title: Epidemiology of patients with MSSA versus MRSA infections of orthopedic implants: Retrospective study of 115 patients.
abstract: Factors that predict the occurrence of a surgical site infection due to methicillin-resistant Staphylococcus aureus (MRSA) are not well known; however this information could be used to modify the recommended antimicrobial prophylaxis. We carried out a retrospective study of S. aureus infections on orthopedic implants to determine: (1) whether epidemiological factors can be identified that predict a MRSA infection, (2) the impact of these factors as evidenced by the odds ratio (OR).
  
  
  
  Risk factors for a MRSA infection can be identified from a cohort of patients with S. aureus infections.
  
  
  
  We identified 244 patients who experienced a S. aureus surgical site infection (SSI) in 2011-2012 documented by intraoperative sample collection. Of these 244 patients, those who had a previous SSI (n=44), those with a SSI but no orthopedic implant (n=80) or those who had the infection more than 1-year after the initial surgery (n=5) were excluded. This resulted in 115 patients (53 arthroplasty, 62 bone fixation) being analyzed for this study. There were 24 MRSA infections and 91 MSSA infections. The following factors were evaluated in bivariate and multifactorial analysis: age, sex, type of device (prosthesis/bone fixation), predisposition (diabetes, obesity, kidney failure), and environmental factors (hospitalization in intensive care unit within past 5 years, nursing home stay).
  
  
  
  Two factors were correlated with the occurrence of MRSA infections. (1) Nursing home patients had a higher rate of MRSA infections (67% vs. 18%, P=0.017) with an OR of 8.42 (95% CI: 1.06-66.43). (2) Patients who had undergone bone fixation had a lower rate of MRSA infections than patients who had undergone arthroplasty (13% vs. 30%, P=0.023), OR 0.11 (95% CI: 0.02-0.56). Although the sample size was too small to be statistically significant, all of the patients with kidney failure (n=4) had a MRSA infection.
  
  
  
  Since these MRSA infection risk factors are easy to identify, the antimicrobial prophylaxis could be adapted in these specific patient groups.
authors.affiliation: Clinique d'orthopédie, CHU de Lille, Lille, France; Université de Lille, 59000 Lille, France. Electronic address: anthony.f.deny@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Deny
authors.affiliation: Université de Lille, 59000 Lille, France; Institut de microbiologie, CHU de Lille, Lille, France.
authors.forename: C
authors.initials: C
authors.lastname: Loiez
authors.affiliation: Université de Lille, 59000 Lille, France; Service de biostatistiques, université de Lille, 59000 Lille, France.
authors.forename: V
authors.initials: V
authors.lastname: Deken
authors.affiliation: Clinique d'orthopédie, CHU de Lille, Lille, France; Université de Lille, 59000 Lille, France.
authors.forename: S
authors.initials: S
authors.lastname: Putman
authors.affiliation: Université de Lille, 59000 Lille, France; Service de biostatistiques, université de Lille, 59000 Lille, France.
authors.forename: A
authors.initials: A
authors.lastname: Duhamel
authors.affiliation: Clinique d'orthopédie, CHU de Lille, Lille, France; Université de Lille, 59000 Lille, France.
authors.forename: J
authors.initials: J
authors.lastname: Girard
authors.affiliation: Clinique d'orthopédie, CHU de Lille, Lille, France; Université de Lille, 59000 Lille, France.
authors.forename: G
authors.initials: G
authors.lastname: Pasquier
authors.affiliation: Clinique d'orthopédie, CHU de Lille, Lille, France; Université de Lille, 59000 Lille, France.
authors.forename: C
authors.initials: C
authors.lastname: Chantelot
authors.affiliation: Université de Lille, 59000 Lille, France; Service de maladies infectieuses, centre hospitalier de Dron, 59200 Tourcoing, France.
authors.forename: E
authors.initials: E
authors.lastname: Senneville
authors.affiliation: Clinique d'orthopédie, CHU de Lille, Lille, France; Université de Lille, 59000 Lille, France.
authors.forename: H
authors.initials: H
authors.lastname: Migaud
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D005593:Fracture Fixation, Internal; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects; D007595:Joint Prosthesis / Q000009:adverse effects; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus; D008875:Middle Aged; D016459:Prosthesis-Related Infections / Q000453:epidemiology* / Q000382:microbiology*; D012189:Retrospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000453:epidemiology*; D055815:Young Adult
keywords: Bacterial resistance; Epidemiology; Joint infections; Risk factors; Staphylococcus aureus