[Usefulness of studies of susceptibility of ampicillin, carbenicillin, cefalotin and colistin as a presumptive identification system for the Aeromonas sp. group].

We have studied the restricted antibiotic susceptibility tests for 180 strains belonging to mesophilic Aeromonas sp. isolated from stools samples. Strains has been identified as follows: A. caviae (64.6%), A. hydrophila (17.7%) and A. sobria (17.7%). Antibiotics tested were ampicillin (10 micrograms), carbenicillin (100 micrograms), cephalotin (30 micrograms) and colistin (10 micrograms), by means of agar diffusion tests (disk-plate). We identified four different patterns of antibiotic susceptibility. The most frequent pattern (pattern #1) (77.8%) is characterized by susceptibility only to colistin, and was predominant among A. caviae strains (80%). Pattern #2 (susceptibility to cephalotin and colistin) was found in 18.9% of strains, being predominant in A. sobria (88.2%). We confirm the higher susceptibility of A. sobria sp. to cephalotin as well as the possibility that these different patterns might be used as screening method for species identification among mesophilic group of Aeromonas.