Characterization of a new strain of Aeromonas dhakensis isolated from diseased pacu fish (Piaractus mesopotamicus) in Brazil

Abstract

This study provides a detailed description and characterization of a strain of Aeromonas dhakensis isolated from a diseased juvenile Piaractus mesopotamicus obtained from the fish farm of the National Center for Continental Fish Research and Conservation (CEPTA/ICMBio), in the state of São Paul, Brazil. Biochemical tests using the VITEK 2 automated bacterial identification system identified the isolate to genus level; however, further molecular analysis of the 16S rRNA, gyrB and rpoD genes showed that the strain belonged to the species A. dhakensis. As expected, the isolated A. dhakensis strain was resistant to ampicillin and ampicillin/sulbactam, as resistance to ampicillin is a typical characteristic of the genus Aeromonas. Resistance to cefoxitin and meropenem was also observed, but the strain was susceptible to most of the tested antibiotics. The isolated strain of A. dhakensis caused acute haemorrhagic septicaemia in experimentally infected P. mesopotamicus, with a fifty per cent lethal dose of 1.14 × 10 CFU/fish. This is the first report of the occurrence of an A. dhakensis strain causing an infection in a fish species of South America, providing important epidemiologic data relating to this important pathogenic species.

Aeromonas hydrophilaandAeromonas veroniicause motileAeromonassepticaemia in the cultured Chinese sucker,Myxocyprinus asiaticus

“…Because of its low resolution, 16S rRNA cannot distinguish genetically close species. With a higher resolution than 16S rRNA , cpn60 , a highly conserved protein‐coding gene in bacteria and archaea, is often applied to Aeromonas taxonomic studies (Carriero, Mendes‐Maia, Moro‐Sousa, & Henriquesilva, ). GyrB is a protein‐coding gene associated with DNA replication, transcription, modification and repair (Yamamoto, Bouvet, & Harayama, ) that is suitable for the identification of genetically close species (Soler et al, ).…”

Isolation and identification of pathogens causing haemorrhagic septicaemia in cultured Chinese sturgeon (Acipenser sinensis )

“…However, the taxonomy of the genus Aeromonas based on simple biochemical characteristics and relying on 16S rDNA sequencing is controversial because of its complicated phenotypic and genotypic heterogeneity (Janda & Abbott, ; Khor, Puah, Tan, Puthucheary, & Chua, ; Martinez‐Murcia et al, ). The gyrB and rpoD genes are proven molecular markers suitable for identifying the genus Aeromonas , especially of its closely related species (Carriero, Mendes Maia, Moro Sousa, & Henrique‐Silva, ; Soler et al, ; Zhu et al, ). For this reason, we selected the gyrB and rpoD genes to further identify the pathogens in this outbreak.…”

Isolation, molecular characterization and antimicrobial susceptibility ofAeromonasspp. obtained from Tiger Grouper (Epinephelus fuscoguttatus) and Marble Goby (Oxyeleotris marmoratus) fish in Sabah, Malaysia

“…A. dhakensis was also isolated from wild European eels ( Anguilla anguilla ) caught in lake in Spain which suffered from haemorrhagic septicaemia (Esteve et al., 2012). These researchers have demonstrated that A. dhakensis displayed an LD50 dose of 1.14 × 10 5 –3.31 × 10 6 CFU/fish in experimental challenges using fish model (Carriero et al., 2016; Esteve et al., 2012; Soto‐Rodriguez et al., 2013). In the present study, our results suggest possible high virulence potential in the four A. dhakensis .…”