Characterization of class 1 integrons associated with R-plasmids in clinical Aeromonas salmonicida isolates from various geographical areas.
Class 1 integrons were found in 26 of 40 antibiotic-resistant isolates of the fish pathogen Aeromonas salmonicida from Northern Europe and North America. Three different dhfr genes, conferring trimethoprim resistance, and one ant(3")1a aminoglycoside resistance gene were identified as gene inserts. The gene cassettes tended to be conserved among isolates from a particular geographical area. Nineteen isolates transferred R-plasmids carrying different tet determinants to Escherichia coli in filter mating assays, and in 15 cases, the class 1 integrons were co-transferred. Transferable sulphadiazine, trimethoprim and streptomycin resistances were invariably encoded by integrons. It thus appears that integron-encoded antibiotic resistance genes contribute substantially to the horizontal spread of antimicrobial resistance within this species, being associated with conjugative plasmids.
Schmidt
A S
AS
Department of Veterinary Microbiology, and Danish Institute of Fisheries Research, The Royal VeterinFary and Agricultural University, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark. ansc@kvl.dk
Bruun
M S
MS
Larsen
J L
JL
Dalsgaard
I
I
D000333:Aeromonas / Q000187:drug effects / Q000235:genetics*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004251:DNA Transposable Elements / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D013307:Streptomycin / Q000494:pharmacology; D014296:Trimethoprim Resistance / Q000235:genetics
D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D013307:Streptomycin