Molecular characterization of plasmid-mediated oxytetracycline resistance in Aeromonas salmonicida.
Using broth conjugation, we found that 19 of 29 (66%) oxytetracycline (OT)-resistant isolates of Aeromonas salmonicida transferred the OT resistance phenotype to Escherichia coli. The OT resistance phenotype was encoded by high-molecular-weight R-plasmids that were capable of transferring OT resistance to both environmental and clinical isolates of Aeromonas spp. The molecular basis for antibiotic resistance in OT-resistant isolates of A. salmonicida was determined. The OT resistance determinant from one plasmid (pASOT) of A. salmonicida was cloned and used in Southern blotting and hybridization experiments as a probe. The determinant was identified on a 5.4-kb EcoRI fragment on R-plasmids from the 19 OT-resistant isolates of A. salmonicida. Hybridization with plasmids encoding the five classes (classes A to E) of OT resistance determinants demonstrated that the OT resistance plasmids of the 19 A. salmonicida isolates carried the class A resistance determinant. Analysis of data generated from restriction enzyme digests showed that the OT resistance plasmids were not identical; three profiles were characterized, two of which showed a high degree of homology.
Adams
C A
CA
Department of Biological Sciences, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, Scotland.
Austin
B
B
Meaden
P G
PG
McIntosh
D
D
D000038:Abscess / Q000382:microbiology; D000333:Aeromonas / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D016980:Aeromonas hydrophila / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D000818:Animals; D003227:Conjugation, Genetic; D006168:Guinea Pigs / Q000382:microbiology; D006801:Humans; D008970:Molecular Weight; D010118:Oxytetracycline / Q000494:pharmacology*; D011815:R Factors / Q000235:genetics / Q000302:isolation & purification; D015183:Restriction Mapping; D012487:Salmonidae / Q000382:microbiology; D013045:Species Specificity; D013753:Tetracycline Resistance / Q000235:genetics*
D010118:Oxytetracycline