Survival of animal and human associated <i>Listeria monocytogenes</i> in drinking water and biofilms

Land slugs are occasionally observed as contaminants in groundwater wells and drinking water treatment plants including storage tanks. Slugs may feed on carrion and feces, and they are potential vectors of pathogens such as Listeria monocytogenes. We isolated L monocytogenes from the pest slug Arion vulgaris and examined the persistence and survival of human- and slug-derived L. monocytogenes in groundwater-based drinking water and biofilms. L monocytogenes survival was evaluated using cultivation and cultivation-independent techniques. L monocytogenes remained culturable for 35-47 days in drinking water with first-order decay rates between 0.314 and 0.457 hr1 (T99 &gt;10 days). Attachment of L monocytogenes to filter sand delayed washout from drinking water filters and increased persistence 2-3-fold. Indigenous biofilms stimulated initial surface attachment 10-100-fold butL. monocytogenes declined more rapidly in drinking water biofilms compared with virgin filters not colonized by microorganisms. Grazing by protozoa likely attenuated L monocytogenes survival in some drinking water biofilms. A comparable survival pattern was observed for L monocytogenes and the fecal indicator bacterium E. coli. The study suggests that live L monocytogenes can persist for weeks as sessile organisms in groundwater-based drinking water supplies and may subsequently be released to the drinking water.</p

Development of body mass and sexual size dimorphism in Danish red foxes (Vulpes vulpes)

<span class="fontstyle0">In this study, we examine the development of body mass and sexual size dimorphism (SSD) in 178 juvenile wild Danish red </span><span class="fontstyle0">foxes </span><span class="fontstyle0">from 99 litters </span><span class="fontstyle0">using </span><span class="fontstyle0">piecewise analyses of regression lines for age </span><span class="fontstyle2">versus</span><span class="fontstyle0"> weight</span><span class="fontstyle0">. When fox cubs are younger than 100 days, only slight (SSD=1.7%) and no significant difference</span><span class="fontstyle0"> (t-test: t=1.2, p=0.24) </span><span class="fontstyle0">was found in the mean weight of </span><span class="fontstyle0">males (2.03± kg) and females (1.93± kg), and</span><span class="fontstyle0"> no significant difference was found in the slope of regression lines </span><span class="fontstyle0">for </span><span class="fontstyle0">males and females </span><span class="fontstyle0">(F=0.97E-5, p = 0.99). In the growth period between 100 days of age and mating around 275 days of age, the regression line in males steepens more than that of females (difference in slopes, F=5.9, p&lt;0.02) and the difference in mean weight of the sexes become highly significant (SSD=7.4%, difference in mean t=4.6, p=2.2E-5). After mating the growth curve levels off i.e. the slope of the regression lines for age </span><span class="fontstyle2">versus</span><span class="fontstyle0"> weight is not significantly different from zero. Yearly variation was revealed in the growth rate of juvenile foxes (difference in slope for males; F=3.9, p&lt;0.01 and females; F=8.6, p&lt;0.001). Conclusion: SSD in red foxes mainly develop </span><span class="fontstyle0">as a result of a faster grow rate in males </span><span class="fontstyle0">between indepency and maturity. Ontogony of red foxes may genetically be disposed to prevent males outcompeting females in the early stages of life (&lt;100 days), when cubs are still fed by adults and the increase in SSD before mating, may be an adaption to selective forces benefitting larger males. </span><span class="fontstyle0">The growth rate of juvenile foxes of both sexes is influenced by environmental variation in different years.</span> <br /