Class D and E tetracycline resistance determinants in gram-negative bacteria from catfish ponds

DNA probes were used to examine tetracycline-resistant Gram-negative bacteria (281 strains representing eight species) from catfish ponds. The isolates, which did not previously hybridize with the Tet A, B and C determinants, were examined for the presence of tetracycline-resistance Tet D and Tet E determinants. The distribution of the Tet D determinant ranged from 0 to 83%, depending on the bacterial species. Tet E was found only in 69% of Aeromonas hydrophila isolates. Eighteen per cent failed to hybridize with any of the five Tet determinants.