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Antibiotic resistance genes as an emerging environmental contaminant
Emerging contaminants, including pharmaceutical and personal care products, are receiving considerable attention owing to their potential to negatively impact the environment and to pose risks to human health. The widespread use of antibiotics and their fate and transport in the environment pose further risks with respect to public health and the development of antibiotic resistant organisms (AROs). While the occurrence of AROs is important, there is increasing interest in antibiotic resistance genes (ARGs). An urgent need exists to improve our understanding of the mechanisms associated with the spread and development of ARGs in both clinical and veterinary settings, the human body (gastrointestinal tract and microbiome) as well as in engineered (wastewater treatment plants) and natural (soil, sediments and water) environments. This review focuses on ARGs as an emerging environmental contaminant. The factors and mechanisms involved in ARG dissemination in a variety of environments are explored in detail. The unique challenges of ARGs with respect to policy-making and environmental monitoring are identified, and recommendations regarding how these challenges might be addressed are provided.
Journal Article
صعود الصين
يقدم كتاب (صعود الصين) والذي قام بتأليفه مايكل إي براون في حوالي (479) صفحة من القطع المتوسط، تقييما لقدرات الصين المتنامية ونواياها، ويعرض الجدل حول التأثير الذي سيترتب على صعود الصين على الأمن في منطقة شرق آسيا والمحيط الهادي، ويقدم سياسات للتعامل مع الصين. ويأخذ المؤلفون النقاش حول الصين بعيدًا عن الشعارات والقوالب النمطية التي ميزت معالجة هذا الموضوع من قبل مما يساعد في تبديد التصريحات التي لا تخلو من الشطط من جانب الذين \"يشيطنون\" الصين لكنها تحذر، في الوقت نفسه، من أن الصين قد تصبح قوة مزعجة.
Book
Comparative genomics of multidrug-resistant Enterococcus spp. isolated from wastewater treatment plants
Background
Wastewater treatment plants (WWTPs) are considered hotspots for the environmental dissemination of antimicrobial resistance (AMR) determinants. Vancomycin-Resistant
Enterococcus
(VRE) are candidates for gauging the degree of AMR bacteria in wastewater.
Enterococcus faecalis
and
Enterococcus faecium
are recognized indicators of fecal contamination in water. Comparative genomics of enterococci isolated from conventional activated sludge (CAS) and biological aerated filter (BAF) WWTPs was conducted.
Results
VRE isolates, including
E. faecalis
(
n
= 24),
E. faecium
(
n
= 11),
E. casseliflavus
(n = 2) and
E. gallinarum
(n = 2) were selected for sequencing based on WWTP source, species and AMR phenotype. The pangenomes of
E. faecium
and
E. faecalis
were both open. The genomic fraction related to the mobilome was positively correlated with genome size in
E. faecium
(
p
< 0.001) and
E. faecalis
(
p
< 0.001) and with the number of AMR genes in
E. faecium
(
p
= 0.005). Genes conferring vancomycin resistance, including
van
A and
van
M (
E. faecium
),
van
G (
E. faecalis
), and
van
C (
E. casseliflavus
/
E. gallinarum
), were detected in 20 genomes. The most prominent functional AMR genes were efflux pumps and transporters. A minimum of 16, 6, 5 and 3 virulence genes were detected in
E. faecium
,
E. faecalis
,
E. casseliflavus
and
E. gallinarum,
respectively. Virulence genes were more common in
E. faecalis
and
E. faecium
, than
E. casseliflavus
and
E. gallinarum
. A number of mobile genetic elements were shared among species. Functional CRISPR/Cas arrays were detected in 13
E. faecalis
genomes, with all but one also containing a prophage. The lack of a functional CRISPR/Cas arrays was associated with multi-drug resistance in
E. faecium
. Phylogenetic analysis demonstrated differential clustering of isolates based on original source but not WWTP. Genes related to phage and CRISPR/Cas arrays could potentially serve as environmental biomarkers.
Conclusions
There was no discernible difference between enterococcal genomes from the CAS and BAF WWTPs.
E. faecalis
and
E. faecium
have smaller genomes and harbor more virulence, AMR, and mobile genetic elements than other
Enterococcus spp
.
Journal Article
Inpainting in Discrete Sobolev Spaces: Structural Information for Uncertainty Reduction
In this article, we introduce a new mathematical functional whose minimization determines the quality of the solution for the exemplar-based inpainting-by-patch problem. The new functional expression includes finite difference terms in a similar fashion to what happens in the theoretical Sobolev spaces: its use reduces the uncertainty in the choice of the most suitable values for each point to inpaint. Moreover, we introduce a probabilistic model by which we prove that the usual principal directions, generally employed for continuous problems, are not enough to achieve consistent reconstructions in the discrete inpainting asset. Finally, we formalize a new priority index and new rules for its dynamic update. The quality of the reconstructions, achieved using a reduced neighborhood size of more than 95% with respect to the current state-of-the-art algorithms based on the same inpainting approach, further provides the experimental validation of the method.
Journal Article
The Effect of Microcystis on the Monitoring of Faecal Indicator Bacteria
The survival of Escherichia coli (E. coli) bacteria, the most common faecal indicator bacteria (FIB), may be significantly affected by cyanobacteria present during a harmful algal bloom (HAB). Therefore, the effect of Microcystis on the survival of FIB E.coli and coliforms was investigated. Microcosms containing two species of Microcystis (M. aeruginosa and M. smithii) were established and then inoculated with four reference strains of E. coli (ATCC 25922, 8739, 51813, and 11775) to explore the cyanobacteria-bacteria dynamics at a laboratory setting. Monitoring over several days showed normal growth of Microcystis, with or without the presence of E. coli. However, Microcystis was shown to dramatically decrease the survival of E. coli over time. Analysis of microcystin production by Microcystis was found to correlate with loss of E. coli, suggesting a toxic effect of microcystins on E. coli bacteria. This phenomenon was also demonstrated for a natural consortium of E. coli and coliform bacteria by inoculating with contaminated lake water. The results indicate that the use of E. coli as FIB may be greatly compromised in the presence of Microcystis spp. such as during a HAB when associated toxins are produced.
Journal Article
A rapid and sensitive fluorimetric β-galactosidase assay for coliform detection using chlorophenol red-β-d-galactopyranoside
We report on a new fluorimetric assay for β-galactosidase (β-gal) and faecal coliform bacteria that utilizes a long-wavelength dye, chlorophenol red-β-
d
-galactopyranoside (CPRG), that has been widely used for colorimetric assays. The novel feature of this new assay is the unexpected development of a large fluorescence response from liberated chorophenol red (CPR) upon complexation with poly-
l
-arginine (pR) in solution. The binding of CPR to pR occurs through the sulphonate group of CPR, causing formation of a charge-transfer complex and up to a 70-fold increase in emission intensity. A major advantage of the assay is the ability to utilize excitation and emission wavelengths in the red end of the spectrum, which avoids common interferences obtained when using UV-absorbing dyes such as 4-methylumbelliferyl-β-
d
-galactopyranoside. We provide data on the utility of CPRG as a fluorimetric reporter for both β-gal and
Escherichia coli
ATCC 25922 and demonstrate optimized reaction conditions for rapid and sensitive detection of
E. coli
at a level of 1 colony-forming unit (cfu)/10 mL after 12 h of culture followed by a 1-h assay, which is below the regulatory limit for testing of recreational water.
Figure
Beta-galacosidase an coliforms can be assayed with CPRG by for mina a fluorescent complex between chlorophenol red and polyarginine
Journal Article
Effects of Environmentally Relevant Residual Levels of Diluted Bitumen on Wild Fathead Minnows (Pimephales promelas)
Transportation of crude oil across North America’s boreal ecozone creates the potential for spills in freshwater where less is known about the sensitivity of resident fish than for marine systems. The sensitivity of wild fathead minnows (FHM) to residual concentrations (ppb range) of the water accommodated fraction (WAF) of diluted bitumen (dilbit) was assessed by exposing them for 21 days followed by a 14 days depuration. Target concentrations were well below detection limits for GC–MS, but were estimated by dilution factor (1:100,000 and 1:1,000,000 WAF:water) to contain less than 0.0003 μg/L of polycyclic aromatic compounds. Confinement and handling stress caused by transfer of wild fish into tanks much smaller than their natural range resulted in mortality and lower body condition among all groups, but interactive effects of oil exposures still resulted in females with smaller cortical alveolar oocytes, and males with larger testicular lobe lumen sizes. Additional studies examining the compounded effects of stress and environmentally relevant oil exposures in wild fishes are needed.
Journal Article
Life cycle assessment of sponge nickel produced by gas atomisation for use in industrial hydrogenation catalysis applications
PURPOSE: This paper presents a cradle-to-grave comparative life cycle assessment (LCA) of new gas atomised (GA) sponge nickel catalysts and evaluates their performance against the current cast and crush standard currently used in the industrial hydrogenation of butyraldehyde to butanol. METHODS: A comparative LCA has been made, accounting for the energy used and emissions throughout the entire life cycle of sponge nickel catalysts—ranging from the upstream production of materials (mainly aluminium and nickel), to the manufacturing, to the operation and finally to the recycling and disposal. The LCA was performed following ISO14040 principles where possible, and subsequently implemented in the software package GaBi 4.3. The CML2001 impact assessment methodology was used, with primary focus on comparing catalysts for equivalent greenhouse gasses generated over their lifetime and their relative global warming potential and secondary focus on acidification potential. This is justified as the lifetime is dominated by energy use in the operational phase, and acidification is dominated by the production of nickel for which existing ISO14040 collected data has been used. A sensitivity analysis was used to provide a number of scenarios and overall environmental performances of the various sponge nickels considered when compared to the existing industrial standard. RESULTS AND DISCUSSION: It was found that the energy and emissions during the operation phase associated with a given catalyst significantly outweigh the primary production, manufacturing and recycling. Primary production of the nickel (and to a lesser extent molybdenum when used as a dopant) also has a significant environmental impact in terms of acidification potential, but this is offset by operational energy savings over the catalysts’ estimated lifetime and end of life recyclability. Finally, the impact of activity improvement and lifetime duration of sponge nickel catalysts was determined as both total life cycle energy for operational use and as a total life cycle global warming potential. CONCLUSIONS: From this assessment, the newly developed, higher activity spongy nickel catalysts produced by gas atomisation could have a significantly lower environmental impact than the current industry standard cast and crush method. Given the potential environmental benefits of such catalysts, applications in other processes that require a catalyst should also be investigated.
Journal Article
Size Effect on the Post-Necking Behaviour of Dual-Phase 800 Steel: Modelling and Experiment
This work investigated the feasibility of using a miniaturised non-standard tensile specimen to predict the post-necking behaviour of the materials manufactured via a rapid alloy prototyping (RAP) approach. The experimental work focused on the determination of the Lankford coefficients (r-value) of dual-phase 800 (DP800) steel and the digital image correlation (DIC) for some cases, which were used to help calibrate the damage model parameters of DP800 steel. The three-dimensional numerical simulations focused on the influence of the size effect (aspect ratio, AR) on the post-necking behaviour, such as the strain/stress/triaxiality evolutions, fracture angles, and necking mode transitions. The modelling showed that although a good correlation can be found between the predicted and experimentally observed ultimate tensile strength (UTS) and total elongation. The standard tensile specimen with a gauge length of 80 mm exhibited a fracture angle of ∼55°, whereas the smaller miniaturised non-standard specimens with low ARs exhibited fractures perpendicular to the loading direction. This shows that care must be taken when comparing the post-necking behaviour of small-scale tensile tests, such as those completed as a part of a RAP approach, to the post-necking behaviours of standard full-size test specimens. However, the modelling work showed that this behaviour is well represented, demonstrating a transition between the fracture angles of the samples between 2.5 and 5. This provides more confidence in understanding the post-necking behaviour of small-scale tensile tests.
Journal Article