Effect of invasive slug populations (Arion vulgaris) on grass silage. II: Microbiological quality and feed safety

AbstractThis study aimed to explore how invasive slug populations of Arion vulgaris influenced the microbiological quality and animal feed safety of grass silage, and the efficiency of silage additives and wilting to control the microbiology of slug contaminated crops. The effect of four slug contamination levels, including control, of a grass crop harvested for silage production, was evaluated in laboratory scale. The crop was wilted to two dry matter (DM) levels: low (253g DM/kg) and high (372g DM/kg). Adult slugs were applied to the low DM crop corresponding to 5 (low level), 10 (medium) and 20 (high level) seven-gram sized Arion vulgaris per m2 in an assumed harvested regrowth yield of 2.5ton DM/ha. For the high DM crop, slug weights corresponding to 6 (low level), 12 (medium) and 24 (high level) slugs per m2 were applied. At low DM level, the effect of four additive treatments; control (C), inoculation with Lactobacillus plantarum (LP), a formic, propionic and benzoic acid mixture (ACID) and a chemical additive containing benzoic acid, NaNO2, hexamethylenetetramine and propionic acid (CHEM) were tested. Slugs, slug feces, grass, soil and silages were analyzed for lactic acid bacteria (LAB), Enterobacteriaceae, Listeria monocytogenes, Clostridium tyrobutyricum, molds and yeasts by cultivation methods and Clostridium botulinum type C by real-time PCR analysis.Increasing slug contamination reduced the microbial quality of silages by increasing C. tyrobutyricum levels at both silage DM levels. Only silages without slugs and silages treated with the nitrite containing additive CHEM had non-detectable mean levels of C. tyrobutyricum. Increasing slug contamination increased LAB enumerations in silages. No microbes of risk to human or animal health were detected in anaerobic silages even at the highest slug contamination

Investigation of an Escherichia coli O145 outbreak in a child day-care centre - extensive sampling and characterization of eae- and stx1-positive E. coli yields epidemiological and socioeconomic insight

<p>Abstract</p> <p>Background</p> <p>On October 29^th2009 the health authorities in the city of Trondheim, Norway were alerted about a case of Shiga toxin-positive <it>E. coli </it>(STEC) O145 in a child with bloody diarrhoea attending a day-care centre. Symptomatic children in this day-care centre were sampled, thereby identifying three more cases. This initiated an outbreak investigation.</p> <p>Methods</p> <p>A case was defined as a child attending the day-care centre, in whom <it>eae- </it>and <it>stx</it>₁- but not <it>stx</it>₂-positive <it>E. coli </it>O145:H28 was diagnosed from a faecal sample, with multilocus variable number of tandem repeat analysis (MLVA) profile identical to the index isolate. All 61 children, a staff of 14 in the day-care centre, and 74 close contacts submitted faecal samples. Staff and parents were interviewed about cases' exposure to foods and animals. Faecal samples from 31 ewes from a sheep herd to which the children were exposed were analyzed for <it>E. coli </it>O145.</p> <p>Results</p> <p>Sixteen cases were identified, from which nine presented diarrhoea but not haemolytic uremic syndrome (HUS). The attack rate was 0.26, and varied between age groups (0.13-0.40) and between the three day-care centre departments (0.20-0.50), and was significantly higher amongst the youngest children. Median duration of shedding was 20 days (0-71 days). Children were excluded from the day-care centre during shedding, requiring parents to take compassionate leave, estimated to be a minimum total of 406 days for all cases. Atypical enteropathogenic <it>E. coli </it>(aEPEC) were detected among 14 children other than cases. These isolates were genotypically different from the outbreak strain. Children in the day-care centre were exposed to faecal pollution from a sheep herd, but <it>E. coli </it>O145 was not detected in the sheep.</p> <p>Conclusions</p> <p>We report an outbreak of <it>stx</it>₁- and <it>eae-</it>positive STEC O145:H28 infection with mild symptoms among children in a day-care centre. Extensive sampling showed occurrence of the outbreak strain as well as other STEC and aEPEC strains in the outbreak population. MLVA-typing of the STEC-isolates strongly indicates a common source of infection. The study describes epidemiological aspects and socioeconomic consequences of a non-O157 STEC outbreak, which are less commonly reported than O157 outbreaks.</p