AAOS Now

Published 3/1/2003
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Robert Brooks, MD, PhD, MBA

Screening for MRSA: An idea whose time has come?

Reducing surgical site infections with simple protocols

The number of hospital admissions associated with methicillin-resistant Staphylococcus aureus (MRSA) has exploded in the last decade, roughly tripling every 5 years. S. aureus is the most common single pathogen in surgical site infections (SSIs), and methicillin-resistant S. aureus often represents 30 percent to 50 percent of all S. aureus SSIs.

Frequent media coverage of MRSA infections in hospitals and among professional athletes has increased awareness and concern among the American public about the risk of acquiring healthcare-associated MRSA (HA-MRSA). Our patients are also aware that students, athletes, and others are at increasing risk for community-associated MRSA (CA-MRSA.)

Because first-generation cephalosporins such as cefazolin are not effective against either type of MRSA, many orthopaedic surgeons are adding vancomycin or clindamycin to their perioperative antibiotic regimen for high-risk patients such as nursing home residents, dialysis patients, and anyone with a history of MRSA colonization.

Overuse of vancomycin may lead to increasing resistance, however. The more resistant vancomycin intermediate sensitive S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA) loom as emerging problems. Overuse of clindamycin may contribute to Clostridium difficile-associated disease.

As a result, identifying and targeting those patients who are at high risk for MRSA or who are asymptomatically colonized is increasingly important. In the past few years, increased concern about HA-MRSA has prompted many hospitals to conduct active surveillance for MRSA in their critical care units, dialysis units, and other high-risk areas. Hospital administrators have also become more aware of the benefits that are derived from absorbing the cost of active surveillance programs for MRSA, such as avoided infections and increased public confidence.

Is preoperative screening the answer?
What is the next step in active surveillance and screening of patients to detect and treat MRSA? In one study published this spring, a group at the University of Pittsburgh screened more than 600 consecutive, otherwise healthy patients for S. aureus as part of their preoperative joint replacement program. They found that approximately one in four community patients who had no prior medical contact were asymptomatic carriers of S. aureus based on nasal cultures. Of this population, 23 percent were colonized with methicillin-sensitive S. aureus (MSSA), and 3 percent were asymptomatic CA-MRSA carriers.

Using a protocol of preoperative chlorhexidine baths at home and nasal use of the antibiotic mupirocin, together with vancomycin prophylaxis for joint replacement patients colonized with MRSA, this program was able to eliminate all S. aureus SSIs during the study year. SSIs caused by other organisms, however, continued at the previous rate.

The authors concluded that S. aureus SSIs in joint replacement patients resulted not from transmission during hospitalization, but from the endogenous source of CA-MRSA and MSSA on their patients’ skin at the time of surgery.

Data suggest that many areas of the United States may have even higher rates of asymptomatic MRSA colonization than the 3 per­cent noted in this study. However, adding vancomycin or clindamycin to the prophylaxis of all elective surgeries is not recommended for two reasons: the very real threat of increasing resistance, and the problem in timing the administration of vancomycin, which needs to be infused slowly over at least 1 hour.

What orthopaedic surgeons can do
Orthopaedic surgeons who are concerned about the S. aureus status of their joint replacement patients may consider preoperative screening of their patients by ordering nasal cultures. The nares culture is a highly correlated marker for MSSA and MRSA colonization of the skin of the patient.

Two types of culture for S. aureus are in common use. In both cases, a swab is taken from deep within both nares of the patient by gentle manipulation over several seconds. The standard culture gives results in 2 days and costs about $20. A faster result—within 2 hours—can be obtained with a polymerase chain reaction (PCR) machine. Single PCR tests for MRSA can cost as much as $200, but by batching large volumes, the per-test cost for PCR-MRSA testing can decrease to about $40.

Orthopaedic implant surgeons are understandably concerned about the best way to target MRSA-prevention interventions. Similarly, sports medicine specialists want to demonstrate their commitment to preventing SSIs to their increasingly concerned patients.

Total joint replacement programs that have a coordinated period of instruction and preoperative preparation provide an ideal opportunity to pilot MRSA and MSSA screening within the community. Not only is the benefit-to-risk ratio high for the patient, but joint replacement service lines are important to hospitals as financial and “branding” centers. Hospital administrators will be interested in piloting a program that will inform the medical staff about MRSA rates within their community, while protecting an important surgical service line.

Although most hospitals have not yet begun universal active surveillance of all patients upon admission and discharge, this may be a reality in the near future. In the meantime, AAOS fellows should consider identifying and targeting those patients known to be at high risk for MRSA and MSSA colonization and attempt interventions to protect their patients.

Robert Brooks, MD, PhD, MBA, is past chair of the AAOS Patient Safety Committee. He can be reached at brooks@dfmc.org

References:

  1. Klevens RM, Morrison MA, Nadle, et al: Invasive methicillin-resistant Staphylococcus aureus infections in the United States. JAMA 2007;298:1763-1771.
  2. Rao N, Cannela B, Crossett LA, Yates AJ, McGough R: A preoperative decolonization protocol for Staphylococcus aureus prevents orthopedic infections. Clin Orthop 2008;466:1343-1348.
  3. Prokuski L: Prophylactic antibiotics in orthopaedic surgery. J Am Acad Orthop Surg 2008;16:283-293.