Complete genome sequence of Bradyrhizobium ottawaense strain MIAE 01942 isolated from soybean nodules grown in antibiotic-amended soil.

Bradyrhizobium ottawaense MIAE 01942 is a symbiotic nitrogen-fixing bacterium isolated from the root nodules of soybeans grown in agricultural soils amended with veterinary antibiotics. The genome consists of a single 8.45 Mb circular chromosome that harbors genes involved in nitrogen fixation, denitrification, and antibiotic and metal resistance.

Persistence and evidence for accelerated biodegradation of streptomycin in agricultural soils.

Some antibiotics are used for the treatment of various bacterial crop diseases, and there is a concern that this practice may represent a selection pressure that increases the reservoir of antibiotic resistance carried by bacteria in crop production systems. Since the 1950s the aminoglycoside antibiotic streptomycin has been widely used for the treatment of some bacterial crop diseases such as fire blight in apples and pears. Following application, the time that bacteria will be exposed to the antibiotic, and therefore the pressure for selection of resistance, will vary according to the environmental persistence of the antibiotic. In the present study, the dissipation of streptomycin was examined in soils supplemented with 5 mg streptomycin/kg soil and incubated for 21 days under laboratory conditions. The impact of two key rate-controlling variables, soil texture (sandy loam, loam, clay loam) and temperature (4, 20, 30 °C) on streptomycin persistence were explored. -Robust methods for streptomycin extraction and analysis by LC-MS/MS were developed. Streptomycin dissipation followed first order kinetics, with the time to dissipate 50 % of the parent compound (DT50) in soils of varying texture incubated at 20 °C ranging from about seven to 15 days. In contrast, the DT50 of streptomycin in autoclaved loam soil incubated at 20 °C was about 111 days. At 4 °C the DT50 ranged from 49 to 137 days. Under no incubation conditions were any extractable transformation products obtained. Streptomycin was dissipated significantly more rapidly in field soil that had a prior history of exposure to the antibiotic than in soil that did not. Taken together, these results indicate that streptomycin is amenable to biodegradation in agricultural soils with DT50s of several days when temperature is permissive.

Dynamic effects of black soldier fly larvae meal on the cecal bacterial microbiota and prevalence of selected antimicrobial resistant determinants in broiler chickens.

BACKGROUND: We had earlier described the growth-promoting and -depressive effects of replacing soybean meal (SBM) with low (12.5% and 25%) and high (50% and 100%) inclusion levels of black soldier fly larvae meal (BSFLM), respectively, in Ross x Ross 708 broiler chicken diets. Herein, using 16S rRNA gene amplicon sequencing, we investigated the effects of replacing SBM with increasing inclusion levels (0-100%) of BSFLM in broiler diets on the cecal bacterial community composition at each growth phase compared to broilers fed a basal corn-SBM diet with or without the in-feed antibiotic, bacitracin methylene disalicylate (BMD). We also evaluated the impact of low (12.5% and 25%) inclusion levels of BSFLM (LIL-BSFLM) on the prevalence of selected antimicrobial resistance genes (ARGs) in litter and cecal samples from 35-day-old birds. RESULTS: Compared to a conventional SBM-based broiler chicken diet, high (50 to100%) inclusion levels of BSFLM (HIL-BSFLM) significantly altered the cecal bacterial composition and structure, whereas LIL-BSFLM had a minimal effect. Differential abundance analysis further revealed that the ceca of birds fed 100% BSFLM consistently harbored a ~ 3 log-fold higher abundance of Romboutsia and a ~ 2 log-fold lower abundance of Shuttleworthia relative to those fed a BMD-supplemented control diet at all growth phases. Transient changes in the abundance of several potentially significant bacterial genera, primarily belonging to the class Clostridia, were also observed for birds fed HIL-BSFLM. At the finisher phase, Enterococci bacteria were enriched in the ceca of chickens raised without antibiotic, regardless of the level of dietary BSFLM. Additionally, bacitracin (bcrR) and macrolide (ermB) resistance genes were found to be less abundant in the ceca of chickens fed antibiotic-free diets, including either a corn-SBM or LIL-BSFLM diet. CONCLUSIONS: Chickens fed a HIL-BSFLM presented with an imbalanced gut bacterial microbiota profile, which may be linked to the previously reported growth-depressing effects of a BSFLM diet. In contrast, LIL-BSFLM had a minimal effect on the composition of the cecal bacterial microbiota and did not enrich for selected ARGs. Thus, substitution of SBM with low levels of BSFLM in broiler diets could be a promising alternative to the antibiotic growth promoter, BMD, with the added-value of not enriching for bacitracin- and macrolide-associated ARGs.

Impacts of climate change on indirect human exposure to pathogens and chemicals from agriculture: [review] / Impactos das mudanças climáticas sobre a exposição humana indireta a elementos patogênicos e químicos da agricultura: [revisão]

Climate change is likely to affect the nature of pathogens/ chemicals in the environment and their fate and transport. We assess the implications of climate change for changes in human exposures to pathogens/chemicals in agricultural systems in the UK and discuss the effects on health impacts, using expert input and literature on climate change; health effects from exposure to pathogens/chemicals arising from agriculture; inputs of chemicals/pathogens to agricultural systems; and human exposure pathways for pathogens/chemicals in agricultural systems. We established the evidence base for health effects of chemicals/pathogens in the agricultural environment; determined the potential implications of climate change on chemical/pathogen inputs in agricultural systems; and explored the effects of climate change on environmental transport and fate of various contaminants. We merged data to assess the implications of climate change in terms of indirect human exposure to pathogens/chemicals in agricultural systems, and defined recommendations on future research and policy changes to manage adverse increases in risks.

É provável que a mudança climática afete a natureza, destino e transporte de elementos patogênicos/químicos no ambiente . Avaliamos as implicações das mudanças climáticas em mudanças na exposição humana a elementos patogênicos/químicos nos sistemas agrícolas no Reino Unido e discutimos os efeitos sobre os impactos à saúde, usando a contribuição de especialistas e literatura; efeitos à saúde da exposição a elementos patogênicos/químicos provenientes da agricultura; introdução de elementos químicos/patogênicos e caminhos de exposição humana a elementos patogênicos/químicos nos sistemas agrícolas. Definimos a base de evidência para efeitos de saúde de elementos químicos/patogênicos no ambiente agrícola; determinamos as possíveis implicações da mudança climática na introdução de elementos químicos/patogênicos nos sistemas agrícolas; e exploramos os efeitos da mudança climática no transporte ambiental e destino de diversos contaminantes. Consolidamos dados para avaliar as implicações das mudanças climáticas em relação à exposição humana indireta a elementos patogênicos/químicos nos sistemas agrícolas e recomendamos futuras pesquisas e mudanças políticas para administrar aumentos adversos nos riscos.