Abstract
The presence of class 1 integrons was investigated in 38 sulfonamide-resistant strains of
Aeromonas salmonicida
subsp.
salmonicida
, atypical
A. salmonicida
and
Escherichia coli
conjugants with R plasmids originating from
A. salmonicida
. The strains originated from Finland, France, Japan, Norway, Scotland, Switzerland, and the United States. Additional resistance determinants
in strains with class 1 integrons were also determined. Of 21 strains containing a class 1 integron, 19 had a single gene cassette, 1 strain had two cassettes, and 1 strain was found to lack an integrated
gene cassette. In the integrons with single cassettes,
aadA2
was present in eight strains,
dfr16
in five strains, and
aadA1
and
dfrIIc
in three strains each. In the integron
with two cassettes,
qacG
and
orfD
were present. Tetracycline resistance was observed in 20 of the integron-positive strains, caused by the determinants Tet A and Tet E, in which Tet A frequently
was associated with Tn
1721
. Class 1 integrons seem to be important in mediating antibiotic resistance also in the marine environment. The gene cassettes reported in this study are all described in
bacteria associated with humans, and this demonstrates once more how the common gene pool is shared between organisms belonging to different environments.