This study aimed to correlate the presence of
ica genes, biofilm formation and antimicrobial resistance in 107 strains of
Staphylococcus epidermidis
isolated from blood cultures. The isolates were analysed to determine their methicillin resistance, staphylococcal cassette chromosome
mec (SCC
mec) type,
ica genes and biofilm formation and the vancomycin minimum inhibitory concentration (MIC) was measured for isolates and subpopulations growing on vancomycin screen agar. The
mecA gene was detected in 81.3% of the
S. epidermidis isolated and 48.2% carried SCC
mec type III. The complete
icaADBC operon was observed in 38.3% of the isolates; of these, 58.5% produced a biofilm. Furthermore, 47.7% of the isolates grew on vancomycin screen agar, with an increase in the MIC in 75.9% of the isolates. Determination of the MIC of subpopulations revealed that 64.7% had an MIC ≥ 4 μg mL
-1 , including 15.7% with an MIC of 8 μg mL
-1 and 2% with an MIC of 16 μg mL
-1 . The presence of the
icaADBC operon, biofilm production and reduced susceptibility to vancomycin were associated with methicillin resistance. This study reveals a high level of methicillin resistance, biofilm formation and reduced susceptibility to vancomycin in subpopulations of
S. epidermidis. These findings may explain the selection of multidrug-resistant isolates in hospital settings and the consequent failure of antimicrobial treatment.
