Comparing the selective and co-selective effects of different antimicrobials in bacterial communities

This is the author accepted manuscript. The final version is available on open access from Elsevier via the DOI in this recordBacterial communities are exposed to a cocktail of antimicrobial agents, including antibiotics, heavy metals and biocidal antimicrobials such as quaternary ammonium compounds (QACs). The extent to which these compounds may select or co-select for antimicrobial resistance (AMR) is not fully understood. In this study, human associated, wastewater derived, bacterial communities were exposed to either benzalkonium chloride (BAC), ciprofloxacin or trimethoprim at sub-point of use concentrations for one week, in order to determine selective and co-selective potential. Metagenome analyses were performed to determine effects on bacterial community structure and prevalence of antibiotic resistance genes (ARGs) and metal or biocide resistance genes (MBRGS). Ciprofloxacin had the greatest co-selective potential, significantly enriching for resistance mechanisms to multiple antibiotic classes. Conversely, BAC exposure significantly reduced relative abundance of ARGs and MBRGS, including the well characterised qac efflux genes. However, BAC exposure significantly impacted bacterial community structure. This suggests BAC and potentially other QACs did not play as significant a role in co-selection for AMR relative to antibiotics such as ciprofloxacin at below point of use concentrations in this study. This approach can be used to identify priority compounds for further study, to better understand evolution of AMR in bacterial communities exposed to sub-point of use concentrations of antimicrobials.Natural Environment Research Council (NERC)Biotechnology and Biological Sciences Research Council (BBSRC

Novel Insights into Selection for Antibiotic Resistance in Complex Microbial Communities

This is the final version of the article. Available from American Society for Microbiology via the DOI in this record.Recent research has demonstrated that selection for antibiotic resistance occurs at very low antibiotic concentrations in single-species experiments, but the relevance of these findings when species are embedded in complex microbial communities is unclear. We show that the strength of selection for naturally occurring resistance alleles in a complex community remains constant from low subinhibitory to above clinically relevant concentrations. Selection increases with antibiotic concentration before reaching a plateau where selection remains constant over a 2-order-magnitude concentration range. This is likely to be due to cross protection of the susceptible bacteria in the community following rapid extracellular antibiotic degradation by the resistant population, shown experimentally through a combination of chemical quantification and bacterial growth experiments. Metagenome and 16S rRNA analyses of sewage-derived bacterial communities evolved under cefotaxime exposure show preferential enrichment for blaCTX-M genes over all other beta-lactamase genes, as well as positive selection and co-selection for antibiotic resistant, opportunistic pathogens. These findings have far-reaching implications for our understanding of the evolution of antibiotic resistance, by challenging the long-standing assumption that selection occurs in a dose-dependent manner.Aimee K. Murray was supported by a BBSRC/AZ CASE Studentship, BB/L502509/1. Lihong Zhang was supported by Natural Environment Research Council grant NE/ M011259/1. Chemical quantification was performed at the University of Exeter Streatham Campus by Maciek Trnzadel and Malcolm Hetheridge, cofunded by Astra Zeneca Global SHE and the University of Exeter

Chromosome manipulation and its exploitation in the genetics and breeding of wheat

Chromosome manipulation in bread wheat uses aneuploid methods to transfer whole chromosomes or segments of chromosomes from one variety into another, or from related species into wheat. These methods have been applied extensively so that an incomparable range of aneuploid and whole chromosome substituion lines now exists in wheat. This has given rise to some of the most detailed genetic studies of economic characters carried out on a crop plant and include the analysis of the semi-dwarfism of Mediterranean wheat and the location of genes affecting grain protein amounts. The applications of this knowledge to wheat breeding is considered as well as the potential that these methods have for promoting the understanding of plant processes and of the molecular organisation of the wheat genome.C. N. LAW, J. W. SNAPE and A. J. WORLAND, Plant Breeding Institute, Maris Lane, Trumpington, Cambridge CB2 2LQ, U. K

The importance of passive integrated transponder (PIT) tags for measuring life-history traits of sea turtles

Capture-mark-recapture studies rely on the identification of individuals through time, using markers or tags, which are assumed to be retained. This assumption, however, may be violated, having implications for population models. In sea turtles, individual identification is typically based on external flipper tags, which can be combined with internal passive integrated transponder (PIT) tags. Despite the extensive use of flipper tags, few studies have modelled tag loss using continuous functions. Using a 26-year dataset for sympatrically nesting green (Chelonia mydas) and loggerhead (Caretta caretta) turtles, this study aims to assess how PIT tag use increases the accuracy of estimates of life-history traits. The addition of PIT tags improved female identification: between 2000 and 2017, 53% of green turtles and 29% of loggerhead turtles were identified from PIT tags alone. We found flipper and PIT tag losses were best described by decreasing logistic curves with lower asymptotes. Excluding PIT tags from our dataset led to underestimation of flipper tag loss, reproductive periodicity, reproductive longevity and annual survival, and overestimation of female abundance and recruitment for both species. This shows the importance of PIT tags in improving the accuracy of estimates of life-history traits. Thus, estimates where tag loss has not been corrected for should be interpreted with caution and could bias IUCN Red List assessments. As such, long-term population monitoring programmes should aim to estimate tag loss and assess the impact of loss on life-history estimates, to provide robust estimates without which population models and stock assessments cannot be derived accurately

Fly ash-derived MCM-41 as a low-cost silica support for polyethyleneimine in post-combustion CO2 capture

The mesoporous silicate molecular sieve, MCM-41, has been synthesized from pulverized coal fly ash (PFA), where the silicate filtrate used is a by-product from hydrothermal zeolite production. Rice husk ash was also used for comparison but fusion with sodium hydroxide was used to prepare the silicate filtrate, along similar lines to earlier reports of using PFA as a precursor for MCM-41 synthesis. The MCM-41 samples are chemically and mineralogically similar to a commercially available sample, but with higher pore volumes dominated by mesopores (0.92–1.13 cf. 0.88 cm3 g−1). After polyethyleneimine (PEI) impregnation for CO2 capture, the ash derived MCM-41 samples displayed higher uptakes than the commercial sample with the maximum achievable PEI loading of 60 Wt.% PEI (dry basis) before particle agglomeration occurs, approximately 13 compared to 11 Wt.%, respectively, the latter being comparable to earlier reports in the literature. The PFA sample that displays the fastest kinetics to achieve 90% of the equilibrium uptake had the largest mesopore volume of 1.13 cm3 g−1. Given the PFA-derived MCM-41 uses a waste silicate solution for hydrothermal preparation and no prior preparation is needed, production costs are estimated to be considerable lower where silicate solutions need to be prepared by base treatment, even if ash is used, as for the RHA derived MCM-41 used here

Meanings of epilepsy in its sociocultural context and implications for stigma: Findings from ethnographic studies in local communities in China and Vietnam

We investigated beliefs about the causes, course, and treatment of epilepsy and its impact on quality of life (QOL) in key target groups, using “mini-ethnographies” involving 141 in-depth interviews and 12 focus groups in China, and 84 in-depth interviews and 16 focus groups in Vietnam. Data were analyzed thematically, using a qualitative data analysis package. In both countries, beliefs about causes and triggers of epilepsy and seizures were a complex interweaving of Western, traditional, and folk medicine concepts. Epilepsy was understood to be chronic, not curable, but controllable, and was seen as enormously socially disruptive, with wide-ranging impact on QOL. Our findings suggest a more “embodied” and benign set of theories about epilepsy than in some other cultural contexts; nonetheless, people with epilepsy are still seen as having low social value and face social rejection. By exploring meanings attached to epilepsy in these two cultural contexts, we have clarified reasons behind previously documented negative attitudes and foci for future intervention studies