Detection of norovirus in food samples collected during suspected food-handler-involved foodborne outbreaks in Tokyo.

Although norovirus (NoV) is the major cause of gastroenteritis, with the largest number of NoV food poisoning cases in Japan, limited information is available regarding NoV detection in food. This study aimed to detect NoV in food samples during the 2015-2016 suspected foodborne outbreaks in Tokyo; 352 food samples from 64 NoV food poisoning outbreaks were collected. Bacterial culturing was performed for sample pretreatment and real-time reverse transcription polymerase chain reaction was conducted for NoV screening. The NoV detection rate was 1·7% (6/352). NoV-positive food samples included leftover boxed lunch, mackerel fillet (foodstuff), aburi salmon slice (partially seared salmon slice), raw tuna as a chirashizushi ingredient, raw amberjack as a sushi topping and ice for drinks. Since fresh fish as sushi toppings or ingredients and ice were consumed without heating, they may present a higher risk of viral infection. NoV-positive food samples were obtained from five outbreaks, wherein food handlers were NoV-positive in four. Each partial VP1 sequence from food samples matched completely with those in NoV-positive individuals and food handlers. Hence, food handlers play a potentially important role in food-based NoV transmission in all five outbreaks; therefore, hygiene education among them is essential to prevent NoV foodborne outbreaks. SIGNIFICANCE AND IMPACT OF THE STUDY: Significance and Impact of the Study: Norovirus (NoV) is a leading cause of foodborne outbreak in Japan. The most frequent route of transmission in NoV foodborne outbreaks is secondary contamination via infected food handlers. However, limited information is available regarding NoV contamination in food samples. This study reports the detection of NoV in food samples to elucidate the source and route of NoV infection leading to outbreaks for 2 years in Tokyo. Our data potentially contribute to education and the development of safe food-handling strategies among food handlers and employees in the food industry through elucidation of risk factors associated with NoV contamination.

Identification and functional activity of a staphylocoagulase type XI variant originating from staphylococcal food poisoning isolates.

UNLABELLED: Staphylocoagulase, an extracellular protein secreted by Staphylococcus aureus, has been used as an epidemiological marker. At least 12 serotypes and 24 genotypes subdivided on the basis of nucleotide sequence have been reported to date. In this study, we identified a novel staphylocoagulase nucleotide sequence, coa310, from staphylococcal food poisoning isolates that had the ability to coagulate plasma, but could not be typed using the conventional method. The protein encoded by coa310 contained the six fundamental conserved domains of staphylocoagulase. The full-length nucleotide sequence of coa310 shared the highest similarity (77·5%) with that of staphylocoagulase-type (SCT) XIa. The sequence of the D1 region, which would be responsible for the determination of SCT, shared the highest similarity (91·8%) with that of SCT XIa. These results suggest that coa310 is a novel variant of SCT XI. Moreover, we demonstrated that coa310 encodes a functioning coagulase, by confirming the coagulating activity of the recombinant protein expressed from coa310. This is the first study to directly demonstrate that Coa310, a putative SCT XI, has coagulating activity. These findings may be useful for the improvement of the staphylocoagulase-typing method, including serotyping and genotyping. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to identify a novel variant of staphylocoagulase type XI based on its nucleotide sequence and to demonstrate coagulating activity in the variant using a recombinant protein. Elucidation of the variety of staphylocoagulases will provide suggestions for further improvement of the staphylocoagulase-typing method and contribute to our understanding of the epidemiologic characterization of Staphylococcus aureus.

Identification and characterization of novel Staphylococcus aureus pathogenicity islands encoding staphylococcal enterotoxins originating from staphylococcal food poisoning isolates.

AIMS: Horizontal transfer of Staphylococcus aureus pathogenicity islands (SaPIs) plays an important role in acquiring pathogenicity. This study aimed to identify novel SaPIs encoding staphylococcal enterotoxins (SEs) and to characterize their SE productivity and replication process. METHODS AND RESULTS: Four novel SaPIs (SaPITokyo12413, SaPITokyo11212, SaPITokyo12571 and SaPITokyo12381) were determined using the SaPI scanning method. These SaPIs were composed of mosaic structures containing reported sequences. Four strains harbouring novel SaPIs produced significant amounts of SEs to cause staphylococcal food poisoning (SFP). With focus on the interaction between the replication initiator protein (Rep) and the replication origin (ori sites) that are proposed to be important for the replication of SaPIs, each Rep was prepared and their two functions were confirmed: binding activity to ori sites and helicase activity. These activities were present in the Reps of SaPITokyo11212, SaPITokyo12571 and SaPITokyo12381, but were both absent in the Rep of SaPITokyo12413. CONCLUSIONS: All four novel SaPIs could give sufficient toxicity to Staph. aureus to cause SFP. However, SaPITokyo12413 may be restricted in its replication capacity, suggesting that it lacks transfer ability unlike the other SaPIs. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report to identify four novel SE-encoding SaPIs and to examine their toxicity and replication capacity. Because SaPIs deeply participate in SE acquisition, it is important to elucidate their characteristics for understanding Staph. aureus virulence and speculating regarding its evolution as a pathogen.

Risk of human infection with Giardia duodenalis from cats in Japan and genotyping of the isolates to assess the route of infection in cats.

The number of facilities in which customers make contact with cats before eating and drinking, called 'cat cafés', has recently increased in Tokyo, Japan. In a survey to clarify the possibility of zoonotic transmission in Giardia duodenalis, the infection rates of G. duodenalis in 321 stool samples of cats from 16 cat cafés, 31 pet shops, and the Animal Care and Consultation Center of Tokyo were 19·1% (22/115), 1·2% (1/85), and 2·5% (3/121), respectively. In the molecular analysis of 26 G. duodenalis isolates, 6 samples from 2 cat cafés belonged to the zoonotic genotype assemblage A I, and 20 other samples were of assemblage F. Moreover, phylogenetic analysis of glutamate dehydrogenase (GDH) and triosephosphate isomerase (TPI) genes of the 20 assemblage F isolates revealed 2 major lineages. The 6 assemblage A isolates belonged to the same cluster with regard to the GDH gene; however, 2 of the 6 isolates belonged to a different cluster from the other 4 isolates with regard to the TPI gene. Therefore, a risk of transmission from cats to humans is suggested because of the detection of zoonotic Giardia genotypes in cat cafés.

Detection and identification of Diphyllobothrium nihonkaiense plerocercoids from wild Pacific salmon (Oncorhynchus spp.) in Japan.

We investigated the risk of diphyllobothriasis from ingestion of wild Pacific salmon in Japan by surveying Diphyllobothrium plerocercoids in 182 salmon samples obtained from Japan. The plerocercoids were not detected in chum salmon (Oncorhynchus keta) (0/26), called Akizake in Japan, caught between September and November. However, the detection rate of plerocercoids in chum salmon, called Tokishirazu in Japan, caught between early April and June, was 51.1% (24/47) with an average of two plerocercoid larvae per fish. The detection rates of cherry salmon (Oncorhynchus masou) and pink salmon (Oncorhynchus gorbuscha) were 12.2% (10/82) and 18.5% (5/27), respectively, and the average number of plerocercoids per fish was 0.45 (37 larvae/82 fishes) and 0.22 larvae (6 larvae/27 fishes), respectively. Plerocercoids isolated from O. keta and O. masou were identified as Diphyllobothrium nihonkaiense on the basis of molecular analysis of the cox1 and nad3 genes. Moreover, four tapeworms (three from O. keta and one from O. masou) were obtained by infecting golden hamsters with plerocercoids. The morphological features of these tapeworms were similar to those of D. nihonkaiense isolated from humans. Therefore, we think that O. keta and not O. masou is the most important source of plerocercoid infections in Japan.

[Increased IL-2 and sIL-2R in sera of infants with HTLV-I infection from mother].

In our laboratory, children born to women are known to be infected with Human T-cell Leukemia Virus type-1 (HTLV-I) have been followed using, detect of gene by PCR and antibody by Western Blot Assay (WB) and Immunofluorescence Assay (IFA) test from 1990 through 1996. Four children out of 123 delivery cases have been confirmed to be infected with HTLV-I. We analyzed the correlation between the concentration of cytokines (IL-2, sIL-2R, IFN-gamma) and HTLV-I infection. IL-2 and sIL-2R in sera increased after HTLV-I infection. There was no correlation between the concentration of IFN-gamma and HTLV-I infection. These result suggested that detection of IL-2 and sIL-2R might be the marker of HTLV-I infection.

[Preliminary screening for antiviral AIDS drugs. VIII. Report for fiscal year 1995].

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 96 samples of different origin tested, two were shown to inhibit the growth of HIV in vitro. One of the positive samples (plant origin) has hopeful signs, as the ranges of effective doses are wider than those of most of positive samples which had been found by us.

The inhibitory effect of the crude extract from a seaweed of Dygenea simplex C. Agardh on the in vitro cytopathic activity of HIV-1 and it's antigen production.

The crude water extract (NS-1) from a seaweed (Digenea simplex C. Agardh Rhodomelaceae) exhibited anti-human immunodeficiency virus (HIV)-1 activity in vitro. The inhibitory effect of the extract on the cytopathic activity of HIV-1 and it's antigen production was examined using a microplate method, immunofluorescent assay, and an HIV antigen detection kit (Abbott). NS-1 inhibited both the cytopathic effect of HIV-1 to MT-4 cells and the giant cell formation of Molt-4 cells infected with HIV-1.

[Studies on maternal transmission of HIV-1].

To investigate HIV-1 transmission from mother to child, samples taken from 3 HIV-1 sero-positive pregnant mothers, 3 children born by caesareans from their mothers and therapeutic abortion from 2 HIV-1 sero-positive mothers were tested for HIV-1 antibody by westernblot, p24 antigen by antigen captured ELISA, proviral DNA by Nested-PCR and isolation of HIV-1 virus from peripheral blood, cord blood, amniotic fluid and placenta. HIV-1 proviral DNA was detected in the peripheral blood of all mothers, but p24 antigen and virus isolation were not detected. None of the HIV-1 markers, except for antibody, was detected in the samples from their children and placenta. These facts strongly suggest that there was no HIV-1 transmission from mother to child.

[Preliminary screening for antiviral AIDS drugs. IV. Report on fiscal year 1992].

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 191 samples tested, seven were found to inhibit the growth of HIV in vitro. Four of seven have hopeful signs, as the ranges of effective doses of the samples are wide.