Antibiotic susceptibilities of Yersinia enterocolitica and Y-intermedia isolates from aquatic environments

Of 37 Yersinia isolates from various aquatic environments, seven were Y. en terocolitica and 30 Y. intermedia. These isolates were biotyped, serotyped and tested for their susceptibility to 20 antibiotics. All Y. enterocolitic a isolates were of biovar 1; those of Y. intermedia were distributed amongs t four biovars (1, 2, 4 and 6), On the basis of combined biotyping and sero typing results, Y. enterocolitica isolates were distributed in five and Y. intermedia in 17 groups. With the exception of one Y. enterocolitica isolat e which was resistant to tetracycline and streptomycin, the isolates were s ensitive to the non-beta-lactam antibiotics. In contrast, various patterns of beta-lactam insensitivity were detected, including ampicillin and ticarc illin (35 isolates), cephalothin (33 isolates), carbenicillin (32 isolates) , amoxycillin/clavulanate (23 isolates) and cefoxitin (22 isolates). No cor relation between biotype or serotype and the susceptibility pattern of the isolates was apparent. Both inducible cephalosporinase activity against thi rd-generation cephalosporins and inhibition of resistance to penicillins we re detected in all Y. enterocolitica and Y. intermedia isolates by double-d isk tests.