M. abscessus
disease. A good outcome was defined as sustained sputum culture conversion (SSCC) without relapse. Random effects models were used to pool studies and estimate proportions of patients with good outcomes. Odds ratios (OR) and 95% confidence intervals (CI) were computed. Sensitivity analyses and metaregression were used to assess the robustness of findings. In 19 studies of 1,533 patients, combination therapy was administered to 508 patients with
M. abscessus
subsp.
abscessus
, 204 with
M. abscessus
subsp.
massiliense
, and 301 with
M. abscessus
with no subspecies specified. Macrolide-containing regimens achieved SSCC in only 77/233 (34%) new
M. abscessus
subsp.
abscessus
patients versus 117/141 (54%)
M. abscessus
subsp.
massiliense
patients (OR, 0.108 [95% CI, 0.066 to 0.181]). In refractory disease, SSCC was achieved in 20% (95% CI, 7 to 36%) of patients, which was not significantly different across subspecies. The estimated recurrent rates per month were 1.835% (range, 1.667 to 3.196%) for
M. abscessus
subsp.
abscessus
versus 0.683% (range, 0.229 to 1.136%) for
M. abscessus
subsp.
massiliense
(OR, 6.189 [95% CI, 2.896 to 13.650]). The proportion of patients with good outcomes was 52/223 (23%) with
M. abscessus
subsp.
abscessus
versus 118/141 (84%) with
M. abscessus
subsp.
massiliense
disease (OR, 0.059 [95% CI, 0.034 to 0.101]).
M. abscessus
subsp.
abscessus
pulmonary disease outcomes with the currently recommended regimens are atrocious, with outcomes similar to those for extensively drug-resistant tuberculosis. Therapeutically, the concept of nontuberculous mycobacteria is misguided. There is an urgent need to craft entirely new treatment regimens.
Chronic Brucella Infection Induces Selective and Persistent Interferon Gamma-Dependent Alterations of Marginal Zone Macrophages in the Spleen
Authors: Machelart Arnaud , Khadrawi Abir , Demars Aurore , Willemart Kevin , De Trez Carl , Letesson Jean-Jacques , Muraille Eric 
Published: August 2017

ABSTRACTThe spleen is known as an important filter for blood-borne pathogens that are trapped by specialized macrophages in the marginal zone (MZ): the CD209+MZ macrophages (MZMs) and the CD169+marginal metallophilic macrophages (MMMs). Acute systemic infection strongly impacts MZ populations and the location of T and B lymphocytes. This phenomenon has been linked to reduced chemokine secretion by stromal cells.Brucellaspp. are the causative agent of brucellosis, a widespread zoonotic disease. Here, we usedBrucella melitensisinfection as a model to investigate the impact of chronic stealth infection on splenic MZ macrophage populations. During the late phase ofBrucellainfection, we observed a loss of both MZMs and MMMs, with a durable disappearance of MZMs, leading to a reduction of the ability of the spleen to take up soluble antigens, beads, and unrelated bacteria. This effect appears to be selective as every other lymphoid and myeloid population analyzed increased during infection, which was also observed followingBrucella abortusandBrucella suisinfection. Comparison of wild-type and deficient mice suggested that MZ macrophage population loss is dependent on interferon gamma (IFN-γ) receptor but independent of T cells or tumor necrosis factor alpha receptor 1 (TNF-αR1) signaling pathways and is not correlated to an alteration of CCL19, CCL21, and CXCL13 chemokine mRNA expression. Our results suggest that MZ macrophage populations are particularly sensitive to persistent low-level IFN-γ-mediated inflammation and thatBrucellainfection could reduce the ability of the spleen to perform certain MZM- and MMM-dependent tasks, such as antigen delivery to lymphocytes and control of systemic infection.
Identification of Staphylococcus aureus Factors Required for Pathogenicity and Growth in Human Blood
Authors: Connolly John , Boldock Emma , Prince Lynne R. , Renshaw Stephen A. , Whyte Moira K. , Foster Simon J. 
Published: August 2017

ABSTRACT

Staphylococcus aureus
is a human commensal but also has devastating potential as an opportunistic pathogen.
S. aureus
bacteremia is often associated with an adverse outcome. To identify potential targets for novel control approaches, we have identified
S. aureus
components that are required for growth in human blood. An ordered transposon mutant library was screened, and 9 genes involved specifically in hemolysis or growth on human blood agar were identified by comparing the mutants to the parental strain. Three genes (
purA
,
purB
, and
pabA
) were subsequently found to be required for pathogenesis in the zebrafish embryo infection model. The
pabA
growth defect was specific to the red blood cell component of human blood, showing no difference from the parental strain in growth in human serum, human plasma, or sheep or horse blood. PabA is required in the tetrahydrofolate (THF) biosynthesis pathway. The
pabA
growth defect was found to be due to a combination of loss of THF-dependent dTMP production by the ThyA enzyme and increased demand for pyrimidines in human blood. Our work highlights
pabA
and the pyrimidine salvage pathway as potential targets for novel therapeutics and suggests a previously undefined role for a human blood factor in the activity of sulfonamide antibiotics.
Influence of the Gut Microbiota Composition on Campylobacter jejuni Colonization in Chickens
Authors: Han Zifeng , Willer Thomas , Li Li , Pielsticker Colin , Rychlik Ivan , Velge Philippe , Kaspers Bernd , Rautenschlein Silke 
Published: August 2017

ABSTRACT

The
Campylobacter jejuni
-host interaction may be affected by the host's gut microbiota through competitive exclusion, metabolites, or modification of the immune response. To understand this interaction,
C. jejuni
colonization and local immune responses were compared in chickens with different gut microbiota compositions. Birds were treated with an antibiotic cocktail (AT) (experiments 1 and 2) or raised under germfree (GF) conditions (experiment 3). At 18 days posthatch (dph), they were orally inoculated either with 10
4
CFU of
C. jejuni
or with diluent. Cecal as well as systemic
C. jejuni
colonization, T- and B-cell numbers in the gut, and gut-associated tissue were compared between the different groups. Significantly higher numbers of CFU of
C. jejuni
were detected in the cecal contents of AT and GF birds, with higher colonization rates in spleen, liver, and ileum, than in birds with a conventional gut microbiota (
P
< 0.05). Significant upregulation of T and B lymphocyte numbers was detected in cecum, cecal tonsils, and bursa of Fabricius of AT or GF birds after
C. jejuni
inoculation compared to the respective controls (
P
< 0.05). This difference was less clear in birds with a conventional gut microbiota. Histopathological gut lesions were observed only in
C. jejuni
-inoculated AT and GF birds but not in microbiota-colonized
C. jejuni
-inoculated hatchmates. These results demonstrate that the gut microbiota may contribute to the control of
C. jejuni
colonization and prevent lesion development. Further studies are needed to identify key players of the gut microbiota and the mechanisms behind their protective role.
Role for FimH in Extraintestinal Pathogenic Escherichia coli Invasion and Translocation through the Intestinal Epithelium
Authors: Poole Nina M. , Green Sabrina I. , Rajan Anubama , Vela Luz E. , Zeng Xi-Lei , Estes Mary K. , Maresso Anthony W. 
Published: August 2017

ABSTRACT

The translocation of bacteria across the intestinal epithelium of immunocompromised patients can lead to bacteremia and life-threatening sepsis. Extraintestinal pathogenic
Escherichia coli
(ExPEC), so named because this pathotype infects tissues distal to the intestinal tract, is a frequent cause of such infections, is often multidrug resistant, and chronically colonizes a sizable portion of the healthy population. Although several virulence factors and their roles in pathogenesis are well described for ExPEC strains that cause urinary tract infections and meningitis, they have not been linked to translocation through intestinal barriers, a fundamentally distant yet important clinical phenomenon. Using untransformed
ex situ
human intestinal enteroids and transformed Caco-2 cells, we report that ExPEC strain CP9 binds to and invades the intestinal epithelium. ExPEC harboring a deletion of the gene encoding the mannose-binding type 1 pilus tip protein FimH demonstrated reduced binding and invasion compared to strains lacking known
E. coli
virulence factors. Furthermore, in a murine model of chemotherapy-induced translocation, ExPEC lacking
fimH
colonized at levels comparable to that of the wild type but demonstrated a statistically significant reduction in translocation to the kidneys, spleen, and lungs. Collectively, this study indicates that FimH is important for ExPEC translocation, suggesting that the type 1 pilus is a therapeutic target for the prevention of this process. Our study also highlights the use of human intestinal enteroids in the study of enteric diseases.
Gene Duplication in Pseudomonas aeruginosa Improves Growth on Adenosine
Authors: Toussaint Jean-Paul , Farrell-Sherman Anna , Feldman Tamar Perla , Smalley Nicole E. , Schaefer Amy L. , Greenberg E. Peter , Dandekar Ajai A. 
Published: August 2017

ABSTRACT

The laboratory strain of
Pseudomonas aeruginosa
, PAO1, activates genes for catabolism of adenosine using quorum sensing (QS). However, this strain is not well-adapted for growth on adenosine, with doubling times greater than 40 h. We previously showed that when PAO1 is grown on adenosine and casein, variants emerge that grow rapidly on adenosine. To understand the mechanism by which this adaptation occurs, we performed whole-genome sequencing of five isolates evolved for rapid growth on adenosine. All five genomes had a gene duplication-amplification (GDA) event covering several genes, including the quorum-regulated nucleoside hydrolase gene,
nuh
, and PA0148, encoding an adenine deaminase. In addition, two of the growth variants also exhibited a
nuh
promoter mutation. We recapitulated the rapid growth phenotype with a plasmid containing six genes common to all the GDA events. We also showed that
nuh
and PA0148, the two genes at either end of the common GDA, were sufficient to confer rapid growth on adenosine. Additionally, we demonstrated that the variant
nuh
promoter increased basal expression of
nuh
but maintained its QS regulation. Therefore, GDA in
P. aeruginosa
confers the ability to grow efficiently on adenosine while maintaining QS regulation of nucleoside catabolism.

IMPORTANCE
Pseudomonas aeruginosa
thrives in many habitats and is an opportunistic pathogen of humans. In these diverse environments,
P. aeruginosa
must adapt to use myriad potential carbon sources.
P. aeruginosa
PAO1 cannot grow efficiently on nucleosides, including adenosine; however, it can acquire this ability through genetic adaptation. We show that the mechanism of adaptation is by amplification of a specific region of the genome and that the amplification preserves the regulation of the adenosine catabolic pathway by quorum sensing. These results demonstrate an underexplored mechanism of adaptation by
P. aeruginosa
, with implications for phenotypes such as development of antibiotic resistance.
Growth- and Stress-Induced PASTA Kinase Phosphorylation in Enterococcus faecalis
Authors: Labbe Benjamin D. , Kristich Christopher J. 
Published: August 2017

ABSTRACTTransmembrane Ser/Thr kinases containing extracellular PASTA domains are ubiquitous amongActinobacteriaandFirmicutes. Such PASTA kinases regulate critical processes, including antibiotic resistance, cell division, toxin production, and virulence, and are essential for viability in certain organisms. Based onin vitrostudies with purified extracellular and intracellular fragments of PASTA kinases, a model for signaling has been proposed, in which the extracellular PASTA domains bind currently undefined ligands (typically thought to be peptidoglycan, or fragments thereof) to drive kinase dimerization, which leads to enhanced kinase autophosphorylation and enhanced phosphorylation of substrates. However, this model has not been rigorously testedin vivo.Enterococcus faecalisis a Gram-positive intestinal commensal and major antibiotic-resistant opportunistic pathogen. InE. faecalis, the PASTA kinase IreK drives intrinsic resistance to cell wall-active antimicrobials, suggesting that such antimicrobials may trigger IreK signaling. Here we show that IreK responds to cell wall stressin vivoby enhancing its phosphorylation and that of a downstream substrate. This response requires both the extracellular PASTA domains and specific phosphorylatable residues in the kinase domain. Thus, our results providein vivoevidence, with an intact full-length PASTA kinase in its native physiological environment, that supports the prevailing model of PASTA kinase signaling. In addition, we show that IreK responds to a signal associated with growth and/or cell division, in the absence of cell wall-active antimicrobials. Surprisingly, the ability of IreK to respond to growth and/or division does not require the extracellular PASTA domains, suggesting that IreK monitors multiple parameters for sensory inputin vivo.IMPORTANCETransmembrane Ser/Thr kinases containing extracellular PASTA domains are ubiquitous amongActinobacteriaandFirmicutesand regulate critical processes. The prevailing model for signaling by PASTA kinases proposes that the extracellular PASTA domains bind ligands to drive kinase dimerization, enhanced autophosphorylation, and enhanced phosphorylation of substrates. However, this model has not been rigorously testedin vivo. We show that the PASTA kinase IreK ofEnterococcus faecalisresponds to cell wall stressin vivoby enhancing its phosphorylation and that of a downstream substrate. This response requires the PASTA domains and phosphorylatable residues in the kinase domain. Thus, our results providein vivoevidence, with an intact full-length PASTA kinase in its native physiological environment, that supports the prevailing model of PASTA kinase signaling.
The Components of the Unique Zur Regulon of Cupriavidus metallidurans Mediate Cytoplasmic Zinc Handling
Authors: Bütof Lucy , Schmidt-Vogler Christopher , Herzberg Martin , Große Cornelia , Nies Dietrich H. 
Published: August 2017

ABSTRACT

Zinc is an essential trace element, yet it is toxic at high concentrations. In the betaproteobacterium
Cupriavidus metallidurans
, the highly efficient removal of surplus zinc from the periplasm is responsible for the outstanding metal resistance of the organism. Rather than having a typical Zur-dependent, high-affinity ATP-binding cassette transporter of the ABC protein superfamily for zinc uptake at low concentrations,
C. metallidurans
has the secondary zinc importer ZupT of the zinc-regulated transporter, iron-regulated transporter (ZRT/IRT)-like protein (ZIP) family. It is important to understand, therefore, how this zinc-resistant bacterium copes with exposure to low zinc concentrations. Members of the Zur regulon in
C. metallidurans
were identified by comparing the transcriptomes of a Δ
zur
mutant and its parent strain. The consensus sequence of the Zur-binding box was derived for the
zupTp
promoter-regulatory region by use of a truncation assay. The motif was used to predict possible Zur boxes upstream of Zur regulon members. The binding of Zur to these boxes was confirmed. Two Zur boxes upstream of the
cobW
1
gene, encoding a putative zinc chaperone, proved to be required for complete repression of
cobW
1
and its downstream genes in cells cultivated in mineral salts medium. A Zur box upstream of each of
zur-cobW
2
,
cobW
3
, and
zupT
permitted both low expression levels of these genes and their upregulation under conditions of zinc starvation. This demonstrates a compartmentalization of zinc homeostasis in
C. metallidurans
, where the periplasm is responsible for the removal of surplus zinc, cytoplasmic components are responsible for the management of zinc as an essential cofactor, and the two compartments are connected by ZupT.

IMPORTANCE
Elucidating zinc homeostasis is necessary for understanding both host-pathogen interactions and the performance of free-living bacteria in their natural environments.
Escherichia coli
acquires zinc under conditions of low zinc concentrations via the Zur-controlled ZnuABC importer of the ABC superfamily, and this was also the paradigm for other bacteria. In contrast, the heavy-metal-resistant bacterium
C. metallidurans
achieves high tolerance to zinc through sophisticated zinc handling and efflux systems operating on periplasmic zinc ions, so that removal of surplus zinc is a periplasmic feature in this bacterium. It is shown here that this process is augmented by the management of zinc by cytoplasmic zinc chaperones, whose synthesis is controlled by the Zur regulator. This demonstrates a new mechanism, involving compartmentalization, for organizing zinc homeostasis.
Conjugative Plasmid Transfer in Xylella fastidiosa Is Dependent on
tra
and
trb
Operon Functions
Authors: Burbank Lindsey P. , Van Horn Christopher R. 
Published: August 2017

ABSTRACT

The insect-transmitted plant pathogen
Xylella fastidiosa
is capable of efficient horizontal gene transfer (HGT) and recombination. Natural transformation occurs at high rates in
X. fastidiosa
, but there also is evidence that certain strains of
X. fastidiosa
carry native plasmids equipped with transfer and mobilization genes, suggesting conjugation as an additional mechanism of HGT in some instances. Two operons,
tra
and
trb
, putatively encoding a conjugative type IV secretion system, are found in some but not all
X. fastidiosa
isolates, often on native plasmids.
X. fastidiosa
strains that carry the conjugative transfer genes can belong to different subspecies and frequently differ in host ranges. Using
X. fastidiosa
strain M23 (
X. fastidiosa
subsp.
fastidiosa
) or Dixon (
X. fastidiosa
subsp.
multiplex
) as the donor strain and Temecula (
X. fastidiosa
subsp.
fastidiosa
) as the recipient strain, plasmid transfer was characterized using the mobilizable broad-host-range vector pBBR5pemIK. Transfer of plasmid pBBR5pemIK was observed under
in vitro
conditions with both donor strains and was dependent on both
tra
and
trb
operon functions. A conjugative mechanism likely contributes to gene transfer between diverse strains of
X. fastidiosa
, possibly facilitating adaptation to new environments or different hosts.

IMPORTANCE
Xylella fastidiosa
is an important plant pathogen worldwide, infecting a wide range of different plant species. The emergence of new diseases caused by
X. fastidiosa
, or host switching of existing strains, is thought to be primarily due to the high frequency of HGT and recombination in this pathogen. Transfer of plasmids by a conjugative mechanism enables movement of larger amounts of genetic material at one time, compared with other routes of gene transfer such as natural transformation. Establishing the prevalence and functionality of this mechanism in
X. fastidiosa
contributes to a better understanding of HGT, adaptation, and disease emergence in this diverse pathogen.