和田 新平

Mycobacterium chelonae is a nontuberculous mycobacterium that causes infections in various animals, including humans. In this study, we report the draft genome sequence of M. chelonae subsp. bovis strain NJB1701, which was isolated from a Baikal seal (Pusa sibirica) in captivity in Japan.

Mycobacterium marinum is a slow-growing, photochromogenic nontuberculous mycobacterium, which can cause mycobacteriosis in various animals, including humans. Several cases of fish mycobacteriosis have been reported to date. Mycobacterium marinum has also been isolated from aquatic environmental sources such as water, sand, biofilms, and plants in the natural environments. Hence, we hypothesized that a wide variety of sources could be involved in the transmission of M. marinum. In this study, we tested this hypothesis by isolating M. marinum from various sources such as fish, invertebrates, seagrass, periphytons, biofilms, sand, and/or water in two aquaria in Japan and conducting a phylogenetic analysis based on single-nucleotide polymorphisms (SNPs) using whole-genome sequences of the isolated strains. The analysis revealed that the strains from animal and environmental sources belonged to the same clusters. This molecular-based study epidemiologically confirmed that various sources, including fish, invertebrates, and environmental sources, could be involved in transmission of M. marinum in a closed-rearing environment. This is the first report where M. marinum was isolated from different sources, and various transmission routes were confirmed in actual cases, which provided essential information to improve the epidemiology of M. marinum.

INTRODUCTION: Mycobacterium montefiorense is one of the causes of non-tuberculous mycobacterial infections in moray eels and salamanders. Although M. montefiorense infection could be a threat to salamanders, little information is available regarding this pathogen and associated infection. This study aimed to provide fundamental information regarding M. montefiorense and its infection in salamanders. METHODS: Nine M. montefiorense strains isolated from three species of salamanders, namely, Japanese black salamander (Hynobius nigrescens), Hakuba salamander (H. hidamontanus), and Tohoku hynobiid salamander (H. lichenatus), between 2010 and 2018, were characterized based on phenotypic and genetic examination. We also pathologically observed salamanders infected with the M. montefiorense strains, including Hakuba salamanders and Tohoku hynobiid salamanders. RESULTS: The microbiological and chemical characteristics of the M. montefiorense salamander and an eel strain (reference strain) matched. Susceptibility testing for antimicrobials suggested that clarithromycin may be effective. Regarding disinfectants, phtharal, peracetic acid, glutaral, sodium hypochlorite, and benzalkonium chloride may be effective. Phylogenetic analyses revealed that the strains isolated from salamanders in 2014 and 2018 were genetically closely related, which could indicate an outbreak. The main gross findings in infected salamanders include skin ulcerative lesions or nodules in the enlarged liver. Microscopically, multifocal to coalescent granulomatous lesions composed of massive macrophages containing numerous acid-fast bacilli were prominently observed in the liver. CONCLUSION: This study contributes to our understanding of the genetic diversity and phenotypic characteristics of M. montefiorense, as well as the pathology of the infection.

クジラ型パラコクシジオイデス症 （paracoccidoioidmycosis ceti：PCM-C) は，イルカを宿主とし，難治性慢性肉芽腫性ケロイド状皮膚炎を特徴とする人獣共通真菌症である。原因菌は非培養性の Paracoccidioides brasiliensis var. ceti で，中南米を流行地とする高度病原性真菌症のパラコクシジオイデス症（PCM） の原因菌 P. brasiliensisと遺伝子型は同一である。確定診断は臨床症状と病理像での酵母細胞の証明であるが，遺伝子情報による診断も重要である。今回，遺伝子情報を欠くものの，PCM-Cが疑われていたイルカ皮膚病変生検組織よりnested-PCRで原因菌の特異的糖タンパク抗原遺伝子であるgp43が検出され，配列は既報のPCM-C国内第３症例目と98.9％相同であった。そこでPCMの診断用に設計されたLAMP法を応用したところ，PCRとLAMP法の組み合わせによりgp43の増幅に成功したことから，この手法は迅速診断法としての有用性が期待できる。