Ascaris lumbricoides or roundworm is one of the key soil-transmitted helminths affecting humans. A small number of infections continue to occur in Japan, suggesting plant foodstuff contamination as the source of infection. To understand the current status of ascariasis incidence and to identify potential sources of infection, we extensively surveyed the available literature and collected data from testing facilities that examined clinical samples or foodstuffs. We observed that from 2002 onwards, there was a decrease in the number of ascariasis cases reported in scientific journals. Data from a clinical testing facility indicated that the number of detected cases declined remarkably from 2009. Foodstuff testing facilities reported that 11 of 10,223 plant foodstuff specimens were contaminated with anisakid nematodes but not with Ascaris. Imported kimchi was suspected as the most probable source of ascarid nematode infection, as one Ascaris egg-positive sample was detected among 60 kimchi samples in a testing facility. Therefore, the sources of Ascaris infection are still not fully known and need to be clarified to establish preventive countermeasures to safeguard Ascaris infections that continue to occur in Japan.
The determination of antibacterial agents for animals in swine muscles was improved by microbiological screening and liquid chromatography-mass spectrometry (LC-MS/MS) analyses. In the first instance, the residual drugs were extracted from the samples using the Na2EDTA-McIlvaine buffer (pH 6.0). Subsequently, the agents were purified utilizing a PLS-3 cartridge and extracted with acetonitrile. Considering the microbiological methods, the sensitivities of the investigated drugs were higher and the test plate conditions were improved using a new reference organism Geobacillus stearothermophilus. As a result, a microbiological screening approach able to detect 33 drugs at MRL was developed in Japan. Remarkable, no false positives were detected. Moreover, the same preparation method enabled rapid and reliable microbiological screening, resulting in efficient screening with no undeterminable results.
Fumonisins, which are secondary metabolites produced by some Fusarium species, are detected mainly in corn and corn-based products. Recently, the presence of modified forms of fumonisins in fumonisin-contaminated food products has been reported. In order to evaluate the health risk of modified forms of fumonisins to the Japanese population, we analyzed modified forms of fumonisins in corn-based products retailed in Japan. The modified and free forms of fumonisins in food samples were hydrolyzed by alkaline treatment. The resulting hydrolyzed fumonisins were quantified by LC-MS/MS, and total fumonisins (sum of modified and free forms) was calculated. A total of 166 samples of corn-based products were analyzed over two years. The relative ratios of mean total fumonisins to mean free fumonisins in the cornflakes, corn snacks, corn flour and powdered corn soup samples were 4.7, 2.8, 2.1 and 1.2, respectively. Total fumonisins in the residual solid of five cornflake and three corn snack samples obtained after extraction with methanol–water (3 : 1) were quantified. In the cornflakes and corn snacks samples, 56–72 and 83–98% of the modified forms of fumonisins were present in the residual solid, respectively. The average daily intake of fumonisins from cornflakes and corn snacks by the Japanese population was estimated at 1.1 to 3.9 ng/kg body weight/day when the results of free fumonisins were used for the estimate, but when the results of total fumonisins were used, average daily intake increased about three times and was estimated at 3.3 to 12.5 ng/kg body weigh/day. These results indicate that a risk assessment of fumonisins, including the modified forms of fumonisins, is necessary in order to evaluate the true risk of fumonisins to Japanese people.
Campylobacter is one of the most important causes of food-borne infectious diseases. Antibiotics are rarely needed to treat campylobacteriosis, but occasionally used in severe or prolonged cases. Consumption of contaminated bovine liver is a source of campylobacteriosis. Bovine liver can be contaminated with Campylobacter on the surface and inside by the bile at slaughterhouses. Therefore, we investigated the current prevalence and characteristics of Campylobacter in bovine bile at a slaughterhouse. Campylobacter was isolated from 35.7% (55/154) of bile samples. C. jejuni and C. fetus were the two most frequent species. High antimicrobial resistant rates in C. jejuni were observed against tetracycline (63.0%) and ciprofloxacin (44.4%). Multi-locus sequence typing divided C. jejuni isolates (27 isolates) into 12 sequence types (STs) in which ST806 was the most frequent ST and accounted for 37.0%. All C. fetus were identified as C. fetus subsp. fetus which can cause systemic infections. High antimicrobial resistant rates in C. fetus were observed against ciprofloxacin (66.6%), streptomycin (58.3%) and tetracycline (33.3%). All the C. fetus isolates were divided into two STs, ST3 (16 isolates) and ST6 (8 isolates). Of the 16 ST3 isolates, 15 (93.8%) were resistant to both streptomycin and ciprofloxacin. Our data shows high prevalence of Campylobacter in bovine bile and their high rates of antimicrobial resistance. Preventing bile contamination of bovine liver at slaughterhouses is thus considered to be one of control measures to reduce the risk of Campylobacter infections.
Staphylococcal food poisoning (SFP) is caused by Staphylococcus aureus, and its typical symptom of vomiting is evoked by staphylococcal enterotoxins (SEs). SEs are classified as classical and new types. SEQ is a new-type enterotoxin predicted to have a high potential risk for SFP. To elucidate the correlation between the number of S. aureus cells and the production of SEs as well as classical and new-type enterotoxins in the food environment, the numbers of S. aureus strain cells carrying sea and seq genes and the production of SEA and SEQ protein were examined under 3 pHs values (pH 6.0, 7.0 and 8.0) and 2 NaCl concentrations (0.5 and 1.0%) conditions. The experiments were performed at 25℃, resembling the setting of scrambled eggs at room temperature after cooking. By 24 hr after incubation, the cell number in the scrambled egg was ≥107/10 g, reaching 109/10 g by 48 hr under all conditions. The productions of both SEA and SEQ were detected in the scrambled egg under all conditions by 48 h. SEQ was detected from 24 hr at all 3 pH values in the egg containing 1.0% NaCl, whereas in the egg containing 0.5% NaCl, it was detected from 24 hr at pH 6.0 and from 48 hr at other pHs. The SEQ production was consistently 100–1,000 times less than that of SEA. These results suggest that the new-type enterotoxin SEQ has the potential to evoke symptoms related to SFP following the consumption of egg products cooked under relative lower pH and water activity.
Staphylococcus aureus food poisoning is caused by the intoxication of staphylococcal enterotoxin (SE) produced in foods. Staphylococcal food poisoning is mostly due to staphylococcal enterotoxin type A (SEA) among SEs. There have been many studies on the growth and SEA production of S. aureus in various foods, but few studies in bread. Thus, the SEA production by S. aureus in dough during fermentation and the SEA inactivation in dough during baking were studied in the normal production processes of bread in this study. No growth of S. aureus or SEA production in dough, whose total weight was about 470 g, was observed during the fermentation at 25 and 35℃ for four hr, suggesting that the risk of SEA production in dough during fermentation under these conditions would be negligible. Any SEA injected at 6.0 and 0.56 ng/g in dough could not be detected after 20 and 10 min of baking at 200℃, respectively. These results showed that the baking process, which was completed in 25 min, was enough to inactivate SEA at those doses of SEA in the dough. The results on the production and inactivation of SEA in dough during the production processes in this study would be useful information on microbiological food safety of bread making.
In this study, we developed an LC-MS/MS-based rapid and simple analytical method for six fungicides; imazalil, o-phenylphenol, thiabendazole, fludioxonil, azoxystrobin and pyrimethanil, the latter three were newly approved for use after 2011. For expediting and simplification, we merged the extraction method with that of the pesticide analysis. For purification step, loading of 1 mL of sample extracts to 500 mg Oasis HLB column and elution with 8 mL of acetonitrile gave satisfactory results. The performance of the present method was confirmed for orange, grapefruit, and lemon samples fortified with the six fungicides. The results showed that the average recovery ranged from 89.7 to 100.0%, intra- and inter-assay CV% ranged from 1.5 to 5.0% and from 0.5 to 4.9%, respectively, achieving the target values of the Japanese official guideline for residual pesticide analysis. The limits of quantification of this method were determined to be 1 mg/kg for o-phenylphenol, and 0.2 mg/kg for the other five fungicides. These values were lower than their corresponding regulation values. In addition, we confirmed the usability of the present method for fungicide inspection of commercially available citrus fruits. During 2017–2019, there was no conflict between the food labeling and the fungicides detected and no fungicide with the concentration exceeding maximum residue level was detected
To determine the relationship between seasons and regions and aflatoxin M1 (AFM1) contamination of milk distributed in Fukuyama City, we conducted a survey once during the summer and once during the winter between June 2018 and January 2019. We compared the AFM1 contamination levels in milk drinks available in Fukuyama City during the same period, to provide more about the factors causing AFM1 contamination. All milk samples examined exhibited AFM1 contamination levels below the standard AFM1 contamination level (0.5 μg/kg). For the comparison based on seasons, one milk sample collected in the summer (0.07 μg/kg) exceeded the EU limit (heat-treated milk: 0.050 μg/kg). However, there was no significant difference in the AFM1 contamination level (p>0.05). For the comparison based on regions, the AFM1 contamination level in the milk sample from the Chugoku Region was significantly higher in the winter and significantly lower in the summer compared to those from other regions. AFM1 contamination of milk did not have a direct relationship with seasons or regions, but was instead influenced by the type, amount, and management of feed supplied to dairy cattle. For the comparison between milk and milk drinks, the AFM1 contamination levels in milk drinks were significantly lower (p<0.01). The highest AFM1 concentration (0.08 μg/kg) was detected in one sample of milk drink sampled during the summer. The AFM1 contamination of milk drinks is likely affected by the level of contamination in raw materials, the proportion of such raw materials in the drinks, and the process type. An increase in non-fat milk solids was assumed to be a factor that increases AFM1 contamination.
In the field of food analysis and regulation, different instruments are used to determine the accuracy of quantification values. This is essential, as inconsistencies in values are commonly encountered. To visualize the degree of these discrepancies in each food matrix, we compiled a validation study based on a routine method developed in our laboratory, for 121 pesticides in six agricultural products, namely the grapefruit, potato, paprika, cabbage, spinach, and brown rice. These were analyzed by GC-MS/MS and LC-MS/MS, and the results were compared mainly on the basis of trueness. According to the results of the validation study when using GC-MS/MS, of the 121 pesticides tested in each product class, the number of analytes that satisfied the criteria of the Japanese validation guidelines was 97 in grapefruit, 111 in potato, 110 in paprika, 118 in cabbage, 111 in spinach, and 63 in brown rice. In contrast, in the analysis of the same samples by using LC-MS/MS, the number of analytes that satisfied the criteria of the validation guidelines was 50 in grapefruit, 114 in potato, 103 in paprika, 112 in cabbage, 100 in spinach, and 103 in brown rice. Inconsistences in the differences of trueness were mainly attributed to matrix effects of each instrument, as well as to food matrices, of which the most diverged matrix was that of brown rice (over 20%).