Alba Sánchez1, Natividad Benito2, Alba Rivera3, Lucas García3, Elisenda Miró3, Isabel Mur2, Yesica González3, Cristina Gutiérrez3, Juan Pablo Horcajada4, Paula Espinal5, Ferran Navarro6. 1. Department 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. 2. Infectious Diseases Unit, Hospital de La Santa Creu I Sant Pau, Institut D'Investigació Biomèdica Sant Pau (IIB Sant Pau), Department of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain. 3. Department of Microbiology, Hospital de La Santa Creu I Sant Pau, Institut D'Investigació Biomèdica Sant Pau (IIB Sant Pau), Barcelona, Spain. 4. Infectious Diseases Department, Hospital Del Mar, Barcelona, Spain. 5. Department of Microbiology, Hospital de La Santa Creu I Sant Pau, Institut D'Investigació Biomèdica Sant Pau (IIB Sant Pau), Barcelona, Spain. Electronic address: pespinal@santpau.cat. 6. Department 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. Electronic address: fnavarror@santpau.cat.
Abstract
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.
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.