Survie in vitro de Yersinia dans les eaux d'alimentation et recuperation par filtration sur membrane

This study was undertaken to determine the survival characters and optimal parameters for the recovery of Yersinia from drinking water samples. Experiments were done by artificial contamination of 4 different water samples with 4 Yersinia strains.The strains tested along this study are: Y. enterocolitica 4052, 0:3 and 4360, 0:9, Y. enterocolitica intermedia 3953, 0:17 and Y. pseudotuberculosis 0:1. The water samples are characterized by an increasing mineralization: Distillated water, Gerardmer water (

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), Nancy water (-4500 ω cm⁻¹—H = 10°) and Vittel water (-730 ω cm⁻¹, H = 71°).Total mineralization does not significantly affect the survival of Yersinia at 20°C, but causes a dramatic decrease of the Yersinia strains at 4°C for the most mineralized water. There is no pH effect from alkaline, neutral and acidic values until pH 4.4 but Yersinia is greatly affected by more acidic pH.The previous stay of Yersinia strains in artificially contaminated water causes a reduction of kinetic growth during cultivation on peptone-water but does not change the recovery rate by filtration method.The recovery rate of the filtration method using cellulose acetate membranes (mean porosity = 0.45 μm) is very poor, ranging from 0 to 8%. The efficiency is significantly higher with the aid of polyester membranes treated by laser (Nucleopore−0.40 μm) ranging from 12 to 53% according to the mineralization of the water. The best recovery rate is obtained with the moderately mineralized water.These results can explain the poor results obtained with the use of water bacteriology classical methods for the search of Yersinia.Thus the best results can be predicted from the concentration of fairly mineralized water by filtration on polyester membrane at neutral, alkaline or weakly acidic pH.