Abstract
Antimicrobial susceptibility profiles of clinical and environmental isolates of Edwardsiella demonstrate that the three species are susceptible to beta-lactam antibiotics. All strains were susceptible to two quinolones tested and to gentamicin and doxycycline. E. tarda and E. hoshinae were resistant to clindamycin, whereas E. ictaluri was moderately susceptible. beta-Lactamase was produced by all strains of E. tarda, but not by E. hoshinae or E. ictaluri. A 54-kb plasmid was detected in six of 13 E. hoshinae strains. Five of the 10 E. tarda isolates studied gave an identical plasmid pattern of four plasmids ranging in size from 76-kb to 5.0-kb. One strain exhibited a 54-kb plasmid; four strains did not contain plasmid DNA. All E. ictaluri isolates contained a 5.7-kb and a 4.9-kb plasmid. E. tarda and E. ictaluri strains were resistant to human serum 20%; 12 of 13 strains of E. hoshinae were also serum resistant. Serum resistance may play an important part in the pathogenicity of these species.