Food safety (Tokyo, Japan)最新文献

In this study, a method using a recombinant phage for detection of E. coli O157:H7 in fresh vegetables was investigated. Four kinds of fresh vegetables, i.e. lettuce (Lactuca sativa), mustard greens (Brassica juncea), coriander (Coriandrum sativum), and soybean sprouts were selected since they are commonly used in meals in Vietnam. Firstly, a phage-based method was investigated for detection of E. coli O157:H7 in the four types of vegetables. To support the detection by suppressing growth of background bacteria in vegetables, selective antibiotics, i.e. novobiocin (N) and vancomycin (V) in combination with BHI medium were examined. Secondly, quality of the method was evaluated in terms of sensitivity, specificity, and rapidity. The method enabled the detection of E. coli O157:H7 inoculated at 10³, 10², or 10¹ CFU/ 10 mL of sterile 0.8% NaCl containing 5 g of vegetable and in the presence of several Gram-positive and Gram-negative bacteria inoculated at 10⁷ CFU/10 mL. The time for detection was approximately 16.5 hours for E. coli O157:H7 inoculated at 10 CFU/10 mL of sterile 0.8% NaCl containing 5 g of vegetable. The limit of detection was considered to be 2 CFU g^-1 vegetable.

Fluoroquinolone is widely used for the treatment of bacterial diseases, and the emergence of quinolone resistance has become a serious concern in recent years, owing to an increase and inappropriate use of antimicrobials. Here, we attempted to understand the differences in the emergence frequency of quinolone-resistant bacterial variants in three Salmonella serotypes S. Infantis, S. Schwarzengrund, and S. Manhattan-which are mainly found in broiler industries in Japan. Emergence frequency tests for quinolone-resistant variants using enrofloxacin-containing agar plates and sequence analysis in the quinolone resistance-determining region (QRDR) of gyrA in DNA gyrase were performed. The results showed no significant difference in the emergence frequency among the three serotypes, and most of the resistant variants had mutations in the QRDR region. These findings suggest that differences in the serotypes tested are not associated with the emergence frequency of quinolone-resistant variants.

In the toxicological evaluation of pesticides (agricultural chemicals), their toxicities have been evaluated based on studies in rodents such as rats and mice as well as in non-rodents such as rabbits and dogs. Here, reflecting a research performed under the Food Safety Commission of Japan (FSCJ) grant on pesticide toxicity study¹⁾, international trends and also scientific points of view, the necessity of chronic dog toxicity studies was reconsidered for the use in toxicological evaluation of pesticides.

Salmonella enterica subsp. enterica serovar Enteritidis (SE) is one of the major causes of food poisoning. Much effort has been made to develop a vaccine for the prevention of SE colonization and infection in poultry. However, the effect of inactivated whole-cell SE vaccines on the bacterial attachment has not been clarified. This study investigated the immune responses to a killed whole-cell SE vaccine in chickens and the effect of vaccination on the bacterial attachment of SE to cultured Vero cells. A 1 ml dose of 10⁸-10⁹ CFU viable SE bacterial cells was orally administered to chickens at 4 weeks or 10 months post vaccination. The number (CFU) of SE in 1 g of cecal droppings was counted on day 6 after administration. The SE CFUs were significantly lower (p < 0.05) in the vaccinated chickens, not only at 4 weeks but also at 10 months after vaccination, than in the unvaccinated control chickens. Anti-SE IgG and anti-SE IgA were detected using enzyme-linked immunosorbent assay (ELISA) in serum and intestinal and oviduct fluid samples from vaccinated chickens. Adhesion of heat-killed SE cells to Vero cells was reduced by pre-treatment of the bacteria by the vaccinated chicken-derived intestinal fluid, indicating the potential of the vaccine-induced antibody to prevent SE adhesion to epithelial cell surfaces.

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of dexamethasone (CAS No. 50-02-2), a synthetic adrenocortical hormone, using mainly the evaluation reports from the Joint FAO/WHO Expert Committee on Food Additives (JECFA), and the European Medicines Agency (EMEA). Major adverse effects of dexamethasone were observed in the decrease in white blood cell count (WBC), atrophy of thymus and spleen as well as the decrease in adrenal weights, which were found in various toxicity studies. These effects are attributable to the glucocorticoid action. FSCJ supported the EMEA's judgment "dexamethasone lacks structural similarity with known carcinogens", and concluded that this drug is unlikely to be carcinogenic. Teratogenicity was observed in rats developmental toxicity studies and the no-observed-adverse-effect level (NOAEL) for fetus was 10 μg/kg bw/day. The effect observed at the lowest dose in various toxicological studies was decreased WBC in rats in an endocrinological study. The NOAEL in this study was 1μg/kg bw/day. JECFA and EMEA specified an acceptable daily intake (ADI) based on the pharmacological action, the induction of tyrosine aminotransferase activity (TAT), in rat liver. However FSCJ judged this endpoint is not appropriate to establish an ADI, because the increase of TAT in response to glucocorticoid was a physiological response, and the relationship of changes in TAT with the toxicological findings was obscure. Consequently, FSCJ specified the ADI for dexamethasone at 0.01μg/kg bw/day, based on NOAEL of 1μg/kg bw/day, which was obtained in rats in an endocrinological study, applying a safety factor of 100.

The Listerial flora and Listeria monocytogenes bio-load associated with 411 ready-to-eat (RTE) foods sold at several locations in southern Nigeria was evaluated using phenotypic procedures which included serial dilution and pour plate techniques. Selected L. monocytogenes strains phenotypically identified from the RTE foods were further identified using virulence gene markers and 16srRNA amplification procedures. All the 90 L. monocytogenes strains cultured from the RTE foods were subjected to antibiogram analysis using disc diffusion. Some of the antibiotics employed included; Ceftazidine, cefuroxime, gentamicin, ofloxacin, augumentin, tetracycline and erythromycin. L. monocytogenes L. ivanovii, L. grayi, L.welshimeri, L. seeligeri and L. innocua were detected in the RTE foods. Haemolysin (hlyA) gene, Internalin gene (inlA) and invasive gene (iap) were detected in all L. monocytogenes isolates. L. monocytogenes LMEW70 with accession number KY053295 was 93% similar to L. monocytogenes L1846. All the L. monocytogenes isolates were resistant to amoxicillin, cloxacillin, augumentin and ceftazidime.

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of desmedipham (CAS No. 13684-56-5), a carbanilate herbicides, based on results from various studies. Major adverse effects of desmedipham were suppressed body weight, hemolytic anemia, methemoglobinemia and follicular cell hypertrophy in thyroid. Neither carcinogenicity, reproductive toxicity, nor genotoxicity relevant to human health was observed on desmedipham. Desmedipham, at the dose with maternal toxicity, caused external anomalies such as mandibular malformation and cleft palate, visceral anomalies such as ventricular septum defect, and skeletal anomalies such as defect of sternum and asymmetric alignment of seternebral hemicentres in developmental toxicity studies in rats. No teratogenetic effects were observed in rabbits. The lowest no-observed-effect level (NOAEL) obtained in all studies was 3.2 mg/kg bw/day in a two-year combined chronic toxicity/carcinogenicity in rats. FSCJ specified an acceptable (ADI) of 0.032 mg/kg bw/day, applying a safety factor of 100 to the NOAEL. The lowest NOAEL for adverse effects elicited by a single oral administration of desmedipham was 90 mg/kg bw/day obtained from the developmental toxicity study in rabbits (the 2^nd study in the Table 2). Consequently, FSCJ specified an acute reference dose (ARfD) of 0.9 mg/kg bw applying a safety factor of 100 to the NOAEL.

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of dicycranil (CAS No. 112636-83-6), a pyrimidine-derived insect growth regulator, using the evaluation reports from the Joint FAO/WHO Expert Committee on Food Additives (JECFA), the European Medicines Agency (EMEA), and also the Australian government. In an 18-month chronic toxicity/carcinogenicity study in mice, increased incidences of hepatocellular adenomas and carcinomas were observed in females in the 500 ppm group. In spite of a recent experiment implying the possible indirect genotoxicity of dicyclanil on the carcinogenicity, dicyclanil is unlikely to exert the carcinogenicity in vivo through the genotoxic mechanism judging from other studies. FSCJ recognized it as feasible to set the threshold value. Adverse effects detected at the lowest dose in various toxicological studies were the increased plasma levels of cholesterol and phospholipid at 100 ppm (equivalent to 2.7 mg/kg bw/day in males and 3.5 mg/kg bw/day in females) in a 90-day subacute toxicity study in dogs. No-observed-adverse-effect level (NOAEL) of this study was 20 ppm (equivalent to 0.61 mg/kg bw/day in males and 0.71 mg/kg bw/day in females). On the other hand, the NOAEL in a long term study, a 12-month chronic toxicity study in dogs was 25 ppm (equivalent to 0.71 mg/kg bw/day in males) based on increased level of plasma cholesterol observed only in males at 150 ppm (equivalent to 4.4 mg/kg bw/day in males and 5.1 mg/kg bw/day in females). The increased cholesterol levels in plasma were common in both studies in dogs. It was appropriate to choose the NOAEL for the effect on cholesterol in the longer term treatment, and thus FSCJ adopted the NOAEL of 0.71 mg/kg bw/day. Consequently, FSCJ specified the ADI of 0.0071 mg/kg bw/day for dicyclanil based on the NOAEL of 0.71 mg/kg bw/day in the 12-month chronic toxicity study in dogs, by applying a safety factor of 100.