Rapid detection of Escherichia coli in waters using fluorescent in situ hybridization, direct viable counting and solid phase cytometry

Aims: We developed an improved Fluorescent In Situ Hybridization FISHbased method to detect viable Escherichia coli cells by solid phase cytometry (SPC), and results were compared to those obtained by the standard culture method. Methods and Results: The method includes a direct viable count (DVC) assay, multi-probes labelled and unlabelled (helpers) to detect specifically viable E. coli cells and to enhance SPC cell counts. We demonstrate that helpers increase the fluorescence intensity of hybridized E. coli cells as detected by SPC and assess the high specificity of the DVC-FISH procedure on a large panel of cultured strains. Application to seawater, freshwater and wastewater samples showed a good correlation between SPC cells counts and standard plate counts. Conclusion: The high specificity of the procedure was demonstrated as well as its accuracy for detecting and counting viable E. coli cells in environmental samples. Significance and Impact of the Study: The developed approach may be used to monitor faecal contamination sources and to investigate the occurrence of viable E. coli in natural environments

High Diversity and Abundance of Legionella spp. in a Pristine River and Impact of Seasonal and Anthropogenic Effects ▿ †

The diversity and dynamics of Legionella species along a French river watershed subject to different thermal and wastewater discharges during an annual cycle were assessed by 16S rRNA gene sequencing and by a fingerprint technique, single-strand conformation polymorphism. A high diversity of Legionella spp. was observed at all the sampling sites, and the dominant Legionella clusters identified were most closely related to uncultured bacteria. The monthly monitoring revealed that Legionella sp. diversity changes were linked only to season at the wastewater site whereas there was some evidence for anthropogenic effects on Legionella sp. diversity downstream of the thermal bath. Quantification of Legionella pneumophila and Legionella spp. by culture and quantitative PCR (qPCR) was performed. Whereas only L. pneumophila was quantified on culture media, the qPCR assay revealed that Legionella spp. were ubiquitous and abundant from the pristine source of the river to the downstream sampling sites. These results suggest that Legionella spp. may be present at significant concentrations in many more freshwater environments than previously thought, highlighting the need for further ecological studies and culturing efforts

Relationship between cell size, activity and diversity in aquatic systems combining cell sorting, physiological probes and molecular techniques

info:eu-repo/semantics/nonPublishe

Rapid quantification of viable Legionella in nuclear cooling tower waters using filter cultivation, fluorescent in situ hybridization, and solid phase cytometry

International audienceTo develop a rapid and sensitive method to quantify viable Legionella spp. in cooling tower water samples. A rapid, culture-based method capable of quantifying as few as 600 Legionella microcolonies per litre within 2 days in industrial waters was developed. The method combines a short cultivation step of microcolonies on GVPC agar plate, specific detection of Legionella cells by a fluorescent in situ hybridization (FISH) approach, and a sensitive enumeration using a solid-phase cytometer. Following optimization of the cultivation conditions, the qualitative and quantitative performance of the method was assessed and the method was applied to 262 nuclear power plant cooling water samples. The performance of this method was in accordance with the culture method (NF-T 90-431) for Legionella enumeration. The rapid detection of viable Legionella in water is a major concern to the effective monitoring of this pathogenic bacterium in the main water sources involved in the transmission of legionellosis infection (Legionnaires' disease). The new method proposed here appears to be a robust, efficient and innovative means for rapidly quantifying cultivable Legionella in cooling tower water samples within 48 h

Determination of Soret coefficient and heat of transport in a binary liquid mixture using X-ray microscopy

With a laboratory built X-ray microscope, analysis of a thermal diffusion process in a KBr solution has been performed. A solution of a salt submitted to a constant temperature gradient gives rise to a stationary concentration gradient of the species after a few hours: this is the so called Soret effect. From the digital image of the liquid, acquired in the steady state of the process, it is easy to obtain the concentration map of the species in the solution. The average concentration profile then deduced permits to reach the value of the Soret coefficient and the heat of transport of the binary compound. X-ray radiography is an alternative powerful technique to analyse this kind of complicated phenomenon where composition matter fluxes are driven by both temperature and composition gradient

Coliformes en réseau de distribution d'eau potable: nouveaux outils et nouvelle approche pour un meilleur contrôle

info:eu-repo/semantics/publishe