244 research outputs found
Escherichia coli as Reservoir for Macrolide Resistance Genes
The plasmid-borne mph(A) gene that confers resistance to azithromycin and has recently emerged in Shigella sonnei is present in multidrug- and non–multidrug-resistant Escherichia coli isolates from 4 continents. Further spread of mph(A) to Shigella and Salmonella spp. may be expected
The MUSE Hubble Ultra Deep Field Survey X. Ly Equivalent Widths at
We present rest-frame Ly equivalent widths (EW) of 417 Ly
emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the
Very Large Telescope (VLT) at in the Hubble Ultra Deep Field.
Based on the deep MUSE spectroscopy and ancillary Hubble Space Telescope (HST)
photometry data, we carefully measured EW values taking into account extended
Ly emission and UV continuum slopes (). Our LAEs reach
unprecedented depths, both in Ly luminosities and UV absolute
magnitudes, from log(/erg s) 41.0 to 43.0 and
from Muv -16 to -21 (0.01-1.0 ). The EW values span the
range of 5 to 240 \AA\ or larger, and their distribution can be well
fitted by an exponential law exp(EW/). Owing to
the high dynamic range in Muv, we find that the scale factor, ,
depends on Muv in the sense that including fainter Muv objects increases
, i.e., the Ando effect. The results indicate that selection
functions affect the EW scale factor. Taking these effects into account, we
find that our values are consistent with those in the literature
within uncertainties at at a given threshold of Muv
and . Interestingly, we find 12 objects with EW \AA\
above uncertainties. Two of these 12 LAEs show signatures of merger
or AGN activity: the weak CIV emission line. For the remaining
10 very large EW LAEs, we find that the EW values can be reproduced by young
stellar ages ( Myr) and low metallicities ( ). Otherwise, at least part of the Ly emission in these LAEs
needs to arise from anisotropic radiative transfer effects, fluorescence by
hidden AGN or quasi-stellar object activity, or gravitational cooling.Comment: 22 pages, 12 figures, 9 tables, accepted for publication in A&A (MUSE
UDF Series Paper X
Median Surface Brightness Profiles of Lyman- Haloes in the MUSE Extremely Deep Field
We present the median surface brightness profiles of diffuse Ly
haloes (LAHs) around star-forming galaxies by stacking 155 spectroscopically
confirmed Ly emitters (LAEs) at 3<z<4 in the MUSE Extremely Deep Field
(MXDF), with median Ly luminosity . After correcting for a systematic surface brightness
offset we identified in the datacube, we detect extended Ly emission
out to a distance of 270 kpc. The median Ly surface brightness profile
shows a power-law decrease in the inner 20 kpc, and a possible flattening trend
at larger distance. This shape is similar for LAEs with different Ly
luminosities, but the normalisation of the surface brightness profile increases
with luminosity. At distances larger than 50 kpc, we observe strong overlap of
adjacent LAHs, and the Ly surface brightness is dominated by the LAHs
of nearby LAEs. We find no clear evidence of redshift evolution of the observed
Ly profiles when comparing with samples at 4<z<5 and 5<z<6. Our results
are consistent with a scenario in which the inner 20 kpc of the LAH is powered
by star formation in the central galaxy, while the LAH beyond a radius of 50
kpc is dominated by photons from surrounding galaxies.Comment: Submitted to A&
AsrR Is an Oxidative Stress Sensing Regulator Modulating Enterococcus faecium Opportunistic Traits, Antimicrobial Resistance, and Pathogenicity
Oxidative stress serves as an important host/environmental signal that triggers a wide range of responses in microorganisms. Here, we identified an oxidative stress sensor and response regulator in the important multidrug-resistant nosocomial pathogen Enterococcus faecium belonging to the MarR family and called AsrR (antibiotic and stress response regulator). The AsrR regulator used cysteine oxidation to sense the hydrogen peroxide which results in its dissociation to promoter DNA. Transcriptome analysis showed that the AsrR regulon was composed of 181 genes, including representing functionally diverse groups involved in pathogenesis, antibiotic and antimicrobial peptide resistance, oxidative stress, and adaptive responses. Consistent with the upregulated expression of the pbp5 gene, encoding a low-affinity penicillin-binding protein, the asrR null mutant was found to be more resistant to \u3b2-lactam antibiotics. Deletion of asrR markedly decreased the bactericidal activity of ampicillin and vancomycin, which are both commonly used to treat infections due to enterococci, and also led to over-expression of two major adhesins, acm and ecbA, which resulted in enhanced in vitro adhesion to human intestinal cells. Additional pathogenic traits were also reinforced in the asrR null mutant including greater capacity than the parental strain to form biofilm in vitro and greater persistance in Galleria mellonella colonization and mouse systemic infection models. Despite overexpression of oxidative stress-response genes, deletion of asrR was associated with a decreased oxidative stress resistance in vitro, which correlated with a reduced resistance to phagocytic killing by murine macrophages. Interestingly, both strains showed similar amounts of intracellular reactive oxygen species. Finally, we observed a mutator phenotype and enhanced DNA transfer frequencies in the asrR deleted strain. These data indicate that AsrR plays a major role in antimicrobial resistance and adaptation for survival within the host, thereby contributes importantly to the opportunistic traits of E. faecium
Macrolide-Resistant Shigella sonnei
Shigella sonnei UCN59, isolated during an outbreak of S. sonnei in January 2007, was resistant to azithromycin (MIC 64 mg/L). The isolate contained a plasmid-borne mph(A) gene encoding a macrolide 2′-phosphotransferase that inactivates macrolides. Emergence of the mph(A) gene in S. sonnei may limit usefulness of azithromycin for treatment of shigellosis
JWST/NIRSpec Measurements of Extremely Low Metallicities in High Equivalent Width Lyman- Emitters
Deep VLT/MUSE optical integral field spectroscopy has recently revealed an
abundant population of ultra-faint galaxies (15; 0.01 )
at 2.96.7 due to their strong Lyman- emission. The implied
Lyman- equivalent widths are in excess of 100-200 Angstrom, challenging
existing models of normal star formation and implying extremely young ages,
small stellar masses, and a very low amount of metal enrichment. We use
JWST/NIRSpec's microshutter array to follow-up 45 of these galaxies (11h in
G235M/F170LP and 7h in G395M/F290LP), as well as 45 lower-equivalent width
Lyman- emitters. Our spectroscopy covers the range 1.75.1 micron in
order to target strong optical emission lines: H, [OIII], H, and
[NII]. Individual measurements as well as stacks reveal line ratios consistent
with a metal poor nature (230% ) and intense ionizing radiation
fields. The galaxies with the highest equivalent widths of Lyman-, in
excess of 120 Angstrom, have lower gas-phase metallicities than those with
lower equivalent widths. This implies a selection based on Lyman-
equivalent width is an efficient technique for identifying younger, less
chemically enriched systems.Comment: 13 pages, 4 appendices; submitted to AAS Journal
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The MUSE Extremely Deep Field: The cosmic web in emission at high redshift
We report the discovery of diffuse extended Lyα emission from redshift 3.1 to 4.5, tracing cosmic web filaments on scales of 2.5-4 cMpc. These structures have been observed in overdensities of Lyα emitters in the MUSE Extremely Deep Field, a 140 h deep MUSE observation located in the Hubble Ultra-Deep Field. Among the 22 overdense regions identified, five are likely to harbor very extended Lyα emission at high significance with an average surface brightness of 5 × 10-20 erg s-1 cm-2 arcsec-2. Remarkably, 70% of the total Lyα luminosity from these filaments comes from beyond the circumgalactic medium of any identified Lyα emitter. Fluorescent Lyα emission powered by the cosmic UV background can only account for less than 34% of this emission at z ≈ 3 and for not more than 10% at higher redshift. We find that the bulk of this diffuse emission can be reproduced by the unresolved Lyα emission of a large population of ultra low-luminosity Lyα emitters (< 1040 erg s-1), provided that the faint end of the Lyα luminosity function is steep (α ⪅ -1.8), it extends down to luminosities lower than 1038 - 1037 erg s-1, and the clustering of these Lyα emitters is significant (filling factor < 1/6). If these Lyα emitters are powered by star formation, then this implies their luminosity function needs to extend down to star formation rates < 10-4M yr-1. These observations provide the first detection of the cosmic web in Lyα emission in typical filamentary environments and the first observational clue indicating the existence of a large population of ultra low-luminosity Lyα emitters at high redshift. © R. Bacon et al. 2021
Dark galaxy candidates at redshift∼ 3.5 detected with MUSE
Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies
are gas rich but inefficient at forming stars: a “dark galaxy” phase. Here, we report the results of our Multi-Unit
Spectroscopic Explorer (MUSE) survey for dark galaxies fluorescently illuminated by quasars at z > 3. Compared
to previous studies which are based on deep narrowband (NB) imaging, our integral field survey provides a nearly
uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral
information at each location. Thanks to these unique features, we are able to build control samples at large redshift
distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame
equivalent width (EW0) distributions of the Lyα sources detected in proximity to the quasars and in control
samples, we detect a clear correlation between the locations of high-EW0 objects and the quasars. This correlation
is not seen in other properties, such as Lyα luminosities or volume overdensities, suggesting the possible
fluorescent nature of at least some of these objects. Among these, we find six sources without continuum
counterparts and EW0 limits larger than 240 Å that are the best candidates for dark galaxies in our survey at
z > 3.5. The volume densities and properties, including inferred gas masses and star formation efficiencies, of
these dark galaxy candidates are similar to those of previously detected candidates at z ≈ 2.4 in NB surveys.
Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower
limit of t = 60 Myr on the quasar lifetime.peer-reviewe
Circulating microRNAs in sera correlate with soluble biomarkers of immune activation but do not predict mortality in ART treated individuals with HIV-1 infection: A case control study
Introduction: The use of anti-retroviral therapy (ART) has dramatically reduced HIV-1 associated morbidity and mortality. However, HIV-1 infected individuals have increased rates of morbidity and mortality compared to the non-HIV-1 infected population and this appears to be related to end-organ diseases collectively referred to as Serious Non-AIDS Events (SNAEs). Circulating miRNAs are reported as promising biomarkers for a number of human disease conditions including those that constitute SNAEs. Our study sought to investigate the potential of selected miRNAs in predicting mortality in HIV-1 infected ART treated individuals. Materials and Methods: A set of miRNAs was chosen based on published associations with human disease conditions that constitute SNAEs. This case: control study compared 126 cases (individuals who died whilst on therapy), and 247 matched controls (individuals who remained alive). Cases and controls were ART treated participants of two pivotal HIV-1 trials. The relative abundance of each miRNA in serum was measured, by RTqPCR. Associations with mortality (all-cause, cardiovascular and malignancy) were assessed by logistic regression analysis. Correlations between miRNAs and CD4+ T cell count, hs-CRP, IL-6 and D-dimer were also assessed. Results: None of the selected miRNAs was associated with all-cause, cardiovascular or malignancy mortality. The levels of three miRNAs (miRs -21, -122 and -200a) correlated with IL-6 while miR-21 also correlated with D-dimer. Additionally, the abundance of miRs -31, -150 and -223, correlated with baseline CD4+ T cell count while the same three miRNAs plus miR- 145 correlated with nadir CD4+ T cell count. Discussion: No associations with mortality were found with any circulating miRNA studied. These results cast doubt onto the effectiveness of circulating miRNA as early predictors of mortality or the major underlying diseases that contribute to mortality in participants treated for HIV-1 infection
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