Study of the prevalence of Listeria spp. in surface water.

The quantity of Listeria species was determined in 49 samples of various types of water (river, brackish water, urban wastewater). Twenty nine strains of Listeria were isolated. These were mainly identified as Listeria monocytogenes (72,4%), but Listeria innocua, Listeria grayi, Listeria ivanohovii and Listeria welshimeri were also present. With the exception of water taken from the estuary, 74.4% of samples contained Listeria in mean concentrations of between 2 MPN/100 ml and 1320 MPN/100 ml in fresh surface water and untreated sewage respectively.