Affiliation:
1. Department of Pharmacology, Microbiology, and Food Hygiene, Norwegian School of Veterinary Science, Oslo, Norway
Abstract
ABSTRACT
A 45-kb R plasmid, pRAS1, that confers resistance to tetracyclines, trimethoprim, and sulfonamides was isolated in 1989 from an atypical strain of the fish pathogen
Aeromonas salmonicida
. This plasmid could be transferred by conjugation to
Escherichia coli
with a high degree of efficiency (frequency, 0.48). The following year pRAS1 was isolated from
A. salmonicida
subsp.
salmonicida
in the same area. Incompatibility group U plasmid pRAS1 contained a drug resistance-determining region of 12 kb consisting of a class 1 integron similar to In4 of Tn
1696
but with a
dfrA16
gene cassette inserted. Close to IS
6100
at the right end of Tn4 was a truncated Tn
1721
. Restriction enzyme analysis showed that R plasmid pAr-32, isolated from
A. salmonicida
in Japan in 1970, had the same backbone structure as pRAS1, while the drug resistance-determining region contained a complex class 1 integron with an
aadA2
cassette; the chloramphenicol resistance gene
catA2
, as in In6 of pSa; and a duplicate of the 3′ conserved segment of the integron.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology