Comparison of phenotypical and genetic identification of Aeromonas strains isolated from diseased fish

• Published in: Systematic and applied microbiology 2010-04, Vol.33 (3), p.149-153
• Main Authors: Beaz-Hidalgo, Roxana, Alperi, Anabel, Buján, Noemí, Romalde, Jesús L., Figueras, Maria José
• Format: Article
• Language: English
• Subjects: 16SrDNA-RFLP; Aeromonas; Aeromonas - classification; Aeromonas - genetics; Aeromonas - isolation & purification; Aeromonas - physiology; Animals; Bacterial Proteins - genetics; Bacterial Typing Techniques; Biological and medical sciences; Cluster Analysis; Diseased fish; DNA Fingerprinting; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; DNA, Ribosomal - genetics; DNA-Directed RNA Polymerases - genetics; Fish Diseases - microbiology; Fishes; Fundamental and applied biological sciences. Psychology; Gram-Negative Bacterial Infections - microbiology; Gram-Negative Bacterial Infections - veterinary; Microbiology; Molecular Sequence Data; Phenotypic identification; Phylogeny; Piscicola; Polymorphism, Restriction Fragment Length; RNA, Ribosomal, 16S - genetics; rpoD; Salmonidae; Sequence Analysis, DNA; Sigma Factor - genetics
• ISSN: 0723-2020; 1618-0984
• DOI: 10.1016/j.syapm.2010.02.002

Phenotypicaly identified Aeromonas strains (n=119) recovered mainly from diseased fish were genetically re-identified and the concordance between the results was analysed. Molecular characterization based on the GCAT genus specific gene showed that only 90 (75.6%) strains belonged to the genus Aeromonas. The 16S rDNA-RFLP method identified correctly most of the strains with the exception of a few that belonged to A. bestiarum, A. salmonicida or A. piscicola. Separation of these 3 species was correctly assessed with the rpoD gene sequences, which revealed that 5 strains with the RFLP pattern of A. salmonicida belonged to A. piscicola, as did 1 strain with the pattern of A. bestiarum. Correct phenotypic identification occurred in only 32 (35.5%) of the 90 strains. Only 14 (21.8%) of the 64 phenotypically identified A. hydrophila strains belonged to this species. However, coincident results were obtained in 88% (15/17) of the genetically identified A. salmonicida strains. Phenotypic tests were re-evaluated on the 90 genetically characterized Aeromonas strains and there were contradictions in the species A. sobria for a number of previously published species-specific traits. After genetic identification, the prevailing species were A. sobria, A. salmonicida, A. bestiarum, A. hydrophila, A. piscicola and A. media but we could also identify a new isolate of the recently described species A. tecta. This work emphasizes the need to rely on the 16S rDNA-RFLP method and sequencing of housekeeping genes such as rpoD for the correct identification of Aeromonas strains.