17
Sep
Pesticide Residue Impacts Microbial Health
(Beyond Pesticides, September 17, 2024) Today, International Microorganism Day, is a prime moment to focus on the complexity of billions of living beings that establish the foundation of land management and food production. Organic advocates, community members, and farmers identify the protection and enhancement of biological diversity in the soil as a key goal, especially in light of mounting concerns over rising microbial resistance to chemical-intensive practices.
A recent article in British Journal of Environmental Sciences points to several microbial populations adversely affected by pesticide-contaminated soil on various farmland plots in Nigeria. There are significant variations in bacteria presence between pesticide-treated and control plots, with a lab analysis finding “[s]eventy-five percent (75%) of pesticide residue was detected in the soil samples,†which includes paraquat dichloride, endosulfan, diazinon, and N-(phosponomethyl)glycine [glyphosate]. This report builds on years of research from higher education institutions worldwide, including participatory research centering applied experiments on farmland, demonstrating the consequences of relying on pesticide-intensive agriculture and land management.
The main goal of this report is to “determine the influence of pesticide contamination on the microbial population, physiochemical parameters and pesticide residue of soil of selected farmlands in Otuoke, Bayelsa State, Nigeria.†Researchers document the presence of eleven different bacteria isolates and sixteen different fungi across four different farmland sites (with one site serving as the control in which no pesticides were sprayed during the course of the experiment), since researchers identified in previous research that several selected bacteria “thrive as a response to environmental stress, possibly induced by pesticide contamination.†[The sites are identified as Bakery 1, Bakery 2, Dorcas, PGS, and Control.]
Researchers found high variability between levels of different bacteria and fungi across the experimental and control sites, indicating that pesticide contamination influences microbial activity. Across all five sites, there was relatively higher microbial activity at the control site corresponding with limited pesticide residue (except a small presence of paraquat across all sites). For example, the highest occurrence of beneficial fungi including Trichoderma species (14.3%), Lichtheimia hyalospora (28.6%), Penicillium camemberti (14.3%), as well as beneficial bacteria including Streptomyces coelicolor (29.4%), were found at the control site.
Some additional main takeaways include:
- “Pseudomonas aeruginosa shows a significant presence at Bakery 2 (10.4%) and Control (40.6%), but it is absent at the other farmlands. Since Pseudomonas aeruginosa is known for its adaptability and can thrive in various conditions, its prevalence at Bakery 2 might indicate its ability to thrive despite the contamination of the pesticides (Diazinon) and environmental conditions in this farmland [].â€
- “Rhodotorula glutinis is prevalent at Bakery 1 (82.3%), Bakery 2 (77.5%), and Dorcas (81.1%). Rhodotorula species are known to be resilient to various stress factors, including pesticides [].â€
These bacteria include Pseudomonas aeruginosa, Streptomyces coelicolor, Streptomyces scabies, Actinomyces isrealii, Streptomyces aureofaciens, Streptomyces griseus, Nocardia asteroids, Proteus vulgaris, Streptococcus pyogenes, Klebsiella pneumoniae, and Bacillus subtilis. The fungi types include Alternaria alternata, Fusarium oxysporum, Candida tropicalis, Rhodotorula glutinis, Lichtheimia hyalospora, Rhizopus arrhizus, Fusarium chlamydosporium, Rhizopus stolonifera, Penicillium camemberti, Fusarium fumonisin, Trichoderma spp, Aspergillus flavus, Phytophthora occultans, Penicillium italicum, Aspergillus niger, and Cladosporium hyalospora.
This study was published on August 17, 2024 in a publication of the European Center for Research Training and Development in the United Kingdom. The main authors specialize in microbiology and botany from Nigerian universities, including Federal University Otuoke, University of Lagos, and Rivers State University. One of the leading researchers, Omokaro Obire, PhD, is a professor of environmental microbiology at Rivers State University and has authored approximately twenty studies garnering over 1,600 citations since her first publication in 1996. She is also the editor-in-chief of International Journal of Microbiology and Applied Sciences — the official journal for Rivers State University.
The increased use of antimicrobial products alarms scientists, public health professionals, farmers, and various other stakeholders concerned with holistic environmental health. The Food and Drug Administration (FDA) warned nine manufacturers and distributors in December last year to stop selling unapproved and misbranded antimicrobial animal drugs over concerns about co-resistance and cross-resistance mechanisms. Antimicrobial resistance (AMR) is a global crisis, as recorded in a 2019 study published in Science where researchers identified hotspots of resistance in northeastern India, northeastern China, northern Pakistan, Iran, eastern Turkey, the south coast of Brazil, Egypt, the Red River Delta in Vietnam, and the areas surrounding Mexico City and Johannesburg. Additional studies have documented antimicrobial pesticide exposure to cause adverse impacts regarding gut microbiome health and fungal resistance leading to deadly infections, among others. According to the study published in Nature Communications, triclosan (antibacterial) worsens the effects of ulcerative colitis, an inflammatory bowel disease (IBD), through the retention of harmful bacteria. On the matter of fungal resistance, a recent study conducted by scientists at the University of Georgia finds fungicide use in agriculture is driving the spread of multi-fungicide resistant human pathogens.Â
As Beyond Pesticides has reported previously on microbial resistance to pesticides, resistant genes move from the farm after being treated with antibiotics or antifungals—or other chemicals like the weed killer glyphosate, which has antibiotic properties—through society as the efficacy of antibiotic and antifungal medicines declines. A pool of resistant soil bacteria or commensal gut bacteria can provide the genetic material for resistance in human pathogens. The basic mechanism is as follows. If bacteria on the plants and in the soil are sprayed with an antibiotic, those organisms with genes for resistance to the chemical increase compared to those susceptible to the antibiotic. These chemical sprays increase the frequency of resistant genotypes by killing those susceptible to the antibiotic and spare the others. Those genes may be taken up by other bacteria through a number of mechanisms, collectively known as “horizontal gene transfer.†(See Daily News.)
In the early months of the Covid-19 pandemic, there were wide concerns about the health impacts of contracting the disease and public officials attempting to mitigate risk. Following reporting from local news outlets amplified by Beyond Pesticides and advocacy led by the Tennessee Black Caucasus of State Legislators, free masks were recalled in the state upon discovery that they were treated with a toxic antimicrobial chemical. (See Pesticides and You article, “Antimicrobial†Facemask Unnecessarily Toxic, here for more information). Public health officials have warned about the increased risk of future global pandemics amidst increasing antimicrobial resistance, in a 2020 study published in The Lancet. For more research on the impacts of antimicrobial resistance and antimicrobial products, see Daily News section on antimicrobials as well as our dedicated page on Disinfectants, Sanitizers, and Microbials.
While celebrating International Microorganism Day today, this month is also National Organic Month. To improve the viability and expand the reach of organic agricultural systems in the United States, communities should feel empowered to engage in strengthening federal organic standards, research, and policies in service of public health, biodiversity, and climate resilience.
See Keeping Organic Strong to access opportunities to engage in the Fall 2024 National Organic Standards Board public comments process before the deadline on September 30.
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All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: British Journal of Environmental Sciences
