Prevalence of macrolide-resistance genes in Staphylococcus aureus and Enterococcus faecium isolates from 24 European university hospitals

Abstract

The polymerase chain reaction (PCR) was used to study the prevalence of the macrolide resistance genes ermA, ermB, ermC, msrA/msrB, ereA and ereB, in 851 clinical isolates of Staphylococcus aureus and 75 clinical isolates of Enterococcus faecium that were erythromycin resistant. The isolates were from 24 European university hospitals. In S. aureus, the ermA gene was more common in methicillin-resistant S. aureus (MRSA) isolates (88%) than in methicillin-susceptible S. aureus (MSSA) isolates (38%), and occurred mainly in strains with constitutive MLS(B) expression. In contrast, ermC was more common in MSSA (47%) than in MRSA (5%), occurring mainly in strains with inducible expression. The ereB gene was only found in MRSA isolates expressing a constitutive MLS(B) phenotype (1%). The ereA gene was not detected. Macrolide resistance by efflux due to the msrA/msrB gene was only detected in MSSA isolates (13%). In contrast to S. aureus, erythromycin resistance in E. faecium was almost exclusively due to the presence of the ermB gene (93%).

Molecular Detection of Antimicrobial Resistance

“…Moreover, they found the gene to be prevalent in only 2.1% of the 144 S. aureus strains tested. In line with their observations, however, no combination of msrA/msrB and another macrolide resistance determinant was found by Schmitz et al (297). In CNS isolates, ermC was the most predominant gene in MRCNS and MSCNS, followed by ermA.…”

“…The ereB gene, coding for a macrolide-inactivating enzyme, was found only in MRSA isolates expressing the constitutive MLS B phenotype (1%). Neither ereA nor a combination of ereB and another macrolide-resistant determinant was found (297). Macrolide resistance by efflux due to the msrA/msrB gene was found only in MSSA isolates (13%).…”

“…In a recent study (297), the prevalence of the macrolide resistance genes, ermA, ermB, ermC, msrA/msrB, ereA, and ereB was analyzed using PCR in 851 unrelated clinical erythromycin-resistant S. aureus isolates, comprising 358 MSSA and 493 MRSA isolates, which had been sent from 24 different European university hospitals. Oligonucleotide primers for use in the PCRs were selected from the DNA sequences published by Sutcliffe et al (326).…”

Distribution of erm genes and low prevalence of inducible resistance to clindamycin among staphylococci isolates

“…22 This may be due to the lack of expression of erm genes due to factors which down regulate the expression of this gene. 22,23 In our study we found six S. aureus isolates and one CNS resistant to erythromycin and clindamycin but with negative genotypic test. These results were probably associated with the presence of other genes, such as msrA and msrB, with low frequency in Staphylococci species isolated form humans, 25 which were not evaluated in this study.…”

“…22 A multicenter study in 24 European university hospitals confi rmed the high prevalence of ermA gene and the low prevalence of ermC and ermB genes among 851 S. aureus. 23 Lina et al found 63.2% of S. aureus with ermA gene positive and 44% of CNS strains ermC gene positive, while the ermB gene was present in only 1% of staphylococci. 14 The results reported by Westh et al in Denmark, also showed a high prevalence of the ermA gene in S. aureus isolates and the ermC gene in CNS strains, as well as a low prevalence for the ermB gene.…”