bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clinical Evolution of New Delhi Metallo-β-Lactamase (NDM) Optimizes Resistance under Zn(II) Deprivation
Authors: Bahr Guillermo , Vitor-Horen Luisina , Bethel Christopher R. , Bonomo Robert A. , González Lisandro J. , Vila Alejandro J. 
Published: October 2017

ABSTRACT

Carbapenem-resistant
Enterobacteriaceae
(CRE) are rapidly spreading and taking a staggering toll on all health care systems, largely due to the dissemination of genes coding for potent carbapenemases. An important family of carbapenemases are the Zn(II)-dependent β-lactamases, known as metallo-β-lactamases (MBLs). Among them, the New Delhi metallo-β-lactamase (NDM) has experienced the fastest and widest geographical spread. While other clinically important MBLs are soluble periplasmic enzymes, NDMs are lipoproteins anchored to the outer membrane in Gram-negative bacteria. This unique cellular localization endows NDMs with enhanced stability upon the Zn(II) starvation elicited by the immune system response at the sites of infection. Since the first report of NDM-1, new allelic variants (16 in total) have been identified in clinical isolates differing by a limited number of substitutions. Here, we show that these variants have evolved by accumulating mutations that enhance their stability or the Zn(II) binding affinity
in vivo
, overriding the most common evolutionary pressure acting on catalytic efficiency. We identified the ubiquitous substitution M154L as responsible for improving the Zn(II) binding capabilities of the NDM variants. These results also reveal that Zn(II) deprivation imposes a strict constraint on the evolution of this MBL, overriding the most common pressures acting on catalytic performance, and shed light on possible inhibitory strategies.
CTX-M-15-Producing Shewanella Species Clinical Isolate Expressing OXA-535, a Chromosome-Encoded OXA-48 Variant, Putative Progenitor of the Plasmid-Encoded OXA-436
Authors: Jousset Agnès B. , Dabos Laura , Bonnin Rémy A. , Girlich Delphine , Potron Anaïs , Cabanel Nicolas , Dortet Laurent , Glaser Philippe , Naas Thierry 
Published: October 2017

ABSTRACT

Shewanella
spp. constitute a reservoir of antibiotic resistance determinants. In a bile sample, we identified three extended-spectrum-β-lactamase (ESBL)-producing bacteria (
Escherichia coli
,
Klebsiella pneumoniae
, and
Shewanella
sp. strain JAB-1) isolated from a child suffering from cholangitis. Our objectives were to characterize the genome and the resistome of the first ESBL-producing isolate of the genus
Shewanella
and determine whether plasmidic exchange occurred between the three bacterial species. Bacterial isolates were characterized using matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), standard biochemical tools, and antimicrobial susceptibility testing.
Shewanella
sp. JAB-1 and ESBL gene-encoding plasmids were characterized using PacBio and Illumina whole-genome sequencing, respectively. The
Shewanella
sp. JAB-1 chromosome-encoded OXA-48 variant was cloned and functionally characterized. Whole-genome sequencing (WGS) of the
Shewanella
sp. clinical isolate JAB-1 revealed the presence of a 193-kb plasmid belonging to the IncA/C incompatibility group and harboring two ESBL genes,
bla
CTX-M-15
and
bla
SHV-2a
.
bla
CTX-M-15
gene-carrying plasmids belonging to the IncY and IncR incompatibility groups were also found in the
E. coli
and
K. pneumoniae
isolates from the same patient, respectively. A comparison of the
bla
CTX-M-15
genetic environment indicated the independent origin of these plasmids and dismissed
in vivo
transfers. Furthermore, characterization of the resistome of
Shewanella
sp. JAB-1 revealed the presence of a chromosome-carried
bla
OXA-535
gene, likely the progenitor of the plasmid-carried
bla
OXA-436
gene, a novel
bla
OXA-48
-like gene. The expression of
bla
OXA-535
in
E. coli
showed the carbapenem-hydrolyzing activity of OXA-535. The production of OXA-535 in
Shewanella
sp. JAB-1 could be evidenced using molecular and immunoenzymatic tests, but not with biochemical tests that monitor carbapenem hydrolysis. In this study, we have identified a CTX-M-15-producing
Shewanella
species that was responsible for a hepatobiliary infection and that is likely the progenitor of OXA-436, a novel plasmid-encoded OXA-48-like class D carbapenemase.
Modulators of Enterococcus faecalis Cell Envelope Integrity and Antimicrobial Resistance Influence Stable Colonization of the Mammalian Gastrointestinal Tract
Authors: Banla Ismael L. , Kommineni Sushma , Hayward Michael , Rodrigues Marinelle , Palmer Kelli L. , Salzman Nita H. , Kristich Christopher J. 
Published: October 2017

ABSTRACT

The Gram-positive bacterium
Enterococcus faecalis
is both a colonizer of the gastrointestinal tract (GIT) and an agent of serious nosocomial infections. Although it is typically required for pathogenesis, GIT colonization by
E. faecalis
is poorly understood.
E. faecalis
tolerates high concentrations of GIT antimicrobials, like cholate and lysozyme, leading us to hypothesize that resistance to intestinal antimicrobials is essential for long-term GIT colonization. Analyses of
E. faecalis
mutants exhibiting defects in antimicrobial resistance revealed that IreK, a determinant of envelope integrity and antimicrobial resistance, is required for long-term GIT colonization. IreK is a member of the PASTA kinase protein family, bacterial transmembrane signaling proteins implicated in the regulation of cell wall homeostasis. Among several determinants of cholate and lysozyme resistance in
E. faecalis
, IreK was the only one found to be required for intestinal colonization, emphasizing the importance of this protein to enterococcal adaptation to the GIT. By studying Δ
ireK
suppressor mutants that recovered the ability to colonize the GIT, we identified two conserved enterococcal proteins (OG1RF_11271 and OG1RF_11272) that function antagonistically to IreK and interfere with cell envelope integrity, antimicrobial resistance, and GIT colonization. Our data suggest that IreK, through its kinase activity, inhibits the actions of these proteins. IreK, OG1RF_11271, and OG1RF_11272 are found in all enterococci, suggesting that their effect on GIT colonization is universal across enterococci. Thus, we have defined conserved genes in the enterococcal core genome that influence GIT colonization through their effect on enterococcal envelope integrity and antimicrobial resistance.
Plasmodium falciparum PfEMP1 Modulates Monocyte/Macrophage Transcription Factor Activation and Cytokine and Chemokine Responses
Authors: Sampaio Natália Guimarães , Eriksson Emily Marie , Schofield Louis 
Published: October 2017

ABSTRACT

Immunity to
Plasmodium falciparum
malaria is slow to develop, and it is often asserted that malaria suppresses host immunity, although this is poorly understood and the molecular basis for such activity remains unknown.
P. falciparum
erythrocyte membrane protein 1 (PfEMP1) is a virulence factor that plays a key role in parasite-host interactions. We investigated the immunosuppressive effect of PfEMP1 on monocytes/macrophages, which are central to the antiparasitic innate response. RAW macrophages and human primary monocytes were stimulated with wild-type 3D7 or CS2 parasites or transgenic PfEMP1-null parasites. To study the immunomodulatory effect of PfEMP1, transcription factor activation and cytokine and chemokine responses were measured. The level of activation of NF-κB was significantly lower in macrophages stimulated with parasites that express PfEMP1 at the red blood cell surface membrane than in macrophages stimulated with PfEMP1-null parasites. Modulation of additional transcription factors, including CREB, also occurred, resulting in reduced immune gene expression and decreased tumor necrosis factor (TNF) and interleukin-10 (IL-10) release. Similarly, human monocytes released less IL-1β, IL-6, IL-10, monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein 1α (MIP-1α), MIP-1β, and TNF specifically in response to VAR2CSA PfEMP1-containing parasites than in response to PfEMP1-null parasites, suggesting that this immune regulation by PfEMP1 is important in naturally occurring infections. These results indicate that PfEMP1 is an immunomodulatory molecule that affects the activation of a range of transcription factors, dampening cytokine and chemokine responses. Therefore, these findings describe a potential molecular basis for immune suppression by
P. falciparum
.
Transcervical Inoculation with Chlamydia trachomatis Induces Infertility in HLA-DR4 Transgenic and Wild-Type Mice
Authors: Pal Sukumar , Tifrea Delia F. , Zhong Guangming , de la Maza Luis M. 
Published: October 2017

ABSTRACTChlamydia trachomatisis the leading cause of infection-induced infertility in women. Attempts to control this epidemic with screening programs and antibiotic therapy have failed. Currently, a vaccine to preventC. trachomatisinfections is not available. In order to develop an animal model for evaluating vaccine antigens that can be applied to humans, we usedC. trachomatisserovar D (strain UW-3/Cx) to induce infertility in mice whose major histocompatibility complex class II antigen was replaced with the human leukocyte antigen DR4 (HLA-DR4). Transcervical inoculation of medroxyprogesterone-treated HLA-DR4 transgenic mice with 5 × 105C. trachomatisD inclusion forming units (IFU) induced a significant reduction in fertility, with a mean number of embryos/mouse of 4.4 ± 1.3 compared to 7.8 ± 0.5 for the uninfected control mice (P< 0.05). A similar fertility reduction was elicited in the wild-type (WT) C57BL/6 mice (4.3 ± 1.4 embryos/mouse) compared to the levels of the WT controls (9.1 ± 0.4 embryos/mouse) (P< 0.05). Following infection, WT mice mounted more robust humoral and cellular immune responses than HLA-DR4 mice. As determined by vaginal shedding, HLA-DR4 mice were more susceptible to a transcervicalC. trachomatisD infection than WT mice. To assess if HLA-DR4 transgenic and WT mice could be protected by vaccination, 104IFU ofC. trachomatisD was delivered intranasally, and mice were challenged transcervically 6 weeks later with 5 × 105IFU ofC. trachomatisD. As determined by severity and length of vaginal shedding, WT C57BL/6 and HLA-DR4 mice were significantly protected by vaccination. The advantages and limitations of the HLA-DR4 transgenic mouse model for evaluating humanC. trachomatisvaccine antigens are discussed.
Native or Proteolytically Activated NanI Sialidase Enhances the Binding and Cytotoxic Activity of Clostridium perfringens Enterotoxin and Beta Toxin
Authors: Theoret James R. , Li Jihong , Navarro Mauricio A. , Garcia Jorge P. , Uzal Francisco A. , McClane Bruce A. 
Published: October 2017

ABSTRACT

Many
Clostridium perfringens
strains produce NanI as their major sialidase. Previous studies showed that NanI could potentiate
C. perfringens
epsilon toxin cytotoxicity by enhancing the binding of this toxin to host cells. The present study first determined that NanI exerts similar cytotoxicity-enhancing effects on
C. perfringens
enterotoxin and beta toxin, which are also important toxins for
C. perfringens
diseases (enteritis and enterotoxemia) originating in the gastrointestinal (GI) tract. Building upon previous work demonstrating that purified trypsin can activate NanI activity, this study next determined that purified chymotrypsin or mouse intestinal fluids can also activate NanI activity. Amino acid sequencing then showed that this effect involves the N-terminal processing of the NanI protein. Recombinant NanI (rNanI) species corresponding to major chymotrypsin- or small intestinal fluid-generated NanI fragments possessed more sialidase activity than did full-length rNanI, further supporting the proteolytic activation of NanI activity. rNanI species corresponding to proteolysis products also promoted the cytotoxic activity and binding of enterotoxin and beta toxin more strongly than did full-length rNanI. Since enterotoxin and beta toxin are produced in the intestines during human and animal disease, these findings suggest that intestinal proteases may enhance NanI activity, which in turn could further potentiate the activity of intestinally active toxins during disease. Coupling these new results with previous findings demonstrating that NanI is important for the adherence of
C. perfringens
to enterocyte-like cells, NanI sialidase is now emerging as a potential auxiliary virulence factor for
C. perfringens
enteritis and enterotoxemia.
A Single-Cell View of the BtsSR/YpdAB Pyruvate Sensing Network in Escherichia coli and Its Biological Relevance
Authors: Vilhena Cláudia , Kaganovitch Eugen , Shin Jae Yen , Grünberger Alexander , Behr Stefan , Kristoficova Ivica , Brameyer Sophie , Kohlheyer Dietrich , Jung Kirsten 
Published: October 2017

ABSTRACT

Fluctuating environments and individual physiological diversity force bacteria to constantly adapt and optimize the uptake of substrates. We focus here on two very similar two-component systems (TCSs) of
Escherichia coli
belonging to the LytS/LytTR family: BtsS/BtsR (formerly YehU/YehT) and YpdA/YpdB. Both TCSs respond to extracellular pyruvate, albeit with different affinities, typically during postexponential growth, and each system regulates expression of a single transporter gene,
yjiY
and
yhjX
, respectively. To obtain insights into the biological significance of these TCSs, we analyzed the activation of the target promoters at the single-cell level. We found unimodal cell-to-cell variability; however, the degree of variance was strongly influenced by the available nutrients and differed between the two TCSs. We hypothesized that activation of either of the TCSs helps individual cells to replenish carbon resources. To test this hypothesis, we compared wild-type cells with the
btsSR ypdAB
mutant under two metabolically modulated conditions: protein overproduction and persister formation. Although all wild-type cells were able to overproduce green fluorescent protein (GFP), about half of the
btsSR ypdAB
population was unable to overexpress GFP. Moreover, the percentage of persister cells, which tolerate antibiotic stress, was significantly lower in the wild-type cells than in the
btsSR ypdAB
population. Hence, we suggest that the BtsS/BtsR and YpdA/YpdB network contributes to a balancing of the physiological state of all cells within a population.

IMPORTANCE
Histidine kinase/response regulator (HK/RR) systems enable bacteria to respond to environmental and physiological fluctuations.
Escherichia coli
and other members of the
Enterobacteriaceae
possess two similar LytS/LytTR-type HK/RRs, BtsS/BtsR (formerly YehU/YehT) and YpdA/YpdB, which form a functional network. Both systems are activated in response to external pyruvate, typically when cells face overflow metabolism during post-exponential growth. Single-cell analysis of the activation of their respective target genes
yjiY
and
yhjX
revealed cell-to-cell variability, and the range of variation was strongly influenced by externally available nutrients. Based on the phenotypic characterization of a
btsSR ypdAB
mutant compared to the parental strain, we suggest that this TCS network supports an optimization of the physiological state of the individuals within the population.
Conversion of Norepinephrine to 3,4-Dihdroxymandelic Acid in Escherichia coli Requires the QseBC Quorum-Sensing System and the FeaR Transcription Factor
Authors: Pasupuleti Sasikiran , Sule Nitesh , Manson Michael D. , Jayaraman Arul 
Published: October 2017

ABSTRACT

The detection of norepinephrine (NE) as a chemoattractant by
Escherichia coli
strain K-12 requires the combined action of the TynA monoamine oxidase and the FeaB aromatic aldehyde dehydrogenase. The role of these enzymes is to convert NE into 3,4-dihydroxymandelic acid (DHMA), which is a potent chemoattractant sensed by the Tsr chemoreceptor. These two enzymes must be induced by prior exposure to NE, and cells that are exposed to NE for the first time initially show minimal chemotaxis toward it. The induction of TynA and FeaB requires the QseC quorum-sensing histidine kinase, and the signaling cascade requires new protein synthesis. Here, we demonstrate that the cognate response regulator for QseC, the transcription factor QseB, is also required for induction. The related quorum-sensing kinase QseE appears not to be part of the signaling pathway, but its cognate response regulator, QseF, which is also a substrate for phosphotransfer from QseC, plays a nonessential role. The promoter of the
feaR
gene, which encodes a transcription factor that has been shown to be essential for the expression of
tynA
and
feaB
, has two predicted QseB-binding sites. One of these sites appears to be in an appropriate position to stimulate transcription from the P
1
promoter of the
feaR
gene. This study unites two well-known pathways: one for expression of genes regulated by catecholamines (QseBC) and one for expression of genes required for metabolism of aromatic amines (FeaR, TynA, and FeaB). This cross talk allows
E. coli
to convert the host-derived and chemotactically inert NE into the potent bacterial chemoattractant DHMA.

IMPORTANCE
The chemotaxis of
E. coli
K-12 to norepinephrine (NE) requires the conversion of NE to 3,4-dihydroxymandleic acid (DHMA), and DHMA is both an attractant and inducer of virulence gene expression for a pathogenic enterohemorrhagic
E. coli
(EHEC) strain. The induction of virulence by DHMA and NE requires QseC. The results described here show that the cognate response regulator for QseC, QseB, is also required for conversion of NE into DHMA. Production of DHMA requires induction of a pathway involved in the metabolism of aromatic amines. Thus, the QseBC sensory system provides a direct link between virulence and chemotaxis, suggesting that chemotaxis to host signaling molecules may require that those molecules are first metabolized by bacterial enzymes to generate the actual chemoattractant.
Evaluation of a type 2 diabetes prevention program using a commercial weight management provider for non-diabetic hyperglycemic patients referred by primary care in the UK
Authors: Piper Carolyn , Marossy Agnes , Griffiths Zoe , Adegboye Amanda 
Published: October 2017

ObjectivesTo determine if a diabetes prevention program (DPP) delivered by a commercial weight management provider using a UK primary care referral pathway could reduce the progression to type 2 diabetes (T2D) in those diagnosed with non-diabetic hyperglycemia (NDH—being at high risk of developing T2D).Research designThis is a quasi-experimental translational research study.Methods14 primary care practices identified, recruited and referred patients with NDH (fasting plasma glucose ≥5.5 to ≤6.9 mmol/L and/or glycated hemoglobin (HbA1c) ≥42 to 47 mmol/mol (6.0%–6.4%)) and a body mass index (BMI) ≥30 kg/m2to a DPP. Eligible patients were asked to contact Weight Watchers to book onto their DPP, an intensive lifestyle intervention which included a 90 min activation session followed by the offer of 48 weekly Weight Watchers community group meetings. Patients’ blood tests were repeated by primary care, weight change plus self-reported data was recorded by Weight Watchers.Results166 patients were referred to the program and 149 were eligible. 79% of eligible patients attended an activation session (117 eligible patients) and 77% started the weekly sessions. The study sample was primarily female (75%), white (90%), with 5% living in the most deprived quintile in the UK. Using intention-to-treat analysis, the DPP resulted in a mean reduction in HbA1c of 2.84 mmol/mol at 12 months (from 43.42±1.28 to 40.58±3.41, p<0.01). 38% of patients returned to normoglycemia and 3% developed T2D at 12 months. There was a mean weight reduction in BMI of 3.2 kg/m2at 12 months (35.5 kg/m2±5.4 to 32.3 kg/m2±5.2, p<0.01).ConclusionA UK primary care referral route partnered with this commercial weight management provider can deliver an effective DPP. The lifestyle changes and weight loss achieved in the intervention translated into considerable reductions in diabetes risk, with an immediate and significant public health impact.
Prevalence of substandard and falsified artemisinin-based combination antimalarial medicines on Bioko Island, Equatorial Guinea
Authors: Kaur Harparkash , Allan Elizabeth Louise , Mamadu Ibrahim , Hall Zoe , Green Michael D , Swamidos Isabel , Dwivedi Prabha , Culzoni Maria Julia , Fernandez Facundo M , Garcia Guillermo , Hergott Dianna , Monti Feliciano 
Published: October 2017

IntroductionPoor-quality artemisinin-containing antimalarials (ACAs), including falsified and substandard formulations, pose serious health concerns in malaria endemic countries. They can harm patients, contribute to the rise in drug resistance and increase the public’s mistrust of health systems. Systematic assessment of drug quality is needed to gain knowledge on the prevalence of the problem, to provide Ministries of Health with evidence on which local regulators can take action.MethodsWe used three sampling approaches to purchase 677 ACAs from 278 outlets on Bioko Island, Equatorial Guinea as follows: convenience survey using mystery client (n=16 outlets, 31 samples), full island-wide survey using mystery client (n=174 outlets, 368 samples) and randomised survey using an overt sampling approach (n=88 outlets, 278 samples). The stated active pharmaceutical ingredients (SAPIs) were assessed using high-performance liquid chromatography and confirmed by mass spectrometry at three independent laboratories.ResultsContent analysis showed 91.0% of ACAs were of acceptable quality, 1.6% were substandard and 7.4% falsified. No degraded medicines were detected. The prevalence of medicines without the SAPIs was higher for ACAs purchased in the convenience survey compared with the estimates obtained using the full island-wide survey-mystery client and randomised-overt sampling approaches. Comparable results were obtained for full island survey-mystery client and randomised overt.However, the availability of purchased artesunate monotherapies differed substantially according to the sampling approach used (convenience, 45.2%; full island-wide survey-mystery client, 32.6%; random-overt sampling approach, 21.9%). Of concern is that 37.1% (n=62) of these were falsified.ConclusionFalsified ACAs were found on Bioko Island, with the prevalence ranging between 6.1% and 16.1%, depending on the sampling method used. These findings underscore the vital need for national authorities to track the scale of ineffective medicines that jeopardise treatment of life-threatening diseases and value of a representative sampling approach to obtain/measure the true prevalence of poor-quality medicines.