The isolation of Listeria species from fresh-water sites in Cheshire and North Wales

We report a study to determine the presence of Listeria species in surface waters. One hundred ml volumes of 30 water samples taken from 21 different sites were analysed. Most of the samples examined were from ponds and lakes. Listeria species were isolated on eight (27%) occasions, six of these isolates were L. seeligeri, one was L. innocua and one L. welshimeri. Although not statistically significant, coliform and Escherichia coli counts were higher in waters that were positive than were negative for Listeria spp. It is suggested that the low isolation rate of listeria in this study reflects the fact that most waters examined did not receive sewage outfalls. Water sports activities are unlikely to be a risk factor for listeriosis.