Bakteriologisk kvalitet av salat gjødsla med storfegjødsel

Målet med denne undersøkinga var å samanlikna den bakteriologiske kvaliteten, inkludert førekomsten av visse patogen, av økologisk dyrka salat gjødsla med ulike typar storfegjødsel. Feltforsøk med isbergsalat ( Lactuca sativavar. Crispum, ’Iglo’) vart utført i 2001 og 2002. Behandlingane var blautgjødsel, fastgjødsel, kompostert storfegjødsel og mineralgjødsel. Prøvar av jord, gjødsel, gjødsla jord, oppalsplantar, salat og dei ytre blada av salatplantane (i 2002) vart analysert for indikatorbakteriar for fekal forureining (termotolerante koliforme bakteriar (TKB) og Escherichia coli), E. coli O157:H7, Salmonella spp. og L. monocytogenes. Det vart funne statistisk sikker forskjell mellom behandlingane i mengde TKB i gjødsla jord, men det vart ikkje funne noko forskjell i bakteriologisk kvalitet på salat ved hausting. I 2002 vart det funne E. coli O157:H7 i blautgjødsel og fastgjødsel, og jord gjødsla med blautgjødsel og fastgjødsel ei veke etter gjødsling. Bakterien vart ikkje funne på salat ved hausting. Ingen prøvar i undersøkinga inneheld Salmonella spp. eller L. monocytogenes. Resultata frå forsøket tyder på ingen forskjell i bakteriologisk kvalitet på økologisk dyrka isbergsalat gjødsla med ulike typar storfegjødsel

The ability to enter into an avirulent viable but non-culturable (VBNC) form is widespread among Listeria monocytogenes isolates from salmon, patients and environment

Media-based bacteriological testing will fail to detect non-culturable organisms and the risk of consuming viable but non-culturable (VBNC) Listeria monocytogenes is unknown. We have here studied whether L. monocytogenes obtained from seafoods, processing environment and clinical cases enter the VBNC state and assessed the virulence of the non-culturable forms of the bacteria. A number of 16 L. monocytogenes strains were starved in microcosm water at 4 °C until loss of culturability. Metabolic activity in the VBNC form was measured as ATP generation using a luciferase assay and membrane integrity was examined using the LIVE/DEAD BacLight assay. All tested L. monocytogenes strains entered the VBNC state after starvation in microcosm water. Ongoing mRNA synthesis of hly in VBNC L. monocytogenes cells re-incubated in culture medium indicated a potential virulence of these forms. Sodium pyruvate and replenishment of nutrient were used in attempts to resuscitate VBNC cells. However, VBNC L. monocytogenes were not resuscitated under these conditions. VBNC L. monocytogenes were tested for virulence in a cell plaque assay and by intraperitoneally inoculation in immunodeficient RAG1−/− mice. Inoculation of VBNC L. monocytogenes in immunodeficient mice did not cause morbidity, and plaque assay on HT-29 cells in culture indicated that the VBNC cells were avirulent. The results indicate that the risk of non-culturable L. monocytogenes in foods, when the VBNC state is induced by starvation, is negligible

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

Genetic characterization of trh positive Vibrio spp. isolated from Norway

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Occurrence of Vibrio parahaemolyticus, V. cholerae, and V. vulnificus in Norwegian Blue Mussels (Mytilus edulis)

Vibrio parahaemolyticus, V. cholerae, and V. vulnificus were isolated from 10.3%, 1.0%, and 0.1% of 885 blue mussel samples, respectively. Four of the samples contained trh(+) V. parahaemolyticus, while no tdh-positive isolates were detected. The V. cholerae isolates were non-O:1/non-O:139 serotypes and were ctxA negative

Potential Uptake of Escherichia coli O157:H7 from Organic Manure into Crisphead Lettuce

To investigate the potential transfer of Escherichia coli O157:H7 from contaminated manure to fresh produce, lettuce seedlings were transplanted into soil fertilized with bovine manure which had been inoculated with approximately 10(4) CFU g(−1) E. coli O157:H7. The lettuce was grown for approximately 50 days in beds in climate-controlled rooms in a greenhouse. As the bacterium was not detected in the edible parts of the lettuce, the outer leaves of the lettuce, or the lettuce roots at harvest it was concluded that transmission of E. coli O157:H7 from contaminated soil to lettuce did not occur. The pathogen persisted in the soil for at least 8 weeks after fertilizing but was not detected after 12 weeks. Indigenous E. coli was detected only sporadically on the lettuce at harvest, and enterococci were not detected at all. The numbers of enterococci declined more rapidly than those of E. coli in the soil. Pseudomonas fluorescens, which inhibited growth of E. coli O157:H7 in vitro, was isolated from the rhizosphere

Risikovurdering vedrørende Listeria monocytogenes relatert til gravides konsum av sushi. Faggruppe for hygiene og smittestoffer i Vitenskapskomiteen for mattrygghet

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