Incidence of Methicillin-Resistant Staphylococcus Aureus Colonization in Primary Hip and Knee Arthroplasty
John Kadzielski, MD
Harvard Combined Orthopaedic Residency Program
Massachusetts General Hospital
55 Fruit Street, White 535, Boston, MA 02114
John Siliski, MD
Massachusetts General Hospital, Department of Orthopaedic Surgery
55 Fruit Street, White 535, Boston, MA 02114
Introduction: Staphylococcus aureus is one of the most common pathogens in hip and knee arthroplasty. The incidence of MRSA is climbing in the community. Surgeons may need to screen for MRSA colonization or provide appropriate prophylaxis to continue to provide safe arthroplasty care in the future. The purpose of this paper is to determine the incidence of MRSA colonization in our total joint population.
Methods: From 2007 to 2009, patients received a nasal swab MRSA screening test during their preoperative anesthesia testing appointment in preparation for hip or knee arthroplasty.
Results: The incidence of MRSA colonization in our population was 3.6%. Patients identified as MRSA carriers were treated with mupirocin preoperatively and received vancomycin for perioperative antibiotics. None of the MRSA-colonized patients had an infectious complication. Healthcare workers had a significantly higher percentage of MRSA colonization than non-healthcare workers.
Conclusions: The incidence of MRSA colonization in our sample is not negligible. Out patients were successfully managed with mupirocin treatment and perioperative vancomycin. Healthcare workers should be considered at elevated risk for MRSA colonization.
Fifteen to 30% of all surgical site infections are related to Staphylococcus aureus, and most of them are thought to be due to preoperative colonization (1-3). In total joint arthroplasty infection, Staphylococcus aureus and Staphylococcus epidermidis are the most common pathogens (4) The incidence of Methicillin Resistant Staphylococcus Aureus (MRSA) is increasing and is now found widely in the community.4 On average, 59% of the soft tissue infections presenting to emergency departments around the country are now MRSA (5). The incidence of MRSA carriage in one sample of orthopaedic patients presenting for elective surgery was reported to be 4.4% (6), and there is some retrospective evidence that suggests screening and decolonization significantly decreases the rate of MRSA infections in arthroplasty patients (7). Given the increasing incidence of this resistant organism in the community, it may become necessary to alter our current antibiotic practices to provide sufficient protection against resistant bacteria. Other hospitals in Boston have started screening their orthopaedic patients preoperatively in the hopes of eradicating MRSA before patients even get to the operating room.6 In keeping with this emerging standard of care, we set out to determine the incidence of MRSA in our elective adult arthroplasty population.
Consecutive patients of a single surgeon undergoing total hip or total knee arthroplasty at a large academic institution were screened for MRSA nasal colonization as part of their preoperative evaluation. Demographic data including occupation were recorded and postoperative infection data were recorded. If results were positive, patients were given mupirocin to eradicate the MRSA colonization preoperatively. Patients were not retested to prove eradication prior to their operation. After being treated for MRSA colonization, patients underwent arthroplasty with routine preoperative antibiotic prophylaxis with vancomycin started within one hour prior to the incision. Implants were cemented without antibiotics in the cement unless they were a revision from a previous infection. Patients received two doses of antibiotics postoperatively within 24 hours of the surgery. There were no alterations in operative or postoperative protocols.
From 2007 to 2009, a total of 349 nasal swabs were done in 337 patients during their preoperative anesthesia testing appointment in preparation for either total knee or total hip arthroplasty. Patients who had two arthroplasties or who cancelled surgery and rescheduled during the three year inclusion period were swabbed during each preoperative anesthesia testing appointment. Nasal swab data was absent in 15 patients either because the patients did not have the test, the results were invalid or they were lost. This left 334 valid MRSA preoperative screening swabs. Five patients did not undergo surgery despite having completed their preoperative evaluation including MRSA screening. Twelve out of the 334 MRSA nasal swabs were positive. (Figure 1) The incidence of MRSA colonization in our elective total joint arthroplasty population was 3.6%. Five of the 12 people who tested positive worked in the healthcare field. There was significantly higher MRSA colonization in healthcare workers than non-healthcare workers (χ2 = 5.352, p = 0.02). (Table 1) Thirty-eight people did not report their occupation. None of the patients who tested positive for MRSA colonization and were treated had an infectious complication after surgery. In our sample overall, there were 3 infections, all of which occurred in patients who tested negative for MRSA. There was one deep MSSA infection, 1 deep Staphylococcus epidermidis infection and one superficial wound infection.
The incidence of MRSA colonization in our elective total joint arthroplasty sample was 3.6%. Although authors have written on antibiotic prophylaxis in hip and knee arthroplasty and the role of screening for MRSA (4,7,8), the clinical utility, cost-effectiveness and medicolegal implications remain unclear. While this prospective database was not designed to address this question definitively, mupirocin ointment and vancomycin perioperative antibiotics appear to clinically neutralize MRSA. With the current regiment, we were able to provide safe arthroplasty care with no infections attributable to MRSA despite the emergence of resistant bacteria in the community. In our sample, people who worked in healthcare were significantly more likely to be a carrier of MRSA than people in other occupations. Other researchers have found rates of MRSA colonization in healthcare workers to be similar to their high-risk groups (9). Surgeons should consider routine MRSA screening of patients who work in healthcare.
Additional studies have shown a decrease in the rate of MRSA infections through additional measures, e.g., dedicated orthopaedic wards away from other patients.10 Others have warned that simply screening for MRSA is not enough given the prevalence of coagulase-negative staphylococci, which one group has found to be over 50% methicillin-resistant on screening (11). And even though the majority of MRSA is now community acquired, it is important that surgeons continue to use hospital protocols and hand-washing to prevent iatrogenic infection (12). Last year, an American Academy of Orthopaedic Surgeons Instructional Course Lecture using a comprehensive evidence-based approach recommended that strategies to reduce infections include “…identification of high-risk patients, screening and decolonization of patients with methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus…” in addition to other measures (13). Our paper identifies a group that is at high-risk and demonstrates effective screening and decolonization methodologies that can be put into practice by our surgeons at our hospitals
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