Disinfection and removal of human pathogenic bacteria in arctic waste stabilization ponds

Asymptomatic Carriage of Listeria monocytogenes by Animals and Humans and Its Impact on the Food Chain

Humans and animals can become asymptomatic carriers of Listeria monocytogenes and introduce the pathogen into their environment with their feces. In turn, this environmental contamination can become the source of food- and feed-borne illnesses in humans and animals, with the food production chain representing a continuum between the farm environment and human populations that are susceptible to listeriosis. Here, we update a review from 2012 and summarize the current knowledge on the asymptomatic carrier statuses in humans and animals. The data on fecal shedding by species with an impact on the food chain are summarized, and the ways by which asymptomatic carriers contribute to the risk of listeriosis in humans and animals are reviewed.

Study of coliforms and Clostridium bacteria inactivation in wastewaters by a pilot photolysis process and by the maturation lagoons of a low-cost nature-based WWTP

The inactivation processes of coliform bacteria (total and fecal) and sulphito-reducing Clostridium bacteria (vegetative species and spores) in water maturation lagoon of a low-cost nature-based wastewater treatment plant using constructed wetlands and through processes of photolysis in a pilot photoreactor have been comparatively studied. The different inactivation mechanisms by photolysis of these bacteria have been studied following the criteria of different statistical and kinetic models. Clostridium disinfection treatments fit models in which two types of bacteria populations coexist, one sensitive (vegetative species) and the other (spores) resistant to the treatment, the sensitive one (94%) with an inactivation rate of k = 0.24 ± 0.07 min-1 and the resistant one (6%) with k = 0.11 ± 0.05 min-1. Total coliform photolytic disinfection also shows two populations with different physiological state. The time required to reduce the first logarithmic decimal cycle of the different types of bacteria (physiological states) are δ1 = 4.2 ± 0.9 and δ2 = 8.3 ± 1.1 min, respectively. For fecal coliform photolytic disinfection, only bacteria population, with k = 1.15 ± 0.19 min-1, is found. The results obtained confirm the photolytic disinfection processes and maturation lagoon are effective systems for Clostridia bacteria removal after water treatment by nature-based systems. Total removal of coliform bacteria is not achieved by maturation lagoons, but their reduction is significant using low doses of cumulative radiation.

Climate Change and Enteric Infections in the Canadian Arctic: Do We Know What’s on the Horizon?

The Canadian Arctic has a long history with diarrheal disease, including outbreaks of campylobacteriosis, giardiasis, and salmonellosis. Due to climate change, the Canadian Arctic is experiencing rapid environmental transformation, which not only threatens the livelihood of local Indigenous Peoples, but also supports the spread, frequency, and intensity of enteric pathogen outbreaks. Advances in diagnostic testing and detection have brought to attention the current burden of disease due to Cryptosporidium, Campylobacter, and Helicobacter pylori. As climate change is known to influence pathogen transmission (e.g., food and water), Arctic communities need support in developing prevention and surveillance strategies that are culturally appropriate. This review aims to provide an overview of how climate change is currently and is expected to impact enteric pathogens in the Canadian Arctic.

Monitoring Microbial Populations and Antibiotic Resistance Gene Enrichment Associated with Arctic Waste Stabilization Ponds

Given that the microbial communities of Arctic waste stabilization ponds (WSPs) are poorly studied to date, our characterization of multiple WSP systems and time points provides important baseline data that will assist with ongoing monitoring of effluent impacts on downstream aquatic ecosystems in the Arctic. This research also identifies indicator amplicon sequence variants (ASVs) of WSPs that will be helpful for future monitoring for WSP effluent attenuation and demonstrates that WSP microbial communities are enriched in antibiotic resistance genes.

Wastewater management in the Canadian Arctic is challenging due to climate extremes, small population sizes, and lack of conventional infrastructure for wastewater treatment. Although many northern communities use waste stabilization ponds (WSPs) as their primary form of wastewater treatment, few studies have explored WSP microbial communities and assessed effluent impacts on receiving waters from a microbiological perspective. Here, we used 16S rRNA gene and metagenome sequencing to characterize WSP and receiving water microbial communities for two time points bracketing the spring WSP thaw in Baker Lake (Nunavut) and compared these results to other Nunavut WSPs in Cambridge Bay and Kugluktuk. Most amplicon sequence variants (ASVs) recovered from these WSP samples belonged to the phylum Proteobacteria, with considerable variation between the three locations and only six ASVs shared among the WSPs at >0.2% relative abundance. Wastewater indicator ASVs for the Baker Lake WSP were identified, and few indicator ASVs were detected in samples originating from other upstream or downstream sites. The metagenomic data revealed a strong enrichment of antibiotic resistance genes for WSP samples relative to downstream and reference samples, especially for genes associated with macrolide resistance. Together, our results provide a baseline characterization for WSP microbial communities, demonstrate how indicator ASVs can be used to monitor attenuation and dilution of effluent microorganisms, and reveal that WSPs can serve as hot spots for antibiotic resistance genes.

IMPORTANCE Given that the microbial communities of Arctic waste stabilization ponds (WSPs) are poorly studied to date, our characterization of multiple WSP systems and time points provides important baseline data that will assist with ongoing monitoring of effluent impacts on downstream aquatic ecosystems in the Arctic. This research also identifies indicator amplicon sequence variants (ASVs) of WSPs that will be helpful for future monitoring for WSP effluent attenuation and demonstrates that WSP microbial communities are enriched in antibiotic resistance genes. Given operational and infrastructure changes anticipated for wastewater treatment systems in the Arctic, baseline data such as these are essential for further development of safe and effective wastewater treatment systems.

Wastewater Treatment Lagoons: Local Pathways of Perfluoroalkyl Acids and Brominated Flame Retardants to the Arctic Environment

Concentrations of perfluoroalkyl acids (PFAAs), polybrominated diphenyl ethers (PBDEs), and "novel" brominated flame retardants (NBFRs) were determined in lagoons processing wastewater from two high-Arctic and two sub-Arctic of Canada communities to assess the importance of local anthropogenic sources. ∑PFAAs in influent and effluent of the Arctic lagoons were within the lower end of the range of concentrations previously observed in Canadian temperate wastewater treatment plants (WWTPs). In comparison, influent and effluent concentrations of ∑PBDEs and NBFRs were significantly greater (p < 0.05) in high-Arctic lagoons compared to sub-Arctic and temperate plants. The surprisingly elevated concentrations of PBDEs and NBFRs in high-Arctic lagoons were probably related to high organic matter found in Arctic wastewater due to lower consumption of potable water leading to less dilution compared to temperate regions. Although PFAAs also sorb to solids, the wastewater samples were filtered prior to analysis of PFAAs (but not PBDEs and NBFRs), which likely reduced the impacts of solids on the results for PFAAs. Based on an extrapolation of per capita mass effluent loadings of the four Arctic lagoons, mass loadings to the Arctic of Canada via WWTP effluent were estimated as 1405 g/year and 549 g/year for ∑PFAAs and ∑PBDEs, respectively.

A long-amplicon quantitative PCR assay with propidium monoazide to enumerate viable Listeria monocytogenes after heat and desiccation treatments

The objective of this study was to develop a qPCR method for specific enumeration of viable Listeria monocytogenes in food processing facilities and heat treated products. Primers specific for L. monocytogenes were designed to amplify a short (199 bp) or long (1561 bp) fragment of the listeriolysin (hly) gene. The short- and long-amplicon qPCR methods with and without propidium monoazide (PMA) treatment of the cells were tested for their ability to discriminate between viable (no heat) and heat-killed cells (90 °C, 10 min). The PMA-qPCR methods were subsequently used to assess the survival of L. monocytogenes during desiccation (33% RH, 15 °C) on stainless steel surfaces for ten days with and without prior biofilm formation. The long-amplicon qPCR method had a limit of quantification (LOQ) of 1.32 log CFU/reaction (efficiency 92%, R² = 0.991), while the LOQ for the short-amplicon qPCR method was 1.44 log CFU/reaction (efficiency 102%, R² = 0.991). PMA was essential for detection of viable cells, and the long-amplicon PMA-qPCR significantly (p < 0.05) reduced the signal from heat-killed cells compared to the short-amplicon method. L. monocytogenes survival during desiccation without biofilm formation was accurately enumerated with the long-amplicon PMA-qPCR method. However, when L. monocytogenes had formed biofilm prior to desiccation, the long-amplicon PMA-qPCR accurately measured the log fold inactivation but underestimated the number of viable cells even with use of an optimized DNA extraction method. This long-amplicon PMA-qPCR method can aid in the detection and enumeration of viable L. monocytogenes cells to further the understanding of its survival and persistence in food processing facilities. The developed method was demonstrated to work on both heat and desiccation treated cells and highlights the importance of amplicon size in viability-qPCR.

Chemical and microbial characteristics of municipal drinking water supply systems in the Canadian Arctic

Drinking water in the vast Arctic Canadian territory of Nunavut is sourced from surface water lakes or rivers and transferred to man-made or natural reservoirs. The raw water is at a minimum treated by chlorination and distributed to customers either by trucks delivering to a water storage tank inside buildings or through a piped distribution system. The objective of this study was to characterize the chemical and microbial drinking water quality from source to tap in three hamlets (Coral Harbour, Pond Inlet and Pangnirtung-each has a population of <2000) on trucked service, and in Iqaluit (population ~6700), which uses a combination of trucked and piped water conveyance. Generally, the source and drinking water was of satisfactory microbial quality, containing Escherichia coli levels of <1 MPN/100 mL with a few exceptions, and selected pathogenic bacteria and parasites were below detection limits using quantitative polymerase chain reaction (qPCR) methods. Tap water in households receiving trucked water contained less than the recommended 0.2 mg/L of free chlorine, while piped drinking water in Iqaluit complied with Health Canada guidelines for residual chlorine (i.e. >0.2 mg/L free chlorine). Some buildings in the four communities contained manganese (Mn), copper (Cu), iron (Fe) and/or lead (Pb) concentrations above Health Canada guideline values for the aesthetic (Mn, Cu and Fe) and health (Pb) objectives. Corrosion of components of the drinking water distribution system (household storage tanks, premise plumbing) could be contributing to Pb, Cu and Fe levels, as the source water in three of the four communities had low alkalinity. The results point to the need for robust disinfection, which may include secondary disinfection or point-of-use disinfection, to prevent microbial risks in drinking water tanks in buildings and ultimately at the tap.