Phylogenetic analysis of members of the genus Aeromonas based on gyrB gene sequences

Abstract

The phylogenetic relationships of all known species of the genus Aeromonas were investigated by using the sequence of gyrB, a gene that encodes the B-subunit of DNA gyrase. Nucleotide sequences of gyrB were determined from 53 Aeromonas strains, including some new isolates, which were also characterized by analysis of the 16S rDNA variable regions. The results support the recognition of the family Aeromonadaceae, as distinct from Plesiomonas shigelloides and other enteric bacteria. This phylogenetic marker revealed strain groupings that are consistent with the taxonomic organization of all Aeromonas species described to date. In particular, gyrB results agreed with 16S rDNA analysis; moreover, the former showed a higher capacity to differentiate between species. The present analysis was useful for the elucidation of reported discrepancies between different DNA-DNA hybridization sets. Additionally, due to the sequence diversity found at the intraspecies level, gyrB is proposed as a useful target for simultaneous identification of species and strains. In conclusion, the gyrB gene has proved to be an excellent molecular chronometer for phylogenetic studies of the genus Aeromonas. INTRODUCTIONThe genus Aeromonas comprises a collection of oxidaseand catalase-positive, glucose-fermenting, facultatively anaerobic, Gram-negative, rod-shaped bacteria that are resistant to the vibriostatic agent O/129 and are generally motile by means of polar flagella (Popoff, 1984). Aeromonads are autochthonous to aquatic environments worldwide and have been implicated in the aetiology of a variety of fish and human diseases, frequently including diarrhoea and occasionally systemic infections (Janda, 1991). Over the past few years, interest in the genus Aeromonas as an emergent human pathogen has increased significantly Joseph & Carnahan, 2000).The classification of the genus Aeromonas has been dogged by confusion and controversy. In Bergey's Manual of Systematic Bacteriology (Popoff, 1984), the genus was divided into three mesophilic and motile species (Aeromonas hydrophila, Aeromonas caviae and Aeromonas sobria) and the psychrophilic, non-motile species Aeromonas salmonicida. Extensive DNA-DNA hybridization studies (Popoff et al., 1981;Hickman-Brenner et al., 1987Kuijper et al., 1989;Carnahan et al., 1991) have resulted in the recognition of 14 so-called DNA homology groups (HGs): A. hydrophila (HG1), Aeromonas sp. (unnamed; HG2), A. salmonicida (HG3), A. caviae (HG4), Aeromonas media (HG5), Aeromonas eucrenophila (HG6), A. sobria (HG7), Aeromonas veronii biogroup sobria (HG8), Aeromonas jandaei (HG9), A. veronii biogroup veronii (HG10), Aeromonas sp. (unnamed; HG11), A. schubertii (HG12), Aeromonas group 501 (HG13; formerly Enteric group 501) and Aeromonas trota (HG14). The name Aeromonas bestiarum has been proposed for strains included in HG2 (Ali et al., 1996). During the past decade, three novel species have been described: Aeromonas allosaccharophila (Martínez-Murcia et al., 1992b), Aeromonas encheleia (Esteve et al., 1995b) and A...

Unexpected Occurrence of Plasmid-Mediated Quinolone Resistance Determinants in EnvironmentalAeromonasspp.

“…Finally, each colony was tested by multiplex PCR for detection of qnr genes (see below). Further identifi cation of qnr-positive isolates was performed by conventional biochemical techniques (API-20E and API-NE systems [bioMérieux, Marcy-l'Etoile, France]), and by sequencing of 16S rDNA and gyrB genes, as previously described (14,15).…”

“…Isolate A37 was identifi ed as A. trota or A. punctata (formerly A. caviae) (only 1 nt difference) and isolate A42 as A. hydrophila or A. media (only 1 nt change). Because gyrB sequence divergence is greater than that of 16S rDNA, phylogenetic analysis based on gyrB sequence (allowing more reliable identifi cation of members of the genus Aeromonas [15]) identifi ed isolate A37 as A. punctata subsp. punctata and isolate A39 as A. media.…”

Detection of hemolytic strains of Aeromonas hydrophila and A. sobria along with other Aeromonas spp. from fish and fishery products by multiplex PCR

“…Although Aeromonas spp. has recently received increasing attention as an agent of food-borne diarrhoeal diseases in healthy people (Janda and Abbott 2010), the PCR has been mostly used for the characterization of isolates either for their virulence properties or for the phylogenetic positions (Yanez et al 2003;Bin Kingombe et al 2010;Fontes et al 2011). In this study, hemolytic strains of A .…”

Antimicrobial Resistance Patterns of Aeromonas spp. Isolated from Ornamental Fish

“…They are facultative anaerobic, oxidase, catalase and indol-positive, able to reduce nitrate to nitrite and are, glucose-fermenting, generally resistant to the vibriostatic agent O/129 [4,5].…”