Coagulase-negative staphylococci, particularly
Staphylococcus epidermidis
, can be regarded as potential reservoirs
of resistance genes for pathogenic strains, e.g.,
Staphylococcus aureus
. The aim of this study was to assess the
prevalence of different resistance phenotypes to macrolide, lincosamide, and streptogramins B (MLS
B) antibiotics
among erythromycin-resistant
S. epidermidis, together with the evaluation of genes promoting the following different
types of MLS
B resistance:
ermA,
ermB,
ermC,
msrA,
mphC, and
linA/A’. Susceptibility to spiramycin was also
examined. Among 75 erythromycin-resistant
S. epidermidis isolates, the most frequent phenotypes were macrolides
and streptogramins B (MS
B) and constitutive MLS
B (cMLS
B). Moreover, all strains with the cMLS
B phenotype and the
majority of inducible MLS
B (iMLS
B) isolates were resistant to spiramycin, whereas strains with the MS
B phenotype
were sensitive to this antibiotic. The D-shape zone of inhibition around the clindamycin disc near the spiramycin disc
was found for some spiramycin-resistant strains with the iMLS
B phenotype, suggesting an induction of resistance
to clindamycin by this 16-membered macrolide. The most frequently isolated gene was
ermC, irrespective of the
MLS
B resistance phenotype, whereas the most often noted gene combination was
ermC,
mphC,
linA/A’. The results
obtained showed that the genes responsible for different mechanisms of MLS
B resistance in
S. epidermidis generally
coexist, often without the phenotypic expression of each of them.
