Genotype and virulence gene analyses of Bacillus cereus group clinical isolates from the Chinese softshell turtle (Pelodiscus sinensis) in Taiwan

• Published in: Journal of fish diseases Vol. 44; no. 10; pp. 1515 - 1529
• Main Authors: Cheng, Li‐Wu, Rao, Shreesha, Poudyal, Sayuj, Wang, Pei‐Chi, Chen, Shih‐Chu
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.10.2021
• Subjects: Analytical methods; Aquatic animals; Aquatic insects; Bacillus cereus; Bacillus cereus group; Cereulide; Chinese softshell turtles; Clinical isolates; DNA; Electrophoresis; enterobacterial repetitive intergenic consensus–polymerase chain reaction; Farms; Gel electrophoresis; Gels; Genes; Genotypes; Insects; Nucleotide sequence; Pathogens; PCR; Pelodiscus sinensis; Peptide synthase; Phylogenetics; Phylogeny; Polymerase chain reaction; pulsed‐field gel electrophoresis; Pyruvate carboxylase; Pyruvic acid; rRNA 16S; Turtles; Virulence; Taiwan
• ISSN: 0140-7775; 1365-2761
• DOI: 10.1111/jfd.13473

Chinese softshell turtles (Pelodiscus sinensis) (CST) are susceptible to infections by bacteria belonging to the Bacillus cereus group (Bcg). Bcg includes several closely related species, two of which, B. cereus and B. thuringiensis, are pathogens of aquatic animals or insects. In the present study, we collected 57 Bcg isolates obtained from diseased CST from 2016 to 2019 in Kaohsiung and Pingtung, the areas with the most CST farms in Taiwan. All isolates were divided into four genotypes with two restriction enzymes, SmaI and NotI, by pulsed‐field gel electrophoresis and enterobacterial repetitive intergenic consensus–polymerase chain reaction (ERIC‐PCR). Representative isolates from each genotype were subjected to phylogenetic tree analysis using 16S rDNA and pyruvate carboxylase genes as phylogenetic markers, and these CST isolates appeared in different clades. PCR was performed targeting six selected virulence genes, four of which were detected in CST isolates, including cytotoxin K (1/57), hblC of the haemolysin BL complex (46/57), nheA of the non‐haemolytic enterotoxin complex (52/57) and enterotoxin FM (57/57), whereas cereulide synthetase and cereulide peptide synthase‐like genes were not detected in any isolates.