ARPHA Conference Abstracts :
Conference Abstract
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Corresponding author: Louise Weaver (louise.weaver@esr.cri.nz)
Received: 27 Jun 2023 | Published: 23 Oct 2023
© 2023 Louise Weaver, Erin McGill, Panan Sitthirit, Judith Webber, Phil Abraham, Murray Close
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Weaver L, McGill E, Sitthirit P, Webber J, Abraham P, Close M (2023) Pathogen survival in groundwater: Influence of redox and organic matter. ARPHA Conference Abstracts 6: e108697. https://doi.org/10.3897/aca.6.e108697
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Microbial pathogen survival within the environment can be variable and can depend on many criteria, including environmental conditions e.g. oxygen concentration, temperature, pH, sunlight, etc. (e.g.,
To elucidate these discrepancies two experiments were designed: The first, hypothesised that, due to Campylobacters' low tolerance to high oxygen levels, survival in oxic (dissolved oxygen (DO) levels over 5 mg per L) would be less than in anoxic groundwater (DO levels below 2 mg per L). The second hypothesised that the survival of the pathogen Salmonella typhimurium, in groundwater, will be enhanced by organic carbon.
METHODS
Campylobacter experiment:
Campylobacter jejuni isolated from the Havelock North drinking water source was used (designated HN16) (
Salmonella experiment:
For this experiment, environmental isolates were used rather than laboratory strains. Salmonella, isolated from a stream in Wellington, New Zealand, was identified as Salmonella enterica serovar Typhimurium. The Escherichia coli used was a phylogroup A, isolated from stream sediment in Whangarei Falls, New Zealand.
Mesocosm experiments were established containing groundwater (oxic and anoxic for Campylobacter experiment and ultrafiltered, groundwater, groundwater amended with 1% or 10% dissolved organic carbon (DOC). pH, dissolved oxygen (DO), and temperature were monitored over the experimental period. The temperature was maintained at 12-14°C during both experiments.
Samples (5 mL) of the groundwater from each jar were taken aseptically at set time points over the experimental period. Samples were then serially diluted in sterile peptone water to give a dilution series from 10-1 to 10-4. Samples were analysed by plating onto selective media.
RESULTS
Campylobacter experiment:
The results presented demonstrated differences in the survival of the two Campylobacter strains tested and differences in survival of Campylobacter HN16 depending on groundwater type. Fig.
Salmonella experiment:
Die-of rates for Salmonella were similar over the course of the experiment when no or low levels of DOC were present (Fig.
Salmonella and E. coli survival in different groundwaters. UF denotes ultrafiltered groundwater, low DOC is 1% dissolved organic carbon, and high DOC is 10% dissolved organic carbon. Control counts are shown as comparison to treatments
Conclusions and significance
Both experiments demonstrated the survival of pathogenic microorganisms in varying groundwater conditions. The variation in the outbreak strain Campylobacter compared to the type strain indicated variation within species that may lead to enhanced survival in the environment. The Salmonella experiment indicated the presence of additional organic carbon can enhance the survival of pathogens in groundwater. In addition, the variation between the microbial indicator E. coli and Salmonella provides evidence of differences in the survival of microbes in the environment and indicates caution is needed when considering the survival of pathogens in groundwater if reliance is made on microbial indicator organisms.
Murray Close
2nd Joint Symposium of the International Societies for Environmental Biogeochemistry & Subsurface Microbiology, Banff, Alberta, Canada, 22-28th October 2023
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