Abstract
Macrolide-resistance genes were investigated in 103 macrolide-resistant strains of
Streptococcus pyogenes
, isolated from children with pharyngotonsillitis. The presence of
mef
(A),
erm
(B),
and
erm
(TR) genes was detected by PCR.
mef
(A) was found in 48 out of 103 (46.6%) strains, whereas
erm
(B) was detected in 43 isolates (41.7%). All
mef
(A) strains showed a typical
M phenotype (resistance to 14- and 15-membered macrolides, and sensitivity to lincosamides and streptogramin B), whereas
erm
(B) strains had the MLS
B
phenotype (resistance to macrolides,
lincosamides, and streptogramin B antibiotics).
erm
(TR) was found in 10 strains, always together with other resistance genes. In seven cases
erm
(TR) was associated with
erm
(B), and
three cases with
mef
(A). In two isolates with the M phenotype (1.9%), it was not possible to detect the presence of any of the three macrolide resistance genes tested. Inducible resistance to macrolides
was shown for 24 out of the 53 MLS
B
strains. Analysis of macrorestriction fragment patterns by pulsed-field gel electrophoresis showed that erythromycin-resistant
S. pyogenes
are polyclonal,
however each phenotype, MLS
B
and M, formed essentially homogeneous groups.