Comparaison de methodes directes (microscopiques) et indirectes (par mise en culture) dans l'evaluation d'une pollution bacterienne d'origine fecale. Etude preliminaire

Cells of two serotypes of Escherichia coli (O26B6 and 0111B4) were counted using epifluorescence and immunofluorescence microscopy (nonavalent serum) and plate count on specific medium. Values from indirect counts were 10 fold smaller than those from both microscopic counts. In a sample of sea water from an area receiving a fecal pollution, the highest number of bacteria was obtained by epifluorescence microscopy. In that case, the number of cells counted by immunofluorescence microscopy was 10 fold smaller than the number of bacteria able to grow on the medium. It could be due to: the diversity of the natural community, the possibility to other bacteria than E. coli to grow on the used culture medium, the restrictiveness of the serum for "pathogenic serotypes".