Oligonucleotide probe determination of tetracycline-resistant bacteria isolated from catfish ponds.

Oligonucleotide probes for class A, B and C tetracycline resistance determinants were synthesized and tested individually and in combination for hybridization with Gram-negative isolates previously characterized by restriction fragment DNA probes. Similar hybridization patterns were observed with either probe type. Gram-negative catfish pond bacteria were characterized by these oligonucleotide probes. The most common bacteria were Plesiomonas shigelloides (47.7%), Aeromonas hydrophila (28.8%) and Citrobacter freundii (13.3%). The class A (46.4%) tetracycline resistance determinant was more prevalent than B (19.8%) and C (0.3%). Some tetracycline-resistant isolates of each species, including most A. hydrophila (62.1%) isolates, failed to hybridize with any of the probes.