Published 8/1/2010
Mary Ann Porucznik

Prevalence and prescreening for S aureus

Studies examine rates of colonization, effectiveness of detection, eradication

Increasing rates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) are causing concern among orthopaedic healthcare providers. S aureus is often responsible for hospital-acquired infections, including surgical site infections, and the cost of treating patients infected with resistant strains is substantial. Two studies in the August issue of The Journal of Bone and Joint Surgery focus on the prevalence of S aureus colonization among healthcare providers and the effectiveness of prescreening programs in reducing surgical site infections.

A prospective cohort controlled study conducted by Ran Schwarzkopf, MD, MS; Richelle C. Takemoto, MD; Igor Immerman, MD; James D. Slover, MD, MS; and Joseph A. Bosco, MD, examined the “Prevalence of S aureus Colonization in Orthopaedic Surgeons and Their Patients.” A nonrelated study on a program of “Institutional Prescreening for Detection and Eradication of Methicillin-Resistant S aureus in Patients Undergoing Elective Orthopaedic Surgery” was conducted by David H. Kim, MD; Maureen Spencer, RN; Susan M. Davidson, MD; Ling Li, MSPH; Diane Gulczynski, RN; David J. Hunter, MD, PhD; Juli F. Martha, MPH; Gerald B. Miley, MD; Stephen J. Parazin, MD; Pamela Dejoie; and John C. Richmond, MD.

A cautionary tale
According to Dr. Bosco, nasal cultures of orthopaedic attending surgeons, residents, and patients at a single institution found a significantly higher rate of MSSA colonization in surgeons (35.7 percent) than in high-risk patients (18 percent). Rates of MSSA colonization for residents were even higher—59 percent. But there was no difference among the groups in prevalence of MRSA.

“Previous studies have shown that the more time people spend in hospitals, the more likely they are to be colonized by either MSSA or MRSA,” said Dr. Bosco. “Healthcare workers are likely to be asymptomatic, but colonization may be an occupational hazard.”

Dr. Bosco was quick to point out that no studies have shown a correlation between carriage and transfer of S aureus between doctors and their patients.

“The patient is not at risk,” he said, particularly if the healthcare workers are vigilant about following hand and equipment hygiene guidelines. But he does advise physicians to be aware of their practice patterns. Physicians whose patients have a higher rate of infection than their colleagues or who notice a cluster of infections among their patients should be tested.

Additionally, the fact that surgeons may be carrying the bacteria may make them more susceptible to infection if they become patients.

“It’s anecdotal that doctors and their families have more complications after surgery,” he said, “and this may be one reason why.” He recommends that any orthopaedic practitioner who is planning to have any type of elective surgery undergo a decolonization protocol as a matter of course.

The high rate of MSSA colonization among residents was a surprising aspect of the study. Dr. Bosco noted, however, that residents are frequently responsible for administering day-to-day care, including changing dressings. According to the study, “this may explain why junior residents exhibit the same prevalence of MSSA colonization as institutionalized patients.”

Screening patients works
In the second study, a universal prescreening program was instituted to determine effectiveness in reducing rates of surgical site infections. Approximately one in five patients screened were identified as MSSA carriers, and 4 percent were MRSA carriers. As expected, surgical site infections were significantly higher among MRSA carriers.

During the year-long study, adults scheduled for elective inpatient orthopaedic surgery at the institution were tested using a polymerase chain reaction (PCR)-based diagnostic test (for MRSA) and a standard culture test (for MSSA). Patients who tested positive were treated for 3 days with an intranasal mupirocin ointment (twice daily) and for 5 days with a chlorhexidine shower, then tested to ensure that the bacteria had been eradicated.

“Our initial surgical site infection rate was lower than the national average—about 0.5 percent,” said Dr. Kim. “But with this protocol, we saw a 61 percent drop in surgical site infections, so the rate dropped to about 0.19 percent.” According to the study, the reduction was greater in MRSA-associated surgical site infections (0.06 percent during the study period compared with 0.18 percent during the control period) than for MSSA infections (0.13 percent during the study period compared with 0.26 percent during the control period).

The results were so convincing that institution-wide prescreening for MRSA is now routine at the hospital. According to Dr. Kim, “Several studies have been published describing prescreening efforts at individual hospitals, and interest among policymakers to mandate prescreening and stem the increase in MRSA infections is growing.”

Mary Ann Porucznik is managing editor of AAOS Now. She can be reached at porucznik@aaos.org

Bottom Line

    • Surgeons and residents may have significantly higher rates of MSSA colonization than patients, although rates of MRSA colonization are similar among surgeons, residents, and patients.

    • A universal screening program for MRSA and MSSA among patients scheduled for elective orthopaedic surgery and a treatment protocol to ensure eradication can result in a significant reduction in the incidence of surgical site infections.