Since around the 2000s, Escherichia coli (E. coli) resistant to both oxyimino-cephalosporins and fluoroquinolones has remarkably increased worldwide in clinical settings. The kind of E. coli is also identified in patients suffering from community-onset infectious diseases such as urinary tract infections. Moreover, recoveries of multi-drug resistant E. coli from the feces of healthy people have been increasingly documented in recent years, although the actual state remains uncertain. These E. coli isolates usually produce extended-spectrum β-lactamase (ESBL), as well as acquisition of amino acid substitutions in the quinolone-resistance determining regions (QRDRs) of GyrA and/or ParC, together with plasmid-mediated quinolone resistance determinants such as Qnr, AAC(6’)-Ib-cr, and QepA. The actual state of ESBL-producing E. coli in hospitalized patients has been carefully investigated in many countries, while that in healthy people still remains uncertain, although high fecal carriage rates of ESBL producers in healthy people have been reported especially in Asian and South American countries. The issues regarding the ESBL producers have become very complicated and chaotic due to rapid increase of both ESBL variants and plasmids mediating ESBL genes, together with the emergence of various “epidemic strains” or “international clones” of E. coli and Klebsiella pneumoniae harboring transferable-plasmids carrying multiple antimicrobial resistance genes. Thus, the current state of ESBL producers outside hospital settings was overviewed together with the relation among those recovered from livestock, foods, pets, environments and wildlife from the viewpoint of molecular epidemiology. This mini review may contribute to better understanding about ESBL producers among people who are not familiar with the antimicrobial resistance (AMR) threatening rising globally.
To clarify sensitivities of juvenile exposure to radiation on uterine carcinogenesis, female Donryu rats, a high yield strain of uterine corpus cancer, were exposed to 0.2 and 1.0 Gy of gamma radiation at postnatal day 14. Sequential changes in their reproductive organs and hematology, and the effects on uterine tumor development were compared to those in adult rats exposed to the same doses. Half number of the rats in each group was treated with N-ethyl-N’-nitro-N-nitrosoguanidine (ENNG) after the radiation to accelerate the development of uterine cancer. Severe apoptosis and depletion of oocytes in the primordial/primary follicles were immediately induced after juvenile exposure at 1.0 Gy only. The ovaries in rats exposed to 1.0 Gy at juvenile showed severe atrophy characterized by the loss of all types of follicles and a lack of corpora lutea by 2 months of age, and all rats elicited an early onset of persistent estrus corresponding to the atrophy. At the termination of 9 months of age, juvenile 1.0 Gy exposure with ENNG treatment increased the incidence of endometrial adenocarcinoma and the multiplicities of combined endometrial adenocarcinomas and their precancerous lesions. Enhancement of uterine cancer development was not apparent at the same exposure without ENNG. In comet assays, neither 0.2 nor 1.0 Gy juvenile exposure induced direct DNA damage to uteri though the damage was found in the ovary at 1.0 Gy. The present results indicated that juvenile exposure to gamma radiation indirectly enhanced uterine cancer development in rats through direct damage to oocytes resulting in serious atrophy of the ovary accompanying early onset of persistent estrus. The damage to ovary was more sensitive at juvenile than adults. The result in comet assay suggested that direct DNA damage to the uterus by radiation was excluded.
Food Safety Commission of Japan (FSCJ) conducted a risk assessment of melengestrol acetate (MGA, CAS No. 2919-66-6), a synthetic hormone, based on results from various studies. MGA was recognized to have no genotoxicity relevant to human health, and it enabled FSCJ to specify an acceptable daily intake (ADI) in the assessment. In vitro studies using various human hormone-receptors showed that MGA exerts biological action primarily as progestogens and secondarily as glucocorticoids. Major adverse effects of MGA observed were mammary gland hyperplasia, endometrial hyperplasia, and a lack of corpora lutea, accompanying the elevated level of serum prolactin. Increased incidence of mammary gland tumor was observed in C3Han/f mice at the dose of 1.5 mg/kg bw/day in a carcinogenicity study. The increase was presumably due to MGA-induced hyperprolactinemia, but not a direct effect of MGA from the experiment, using a prolactin inhibitor. Inhibitions of estrus and ovulation, in addition to dystocia, were observed in female animals in the reproductive and developmental toxicity studies. Malformations such as cleft palate, clubfoot, umbilical hernia, and defective skeletal ossification were observed in rabbits at doses of 0.8 and 1.6 mg/kg bw/day in a developmental toxicity study. However, these were likely due to the corticosteroidal (glucocorticoid) action of MGA. The no-observed-adverse-effect level (NOAEL) was obtained from a rhesus monkey study given orally 1.5 µg/kg bw/day of MGA over the one menstrual-cycle. The value was, however, the result of the study using the large common ratio of 10. In another study, the lowest-observed-adverse-effect level (LOAEL) of 5 µg/kg bw/day, obtained from a cynomolgus monkey given MGA over the three menstrual-cycles. The LOAEL value was estimated close to the biological threshold, because of no obvious hormonal disorders despite of minimal change of menstrual cycle. Therefore, FSCJ considered it appropriate to specify an ADI on the basis of the LOAEL obtained from a cynomolgus monkey study over the three menstrual-cycles, and to add an additional safety factor of 2. Consequently, FSCJ specified the ADI of 0.025 µg/kg bw/day by applying a safety factor of 200 to the LOAEL of 5 µg/kg bw/day in a cynomolgus monkey study over the three menstrual-cycles.
Pufferfish is categorized as one of foods which contain or are covered with toxic or harmful substances or are suspected to contain or be covered with such substances” in Article 6, Item (ii) of the Food Sanitation Act (Act No. 233 of December 24, 1947). The issue, however, stipulates in the proviso “that this shall not apply to cases where the Minister of Health, Labour and Welfare (MHLW) specifies that such articles involve no risk to human health”. Based on the proviso, the pufferfish species and the edible parts, which involve no risk to human health, were specified in the notice titled “New Rules for Measures to Secure Sanitation Regarding Pufferfish”. Currently, the liver of Japanese pufferfish (Takifugu rubripes, hereinafter referred to as “Torafugu”) is not included in the notice, thus shall not be sold based on Article 6, Item (ii) of the Act. A proposal to add the liver of Torafugu as a food which involves no risk to human health, as one of the cases stipulated in the proviso, was submitted to the MHLW. In response to the request from MHLW, Food Safety Commission of Japan (FSCJ) conducted a risk assessment on the liver of Torafugu that is aquacultured and served to the customer under the controlled procedures proposed by Saga prefecture and a business operator in the prefecture (hereinafter referred to as “the specified operator”). The proposed procedures are: 1) Torafugu is aquacultured on land under the control of the specified operator. 2) Using a HPLC-FL method, TTX level of a part of liver tissue from every Torafugu fish is determined. 3) Only the liver showing below the detection limit of TTX will be served exclusively in the restaurants managed by the specified operator. FSCJ conducted the risk assessment mainly from the view points; 1) toxificating mechanisms of Torafugu, as well as hazards and risk control points in the on-land aquaculture, 2) validity of the HPLC-FL method for TTX analysis, 3) reliability of the sampling part for TTX-level determination, 4) acceptability of exclusive determination of TTX. Based on the current findings and data in the documents submitted, FSCJ concluded that the safety of the liver of Torafugu aquacultured on land through the proposed procedures could not be secured, even with the determination of TTX in the individual liver.
Food Safety Commission of Japan (FSCJ) conducted a risk assessment of 2,4-D1) (CAS No. 94-75-7), a phenoxy herbicide, based on results from various studies. Major adverse effects of 2,4-D observed were suppressed body weight, renal tubular degeneration, hypertrophy of hepatocytes, reduced weight of testis and retinal degeneration in rats. No adverse effects were detected in carcinogenicity, reproductive toxicity, teratogenicity and genotoxicity relevant to human health. The relevant substance to the residue definition for dietary risk assessment was identified as 2,4-D and metabolite C2) in agricultural products and 2,4-D (parent compound only) in livestock products. The lowest no-observed-effect level (NOAEL) obtained from all the studies was 0.99 mg/kg bw/day in a two-year combined chronic toxicity/carcinogenicity study (the 1st study in Table 1) in rats. FSCJ specified an acceptable daily intake (ADI) of 0.0099 mg/kg bw/day by applying a safety factor of 100 to the NOAEL. The lowest NOAEL for adverse effects likely to be elicited by a single oral administration of 2,4-D was 15 mg/kg bw/day obtained from the acute neurotoxicity study in rats. Consequently, FSCJ specified an acute reference dose (ARfD) of 0.15 mg/kg bw by applying a safety factor of 100 to the NOAEL.