At the 2011 Annual Meeting in San Diego, Scott M. Sporer, MD, reported that implementing a preoperative Staphylococcus screening and treatment program among total joint arthroplasty (TJA) patients at his institution decreased the surgical-site infection (SSI) rate by 82 percent.

“SSI can be reduced,” he concluded, “by instituting a standardized nasal screening and decolonization protocol for patients undergoing elective TJA who are carriers of either methicillin-resistant S aureus (MRSA) or methicillin-sensitive S aureus (MSSA).”

MRSA/MSSA screening
According to Dr. Sporer, 1,200 of 1,250 primary total hip arthroplasty or total knee arthroplasty patients at his institution underwent preoperative Staphylococcus nasal screening between January 2009 and July 2009. He noted that 1,100 patients who underwent elective TJA between July 2008 and December 2008 served as the control cohort.

Study participants were instructed to obtain a nasal swab at least 14 days before their procedure. Researchers used standard microbiologic culture methods to identify MSSA and MRSA strains.

Patients who tested positive for S aureus were notified of their results and were instructed to apply a 2-percent mupirocin ointment intranasally. They were also told to take a 2-percent chlorhexidine shower daily for 5 days prior to admission to the hospital.

Antimicrobial resistance to methicillin was then tested among patients who tested positive for S aureus. Study participants who did not test positive for MRSA were treated with cefazolin within 1 hour of surgery, while patients who tested positive for MRSA were treated with vancomycin within 2 hours of surgery. Antibiotic prophylaxis was discontinued within 24 hours after the surgical procedure.

“Additionally,” said Dr. Sporer, “patients who tested positive for MRSA colonization were placed on contact precautions that included the use of barrier gowns and gloves during patient contact.”

Patients who were identified as being positive for MSSA or MRSA less than 5 days prior to admission were told to begin chlorhexidine showers as soon as possible and continue them until admission.

“Nasal swabs were obtained the day of admission on patients who did not have preoperative screening,” he said. “Mupirocin was administered immediately prior to surgery in this cohort of patients, and was continued postoperatively until the results were negative for either MSSA or MRSA. A 10-dose decolonization regimen was continued among patients who subsequently were positive for either MSSA or MRSA.”

All patients, regardless of nasal colonization, were required to shower the night before surgery and apply a chlorhexidine cloth to all skin, except on the face and genitals, a minimum of 1 hour after showering.

“The topical skin preparation with the chlorhexadine cloth was continued the morning of surgery in the surgery holding area,” explained Dr. Sporer. Researchers used the following criteria for determining an SSI:

• purulent drainage from the wound
• serosanguineous drainage from an erythematous incision with a positive wound culture
• a note in the medical record from a physician stating that the wound was infected

“The overall incidence of SSI was determined for the cohorts of patients both before and after the implementation of routine Staphylococcus screening,” said Dr. Sporer. “Additionally, the infecting organism among patients determined to have an SSI was identified and compared between cohorts.”

Examining the results
Researchers found that 4.3 percent of preoperatively screened patients tested positive for MRSA, while 18 percent of patients tested positive for MSSA.

The rate of SSI in the control group was 1.74 percent, while the rate of SSI in the screening group was 0.3 percent (p < 0.05), yielding an 82 percent decrease in the prevalence of SSI from 2008 to 2009. He also noted that MSSA or MRSA was identified in 56 percent of the SSIs prior to nasal screening, while MSSA or MRSA was identified in 43 percent of the SSIs after routine screening (p > 0.05).

“Weaknesses of the current study design include the inability to identify all patients with SSIs,” said Dr. Sporer. “Patients with an SSI may have been treated at another institution that did not report its results, or treatment may have occurred as an outpatient.”

He also pointed out that he and his fellow investigators were unable to specifically identify which clinical factor resulted in the decreased infection rate.

“Patients who screened positive for MRSA underwent decolonization with mupirocin and chlorhexidine baths and received vancomycin for preoperative antibiotics,” he said. “Although there was a dramatic reduction in the rate of infection among both MRSA carriers and noncarriers, it is possible that the preoperative antibiotics alone were responsible for the decreased incidence.”

Despite these limitations, noted Dr. Sporer, the study results have prompted his institution “to continue to use a standardized universal screening and selective decolonization process for all patients undergoing elective TJA.”

Dr. Sporer’s coauthors for “Preoperative Staphylococcus aureus Screening to Reduce Surgical-Site Infection” include Karen Hjerstedt, RN; Jill Coleman, RN; Linda Abella, ONC; Rose Kelem, RN; Judi Werkema, RN; Anne Molloy, RN; Bushra Khan, RN; and Jonathan Pinsky, MD.

Disclosure information: Dr. Sporer—Smith & Nephew, Zimmer, Coolsystems, SLACK Inc.; Ms. Coleman—Sanofi Aventis; Ms. Abella and Ms. Molloy—no conflicts reported. Ms. Hjerstedt, Ms. Kelem, Ms. Werkema, Bushra Khan, and Dr. Pinsky—no information available.

Additional Resources:
Molecular Markers for Diagnosis of Periprosthetic Joint Infection

Bottom Line

• This is a single-institution, prospective study on the effectiveness of conducting preoperative screening for MRSA and MSSA colonization among elective surgery patients to reduce SSI.
• Researchers found that 4.3 percent of preoperatively screened patients tested positive for MRSA, while 18 percent of patients tested positive for MSSA.
• After institution of the preoperative screening and treatment processes, the rate of SSI dropped from 1.74 percent to 0.3 percent (p < 0.05)—an 82 percent decrease in prevalence.

Jennie McKee is a staff writer for AAOS Now. She can be reached at mckee@aaos.org