Abstract
Clinical strains of
Staphylococcus aureus
UCN7 and UCN8 were inducibly resistant to erythromycin, clindamycin, lincomycin, and quinupristin. This unusual inducible MLS
B
resistance was
due to the presence of an
erm
(A) or an
erm
(B) gene, which both encode a ribosomal methylase, in
S. aureus
UCN8 and UCN7, respectively. The inducible cross resistance expressed by
S.
aureus
UCN8 was associated with an 83-bp deletion in the attenuator of the
erm
(A) gene that removed the second of the two leader peptides and several inverted repeats. The presence of an inducible
erm
(B) gene in
S. aureus
UCN7 conferred a cross-resistance MLS
B
phenotype, similar to that usually observed in streptococci. Therefore, in
S. aureus
, besides the classical
inducible MLS
B
phenotype characterized by inducible resistance to 14- to 15-membered ring macrolides, an additional type of inducible cross resistance to macrolides, lincosamides, and streptogramins
B due to variants of
erm
(A) or
erm
(B) genes exist.