Biology subjects

Hinenoya, A.

Publications and source records attributed to Hinenoya, A..

3 recordsLinked to original sources

bioRxiv2020

Identification of a recently dominate sublineage in Salmonella 4,,12:i:- sequence type 34 isolated from food animals in Japan

Salmonella Typhimurium and its monophasic variant (Salmonella 4,[5],12:i:-) are classified into nine clades. Clade 9 is composed of ST34 strains, including the Salmonella 4,[5],12:i:-European clone, which has rapidly disseminated in humans and animals worldwide since the 2000s. To reveal the microevolution of ST34/clade 9, we analyzed the whole-genome-based phylogenetic relationships of 230 Salmonella Typhimurium and Salmonella 4,[5],12:i:-strains isolated between 1998 and 2017 in Japan and other countries. We identified clade 9-2, a novel sublineage derived from the conventional Salmonella 4,[5],12:i:-clade 9 that exclusively consists of Japanese isolates. Clade 9-2 was generated by mobile genetic element-mediated stepwise genome reductions caused by IS26 and prophages. Furthermore, the recently identified strains developed further resistance to antimicrobials via the acquisition of resistance genes. During this microevolution, Salmonella 4,[5],12:i:-clade 9-2 has dominated among recent isolates from food animals in Japan via the emergence of clonally expanding and/or multiple host-adapted subclades.

microbiology↗

bioRxiv2019

Salmonella genomic island 3 is an integrative and conjugative element and contributes to copper and arsenic resistance of Salmonella enterica

Salmonella genomic island 3 (SGI3) was first described as a chromosomal island in Salmonella 4,[5],12:i:-, a monophasic variant of Salmonella enterica subsp. enterica serovar Typhimurium. The SGI3 DNA sequence detected from Salmonella 4,[5],12:i:-isolated in Japan was identical to that of a previously reported one across entire length of 81 kb. SGI3 consists of 86 open reading frames, including a copper homeostasis and silver resistance island (CHASRI) and an arsenic resistance operon in addition to genes related to conjugative transfer and DNA replication or partitioning, suggesting that the island is a mobile genetic element. We successfully selected transconjugants that acquired SGI3 after filter mating experiments using the S. enterica serovars Typhimurium, Heidelberg, Hadar, Newport, Cerro, and Thompson as recipients. Southern blot analysis using I-CeuI-digested genomic DNA demonstrated that SGI3 was integrated into a chromosomal fragment of the transconjugants. PCR and sequencing analysis demonstrated that SGI3 was inserted into the 3' end of the tRNA genes pheV or pheR. The length of the target site was 52 or 55 bp, and a 55-bp attI sequence indicating generation of the circular form of SGI3 was also detected. The transconjugants had a higher MIC against CuSO4 compared with the recipient strains under anaerobic conditions. Resistance was defined by the cus gene cluster in the CHASRI. The transconjugants also had distinctly higher MICs against Na2HAsO4 compared with recipient strains under aerobic conditions. These findings clearly demonstrate that SGI3 is an integrative and conjugative element and contributes to the copper and arsenic resistance of S. enterica.

microbiology↗

bioRxiv2018

Novel cholera toxin variant and ToxT regulon in environmental Vibrio mimicus strains: potential resources for the evolution of Vibrio cholerae hybrid strains

Atypical El Tor strains of Vibrio cholerae O1 harboring variant ctxB genes of cholera toxin (CT) are gradually becoming a major cause of recent cholera epidemics. Vibrio mimicus occasionally contains virulence factors associated with cholera, e.g., CT, encoded by ctxAB on CTX[FE] genome; and TCP, the CTX[FE]-specific receptor. This study carried out extensive molecular characterization of CTX[FE] and ToxT regulon in ctx+ve strains of V. mimicus isolated from the Bengal coast. Southern hybridization, PCR, and DNA sequencing of virulence related-genes revealed the presence of an El Tor type CTX prophage (CTXET) carrying a novel ctxAB, tandem copies of environmental type pre-CTX prophage (pre-CTXEnv), and RS1 elements, which were organized in an array of RS1-CTXET-RS1-pre-CTXEnv-pre-CTXEnv. Additionally, a novel variant of tcpA and toxT respectively, showing clonal lineage to a phylogenetic clade of V. cholerae non-O1/O139, was identified. The V. mimicus strains lacked the RTX and TLC elements, and Vibrio seventh pandemic islands of the El Tor strains, but contained five heptamer (TTTTGAT) repeats in ctxAB promoter region like some classical strains of V. cholerae O1. PFGE analysis showed all the ctx+ve V. mimicus strains were clonally related. However, their in vitro CT production and in vivo toxigenecity were variable, which could be explained by differential transcription of virulence genes along with ToxR regulon. Taken together, our findings strongly suggest that environmental V. mimicus strains act as potential reservoir of atypical virulence factors, including variant CT and ToxT regulon, and may contribute to the evolution of V. cholerae hybrid strains.\n\nIMPORTANCENatural diversification of CTX[FE] and ctxAB genes certainly influences disease severity and shifting patterns in major etiological agents of cholera, e.g., the overwhelming emergence of hybrid El Tor variants, replacing the prototype El Tor strains of V. cholerae. This study showing the occurrence of CTXET comprising a novel variant of ctxAB in V. mimicus points out a previously unnoticed evolutionary event, independent to that of the El Tor strains of V. cholerae. Identification and cluster analysis of the newly-discovered alleles of tcpA and toxT indicates their horizontal transfer from an uncommon clone of V. cholerae. The genomic content of ToxT regulon, and tandemly arranged multiple pre-CTX[FE]Env and a CTX[FE]ET in V. mimicus probably act as salient raw materials inducing natural recombination among the hallmark virulence genes of hybrid V. cholerae strains. This study will facilitate deeper understanding of the evolution of new variant CT and ToxT regulon, influencing cholera epidemiology.

microbiology↗