Importance of screening for detection of methicillin-resistant staphylococcus for decrease infection in orthopedic surgery
Authors: Boccardo Jimena , Guerrero Liliana , Ganga Romina , Rodriguez Carolina , Manilov Ricardo 
Published: December 2018

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) can lead to considerable morbidity and mortality in orthopedic patients. The complication rate and cost of periprosthetic joint infection with MRSA is considerably higher compared to MSSA. Patients receiving orthopedic implants are most vulnerable, given the potential for biofilm formation and long-term morbility. Yet, worryingly, the incidence of MRSA in orthopedic departments has increased. Nasal colonization is a risk factor, and is 15-30% of the population for methicillin-susceptible strains (MSSA) and 1-3% for methicillin-resistant (MRSA). If combined with inguinal, 82% diagnostic sensitivity is achieved. Measures taken to prevent MRSA infection include screening to detect colonization, treatment of colonization and prophylactic antibiotic stewardship. Objectives: -Determine colonization index by Staphylococcus aureus (S. aureus) in the population of patients previous to an orthopedic procedures with implants in our institution. -Evaluate risk factors associated with colonization. -Compare the sensitivity of nasal screening vs triple screening (nasal, pharyngeal and inguinal) to detect colonization by S. aureus Methods: -Samples of nasal, pharyngeal and inguinal swabs were taken between 7 to 10 days before surgery, from April 2015 to April 2018. -Salted (selective) Mannitol was cultured for 24 h at 37° C. Sensitivity detection on disk. -Data of the surgeries were collected in Ad Hoc cards, (hour incision, antibiotic administration,). - In carriers, a decolonization protocol was initiated with nasal mupirocin 3 times a day for 5 days, and baths with chlorhexidine 3 days prior to surgery. - Infection rates were recorded according to procedures Results: During the period studied, 425 swabs were performed, with 175 positive for S.aureus (41,1%), with a distribution of 73,14% for MSSA and 26,85% for MRSA. The incidence of carriage in the studied population, was 30.11% for MSSA and 11.05% for MRSA. -125 patients were detected by nasal screening (71.42%), and 50 patients were positive in swabs of the jaws or inguinals exclusively (28.57%) Risk factors were analyzed, such as diabetes, rheumatoid arthritis, chronic renal failure, among others. In the statistical analysis only hypothyroidism was a significant factor to predict colonization by s. aureus, regardless of susceptibility. The antibiotic prophylaxis was performed sequentially with vancomycin and cefazolin, beginning two hours before the incision, in all patients colonized with MRSA. During the study period, only SAMS infections occurred, but they showed a reduction rate of surgical site infections in all areas with the decolonization protocol, although no statistical significance was shown. Conclusion: According to our data, the carrying of MRSA is greater than that reported in the literature, and we do not find risk factors that reliably predict portability, so we must perform triple screening, chlorhexidine baths and adequate prophylaxis to the microorganism as part of pre-surgical preparation, in all patients with orthopedic implants. We emphasize the importance of the number of samples, since it increases the detection sensitivity in a third of the patients by adding three anatomical sampling sites.