Rapid detection of Escherichia coli in waters using fluorescent in situ hybridization, direct viable counting and solid phase cytometry.
OBJECTIVE
We developed an improved Fluorescent In Situ Hybridization FISH-based method to detect viable Escherichia coli cells by solid phase cytometry (SPC), and results were compared to those obtained by the standard culture method.


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.


CONCLUSIONS
The high specificity of the procedure was demonstrated as well as its accuracy for detecting and counting viable E. coli cells in environmental samples.


CONCLUSIONS
The developed approach may be used to monitor faecal contamination sources and to investigate the occurrence of viable E. coli in natural environments.
Baudart
J
J
UPMC Université Paris 06, UMR 7621, LOMIC, Observatoire Océanologique, Banyuls/mer, France. baudart@obs-banyuls.fr
Lebaron
P
P
D015169:Colony Count, Microbial; D003592:Cytophotometry / Q000379:methods; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification*; D005618:Fresh Water / Q000382:microbiology; D006824:Hybridization, Genetic; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D050296:Microbial Viability; D012623:Seawater / Q000382:microbiology; D014871:Water Microbiology