ORCID Profile
0000-0001-5852-3902
Current Organisations
University of South Australia
,
University of South Australia Future Industries Institute
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Publisher: Elsevier BV
Date: 11-2022
DOI: 10.1016/J.CHEMOSPHERE.2022.135820
Abstract: Pesticides are known to affect non-targeted soil microorganisms. Still, studies comparing the effect of multiple pesticides on a wide range of microbial endpoints associated with carbon cycling are scarce. Here, we employed fluorescence enzymatic assay and real-time PCR to evaluate the effect of 20 commercial pesticides, applied at their recommended dose and five times their recommended dose, on soil carbon cycling related enzymatic activities (α-1,4-glucosidase, β-1,4-glucosidase, β-d-cellobiohydrolase and β-xylosidase), and on the absolute abundance of functional genes (cbhl and chiA), in three different South Australian agricultural soils. The effects on cellulolytic and chitinolytic microorganisms, and the total microbial community composition were determined using shotgun metagenomic sequencing in selected pesticide-treated and untreated s les. The application of insecticides significantly increased the cbhl and chiA genes absolute abundance in the acidic soil. At the community level, insecticide fipronil had the greatest stimulating effect on cellulolytic and chitinolytic microorganisms, followed by fungicide metalaxyl-M and insecticide imidacloprid. A shift towards a fungal dominated microbial community was observed in metalaxyl-M treated soil. Overall, our results suggest that the application of pesticides might affect the soil carbon cycle and may disrupt the formation of soil organic matter and structure stabilisation.
Publisher: Wiley
Date: 30-09-2019
DOI: 10.1111/VDE.12794
Abstract: Multidrug-resistant pathogens present a major global challenge in antimicrobial therapy and frequently complicate otitis externa in dogs. In vitro efficacy of oregano oil, thyme oil and their main phenolic constituents against bacterial and fungal isolates associated with canine otitis externa were investigated. It was hypothesized that the main phenolic components would have greater antimicrobial activity compared to the relative essential oil. Antimicrobial susceptibility testing was performed using broth microdilution with spot-plating technique to determine minimum inhibitory and bactericidal/fungicidal concentrations (MICs, MBCs and MFCs). A time-kill kinetics assay was performed to confirm the bactericidal and fungicidal activity of the oils and their phenolic constituents. One hundred bacterial and fungal isolates, including meticillin-susceptible Staphylococcus pseudintermedius (n = 10), meticillin-resistant S. pseudintermedius (n = 10), β-haemolytic Streptococcus spp. (n = 20), Pseudomonas aeruginosa (n = 20 including 10 isolates resistant to one or two antimicrobials), Proteus mirabilis (n = 20) and Malassezia pachydermatis (n = 20) from dogs with otitis externa were used. Oregano oil, thyme oil, carvacrol and thymol exhibited antibacterial activity against all bacterial and fungal isolates tested. MIC Oregano oil, thyme oil, carvacrol and thymol showed good in vitro bactericidal and fungicidal activity against 100 isolates from dogs with otitis externa, including some highly drug-resistant isolates. These essential oils and their main phenolic constituents have the potential to be further investigated in vivo for the treatment of canine otitis externa.
Publisher: Oxford University Press (OUP)
Date: 21-05-2019
DOI: 10.1111/JAM.14298
Abstract: The antimicrobial activity of cinnamon essential oil and cinnamaldehyde against bacterial and fungal pathogens associated with canine otitis externa, as well as the effect of their combination with EDTA were investigated. Antimicrobial susceptibility testing was performed using the broth microdilution method while spot-plating technique was used to determine their bactericidal activity. Time-kill kinetics and checkerboard assays were performed to confirm the bactericidal activity and combination effects of the compounds. Cinnamon oil and cinnamaldehyde exhibited antimicrobial activity against Gram-positive and Gram-negative pathogens, as well as Malassezia pachydermatis. Synergistic interaction was shown when EDTA (672 μg ml Cinnamon essential oil and cinnamaldehyde, either used alone or in combination with EDTA, were effective against the causative micro-organisms of canine otitis externa. The data suggest that cinnamaldehyde could be a promising antimicrobial agent against canine otitis externa. This study shows that cinnamon essential oil and cinnamaldehyde, especially the latter, could be used in combination with EDTA as novel treatment for sensitive and resistant bacterial and fungal pathogens involved in canine otitis externa.
Publisher: Elsevier BV
Date: 02-2022
DOI: 10.1016/J.SCITOTENV.2021.150734
Abstract: The extensive application of pesticides in agriculture raises concerns about their potential negative impact on soil microorganisms, being the key drivers of nutrient cycling. Most studies have investigated the effect of a single pesticide on a nutrient cycling in single soil type. We, for the first time, investigated the effect of 20 commercial pesticides with different mode of actions, applied at their recommended dose and five times their recommended dose, on nitrogen (N) microbial cycling in three different agricultural soils from southern Australian. Functional effects were determined by measuring soil enzymatic activities of β-1,4-N-acetyliglucosaminidase (NAG) and l-leucine aminopeptidase (LAP), potential nitrification (PN), and the abundance of functional genes involved in N cycling (amoA and nifH). Effects on nitrifiers ersity were determined with licon sequencing. Overall, the pesticides effect on N microbial cycling was dose-independent and soil specific. The fungicides flutriafol and azoxystrobin, the herbicide chlorsulfuron and the insecticide fipronil induced a significant reduction in PN and β-1,4-N-acetylglucosaminidase activity (P < 0.05) (NAG) in the alkaline loam soil with low organic carbon content i.e. a soil with properties which typically favors pesticide bioavailability and therefore potential toxicity. For the nitrifier community, the greatest pesticide effects were on the most dominant Nitrososphaeraceae (ammonia-oxidizing archaea AOA) whose abundance increased significantly compared to the less dominant AOA and other nitrifiers. The inhibiting effects were more evident in the soil s les treated with fungicides. By testing multiple pesticides in a single study, our findings provide crucial information that can be used for pesticide hazard assessment.
Publisher: Frontiers Media SA
Date: 25-04-2019
Publisher: Elsevier BV
Date: 08-2023
Location: Australia
No related grants have been discovered for Jowenna Sim.