Preoperative MRSA Screening May Reduce Surgical Site Infections
Lead author Scott J. Luhmann, MD comments
Preoperative nasal swab MRSA screening may be helpful in reducing surgical site infections (SSIs) when used within a multimodal approach. This is according to a recent study published in Spine Deformity.
Scott J. Luhmann, MD discussed the incorporation of Staphylococcus aureus (S. aureus) testing within a multimodal approach that was included in two pediatric tertiary-care children’s hospitals in St. Louis. Dr. Luhmann is Associate Professor, Pediatric Orthopaedic Surgery and Head of Surgery, Pediatric Orthopedics at Shriners Hospital for Children. “The use of nasal swabbing for MRSA was instituted to attempt to identify MRSA colonized individuals, so we could administer the most appropriate prophylactic antibiotics.”
Although consensus has not been reached in best practice guidelines on the use of preoperative MRSA screening through nasal swabbing, this may primarily be due to a lack of evidence. The authors' novel paper will help contribute to the evidence base of preoperative MRSA screening that is vital to reduce the devastating impact of SSIs.
S. aureus testing was performed on 310 pediatric spine surgery patients (339 screenings) from 2009-2014. Sensitivity testing was performed, which guided preoperative antibiotic determination. Before surgery, those testing MRSA positive were treated with intranasal mupirocin. Furthermore, “preoperative chlorhexidine skin cleansing was used to decrease skin flora concentrations, especially of S. aureus,” Dr. Luhmann said.
Additionally, intraoperative SSI prevention strategies were incorporated, including wound irrigation, decreasing operating room traffic, iodine plastic skin barriers, and vancomycin powder (500-2,000 mg) within the wound.
There was a 22.1% positive screening rate, with 20 (5.9%) MRSA positive and 55 (16.2%) methicillin-sensitive S. aureus (MSSA) positive. Newly identified MRSA was found in 13/20 (65%).
Antibiotic sensitivities were available for 17/20 of MRSA-positive patients. The majority (75%) of cefazolin-resistant patients were also resistant to clindamycin. In the 55 MSSA positive patients, 5 had resistance or intermediate sensitivity to clindamycin and 1 to cefazolin.
Preoperative testing resulted in an ability to alter the antibiotic regimen to cover resistances in 22 patients or 6.5% of the total cohort. Also, according to the authors, “up to 4.7% (n=17; 16 MRSA positive, 1 MSSA positive), may not have received adequate antibiotic coverage during surgery.”
Over the 5-year study period, the SSI rate was 3.6% (n=11; deep wound infection). Of those patients, SSIs were not MRSA or MSSA positive. The overall MRSA positive SSI rate was 0.97%.
The results of the incorporation of this multimodal approach have been remarkable. The overall spine surgery SSI rate in 2008 was 3.1% with a spine MRSA infection rate of 1.6%. In 2014, the overall spine SSI rate dropped to 1.9%, and the spine MRSA infection rate dropped to 0%.
The cost effectiveness of S. aureus screening would seemingly be substantial. Although “the cost savings and minimization of suffering are difficult to calculate or estimate, the cost of a single SSI in pediatric spine deformity may average over $400,000," said Dr. Luhmann. At his institution, the MRSA testing costs $109 and treatment (Bactroban) is $19.
Another benefit to this multimodal program is the reduction in transmission of MRSA to other patients and healthcare workers, by incorporating the use of isolation rooms and protection from additional gloves, gowns, and masks.
Questions and Future Directions
“There seems to be a disconnect for surgeons in thinking nares colonization may impact wound infections,” Dr. Luhmann commented. This may explain at least in part why S. aureus nares screening has not been fully adopted by best practice guidelines.
However, there is the question of the three patients who screened negative and subsequently developed an SSI with positive MRSA cultures. Although not a high percentage of patients, further research is needed to understand why this occurred.
- How often is colonization with MRSA in the nares associated with colonization of MRSA on the skin?
When asked about how this problem of the three negative screenings that led to SSIs could be prevented, Dr. Luhmann responded, “possibly to swab the skin on their backs [instead of the nares].” They have a study in progress to investigate this type of problem. He also mentioned the application of intrawound vancomycin powder as being important.
In conclusion, “the treating surgeon needs to evaluate their practice profile, SSI causation, and their SSI prevention protocol to determine if there is a utility to SA [S. aureus] screenings in some, or all, of their patients.”