Browsing by Author "Horswell J"

Now showing 1 - 5 of 5
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    Co-Selection of Bacterial Metal and Antibiotic Resistance in Soil Laboratory Microcosms.
    (18/04/2023) Heydari A; Kim ND; Biggs PJ; Horswell J; Gielen GJHP; Siggins A; Taylor MD; Bromhead C; Palmer BR
    Accumulation of heavy metals (HMs) in agricultural soil following the application of superphosphate fertilisers seems to induce resistance of soil bacteria to HMs and appears to co-select for resistance to antibiotics (Ab). This study aimed to investigate the selection of co-resistance of soil bacteria to HMs and Ab in uncontaminated soil incubated for 6 weeks at 25 °C in laboratory microcosms spiked with ranges of concentrations of cadmium (Cd), zinc (Zn) and mercury (Hg). Co-selection of HM and Ab resistance was assessed using plate culture on media with a range of HM and Ab concentrations, and pollution-induced community tolerance (PICT) assays. Bacterial diversity was profiled via terminal restriction fragment length polymorphism (TRFLP) assay and 16S rDNA sequencing of genomic DNA isolated from selected microcosms. Based on sequence data, the microbial communities exposed to HMs were found to differ significantly compared to control microcosms with no added HM across a range of taxonomic levels.
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    Co-selection of Heavy Metal and Antibiotic Resistance in Soil Bacteria from Agricultural Soils in New Zealand
    (MDPI (Basel, Switzerland), 2022-02-04) Heydari A; Kim ND; Horswell J; Gielen G; Siggins A; Taylor M; Bromhead C; Palmer BR
    Accumulation of trace elements (including heavy metals) in soil from usage of superphos-phate fertilisers induces resistance of soil bacteria to trace elements of environmental concern (TE-oEC) and may co‐select for resistance to antibiotics (Ab). This study aimed to investigate selection of co‐resistance of soil bacteria to Cd, Zn and Hg, and Ab in soils with varied management histories. Genetic diversity of these bacteria and horizontal transfer of Cd resistance genes (cadA and czcA) were also investigated. Soils with either pastoral and arable management histories and either high levels of Cd and Zn, or indigenous bush with background levels of these TEoEC from the Waikato region, New Zealand were sampled. Plate culturing with a range of TEoEC and Ab concentrations, Pollution Induced Community Tolerance (PICT) assay, antibiotic sensitivity, terminal restriction fragment length polymorphism (TRFLP) and horizontal gene transfer (HGT) analyses were em-ployed to investigate co‐selection of TEoEC and Ab resistance. Higher levels of bacterial resistance to TEoEC and Ab correlated with higher levels of TEoEC in soil. Bacterial community structures were altered in soils with high TEoEC levels. Cd resistance genes were transferred from donor bacterial isolates, to recipients and the transconjugants also had resistance to Zn and/or Hg and a range of Ab.
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    Effects of selected emerging contaminants found in wastewater on antimicrobial resistance and horizontal gene transfer
    (Elsevier B.V., 2023-08-29) van Hamelsveld S; Jamali-Behnam F; Alderton I; Kurenbach B; McCabe AW; Palmer BR; Gutiérrez-Ginés MJ; Weaver L; Horswell J; Tremblay LA; Heinemann JA
    The widespread use of emerging contaminants (ECs) may be compounding the problem of antibiotic resistance. Various non-antibiotic pollutants have been shown to alter bacterial responses to antibiotics and increase horizontal transfer of antimicrobial resistance (AMR) genes. ECs include components of medicines, foods, disinfectants, personal care products and agrichemicals. ECs concentrate in some environments such as in wastewater, where the pollutants and pathogenic microorganisms mix. We investigated the effects on antibiotic resistance and gene transfer of nine ECs and one commercial product formulation (Roundup). We used the bacterium Salmonella enterica serovar Typhimurium and the antibiotics ampicillin and gentamicin as indicators of the effects of antibiotic-EC co-exposures. We measured intra- (Escherichia coli) and interspecies (E. coli x S. enterica) conjugation frequencies during exposure to ECs. Interestingly, the observed effect could change at different antibiotic concentrations. Exposures to increasing concentrations of ECs was associated with increased conjugative transmission within species, but rarely increased interspecies transmission. We report the first test ever of clotrimazole on AMR and horizontal gene transfer and a newly described effect of dimethyl sulfoxide (DMSO), often used as a solvent for organic compounds.
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    Environmental drivers of antimicrobial resistance – cadmium contamination & antibiotic resistance in soil samples from a rural airstrip.
    (2023-12-05) Heydari A; Kim N; Biggs P; Horswell J; Gielen G; Siggins A; Bromhead C; Palmer B
    Environmental contamination with both inorganic and organic compounds is a growing problem globally. In this study we investigated links between heavy metal contamination of soil and selection for antibiotic resistance in soil bacteria. Soil samples taken at 10 m intervals along the length of a 70 m transect of a rural airstrip used for aerial topdressing located in Belmont Regional Park near Wellington were analysed for heavy metal content and resistance profiles of heterotrophic bacteria cultured were characterised. A gradient of cadmium contamination (a known contaminant of superphosphate fertiliser) ranging from 1.14 to 7.20 mg kg-1 of dry soil was detected in the samples. Total bacterial counts were significantly reduced at the most heavily contaminated subsites, with >60% of isolates resistant to 0.01 mM CdCl2. The ratio of antibiotic resistant isolates to total CFU was significantly higher at the most contaminated compared to the least contaminated subsite for five common antibiotics. Metagenomic analysis of total DNA from three subsites showed significantly different profiles at all taxonomic levels. This suggests environmental contamination with heavy metals may be a significant and under-appreciated driver of selection for antimicrobial resistance.
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    The role of emerging organic contaminants in the development of antimicrobial resistance
    (KeAi Communications Co. Ltd. Publishing services by Elsevier BV on behalf of KeAi Communications Co Ltd, 2021-08-05) Alderton I; Palmer BR; Heinemann JA; Pattis I; Weaver L; Gutiérrez-Ginés MJ; Horswell J; Tremblay LA
    Antimicrobial resistance (AMR) threatens human and ecological health worldwide. Unless major changes occur across the human, animal and environmental sectors, the problem will continue to expand. An important component of AMR that deserves greater attention is the influence of emerging organic contaminants (EOCs) – ubiquitous compounds found, amongst others, in pharmaceuticals, personal care products, food, industrial and agricultural products, plastics and building materials. EOCs are widely used and can accumulate in the environment from varied sources, predominantly via waste streams. EOCs can interact with microbial communities potentially leading to the emergence and spread of AMR. Biocides and pharmaceuticals have been demonstrated to promote AMR development. Antimicrobial resistance is a multi-faceted problem that requires input from all sectors, with robust strategies and policies needed to make headway with solving the issues of this important threat.