Rapid detection and discrimination of potentially toxigenic Corynebacterium ulcerans and Corynebacterium pseudotuberculosis by multiplex real-time PCR and amplicon melting curve analysis.

We developed a multiplex real-time PCR assay with amplicon melting curve analysis to rapidly discriminate Corynebacterium ulcerans from Corynebacterium pseudotuberculosis and detect the bacterial diphtheria toxin gene. This assay should be a valuable tool for identification of potentially toxigenic C. ulcerans.

Comparison of Neutralizing Antibody Titers against Japanese Encephalitis Virus Genotype V Strain with Those against Genotype I and III Strains in the Sera of Japanese Encephalitis Patients in Japan in 2016.

Japanese encephalitis (JE) is an acute viral disease caused by the Japanese encephalitis virus (JEV). JEV strains are classified into 5 genotypes (I-V). JEV genotype V strains have never been detected in Japan to date, but they were recently detected in South Korea. In the present analysis, we tried to determine if a JEV genotype V strain caused any JE case in Japan in 2016. Serum and cerebrospinal fluid samples were collected from 10 JE patients reported in Japan in 2016. JEV RNA was not detected in any of the samples. Although JEV is a single-serotype virus, it can be expected that the neutralizing antibody titers against JEV genotype V strains are higher than those against genotype I and III strains in the serum of patients with JE in Japan whose causative JEV was the genotype V strain. The neutralizing antibody titers against the JEV genotype V strain were not higher than those against the genotype I or III strain in any serum samples. Therefore, the evidence that the JEV genotype V strain caused any JE case in Japan in 2016 was absent.

First Identification of Human Adenovirus 57 (HAdV-57) in Japan.

Neutralization tests have been routinely used for the identification of human adenovirus C species (HAdV-C) in Japan until 2007. The aim of this study was to clarify the serological cross-reactivity of antiserum that has been used exclusively in Japan and to describe the first identification of HAdV type 57 (HAdV-57) in Japan. Anti-HAdV serum to HAdV-1, 2, 5, and 6 was quantitatively evaluated for cross-reactivity to the HAdV-57 isolates. Anti-HAdV-6 serum neutralized HAdV-57 with a concentration that was 32 to 64-fold higher than what was necessary to neutralize homologous HAdV-6. HAdV-1, 2, and 5 strains were not neutralized by anti HAdV-6 serum. Furthermore, 28 HAdV-6 strains isolated from 6,476 clinical samples were re-examined for HAdVs detected in the Shimane Prefecture of Japan from 2005 to 2014. These 28 strains were re-examined by PCR-sequencing techniques using the penton, hexon, and fiber regions. 3 isolates were determined to be HAdV-57. These data show that HAdV-57 had already invaded Japan as early as 2005, and that HAdV-57 strains were misidentified as HAdV-6.