Clinically Relevant Aeromonas Species

Sir —In the October 1999 issue of Clinical Infectious Diseases , an update of the current nomenclature, taxonomy, and classification of aerobic and facultative bacteria is presented [ 1 ]. While checking the species of Aeromonas in the updated list, we were surprised to find Aeromonas enteropelogenes included as a valid species, although it was synonymized a long time ago with Aeromonas trota on the basis of 16S rRNA sequences [ 2 ]. This synonymization has been further confirmed in recent studies with other molecular methods [ 3–5 ] and with phenotypical tests [ 6 ]. It is encouraging, however, that Aeromonas sobria , a misnomer classically used by clinicians to refer to Aeromonas veronii biovar sobria , was not included in the list. In fact, Aeromonas sobria sensu stricto is considered a valid species of environmental origin that is not commonly reported in clinical cases [ 7 ]. Another important consideration are the criteria employed for inclusion of species on the list. The genera Aeromonas now encompasses 14 species. In the recent overview/review of the genus carried out by Janda and Abbott [ 7 ], only 5 species, including 1 with 2 biovars, were considered pathogenic. Three of these are referred to as major pathogens (Aeromonas hydrophila, Aeromonas caviae , and A. veronii biovar sobria) , since they account for >85% of clinical isolates of this genus [ 8 ], whereas the other 3 (A. veronii biovar veronii, Aeromonas jandaei , and Aeromonas schubertii) are considered minor pathogens [ 7 ]. The list published in Clinical Infectious Diseases includes these 5 species, as well as 5 others (Aeromonas allosaccharophila, Aeromonas bestiarum, Aeromonas media, Aeromonas salmonicida , and A. trota) , in addition to the invalid species mentioned above. If the detection of these species independently of their pathological significance in clinical samples is the basis for inclusion, it would be appropriate to include these last 5 species, but then Aeromonas encheleia and Aeromonas eucrenophila , isolated from an ankle fracture and a wound, respectively, would be missing [ 7 ]. Aeromonas salmonicida was classified by Janda and Abbott [ 7 ] under the group of environmental species. However, similar to the experience of other investigators, we encountered this species with a low incidence in feces of patients with diarrhea [ 9 ]. We agree, therefore, with the authors of the list published in Clinical Infectious Diseases [ 1 ] that these species should be included. In view of these comments, it is important that the list as published be amended in order to be properly updated.