Comparison of phenotypical and genetic identification of Aeromonas strains isolated from diseased fish.
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.
Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, IISPV, Universitat Rovira i Virgili, Reus, Spain.
Roxana
R
Beaz-Hidalgo
Anabel
A
Alperi
Noemí
N
Buján
Jesús L
JL
Romalde
Maria José
MJ
Figueras
D000333:Aeromonas / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D005393:Fish Diseases / Q000382:microbiology*; D005399:Fishes; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000662:veterinary*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012808:Sigma Factor / Q000235:genetics
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D012808:Sigma Factor; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases