CHARACTERIZATION OF TETRACYCLINE AND ERYTHROMYCIN RESISTANCE IN ACTINOBACILLUS-PLEUROPNEUMONIAE

Minimum inhibitory concentrations to tetracycline and erythromycin wer e determined for nineteen isolates of Actinobacillus pleuropneumoniae of Norwegian origin. The isolates were screened for rRNA methylase det erminants (Erm genes) and for the tetracycline resistance Tet B determ inant, using oligonucleotide probes, polymerase chain reaction and hyb ridization. Ten isolates (53%) carried the Erm C determinant, two isol ates (10%) carried the Erm A determinant, four isolates (21%) carried both the Erm A and the Erm C determinants, and three isolates (16%) ca rried none of the Erm determinants examined. Eight isolates (45%) carr ied the Tet B determinant. Selected isolates were shown to transfer th e Erm C and Erm A determinants at a frequency of 10-(7)-10(-9) per rec ipient cell. This is the first description of A, pleuropneumoniae carr ying either Erm A, Erm C or/and Tet B determinants.