Shiga toxin (verotoxin)-producing Escherichia coli (STEC) is an important cause of foodborne disease. Since outcomes of the infections with STEC have a broad range of manifestation from asymptomatic infection or mild intestinal discomfort, to bloody diarrhea, hemolytic uremic syndrome (HUS), end-stage renal disease (ESRD), and death, the disease is a serious burden in public health and classified as a notifiable infectious disease in many countries. Cattle and other ruminants are considered to be the major reservoirs of STEC though isolation of STEC from other animals have been reported. Hence, the source of contamination extends to a wide range of foods, not only beef products but also fresh produce, water, and environment contaminated by excretes from the animals, mainly cattle. A low- infectious dose of STEC makes the disease relatively contagious, and causes outbreaks with unknown contamination sources and, therefore, as a preventive measure against STEC infection, it is important to obtain characteristics of prevailing STEC isolates in the region through robust surveillance. Analysis of the isolates by pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA) could help finding unrecognized foodborne outbreaks due to consumption of respective contaminated sources. However, though the results of molecular analysis of the isolates could indicate linkage of sporadic cases of STEC infection, it is hardly concluded that the cases are related via contaminated food source if it were not for epidemiological information. Therefore, it is essential to combine the results of strain analysis and epidemiological investigation rapidly to detect rapidly foodborne outbreaks caused by bacteria. This article reviews STEC infection as foodborne disease and further discusses key characteristics of STEC including pathogenesis, clinical manifestation, prevention and control of STEC infection. We also present the recent situation of the disease in Japan based on the surveillance of STEC infection.
Acrylamide has neurotoxicity, carcinogenicity, and genotoxicity in experimental animals and cellular systems. Fried potato is one of the major intake sources of acrylamide in food, and fried onion was reported to contain up to 100 ng/g level of acrylamide. To determine acrylamide concentration in potato and onion stir-fried prior to boiling for simmered dishes such as curry, stew, and Niku-jaga, a typical Japanese meat/potato/onion cuisine, we collected samples stir-fried at homes of volunteers who intended voluntarily to cook these simmered dishes. Acrylamide level was analyzed by GC-MS after the xanthydrol derivatization. Among 53 stir-fried potato samples, median and average values of acrylamide were found to be 2.0 ng/g and 11 ng/g, respectively. Acrylamide levels of 27 samples (51%) were less than limit of detection (LOD) (4 ng/g), and those of 13 samples (25%) were less than limit of quantification (LOQ) (10 ng/g). In cases with less than LOD and less than LOQ of acrylamide levels, one-half of LOD and average of LOD and LOQ were adopted, respectively, to calculate the median and average. This median was markedly lower than those of fried potato (180 ng/g) and potato snacks including potato chips (550 ng/g) reported in monitoring in 2013 fiscal year in Japan. Among 58 stir-fried onion samples, acrylamide level of only one sample (2%) was less than LOD (3 ng/g), and those of 15 samples (26%) were less than LOQ (8 ng/g). The median and average values in the stir-fried onion were 14 ng/g and 36 ng/g, respectively. These values are comparable to those for stir-fried onion reported by Ministry of Agriculture, Forestry and Fisheries, Japan (median 19 ng/g, average 25 ng/g). But the maximum value of stir-fried onion 420 ng/g in the present study is much higher than the reported maximum value (70 ng/g).
Food Safety Commission of Japan (FSCJ) conducted a risk assessment of captan (CAS No. 133-06-2), a phthalimide fungicide, based on results from various studies. Major adverse effects of captan were observed in suppressed body weight, and also in duodenal mucosal hyperplasia in mice. No adverse effect on fertility was detected. Increases in incidence of duodenal adenoma and adenocarcinoma were identified in mice. Negative results were however obtained from a gene mutation assay of the target in transgenic mice. No genotoxicity relevant to human health of captan was recognized in spite of the positive results in vitro. Therefore, a genotoxic mechanism was unlikely involved in the tumor development, and it enabled us to establish a threshold in the assessment. In developmental toxicity studies, captan, at the doses causing maternal toxicity, increased external alterations as well as skeletal and soft tissue alterations in the fetus of rabbits and hamsters. No captan-induced teratogenicity was detected in rats. Captan (parent compound only) was identified as the residue definition for dietary risk assessment in agricultural and livestock products. The lowest no-observed-adverse-effect level (NOAEL) obtained from all the studies was 10 mg/kg bw/day. FSCJ specified an acceptable daily intake (ADI) of 0.1 mg/kg bw/day by applying a safety factor of 100 to the NOAEL. The lowest NOAEL for potential adverse effects of a single oral administration of captan was 30 mg/kg bw/day in a developmental toxicity study in rabbits. FSCJ specified an acute reference dose (ARfD) of 0.3 mg/kg bw, for women who are or may be pregnant, by applying a safety factor of 100 to the NOAEL. In addition, FSCJ specified an ARfD of 3 mg/kg bw, for general population, by applying a safety factor of 100 to the no-observed-effect level (NOEL) of 300 mg/kg bw obtained from a general pharmacology study in mice.
Food Safety Commission of Japan (FSCJ) conducted a risk assessment of folpet (CAS No. 133-07-3), a phthalimide fungicide, based on results from various studies. Major adverse effects of folpet were observed in hyper-keratosis in rats and in duodenal mucosal hyperplasia in mice. No neurotoxicity and adverse effect on fertility were detected. Increases in the incidence of duodenal adenoma and adenocarcinoma were identified in carcinogenicity studies in mice. FSCJ recognized no genotoxicity relevant to human health of folpet in spite of the positive results in vitro. Therefore, a genotoxic mechanism was unlikely involved in the tumor development, and it enabled us to establish a threshold in the assessment. In developmental toxicity studies, no adverse effects observed in fetus at the dose without maternal toxicity. No folpet-induced teratogenicity was detected in rats. Folpet (parent compound only) was identified as the residue definition for dietary risk assessment in agricultural products. The lowest no-observed-adverse-effect level (NOAEL) obtained in all the studies was 10 mg/kg bw/day in several studies in dogs, rats and rabbits. FSCJ specified an acceptable daily intake (ADI) of 0.1 mg/kg bw/day by applying a safety factor of 100 to the NOAEL. The lowest NOAEL for potential adverse effects of a single oral administration of folpet was 10 mg/kg bw/day in a developmental toxicity study in rabbits. FSCJ specified an acute reference dose (ARfD) of 0.1 mg/kg bw/day, for women who are or may be pregnant, by applying a safety factor of 100 to the NOAEL. FSCJ considered it unnecessary to specify ARfD for general population.
Food Safety Commission of Japan (FSCJ) conducted two sets of risk assessment on phytase produced using Schizosaccharomyces pombe ASP595-1 strain. One is the safety assessment on feed additives produced using genetically modified microorganisms. None of new harmful substance is generated in the additive and thus not transferred to animal products, such as meat, milk and eggs. Components associated with genetic modification in the additive are unlikely to yield harmful substances to be accumulated in animal products. The components are unlikely to affect the metabolism of the target animals to generate new harmful substances. No safety concern is thus raised in the products from animals fed with this phytase. The other is the risk assessment related to the revision of the Standards and Specifications of Feeds and Feed Additives. The feed additive was considered to have no genotoxicity relevant to human health. No adverse effects were observed in 14-day and 90-day subacute toxicity studies in rats as well as in feeding trials in pigs and poultry. On the formulations with polyvinyl alcohol, human intake of polyvinyl alcohol via animal products was recognized to be negligible. Consequently, FSCJ judged that the risk on human health via food is negligible as long as the 6-phytase produced using S. pombe ASP595-1 strain is properly used as a feed additive.
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