Affiliation:
1. Institute of Microbiology, University of Ancona Medical School, 60131 Ancona, Italy
2. Department of Pathobiology, University of Washington, Seattle, Washington 98195
Abstract
ABSTRACT
Sixty-three recent Italian clinical isolates of
Streptococcus pyogenes
resistant to both erythromycin (MICs ≥ 1 μg/ml) and tetracycline (MICs ≥ 8 μg/ml) were genotyped for macrolide and tetracycline resistance genes. We found 19 isolates carrying the
mef
(A) and the
tet
(O) genes; 25 isolates carrying the
erm
(A) and
tet
(O) genes; and 2 isolates carrying the
erm
(A),
tet
(M), and
tet
(O) genes. The resistance of all
erm
(A)-containing isolates was inducible, but the isolates could be divided into two groups on the basis of erythromycin MICs of either >128 or 1 to 4 μg/ml. The remaining 17 isolates included 15 isolates carrying the
erm
(B) gene and 2 isolates carrying both the
erm
(B) and the
mef
(A) genes, with all 17 carrying the
tet
(M) gene. Of these, 12 carried Tn
916
-Tn
1545
-like conjugative transposons. Conjugal transfer experiments demonstrated that the
tet
(O) gene moved with and without the
erm
(A) gene and with the
mef
(A) gene. These studies, together with the results of pulsed-field gel electrophoresis experiments and hybridization assays with DNA probes specific for the
tet
(O),
erm
(A), and
mef
(A) genes, suggested a linkage of
tet
(O) with either
erm
(A) or
mef
(A) in erythromycin- and tetracycline-resistant
S. pyogenes
isolates. By amplification and sequencing experiments, we detected the
tet
(O) gene ca. 5.5 kb upstream from the
mef
(A) gene. This is the first report demonstrating the presence of the
tet
(O) gene in
S. pyogenes
and showing that it may be linked with another gene and can be moved by conjugation from one chromosome to another.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Cited by
113 articles.
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