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Pathogenesis of Staphylococcus epidermidis in prosthetic joint infections: Can identification of virulence genes
Alba Sánchez1, Natividad Benito2, Alba Rivera3
1Department of Microbiology, Hospital de La Santa Creu I Sant Pau, Institut D'Investigació Biomèdica Sant Pau (IIB Sant Pau), Barcelona, Spain; Genetics and Microbiology Department. Universitat Autònoma de Barcelona, Barcelona, Spain.
Background:
Staphylococcus epidermidis is a commensal of human skin flora and a frequent causative microorganism in prosthetic joint infections (PJIs). To date, no single marker has been identified to distinguish infecting strains from commensal S. epidermidis populations.
Aim:
We aimed to find possible genetic markers to distinguish between the two populations.
Methods:
We analyzed 50 S. epidermidis strains from patients with PJIs, 50 from skin of healthy individuals (commensal strains) and 17 from the surgical field of patients undergoing primary arthroplasty. In these three groups we studied the antimicrobial susceptibility profile, sequence type, biofilm formation, and virulence factors. Strains from the surgical field have not been compared previously with strains from the other two groups.
Findings:
S. epidermidis strains from PJI patients were significantly more antibiotic resistant than commensal strains and surgical field strains. A wide variety of sequences types was found in commensal and surgical field strains. The predominant sequence type was ST2 and it was only present in PJI strains (44%). Differences in biofilm production did not differ between populations. Virulence genes sdrF and bhp, the complete ica operon, and the insertion sequence IS256 were significantly predominant in PJI strains. In contrast, embp and hld genes and the mobile element ACME were more prevalent in commensal strains. Surgical field strains could be a valid control group to discriminate between infecting and commensal strains.
Conclusion:
A combination of characteristic features can differentiate between infecting and commensal S. epidermidis strains in PJI, while a single marker cannot.
Insights
A combination of genetic markers can differentiate Staphylococcus epidermidis causing prosthetic joint infections (PJIs) from skin commensal strains. This research identifies key virulence factors and antibiotic resistance profiles distinguishing infecting bacteria.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Staphylococcus epidermidis is a common skin bacterium and a leading cause of prosthetic joint infections (PJIs).
- Currently, no single marker reliably distinguishes infecting S. epidermidis from commensal strains on the skin.
Purpose of the Study:
- To identify genetic markers that differentiate S. epidermidis strains causing PJIs from commensal strains.
- To investigate potential differences in antimicrobial susceptibility, sequence types, biofilm formation, and virulence factors between these populations.
Main Methods:
- Analysis of 50 PJI S. epidermidis strains, 50 commensal skin strains, and 17 surgical field strains.
- Assessment of antimicrobial susceptibility, sequence typing, biofilm formation, and presence of specific virulence genes (sdrF, bhp, ica operon, IS256, embp, hld) and mobile elements (ACME).
Main Results:
- PJI strains exhibited significantly higher antibiotic resistance compared to commensal and surgical field strains.
- Specific virulence genes (sdrF, bhp, ica operon, IS256) were more prevalent in PJI strains, while embp, hld, and ACME were more common in commensal strains.
- Sequence type ST2 was predominantly found in PJI strains.
- Biofilm production did not significantly differ between the groups.
Conclusions:
- A combination of genetic features, including specific virulence genes and sequence types, can effectively differentiate infecting S. epidermidis from commensal strains.
- Surgical field strains serve as a useful control group for distinguishing between infecting and commensal S. epidermidis.
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