Community-acquired Clostridium difficile infections have recently been increasing in incidence and severity. Several studies have isolated C. difficile spores from livestock and retail meats, suggesting that food may play a role in transmission. No research has been done, however, on what food conditions might allow for the survival and/or growth of the bacterium. We therefore modelled the minimum thresholds for C. difficile growth under low pH, water activity (aw), and temperature. We also sampled retail ground meats, cheese, and milk for the presence of C. difficile spores and subtyped food isolates for comparison with clinical strains. We found that C. difficile growth could be prevented by refrigeration temperatures. C. difficile spores were also detected for the first time in Canada in ground lamb, ground turkey, ground chicken, cheese and milk. The majority of these food isolates were genetically similar to epidemic strain NAP7/078, suggesting that food may not be a direct vector for C. difficile transmission, but could still be clinically relevant.

Community-acquired Clostridium difficile infections have recently been increasing in incidence and severity. Several studies have isolated C. difficile spores from livestock and retail meats, suggesting that food may play a role in transmission. No research has been done, however, on what food conditions might allow for the survival and/or growth of the bacterium. We therefore modelled the minimum thresholds for C. difficile growth under low pH, water activity (aw), and temperature. We also sampled retail ground meats, cheese, and milk for the presence of C. difficile spores and subtyped food isolates for comparison with clinical strains. We found that C. difficile growth could be prevented by refrigeration temperatures. C. difficile spores were also detected for the first time in Canada in ground lamb, ground turkey, ground chicken, cheese and milk. The majority of these food isolates were genetically similar to epidemic strain NAP7/078, suggesting that food may not be a direct vector for C. difficile transmission, but could still be clinically relevant.

Diss. (sammanfattning) Stockholm : Univ. / Återtagen utgåva. Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 1999. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Community-acquired Clostridium difficile infections have recently been increasing in incidence and severity. Several studies have isolated C. difficile spores from livestock and retail meats, suggesting that food may play a role in transmission. No research has been done, however, on what food conditions might allow for the survival and/or growth of the bacterium. We therefore modelled the minimum thresholds for C. difficile growth under low pH, water activity (aw), and temperature. We also sampled retail ground meats, cheese, and milk for the presence of C. difficile spores and subtyped food isolates for comparison with clinical strains. We found that C. difficile growth could be prevented by refrigeration temperatures. C. difficile spores were also detected for the first time in Canada in ground lamb, ground turkey, ground chicken, cheese and milk. The majority of these food isolates were genetically similar to epidemic strain NAP7/078, suggesting that food may not be a direct vector for C. difficile transmission, but could still be clinically relevant.

Fujinami sarcoma virus encodes a 140/000 m.w. polypeptide (P140) which has been correlated as the agent of transformation in host chicken fibroblasts and mammalian fibroblasts. To conclusively identify the role of P140 in the transformation process it will be necessary to obtain intact/ purified P140. The availability of an antibody monoclonally specific to the N-terminal gag encoded portion of P140 suggested a one-step immunoaffinity purification of P140. After purification of the antibody out of mouse ascites fluid, by 50% ammonium sulfate fractionation and ion exchange chromatography, antibody was linked to a Sepharose 4-B matrix activated with cyanogen bromide. The anti-pl9 affinity matrix bound intact P140 as a doublet relative to a polyclonal anti-pl9. Chaotropic agents, high pH and low pH treatments all failed to elute the bound P140 from the affinity matrix. Failing the purification of intact P140 a method of partial proteolysis was used to produce varying sized fragments of P140/ with the goal of purifying these fragments for further work on the role of P140. Trypsin alone in a limited proteolysis produced small, unstable peptides too close in size distribution to be effectively purified. Chymotrypsin alone produced a broad range of more stable peptides, with a predominance of a 45,000 m.w. peptide. Chymotrypsin-trypsin consecutive proteolysis produced a very stable 35,000 m.w. peptide. Gel filtration of the chymotryptic peptides was ineffective as the peptides coraplexed and were not fractionated. Ion exchange chromatography fractionated the complexing chymotryptic peptides, making possible the purification of these peptides. The stable 45,000 m.w. peptide retained some kinase activity, as it phosphorylated the substrate enolase, similar to but less intense than intact P140. A 30,000 m.w. peptide only phosphorylating after ion exchange did not phosphorylate enolase. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

The culture of the floating aquatic plant, duckweed (Lemna minor), as an agent of domestic sewage treatment was studied in a clarification lagoon at Duncan, British Columbia, during the summer of 1986. Duckweed was grown in plastic fabric tanks (3700 L volume, 1.85 m deep, 2.25 m² water surface area) receiving 290 L of sewage per day or 12.8 d hydraulic retention time. Three treatments were tested: cropped duckweed, uncropped duckweed, and no duckweed. Water quality, plant growth and tissue composition were monitored on the basis of weekly sampling. Removals of VSS, COD, total-N and total-P were greater in the presence than in the absence of duckweed. Unmeasured imports of N and P masked the effect of plant uptake on reducing nutrient concentrations in the tank effluents. Sustainable duckweed yields were possible at both cropping rates, despite a severe infestation of aphids. Dry matter yields of 2.0 g/m².d and 6.4 g/m².d were obtained at the 15%/week and 50%/week cropping rates, respectively. Duckweed contained 6.1 - 6.4% N and 1.1 - 1.4% P (dry wt.). Plant harvest removed 0.14 g N/m².d and 0.03 g P/m².d at the 15%./week and 0.31 g N/m².d and 0.07 g P/m².d at the 50%/week cropping rates. Cropping increased the fraction of total-N and total-P loading that could be removed via plant uptake. Performance of the experimental treatments is analyzed in the light of concentration data, mass balances, and mass flux estimations. Possible sources of unmeasured N and P imports are discussed, and recommendations for future research are provided. The results suggest that duckweed may hold promise under certain conditions as a means of polishing sewage lagoon effluent. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No / Evolutionary biologists are increasingly relying on ancient DNA from archaeological animal bones to study processes such as domestication and population dispersals. As many animal bones found on archaeological sites are likely to have been cooked, the potential for DNA preservation must be carefully considered to maximise the chance of amplification success. Here, we assess the preservation of mitochondrial DNA in a medieval cattle bone assemblage from Coppergate, York, UK. These bones have variable degrees of thermal alterations to bone collagen fibrils, indicative of cooking. Our results show that DNA preservation is not reliant on the presence of intact collagen fibrils. In fact, a greater number of template molecules could be extracted from bones with damaged collagen. We conclude that moderate heating of bone may enhance the retention of DNA fragments. Our results also indicate that ancient DNA preservation is highly variable, even within a relatively recent assemblage from contexts conducive to organic preservation, and that diagenetic parameters based on protein diagenesis are not always useful for predicting ancient DNA survival.