The tetracycline resistance determinant Tet 39 and the sulphonamide resistance gene sulII are common among resistant Acinetobacter spp. isolated from integrated fish farms in Thailand.
OBJECTIVE
To determine the genetic basis for tetracycline and sulphonamide resistance and the prevalence of class I and II integrons in oxytetracycline-resistant Acinetobacter spp. from integrated fish farms in Thailand.


METHODS
A total of 222 isolates were screened for tetracycline resistance genes [tet(A), tet(B), tet(H), tet(M) and tet(39)] and class II integrons by PCR. One hundred and thirty-four of these isolates were also sulphonamide resistant and these isolates were screened for sulphonamide resistance genes (sulII and sulIII) as well as class I integrons. Plasmid extraction and Southern blots with sulII and tet(39) probes were performed on selected isolates.


RESULTS
The recently identified tetracycline resistance gene tet(39) was demonstrated in 75% (166/222) of oxytetracycline-resistant Acinetobacter spp. from integrated fish farms in Thailand. Isolates that were also sulfamethoxazole-resistant contained sulII (96%; 129/134) and/or sulI (14%; 19/134) (as part of class I integrons). sulII and tet(39) were located on plasmids differing in size in the isolates tested.


CONCLUSIONS
The study shows tet(39) and sulII to be common resistance genes among clonally distinct Acinetobacter spp. from integrated fish farms and these bacteria may constitute reservoirs of resistance genes that may increase owing to a selective pressure caused by the use of antimicrobials in the overlaying animal production.
Agersø
Yvonne
Y
Danish Institute for Food and Veterinary Research, Bülowsvej 27, DK-1790 Copenhagen V, Denmark. ya@dfvf.dk
Petersen
Andreas
A
D000150:Acinetobacter / Q000187:drug effects* / Q000235:genetics; D000818:Animals; D017920:Antiporters / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005399:Fishes / Q000382:microbiology*; D032023:Integrons; D008969:Molecular Sequence Data; D010118:Oxytetracycline / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*; D013753:Tetracycline Resistance / Q000235:genetics*
D017920:Antiporters; D001426:Bacterial Proteins; D013449:Sulfonamides; C079051:tetA protein, Bacteria; D010118:Oxytetracycline