Search

Aims To perform a comparative study for determining the optimum culture method (direct plating or enrichment) and medium (ampicillin dextrin agar ( ADA), starch ampicillin agar ( SAA), bile salts irgasan brilliant green modified ( BIBG-m)) for recovering Aeromonas species from water and shellfish samples. Methods and Results By direct culture, Aeromonas was detected in 65% (13/20) of the water samples and in 54·5% (6/11) of the shellfish samples. However, when a pre-enrichment step was included, the number of positive water samples increased to 75% (15/20) and the ones of shellfish to 90·1% (10/11). The enriched culture significantly favoured ( P < 0·05) the isolation of Aeromonas allosaccharophila from water, Aeromonas salmonicida from shellfish and Aeromonas caviae from both types of samples. The most specific ( P < 0·05) culture medium for detecting Aeromonas from water was ADA. However, no differences were observed in the case of shellfish samples ( P > 0·05). Isolation of Aeromonas media from water was favoured ( P < 0·05) in the ADA medium, while SAA enhanced ( P < 0·05) the isolation of Aer. salmonicida from shellfish. Conclusions The culture method and medium used influenced the recovery of some Aeromonas species from water and shellfish samples. Significance and Impact of the Study This fact should be considered in future prevalence studies to avoid overestimating the above mentioned Aeromonas species. [ABSTRACT FROM AUTHOR]

Three groups of Aeromonas strains isolated from Finland lakes experiencing cyanobacterial blooms could not be assigned to any known species of this genus on the basis of 16S rRNA and rpoD gene sequences. The Multilocus Phylogenetic Analysis (MLPA) of the concatenated sequence of seven genes ( gyrB , rpoD , recA , dnaJ , gyrA , dnaX and atpD ; 4093 bp) showed that the three groups of strains did not cluster with any known Aeromonas spp. and formed three independent lineages. This was confirmed by performing the analysis with their closest relatives using 15 genes (the latter 7 and cpn60 , dnaK , gltA , mdh , radA , rpoB , tsf , zipA ; 8751 bp). Furthermore, ANI results between the genomes of the type strains of the three potential new species and those of their close relatives were all <96% which is the previously proposed cutoff value for differentiating species within this genus. The in silico DDH values of the three type strains of the new species also showed a similarity <70% with the most closely related species indicating they belong to different taxa. The three groups of strains could be differentiated from each other and from other known Aeromonas species on the basis of several phenotypic characters. This polyphasic study revealed that the 3 groups of strains represent 3 novel Aeromonas species for which the names Aeromonas aquatica sp. nov. (type strain AE235 T = CECT 8025 T = LMG 26712 T ), Aeromonas finlandiensis sp. nov. (type strain 4287D T = CECT 8028 T = LMG 26709 T ) and Aeromonas lacus sp. nov. (type strain AE122 T = CECT 8024 T = LMG 26710 T ) are proposed. [ABSTRACT FROM AUTHOR]

It is widely recognized that Aeromonas infections produce septicaemia, and ulcerative and haemorrhagic diseases in fish, causing significant mortality in both wild and farmed freshwater and marine fish species that damage the economics of the aquaculture sector. The descriptions of the complete genomes of Aeromonas species have allowed the identification of an important number of virulence genes that affect the pathogenic potential of these bacteria. This review will focus on the most relevant information derived from the available Aeromonas genomes in relation to virulence and on the diverse virulence factors that actively participate in host adherence, colonization and infection, including structural components, extracellular factors, secretion systems, iron acquisition and quorum sensing mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: Four Aeromonas strains (S1.2T, EO-0505, TC1 and TI 1.1) isolated from moribund fish in Spain showed a restriction fragment length polymorphism (RFLP) pattern related to strains of Aeromonas salmonicida and Aeromonas bestiarum but their specific taxonomic position was unclear. Multilocus sequence analysis (MLSA) of housekeeping genes rpoD, gyrB, recA and dnaJ confirmed the allocation of these isolates to an unknown genetic lineage within the genus Aeromonas with A. salmonicida, A. bestiarum and Aeromonas popoffii as the phylogenetically nearest neighbours. Furthermore, a strain biochemically labelled as Aeromonas hydrophila (AH-3), showing a pattern of A. bestiarum based on 16S rDNA-RFLP, also clustered with the unknown genetic lineage. The genes rpoD and gyrB proved to be the best phylogenetic markers for differentiating these isolates from their neighbouring species. Useful phenotypic features for differentiating the novel species from other known Aeromonas species included their ability to hydrolyze elastin, produce acid from l-arabinose and salicin, and their inability to produce acid from lactose and use l-lactate as a sole carbon source. A polyphasic approach using phenotypic characterization, phylogenetic analysis of the 16S rRNA gene and of four housekeeping genes, as well as DNA–DNA hybridization studies and an analysis of the protein profiles by MALDI-TOF-MS, showed that these strains represented a novel species for which the name Aeromonas piscicola sp. nov. is proposed with isolate S1.2T (=CECT 7443T, =LMG 24783T) as the type strain. [Copyright &y& Elsevier]

Four Aeromonas strains from clinical and environmental samples differed from known species on the basis of rpoD gene sequence. Multilocus phylogenetic analysis and in silico DNA-DNA hybridization confirmed them as four new species even though their 16S rRNA gene sequence similarity with their closest relatives was >98.7%, as occurred for other Aeromonas spp. [ABSTRACT FROM AUTHOR]