6533b872fe1ef96bd12d3eb4

RESEARCH PRODUCT

Détection ampérométrique d'Escherichia coli (totaux et producteurs de beta-lactamase à spectre étendu (BLSE) et d'Enterococcus spp. dans les systèmes de traitement des eaux usées et les eaux de baignade

subject

description

Treated wastewaters discharged from wastewater treatment plants (WWTP) and livestock effluents are the main sources of contamination of aquatic environments and of agricultural soils by human and animal fecal micro-organisms. Contaminated waters, especially bathing waters, may present a sanitary risk for humans if the concentrations of fecal micro-organisms are high, thus indicating the potential presence of pathogenic and/or antibiotic resistant strains. Soils and crops also can be contaminated by these micro-organisms when treated wastewaters are used to irrigate cultivated soils. Consequently, microbiological quality controls are mandatory for bathing waters and treated wastewaters to manage and limit sanitary risks. According to the regulation, the microbiological controls of treated wastewaters and bathing waters rely on the quantification of two fecal indicator bacteria : Escherichia coli (E. coli) and intestinal enterococci (IE). However, the methods currently available have one or more of the following disadvantages, i. e. long response time, high cost, complexity of implementation, ex-situ use, analysis of a single indicator. To overcome these disadvantages, the first objective of the thesis was the development of an amperometric method for the detection of E. coli and IE, via the measurement of specific enzymatic activities using single-use screen-printed sensors. It was demonstrated that the amperometric method allowed to enumerate E. coli and IE in treated wastewaters samples and that the results were comparable to those obtained with the ISO 9308-3 and 7899-1 standardized methods, while offering a much shorter analysis time (in 4 to 6 h against 36 to 72 h). Moreover, the application of the amperometric method to the analysis of bathing water samples showed that contrary to the minimum 36 hours required with standardized methods, the amperometric detection provided answers regarding the sanitary quality standards for bathing waters within only 7 hours. Then in a second time, we developed an amperometric method to quantify extended-spectrum β-lactamase (ESBL)-producing E. coli in wastewaters samples. The results showed that amperometric counting obtained in only 4 - 5 h were very close to those provided by the enumeration on selective culture medium obtained after a delay of 24 h. In addition, this work confirmed the release of ESBL-producing strains by most of WWTP, whether or not they received hospital effluents. In conclusion, the proposed amperometric method to detect E. coli and IE provided more rapidly results regarding the sanitary quality of treated wastewaters of WWTP and bathing waters than the standardized methods currently used as references. Moreover, the amperometric detection and enumeration of ESBL-producing E. coli in the wastewaters of WWTP allowed to monitor their role in the environmental dissemination of antibiotic-resistant strains. Owing to the advantages of the developed electrochemical tools, further work will consist in developing a portable analysis device for field applications.