Competition for growth substrates in river water between Escherichia coli and indigenous bacteria illustrated by high-resolution mass spectrometry

Persistence of E. coli O157:H7 in urban recreational waters from Spring and Autumn: a comparison analysis

People might get infected by pathogens found in urban recreational waters during water-contact activities, such as swimming, boating, bathing, and yachting. However, the persistence of pathogenic bacteria in those waters was not well documented. In this study, persistence of E. coli O157:H7 (EcO157) in 48 water samples (24 Spring samples and 24 Autumn samples) from the 3 urban recreational waters was investigated. Multivariate statistical analysis was performed to correlate survival data with water physicochemical properties and bacterial communities. Our data showed that EcO157 survived longer in Spring samples than in Autumn samples regardless of the lakes. Results revealed that recreational water physicochemical properties and bacterial community in Spring samples were different from those in Autumn samples. Mantel and Partial Mantel tests, as well as co-occurrence network analysis illustrated that EC salinity, TOC, and bacterial community were correlated with survival time (ttd) (p < 0.05). Variation partition analysis (VPA) indicated that bacterial community, EC, TOC, and TN explained about 64.81% of overall ttd variation in Spring samples, and bacterial community, EC, pH, and TP accounted for about 56.59% of overall ttd variation in Autumn samples. Structural equation model (SEM) illustrated that EC indirectly positively affected ttd through bacterial community. The correlation between bacterial community and ttd was negative in Spring samples and positive in Autumn samples. TN appeared a direct positive effect on ttd in Spring samples. TP displayed a direct negative effect on ttd in Autumn samples. Our results concluded that there was seasonal variation in environmental factors that directly or indirectly affected the survival of EcO157 in urban recreational waters.

Combining microscopy assays of bacteria-surface interactions to better evaluate antimicrobial polymer coatings

Validation of the antimicrobial performance of contact-killing polymer surfaces through experimental determination of bacterial adhesion or viability is essential for their targeted development and application. However, there is not yet a consensus on a single most appropriate evaluation method or procedure. Combining and benchmarking previously reported assays could reduce the significant variation and misinterpretation of efficacy data obtained from different methods. In this work, we systematically investigated the response of bacteria cells to anti-adhesive and antiseptic polymer coatings by combining (i) bulk solution-based, (ii) thin-film spacer-based and (iii) direct contact assays. In addition, we evaluated the studied assays using a five-point scoring framework that highlights key areas for improvement. Our data suggest that combined microscopy assays provide a more comprehensive representation of antimicrobial performance, thereby helping to identify effective types of antibacterial polymer coatings. Importance We present and evaluate a combination of methods for validating the efficacy of antimicrobial surfaces. Antimicrobial surfaces/coatings based on contact-killing components can be instrumental to functionalise a wide range of products. However, there is not yet a consensus on a single, most appropriate method to evaluate their performance. By combining three microscopy methods, we were able to discern contact killing effects at the single cell level that were not detectable by conventional bulk microbiological analyses. The developed approach is considered advantageous for the future targeted development of robust and sustainable antimicrobial surfaces.

Assessment of organic carbon migration and biofilm formation potential on polymeric tubes in contact with water

Biofilm formation has been frequently identified as a pathway of nosocomial infection in polymeric tubes used for patients of all ages. Biofilm formation on tube surfaces can lead to hygienic failure and cause diarrhea, stomach pain, inflammation, and digestive system disease. This study investigated the influence of polymeric tube materials in contact with water on the biomass formation potential and migration potential of microbially available carbon from plasticizers using a BioMig test. The thermoplastic elastomer tube, which is reusable, leached a relatively low amount of assimilable organic carbon to water. In contrast, the assimilable organic carbon migration potential of polyurethane was the most significant, 6-fold greater than that of the thermoplastic elastomer. Moreover, the same materials (e.g., silicone) produced via different manufacturing processes showed significant differences in migration behaviors. The potential biomass formation observed in polyurethane was approximately 7 × 10⁹ cells cm^-2 for both Aeromonas hydrophila and Escherichia coli strains. This study highlights the importance of choosing the correct material characteristics of polymeric tubes in contact with water to protect them from bacterial contamination. Therefore, manufacturers can use the BioMig test to evaluate and produce more hygienic and biostable tubes.