MRSA, MSSA Decolonization Effective in TJA Patients

Maureen Leahy

Current decolonization protocols using intranasal mupirocin and chlorhexidine body washes are effective for reducing methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) colonization in total joint arthroplasty (TJA) patients, according to study data presented Wednesday by Antonia F. Chen, MD, MBA, of the University of Pittsburgh Medical Center.

S. aureus is a leading cause of surgical site infections (SSIs) in orthopaedic surgery. As a result, TJA patients are routinely screened for MRSA/MSSA, and those who test positive are decolonized prior to surgery to reduce the risk of SSIs. However, until now, no study has directly determined if current decolonization treatment protocols result in successful MRSA and MSSA decolonization in TJA patients, according to Dr. Chen.

MRSA/MSSA screening
The researchers prospectively followed 106 patients undergoing elective TJA at a single institution between March 2011 and March 2012. Patient demographics were as follows:

49 females, 57 males
109 joints: 47 total hips, 62 total knees
average age = 61 years
average body mass index = 30.9
average Charlson Comorbidity Index score = 0.76

Most patients (62 percent) had an anesthesia classification of American Society of Anesthesiologists class III.

Patients were screened for S. aureus colonization, on average, 35 days (range: 1–6 weeks) prior to surgery using a saline-moistened nasal swab in both nares. Researchers used standard microbiologic culture methods to identify MRSA and MSSA strains.

Patients who tested positive for MRSA and/or MSSA underwent decolonization using a 2-percent mupirocin ointment intranasally twice a day and chlorhexidine body wash daily for 5 days prior to surgery. One patient—who was initially MSSA positive and was persistently MSSA positive postoperatively—did not comply with the decolonization protocol. Patients were reswabbed on the day of surgery to determine if the treatment was effective.

Significant reduction in colonization
Twenty-four patients (22 percent) tested positive for MSSA preoperatively, while 5 patients (4.6 percent) tested positive for MRSA. On the day of surgery, 10 of the 29 patients (9.2 percent) tested positive for MSSA, and none of the patients tested positive for MRSA (Fig.1). After statistical analysis, the researchers found the reduction in MSSA colonization to be significant (P < 0.001), whereas the eradication of MRSA colonization approached statistical significance (P = 0.063), due to the small sample size.

“Of the 10 patients who tested positive for MSSA postoperatively, 6 were negative for MSSA preoperatively, and 4 had persistently positive MSSA colonization cultures. One patient who was persistently colonized for MSSA was not compliant with the decolonization protocol. Thus, there were 3 patients who had undergone decolonization and were persistently positive for MSSA at the time of surgery,” explained Dr. Chen.

The patients were followed for an average of 233 days, during which time only one patient developed an SSI—a MRSA periprosthetic joint infection—despite testing negative for MRSA/MSSA preoperatively and on the day of surgery. The patient was successfully treated with two-stage exchange arthroplasty and intravenous antibiotics.

Although this is the first study to directly examine the effectiveness of the MRSA/MSSA decolonization protocol using intranasal mupirocin and chlorhexidine washes in TJA patients, the authors acknowledge that the study did have weaknesses. Among them was the fact that it was not randomized and did not include a comparison group. In addition, the researchers did not evaluate the effectiveness of other treatment modalities, including oral antibiotics. Finally, the study used only culture swabs—and not polymerase chain reaction, which may increase sensitivity—to detect the presence of MRSA/MSSA.

Despite these limitations, noted Dr. Chen, the study results have important implications for orthopaedic surgeons who perform TJA. “Our study found that the current decolonization protocol of intranasal mupirocin and chlorhexidine body wash significantly reduced the rate of MSSA colonization and reduced the rate of MRSA to zero,” she said. “This encourages orthopaedic surgeons to screen for and decolonize elective TJA patients prior to surgery.”

Dr. Chen’s coauthors of “Staphylococcus Decolonization in Total Joint Arthroplasty is Effective” are Alma Heyl, CCRC; Peter Z. Xu, BA; Nalini Rao, MD; and Brian A. Klatt, MD.

Disclosure information: Dr. Chen—Novo Nordisk; SLACK Inc.; Dr. Klatt—SLACK Inc.; Saunders/Mosby-Elsevier Operative Techniques in Orthopaedics; Journal of Arthroplasty; AAOS AAHKS Abstract Review Committee; Dr. Rao, Ms. Heyl, and Mr. Xu,—no conflicts.

2013 Annual Meeting News
Tuesday through Friday, February 19 – 23, 2013.
http://www.aaos.org/news/acadnews/2013/AAOS3_3_21.asp