Relationship Between Staphylococcus aureus Carriage and Surgical Site Infections Following Total Hip and Knee Arthroplasty in the South Asian Population: Protocol for a Prospective Cohort Study.

BACKGROUND: Surgical site infections following total hip or knee arthroplasties have a reported rate of 0.49%-2.5% and can cause significant morbidity as well as tripling the cost of health care expenses. Both methicillin sensitive and methicillin resistant strains of Staphylococcus aureus surgical site infections have been established as a major risk factor for postoperative surgical site infections. S. aureus colonizes the nose, axillae, and perineal region in up to 20%-30% of individuals. Although the literature has reported a higher prevalence of methicillin resistant S. aureus in the South Asian population, routine preoperative screening and prophylaxis have not yet been implemented.

OBJECTIVE: The primary objective of our study is to identify the relationship between preoperative colonization status of S. aureus and incidence of postoperative surgical site infections in patients undergoing following total hip and knee arthroplasties. As part of the secondary objectives of this study, we will also investigate patient characteristics acting as risk factors for S. aureus colonization as well as the outcomes of total hip and knee arthroplasty patients which are affected by surgical site infections.

METHODS: This prospective cohort study will comprise of screening all patients older than 18 years of age admitted to the Aga Khan University Hospital for a primary total hip or knee arthroplasty for preoperative colonization with S. aureus. The patients will be followed postoperatively for up to one year following the surgery to assess the incidence of surgical site infections. The study duration will be 2 years (March 2018 to March 2020). For the purpose of screening, pooled swabs will be taken from the nose, axillae, and groin of each patient and inoculated in a brain heart infusion, followed by subculture onto mannitol salt agar and sheep blood agar. For methicillin resistant S. aureus identification, a cefoxitin disk screen will be done. Data will be analyzed using SPSS v23 and both univariate and multivariate regression analysis will be conducted.

RESULTS: Data collection for this study will commence at the Aga Khan University Hospital, Pakistan during March 2018.

CONCLUSIONS: This study will not only estimate the true burden caused by S. aureus in the population under study but will also help identify the patients at a high risk of surgical site infections so that appropriate interventions, including prophylaxis with antibiotics such as muciprocin ointment or linezolid, can be made. Given the differences in lifestyle, quality, and affordability of health care and the geographical variation in patterns of antibiotic resistance, this study will contribute significantly to providing incentive for routine screening and prophylaxis for S. aureus including methicillin resistant S. aureus colonization in the South Asian population.

REGISTERED REPORT IDENTIFIER: RR1-10.2196/10219.