ABSTRACT
The aims of the present study were to evaluate erythromycin, clindamycin, and streptogramin resistance rates, as well as the phenotypic and genotypic characteristics of erythromycin-resistant staphylococci in a Greek University Hospital. Macrolide, lincosamide, and streptogramin B-type resistance was investigated by double disk diffusion and the D-zone testing, while Minimal inhibitory concentration determination was performed among 656 erythromycin-resistant staphylococcal clinical consecutive isolates, too. The presence of the major genetic determinants ermA, ermB, ermC, and msrA were detected by polymerase chain reaction (PCR). The overall erythromycin resistance rate was 49·70%. One hundred and forty-six of the 322 Staphylococcus aureus were methicillin-resistant S. aureus (MRSA) (45·34%), whereas 176 were methicillin-susceptible S. aureus (54·66%). The macrolides, lincosamides, and streptogramin B-type antibiotics (MLSB)-constitutive phenotype was detected in 126 S. aureus strains (88·7%), whereas the inducible MLSB resistance phenotype was demonstrated in 16 S. aureus (11·3%). The MS phenotype was not detected. ErmC was the most frequently encountered gene responsible for macrolide resistance among S. aureus and coagulase negative staphylococci in this hospital. Pulsed-field gel electrophoresis (PFGE) analysis of SmaI DNA fragments revealed the presence of a single predominant clone among erythromycin-resistant S. aureus. The predominance of constitutive erythromycin resistance is a serious problem and limits the use of clindamycin for severe staphylococcal infections not only in this university hospital, but in many countries worldwide.
