The ability of Listeria monocytogenes to survive or grow during Camembert cheese manufacturing, ripening and storage was examined. Two experimental methods were applied for manufacturing Camembert cheese: using Listeria-contaminated milk (1.6×104cells/ml), and using Listeria-contaminated brine (1.5×106cells/ml).Listeria counts decreased in both cases during the beginning of the ripening process; in the later stage an increase of the count occurred. The count of this organism after ripening was about the same as in the initial stage. After that the number increased gradually, and Listeria counts of 1.7×105cells/g and 1.5×108cells/g were attained after 50 days, respectively.Listeria monocytogenes survived in 18% brine at 12°C for more than 21 days.
SUMMARY A seroepidemiological survey for toxocaral infection was performed using samples from children and adult women in the Yamaguchi area of Western Japan, An enzyme-linked immunosorbent assay using excretory–secretory antigen was applied to these sera. Of samples tested, 3·1% from children and 3·7% from women were positive. It was found that regression analysis of positive rates by age between 20 and 70 or more years was significant in the positive direction. The positive rates from urban, rural and fishing areas were 5·7, 3·9 and 1·7% respectively. Also, the rates from northern, western and eastern parts in the research area were 5·7, 4·7 and 0·5% respectively. These findings suggested that environmental factors are important for toxocaral infection. Further, the rate for 108 samples who answered that they have owned dogs was 6·2% compared to 2·9% of 422 respondents who denied an experience of owning dogs. This fact suggested thatattention should be paid to dog breeding for prevention and control of toxocaral infection in man.
This study describes the presence of circulating toxocaral antigens (CTA) in the sera of dogs infected with Toxocara canis (T. canis) by using a sandwich enzyme-immunoassay (SEIA). A specificity of this assay with different antigens was observed, i.e. the EIA values, which express the antigen concentration, of excretory-secretory antigen from T. canis larvae were higher than those of other antigens (Ascaris lumbricoides, Dirofilaria immitis and Fasciola hepatica). The variability in intra-assay was below 10%. In age distribution of CTA levels, the highest level was observed at 1 month of age. Thereafter, the levels decreased gradually until 6 months of age and then the same levels were maintained until adult age. Also, slightly elevated levels were found in the sera of foetuses. A significant correlation was obtained between age and CTA levels. The positive correlation between the number of worms and CTA levels was significant. As for the IgG, IgM and IgA antibodies, a significant correlation was observed between the IgM antibody activities and CTA levels, but this was not observed with IgG and IgA antibodies. From these results, it was indicated that the immunological response to T. canis infection in dogs may not be reached until 1 or 2 months after birth, although detectable CTA levels were observed in foetal and early life. It was also suggested that the immunological stimulation for canine toxocariasis may be maintained by the excretory-secretory materials from the larvae through life and as a result, IgM antibody production may be observed even in chronically infected adult dogs. The SEIA technique reported in this study may be useful as a diagnostic tool of human toxocariasis, since the CTA can be directly demonstrated by the technique.
