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Summary: Risk assessment is critical for identifying target concentrations of antibiotic resistant pathogens necessary for mitigating potential harmful exposures associated with water reuse. However, there is currently limited available data characterizing the concentrations of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in recycled water to support robust efforts at risk assessment. The objective of this systematic review was to identify and synthesize the existing literature documenting the presence and abundance of ARB and ARGs in recycled water. In addition, this review identifies best practices and explores monitoring targets for studying ARB and ARGs in recycled water to guide future work and identifies key research needs aimed at better supporting quantitative microbial risk assessment focused on recycled water and antibiotic resistance. Future efforts to collect data about ARB and ARG prevalence in recycled water should report concentration data per unit volume. Sample metadata should also be provided, including a description of treatment approach, a description of planned water uses (e.g., potable, irrigation), methods for conveyance to the point of use, and available physicochemical water quality data. Additional research is needed aimed at identifying recommended ARB and ARG monitoring targets and for developing approaches to incorporate metagenomic data into risk assessment. [ABSTRACT FROM AUTHOR]

Legionella pneumophila is an opportunistic bacterial respiratory pathogen that is one of the leading causes of drinking water outbreaks in the United States. Dental offices pose a potential risk for inhalation or aspiration of L. pneumophila due to the high surface area to volume ratio of dental unit water lines—a feature that is conducive to biofilm growth. This is coupled with the use of high-pressure water devices (e.g., ultrasonic scalers) that produce fine aerosols within the breathing zone. Prior research confirms that L. pneumophila occurs in dental unit water lines, but the associated human health risks have not been assessed. We aimed to: (1) synthesize the evidence for transmission and management of Legionnaires' disease in dental offices; (2) create a quantitative modeling framework for predicting associated L. pneumophila infection risk; and (3) highlight influential parameters and research gaps requiring further study. We reviewed outbreaks, management guidance, and exposure studies and used these data to parameterize a quantitative microbial risk assessment (QMRA) model for L. pneumophila in dental applications. Probabilities of infection for dental hygienists and patients were assessed on a per-exposure and annual basis. We also assessed the impact of varying ventilation rates and the use of personal protective equipment (PPE). Following an instrument purge (i.e., flush) and with a ventilation rate of 1.2 air changes per hour, the median per-exposure probability of infection for dental hygienists and patients exceeded a 1-in-10,000 infection risk benchmark. Per-exposure risks for workers during a purge and annual risks for workers wearing N95 masks did not exceed the benchmark. Increasing air change rates in the treatment room from 1.2 to 10 would achieve an ∼85% risk reduction, while utilization of N95 respirators would reduce risks by ∼95%. The concentration of L. pneumophila in dental unit water lines was a dominant parameter in the model and driver of risk. Future risk assessment efforts and refinement of microbiological control protocols would benefit from expanded occurrence datasets for L. pneumophila in dental applications. [ABSTRACT FROM AUTHOR]

Animal fecal contamination in aquatic environments is a major source of zoonotic diseases in humans. While concerns are focused on livestock, companion animals such as dogs can also be a source of a wide range of zoonotic pathogens. Therefore, detection of dog or canine fecal contamination in aquatic environments is important for mitigating risks. In this study, host-sensitivity and specificity of four canine fecal-associated marker genes were evaluated by analyzing 30 canine and 240 non-canine fecal samples. The application of these markers was also tested in water from an urban river under dry weather conditions. The host sensitivity values of the Bacteroides BacCan-UCD, DogBact, DF113 and DF418 were 1.00, 0.90, 0.83, and 0.90, respectively. The host specificity value of the BacCan-UCD, DogBact, DF113 and DF418 were 0.87, 0.98, 0.83, and 0.41, respectively. The mean concentrations of DF418 were highest (7.82 ± 1.13 log 10 gene copies (GC)/g of feces) followed by BacCan-UCD (7.61 ± 1.06 log 10 GC/g) and DogBact (7.15 ± 0.92 log 10 GC/g). The mean concentration of DF113 (5.80 ± 1.25 log 10 GC/g) was 1.5 to 2.5 orders of magnitude lower than the other marker genes. The DogBact marker gene was not detected in any other animal feces other than a small number of untreated sewage samples. The BacCan-UCD marker gene cross-reacted with cat, chicken, and pig fecal samples, while the DF113 marker gene cross-reacted with cat, chicken, cattle fecal and untreated sewage samples. The DF418 marker gene was detected in all sewage and animal feces and deemed not suitable for canine fecal contamination tracking in sub-tropical Australia. Canine fecal contamination was infrequently detected in environmental water samples. Based on the results obtained in this study, we recommend that at least two canine feces-associated marker genes should be used in field studies. Unlabelled Image • BacCan-UCD, DogBact, DF113 and DF418 were highly prevalent in canine feces. • DogBact marker gene was highly specific to canine feces. • Dog marker was occasionally detected in river water samples. • The DF418 marker gene was not suitable for dog fecal pollution tracking in Australia. [ABSTRACT FROM AUTHOR]