Staphylococcus aureus small colony variants in prosthetic joint infection

Clin Infect Dis. 2006 Oct 15;43(8):961-7. doi: 10.1086/507633. Epub 2006 Sep 8.


Background: Small colony variants of Staphylococcus aureus tend to persist despite antimicrobial therapy, especially when involved in implant-associated infections.

Methods: We analyzed 5 cases of hip prosthesis-associated infections due to small colony variants, including their course prior to identification of the pathogen. Biopsy investigations included microbiological examination and, in 1 case, transmission electron microscopy to detect intracellular bacteria in nonprofessional phagocytes. A treatment concept was elaborated on the basis of a published algorithm and patients were managed accordingly.

Results: The patients' mean age was 62.2 years. All patients experienced treatment failures prior to isolation of small colony variants, despite as many as 3 surgical revisions and up to 22 months of antibiotics. Transmission electron microscopy performed on biopsy specimens from periprosthetic tissue revealed intracellular cocci in fibroblasts. All prostheses were removed without implanting a spacer, and antimicrobial agents were administered for 5.5-7 weeks. Reimplantation of the prosthesis was performed for 4 patients. Follow-ups were uneventful in all 5 cases.

Conclusions: In the case of a poor response to adequate antimicrobial and surgical treatment in implant-associated staphylococcal infections, small colony variants should be considered and actively sought. In our case series, a 2-stage exchange without implantation of a spacer combined with antimicrobial therapy for an implant-free interval of 6-8 weeks was associated with successful outcome, with a mean follow-up of 24 months.

MeSH terms

  • Aged
  • Anti-Bacterial Agents / therapeutic use*
  • Arthroplasty, Replacement, Hip / adverse effects*
  • Bacterial Proteins / genetics
  • Clinical Protocols
  • Device Removal
  • Drug Resistance, Microbial*
  • Humans
  • Male
  • Microbial Sensitivity Tests
  • Microscopy, Electron, Transmission / methods
  • Middle Aged
  • Phenotype
  • Prosthesis-Related Infections / drug therapy
  • Prosthesis-Related Infections / microbiology*
  • Staphylococcus aureus / isolation & purification


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • FemA protein, Bacteria