Erm Genes in Erythromycin-Resistant Staphylococcus Aureus and Coagulase-Negative Staphylococci

APMIS. 1995 Mar;103(3):225-32.


Erythromycin-resistant S. aureus from general practice and a dermatology ward with a very high consumption of erythromycin was studied for ermA and ermC content by Southern blot analysis. The prevalence of these erm genes was also studied in coagulase-negative staphylococci from the same dermatology ward and in a collection of 15 S. aureus and 18 coagulase-negative staphylococci found in the same specimen from 15 different patients. ermA was only found as a chromosomal insert and ermC only on small plasmids. In erythromycin-resistant S. aureus from general practice ermC was responsible for 84% of erythromycin resistance, while 16% of the strains contained ermA. In 17 of 18 S. aureus strains from the dermatology ward a 2.5 kb plasmid contained ermC. Among 58 erythromycin-resistant coagulase-negative staphylococci only 2 (3%) had ermA, whereas 44 strains (76%) had ermC. ermA or ermC genes were common in S. epidermidis (36/38). However, in 20 isolates of erythromycin-resistant coagulase-negative staphylococci of other species, 10 had neither ermA nor ermC. ermC was the most common erm gene in both coagulase-negative staphylococci and S. aureus. In 11 of 15 patients with erythromycin-resistant S. aureus the co-isolated erythromycin-resistant coagulase-negative staphylococcus had another resistance mechanism, either another gene or a different phenotypic expression of the same gene. Resistance to pristinamycin, a streptogramin antibiotic only used in animals, was not found in S. aureus but was found in 14% of erythromycin-resistant coagulase-negative staphylococci.

MeSH terms

  • Animals
  • Base Sequence
  • Coagulase / analysis*
  • Coagulase / genetics
  • Drug Resistance, Microbial / genetics
  • Erythromycin / pharmacology*
  • Family Practice
  • Genes, Bacterial*
  • Hospitals
  • Humans
  • Molecular Sequence Data
  • Staphylococcus / drug effects
  • Staphylococcus / enzymology
  • Staphylococcus / genetics*
  • Staphylococcus / isolation & purification
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / genetics


  • Coagulase
  • Erythromycin