Sterigmatocystin is a genotoxic and hepatocarcinogenic mycotoxin that contaminates foods and environments worldwide. Sterigmatocystin is produced as a precursor to aflatoxin B1 or as an end product by certain Aspergilli. Aspergillus section Versicolores is one of the major sections including sterigmatocystin-producing species and is thus a potential health and environmental hazard. Recently, the taxonomy of this section was revised and classified into 14 species on the basis of molecular phylogenetic analysis. However, investigation of the distribution and sterigmatocystin production of each species has been limited; in particular, its distribution in foods has been scarcely reported. In this study, we collected isolates of Aspergillus section Versicolores from various foods and environments in Japan and investigated their distribution and sterigmatocystin production. The isolates were classified into nine species or species groups, which revealed that A. creber, A. puulaauensis/tennesseensis and A. sydowii are the main species/species groups in Japan. In addition, A. versicolor sensu stricto was detected with some frequency, specifically in foods. Furthermore, the two species A. creber and A. versicolor sensu stricto frequently produced sterigmatocystin. It is therefore important for food safety to intensively monitor these two species and distinguish them from other species, especially A. sydowii, which is not considered to produce sterigmatocystin.
The prevalence and antimicrobial susceptibility of Salmonella in 512 poultry meat samples collected from retail stores and poultry-processing plants in Japan between 2015 and 2016 were investigated. The results showed that 55.9% of poultry meat samples were contaminated with Salmonella, with nine different serotypes represented. The most frequent serovar was Salmonella enterica serovar Infantis, followed by S. Schwarzengrund, together accounting for 78.2% of the isolates. High antimicrobial resistance rates were observed against tetracycline (80.9% S. Infantis and 83.9% S. Schwarzengrund), streptomycin (53.4% S. Infantis and 76.8% S. Schwarzengrund), and kanamycin (33.6% S. Infantis and 82.1% S. Schwarzengrund). All tested isolates were susceptible to colistin and ciprofloxacin. In addition, a high proportion (65.6% of S. Infantis, 85.7% of S. Schwarzengrund) of Salmonella isolates were resistant to two or more antimicrobials, and 22 and 17 different resistance patterns were observed in the two strains, respectively. The predominant antibiotic resistance patterns were streptomycin-tetracycline (32/131, 24.4% of S. Infantis) and streptomycin-kanamycin-tetracycline-sulfamethoxazole/trimethoprim (43/112, 38.4% of S. Schwarzengrund). These data indicate that multidrug-resistant S. Infantis and S. Schwarzengrund have spread among poultry meat in Japan.
Recently, a long-term (1-year) dog toxicity study has not been a mandatory toxicity study for application of agricultural chemical in the United States (US) and the European Union (EU). This study was conducted to propose a guide for making science-based judgement on the necessity of long-term dog toxicity study, which is one of required toxicity studies at toxicological evaluation in Japanese pesticide regulation system. In order to carry out the proposal we analyzed the results of toxicity studies including subacute (3-month) toxicity study in dogs or toxicity studies in other species in the pesticide evaluation reports published by the Food Safety Commission of Japan (FSCJ), the responsible regulatory body for toxicological evaluation of pesticides in food. In the analysis of evaluation reports of 286 pesticides ADI (acceptable daily intake) of 93 pesticides (32.5%) were established based on dog studies. The ADIs of 74 pesticides among them, however were not considered to have a big influence if the long-term dog toxicity study was omitted. With regard to the other four agents the possibility that the long-term dog study becomes unnecessary was considered by adding detailed examination. With respect to the remaining 15 agents, we could not judge that long-term dog study were unnecessary. The analysis indicated that the dog long term test could be omitted in most cases. On the other hand, it should be considered carefully necessity of the long-term dog study when the toxicological profiles observed in dogs and rats were different, when the toxicity susceptibility in dogs was considered high, when no no-observed-adverse-effect level (NOAEL) is specified in subacute toxicity study in dogs or when bioaccumulation in dogs is concerned. We also noted that the studies already conducted for pesticide registered previously should be used for their hazard evaluation.
An adequate supply of standard reference material for paralytic shellfish toxins (PSTs) is critical for the accurate chemical quantification using high performance liquid chromatography (HPLC) with fluorescent detection, liquid chromatography-tandem mass spectrometry (LC-MS/MS), biological analysis of these toxins using enzyme-linked immunosorbent assay (ELISA), and immunochromatography. Large batch cultivation for the chain forming species G. catenatum, producers of PSTs of N-sulfocarbamoyl-11-hydroxysulfate toxins (C1 and C2), gonyautoxin 5 (GTX5) and gonyautoxin 6 (GTX6), was investigated using 10 L round-bottom flasks with aeration for the production of GTX5 and GTX6. Aeration rates of 200 mL/min and 500 mL/min were compared, demonstrating that the 500 mL/min aeration rate was adequate to eliminate aggregation of cells. The highest cell density of G. catenatum in 500 mL/min aeration treatment was 9,878 ± 2,617 cells/ml on day 28. Total toxin yield during 10 L cultivation with 500 mL/min aeration was calculated at 30.9 ± 3.6 µmol on day 25, with GTX5 and GTX6 calculated at 3.9 ± 0.7 µmol and 11.4 ± 1.4 µmol, respectively. This simple aeration method will contribute to the more efficient production of PST reference materials.
This study summarizes the levels of the mycotoxins aflatoxin B1, deoxynivalenol, zearalenone, ochratoxin A, and fumonisin B1 in domestic feed produced in Japan. We collected samples of Japanese domestic feed used in livestock farming establishments or by small farmers from April 2012 to March 2014, and measured mycotoxin concentrations in each sample. Regarding corn, deoxynivalenol had the highest detection rate (84%), maximum value (2370 µg/kg), and mean value (400 µg/kg). These results suggest that deoxynivalenol is a major mycotoxin contaminant in Japanese-produced domestic feed. Zearalenone and fumonisin B1 presented the second highest detection rates. The maximum concentration of zearalenone was 1200 µg/kg in grass samples, but its median was under 25 µg/kg, and, overall, it occurred at low concentrations. The detection rate of fumonisin B1 was about 30%, but its maximum concentration in corn was 2400 μg/kg, slightly higher than deoxynivalenol. Overall, mycotoxin concentrations were lower in grass than in corn. Although deoxynivalenol was detected in samples collected from all regions, concentrations in samples from Hokkaido were particularly high. Fumonisin B1 was mainly distributed in Kanto and the southern regions. Concentrations of ochratoxin A and aflatoxin B1 were low; however, the maximum concentration of aflatoxin B1 was 22 μg/kg in corn. Although aflatoxin B1 and ochratoxin A were rarely detected, they occasionally presented high levels, therefore requiring attention. Overall, mycotoxins produced by Fusarium sp. fungi require attention in Japanese-produced domestic feed.
The in vitro studies of the toxicities of trichothecene mycotoxins deoxynivalenol (DON) and nivalenol (NIV) including cell proliferation, cytokine secretion, and the involvement of heat shock protein 90 (Hsp90) in their toxicities were reviewed. Trichothecene mycotoxins are extremely toxic to leukocytes and leukopenia is one of the leading signs of trichothecene toxicosis, implying that trichothecenes hinder cell proliferation. Both toxins retarded proliferation of all four cell lines tested. NIV was more potent than DON in human promyelocytic leukemia cell line HL60, human lymphoblastic leukemia cell line MOLT-4, and rat aortic myoblast cell line A-10. In contrast, both toxins exhibited almost the same potencies in human hepatoblastoma cell line HepG2. While exposure to 0.3 μg/mL DON greatly induced the secretion of anti-hematopoietic cytokines CCL3 and CCL4, treatment with NIV decreased the secretion of these cytokines in HL60 cells, indicating that the toxicity mechanisms of these mycotoxins differ. Because molecular chaperone Hsp90 occupies a pivotal position in a wide range of pathological processes, the effects of an Hsp90-specific inhibitor radicicol on cytokine secretions were investigated. Radicicol counteracted the effect of DON on cytokine secretion, indicating that Hsp90 plays a crucial role in DON-induced cytokine secretion in HL60 cells. Conversely, the results of co-treatment with NIV and radicicol indicate that radicicol does not mitigate the effect of NIV. Regarding CCL3 and CCL4 secretions, DON and NIV have Hsp90-related and -unrelated mechanisms of toxicities, respectively. Taken together the results suggest that, although these toxins share similar chemical structure, there are differences in their toxic mechanisms.
Noroviruses are the leading cause of acute gastroenteritis and foodborne disease in the United States (U.S.). About 1 in 5 reported norovirus outbreaks are spread through foodborne transmission, presenting opportunities for prevention. We describe the epidemiology of U.S. foodborne norovirus outbreaks reported to national surveillance systems, including differences between genotypes. Foodborne outbreaks that occurred during August 2009–July 2015 with norovirus reported as a single confirmed etiology to the National Outbreak Reporting System (NORS) were matched with outbreaks reported to CaliciNet, a U.S. laboratory norovirus outbreak surveillance network. We analyzed these matched outbreaks stratified by genotype for epidemiologic characteristics, including setting, size and duration, health outcomes of case-patients, implicated food, and outbreak contributing factors. Four hundred ninety-three confirmed foodborne norovirus outbreaks were reported in both NORS and CaliciNet. The most common norovirus genotypes reported were GII.4 (52%), GII.6 (9%), and GI.3 (8%). Compared to non-GII.4 outbreaks, GII.4 outbreaks had higher hospitalization rates (12.8 vs. 4.8 per 1,000 cases, P < 0.01). While contaminated foods were identified and reported in only 35% of outbreaks, molluscan shellfish (4% overall) were more often implicated in non-GII.4 outbreaks than in GII.4 outbreaks (7% vs. 1%, P = 0.04). Of the 240 outbreaks reporting at least one contributing factor, food workers were implicated as the source of contamination in 182 (76%), with no difference between GII.4 and non-GII.4 (73% vs 79%, P = 0.3). Foodborne norovirus outbreaks are frequently reported in the U.S., most of which are caused by GII.4 noroviruses. Viruses of this genotype are associated with higher rates of hospitalization; non-GII.4 noroviruses are more frequently associated with contaminated molluscan shellfish. These surveillance data highlight the diversity of noroviruses causing foodborne disease and can help guide appropriate food safety interventions, including worker hygiene, improved food handling and preparation, and further development of norovirus vaccines.
Diarrhetic shellfish toxins (DST) are a group of phycotoxins that include Okadaic acid (OA) and structurally related toxins. In Japan, the regulatory limit of DST in shellfish for human consumption is a total OA equivalent of 0.16 mg per kg of edible tissue. Distribution and individual differences of DST in scallops collected in Aomori Prefecture were investigated. Fourteen to 20 individual scallops were divided into hepatopancreas, gonads, mantles, gills, adductor muscles, and the concentrations of diarrhetic shellfish poisoning (DSP) in each tissue were quantified by LC/MS/MS after hydrolysis. The dominant toxin in the scallops was Dinophysis toxin 1 (DTX1). More than 97% of the observed DTX1 in the scallop tissue was detected in the hepatopancreas and the average level of DTX1 was higher in mussels than the scallops. The number of individual scallops or mussels required to correctly reflect the DTX1 content of a sample group was estimated by resampling. In scallops, using 10 individuals fell within ± 20% of 30 individual’s average with a probability of 99.8%. On the other hand, in the blue mussel, an average of 19 individuals fell within ± 20% of 30 individual’s average with 98% probability. In addition, the analysis of the DST in ascidians collected from Miyagi Prefecture was carried out. The muscles, gills, hepatopancreas and intestines were analyzed. High concentration of both DTX1 and OA were detected in the hepatopancreas after hydrolysis. Low levels of DST were detected from other tissues, indicating that DST are primarily accumulated in the hepatopancreas in the ascidians.