Estudio taxonómico de aeromonas móviles y salicina negativas
The genus Aeromonas comprises Gram-negative, oxidase- and catalase-positive, heterotrophic, non-halophilic and facultative anaerobic bacilli which are widely distributed in natural waters. There is strong evidence for the role of Aeromonas as aetiological agents of a variety of systemic and localized diseases in poiquilothermic animals for the species A. salmonicida, A. hydrophila and A. jandaei. Moreover, during the last 15 years Aeromonas has been increasingly recognized as a primary, opportunist disease agent in humans, and at least six new Aeromonas species were originally isolated from clinical samples.
This study was undertaken to cluster and identify a large collection of Aeromonas strains. Numerical taxonomy was used to analyze phenotypic data obtained on 54 new isolates from different sources 99 type and reference strains. Each was tested for 121 characters but only the data for 71 were analyzed using the SSM and SJ coefficients, and the UPGMA clustering algorithm. At SJ values of ? 81.6% the strains clustered into 22 phenons which were identified as A. jandaei, A. veronii biogroup veronii, A. sobria, A. ichthiosmia, A. allosaccharophila, A. trota, A. hydrophila, A.caviae, A. encheleia, A. eucrenophila, A. media, A. schubertii y A. salmonicida. A good correlation was generally observed among this phenotypic clustering and previous genomic and phylogenetic data. Three new phenotypic groups were found which may correspond to new Aeromonas species or biotypes.
DNA relatedness between strains grouped in the A. jandaei cluster and A. jandaei CECT 4228T ranged from 70 to 100 %, but was below 50 % when DNAs from A. veronii biogroup sobria CECT 4835, A. veronii biogroup veronii CECT 4257T and A. ichthiosmia CECT 4486T were used. In addition, DNA relatedness between peripheral A. veronii biogroup sobria strains and the species A. jandaei (CECT 4228T), A. veronii (CECT 4257T, CECT 4835) and A. ichthiosmia (CECT 4486T) was always below 54 %, as it was between the species A. ichthiosmia (CECT 4486T) and A. veronii (CECT 4257T, CECT 4835). Emendation of A. jandaei is proposed; this taxon now includes sucrose-positive clinical and environmental strains as well as environmental isolates that are pathogenic for fish and humans.
The DNA G+C content of A. jandaei is also reported for the first time; it ranges from 581 to 611 mol%. The DNA relatedness data support the classification of peripheral reference strains of A. veronii biogroup sobria outside this taxon, indicating that biogroup sobria requires further revision.
Document Full Text
Advisor:Esteve Sánchez, Mª Consuelo; García López, Mª Dolores
School:Universitat de València
Source Type:Master's Thesis
Keywords:microbiologia i ecologia
Date of Publication:05/03/2007