RESUMEN
Traditional methods for the detection and enumeration of bacteria in water samples are growth-based and require several days to obtain the result. New techniques which reduce the time of analysis have been developed. The objective of this work was to test a rapid method for the detection and enumeration of total viable bacteria using direct fluorescent labelling and detection by laser scanning. This method (referred to as TVC for Total Viable Count) was compared to the R2A culture method and the cyano-ditolyl-tetrazolium chloride (CTC) staining method for the analysis of samples before the final chlorination (after GAC filtration) and drinking water samples. For the comparison of TVC and CTC, the outcome depends on the water type: for samples after GAC filtration, TVC counts were significantly lower than CTC counts by up to 2 log10 orders of magnitude. For chlorinated water samples, TVC counts were not significantly different from CTC counts. The comparison of TVC and R2A showed that TVC counts could be lower than R2A counts or equivalent depending on the type of water. For drinking water, the TVC method proved to yield results equivalent to those of the R2A method. The TVC method requires much shorter time frame than others. It is also simple to use and allows the analysis of large volumes (100 ml) of drinking water.
Asunto(s)
Bacterias/aislamiento & purificación , Técnicas Bacteriológicas , Microbiología del Agua , Abastecimiento de Agua , Técnicas Bacteriológicas/instrumentación , Técnicas Bacteriológicas/métodos , Recuento de Colonia Microbiana/métodos , Filtración , Fluorescencia , Colorantes Fluorescentes , Rayos Láser , Factores de Tiempo , Abastecimiento de Agua/normasRESUMEN
The development of rapid and accurate methods for the detection and quantification of bacteria without cultivation is of increasing importance for water monitoring. The aim of this study was to develop a solid phase cytometry detection method for DVC-FISH labelled Escherichia coli cells. In order to allow Stomatic detection with ChemScan RDI, the fluorescein-tyramide was combined with an oligonucleotide probe directly labelled with horseradish peroxidase to increase the fluorescence intensity. The method developed was tested for the enumeration of pure cultures, for GAC-filtered and drinking water samples. The method, which appeared to be equivalent to the culture method, was less sensitive than the DVC-FISH method followed by microscopic analysis. Research is underway to further optimise the labelling conditions.
