Characterization of the bacterial community in shower water before and after chlorination

Longitudinal bacterial community dynamics and sodium hypochlorite intervention in a newly built university building

Urbanisation and building advancements have increased microbial growth in indoor environments, altering human interactions with these microorganisms. Restrooms and their sinks harbour diverse bacterial communities, that differ from those found in natural environments, that could have negative implications for human health. Over two and a half years, this study examined the diversity, temporal dynamics, and resilience of bacterial communities in restroom sink P-traps in a newly built university building. Structured into two phases, the first phase consisted of continuous monitoring of bacterial community dynamics for two years (n = 352), while the second phase involved an intervention with sodium hypochlorite (bleach) and subsequent sampling (n = 132). In the first phase, we show that sink communities converge, becoming more compositionally similar to other sinks within the building. Bacterial families such as Rhodocyclaceae and Flavobacteriaceae dominated across the sinks, and others such as Comamonadaceae, Moraxellaceae and Enterbacteriaceae were highly prevalent. When comparing bacterial structure and composition to other sinks located on the university campus, the mean bacterial dissimilarity decreased over time, indicating compositional similarity, particularly with the newer buildings on campus. The second phase demonstrated resilience by the bacterial sink communities. Following bleach treatments, a distinct increase in Acinetobacter was observed. However, by the fourth week after bleach invention, bacterial communities had re-established to levels observed prior to treatment. This study had the unique opportunity to sample a newly built building before occupancy and for the subsequent two and a half years. The findings provide crucial insights into the development and resilience of sink P-trap bacterial communities in restrooms, laying the groundwork for more targeted approaches to disinfection strategies.

Metagenomic evaluation of bacteria in drinking water using full-length 16S rRNA amplicons

Escherichia coli and total coliforms are important tools for identifying potential faecal contamination in drinking water. However, metagenomics offers a powerful approach for delving deeper into a bacterial community when E. coli or total coliforms are detected. Metagenomics can identify microbes native to water systems, track community changes and potential pathogens introduced by contamination events, and evaluate the effectiveness of treatment processes. Here, we demonstrate how the dual application of traditional monitoring practices and metagenomics can improve monitoring and surveillance for water resource management. The robustness of long-read metagenomics across replicates is demonstrated by the effect and interaction between manganese filters and bacterial communities, as well as the impact of chlorination after coliform detection. These examples reveal how metagenomics can identify the complex bacterial communities in the distribution system and the source waters used to supply drinking water treatment plants (DWTPs). The knowledge gained increases confidence in identified causes and mitigations of potential contamination events. By exploring bacterial communities, we can gain additional insights into the impact of faecal contamination events and treatment processes. This insight enables more precise remediation actions and enhances confidence in communicating health risks to drinking water operators and the public.

Risk Analysis of Otitis Externa (Swimmer’s Ear) in Children Pool Swimmers: A Case Study from Greece

Otitis is an ear inflammation characterized by an accumulation of polluted fluids in the ear, inflating the drum, causing ear pain, and draining the mucous membrane (pus) into the ear canal if the drum is perforated. Swimmer’s otitis, also known as acute external otitis, is a medical condition that frequently affects competitive swimmers. The risk factor analysis study was based on data obtained between May 2018 and May 2019 from four public swimming pools in Patras, Achaia. A checklist was created to evaluate the pools’ operational conditions, and it included information on the pools’ sanitation as well as swimming pool hygiene guidelines. In addition, a questionnaire was devised to collect data on pool swimmers’ use of the pools. Microbiological testing of the pool water was done ahead of time, and data on external otitis cases from hospitals was gathered. Based on this information, a risk factor analysis was conducted. Gender, weight, and age do not appear to have an impact on the number of otitis media cases that occur because of swimming in the pools. There is also no statistically significant link between episodes and the frequency of otitis events in locker rooms, restrooms, or swimming pools. The frequency with which swimmers utilize the pool, rather than the pool’s microbial burden, is the most significant determinant in otitis episodes. Furthermore, there is no statistically significant link between chlorine odor and otitis episodes. Additionally, several abnormalities in the ear or the child’s history do not appear to affect otitis episodes. More research is needed to determine whether infections are linked to microbial load or if other factors are responsible for the emergence of waterborne infections.

Swimming Pool Regulations in the COVID-19 Era: Assessing Acceptability and Compliance in Greek Hotels in Two Consecutive Summer Touristic Periods

The COVID-19 pandemic has urged many countries to issue new regulations to assure safety in pool environments. Greece enforced stricter requirements in 2020 and 2021 for hotel pools. However, even though regulations are important, they can only be effective when accepted by the pool managers and users. The aim of this study was to (a) assess the acceptability of the regulations by hotel managers; (b) assess compliance during the summer touristic periods in 2020 and 2021; and (c) identify challenges during the implementation of the regulations that need to be addressed. Several non-compliances from the regulations were identified. Continuous chlorination with an automatic chlorinator was not a regular practice and suggested water circulation rates were poorly met. The microbiological and chemical testing frequency of the pool water and keeping the number of bathers allowed per surface area in the pool were reported as the most difficult requirements to meet. Most pool managers agreed that new measures contribute to the pool users’ safety; however, they reported increased cost as the main impediment for their implementation. The modernization of regulations governing swimming pools’ function, in terms of risk assessment orientation, will contribute to the adoption of an integrated compliance strategy on emerging health issues, such as COVID-19.

Dissemination of antibiotic resistance genes in swimming pools and implication for human skin

Swimming pools are crowd-gathering places that are associated with numerous outbreaks of water-borne diseases. Herein, we investigated the distribution of antibiotic resistance genes (ARGs) and bacterial communities in swimming pools and determined the influencing factors and potential human exposure. Sixteen swimming pools with different bather loads (0.01-0.16 person/m²·h) were investigated. Water samples were collected, before opening and after closing of the facilities, from six swimming pools, and skin samples were collected from volunteers. Comprehensive approaches, high-throughput qPCR and 16S rRNA gene sequencing, were used. The results showed that swimming pools contained a higher relative abundance (0.62 gene copies/16S rRNA) and absolute abundance (6.57×10⁸ gene copies/L) of ARGs on average. Bather loads contributed to the increase of core ARGs, and the absolute abundance of ARGs significantly increased by 1.47-1.94 orders of magnitude when the bather load was more than 0.1 person/m²·h. Dermal contact was estimated as the main exposure route of ARGs. Eighteen ARGs that were not detected before swimming were found on human skin and remained after showering. Furthermore, the event intake burden of ARGs via dermal contact was higher than that via ingestion when swimming. This study provides an assessment of ARGs and antibiotic-resistant bacteria (ARB) in swimming pools and helps to define the health risks to swimmers.

Yearly microbial cycle of human exposed surfaces in show caves

The human impact upon the subterranean microbiomes is not only a peril to the cave environment but might also affect future visitors. We focused on the changes that humans induced on the surfaces they came in direct or indirect contact with inside two intensely visited Romanian show caves, by means of commercially available microbial rapid test kits and molecular identification.

Overall culturable bacteria abundance in the caves maintained high levels year-round while Enterobacteriaceae, coliform bacteria and Escherichiacoli levels peaked during the touristic season, reaching levels that could pose a threat to the health of the visitors. Culturable fungi abundance usually peaked in the spring, remained at a high level in the summer and started to slowly decrease towards the winter months. Differences were observed between the direct and indirect exposed surfaces, as the later had lower overall levels of bacteria and fungi, with increased Enterobacteriaceae loads. Most of the taxa identified are known biodeteriorants of subterranean surfaces and were previously associated with human altered caves. A Dothideomycete sp. previously unknown to the cave environments was detected.

This was the first study to analyse the dynamics of the microbial communities of delicate subterranean surfaces in show caves through the use of commercially available test kits. We revealed that exposed surfaces in show caves, in direct or indirect contact with tourists, are host to high concentrations of cultivable microbes. The touristic activity was shown to influence the abundance and dynamics of the microbial communities inhabiting surfaces of show caves.