Staph aureus Scheme Cuts Surgical Infection

Daniel M. Keller, PhD

October 18, 2014

PHILADELPHIA — Practices to eliminate Staphylococcus aureus are associated with significantly lower rates of surgical-site infection, according to a new study.

The approach consists of screening the nostrils of patients for S aureus, decolonizing with mupirocin and chlorhexidine baths when necessary, and administering perioperative prophylactic vancomycin and cefazolin to patients with methicillin-resistant S aureus (MRSA).

"We feel that if people actually did implement this bundle, it could substantially reduce patient morbidity and the cost of care," said Loreen Herwaldt, MD, from the University of Iowa Health Care in Iowa City. "Furthermore, it is very important to note that we really saw the effect only with the full bundle."

Dr Herwaldt presented the results of the study here at IDWeek 2014.

The pragmatic quasiexperimental effectiveness study was conducted in 20 hospitals caring for cardiac patients and people undergoing hip or knee arthroplasty. During the 5-year study, a 39-month preintervention period was followed by a 21-month intervention period.

Cardiac operations were performed using median sternotomies. Patients undergoing cardiac transplantation, transapical valve implantation, or arthroplasty revision were excluded from the study, as were patients with infections.

Patients were followed for 90 days after surgery to monitor for surgical-site infection.

Patients were screened for MRSA and methicillin-sensitive S aureus (MSSA) in the month before surgery, and were treated accordingly.

If the screens were positive for any S aureus, patients were asked to apply intranasal mupirocin and to bathe with chlorhexidine for 5 days before surgery.

We feel that if people actually did implement this bundle, it could substantially reduce patient morbidity and the cost of care. Dr Loreen Herwaldt

Patients who were positive for MSSA received cefazolin, and those who were positive for MRSA received cefazolin and vancomycin. Patients whose screening results were not known, as in the case of emergency surgery, were treated as if they were MRSA-positive. Patients who were negative for S aureus bathed with chlorhexidine the night before and the morning of surgery, and received cefazolin.

Of the 42,534 operations in 38,049 patients, 28,218 were performed before the intervention was implemented, and 14,316 were performed during the intervention period. The characteristics of patients treated in the preintervention and intervention periods were similar.

Three months into the intervention, there was full adherence to the bundle by healthcare workers and patients in 48% of cases, partial adherence in 20%, and a lack of adherence in 32%.

The rate of complex S aureus infection at surgical sites for all operations was higher during the preintervention period than during the intervention period (0.36% vs and 0.20%).

In the preintervention period, 2 of 39 months were free of complex S aureus infection; in the intervention period, 8 of 22 months were free of infection (5.1% vs 36%; P = .006), Dr Herwaldt reported.

For cardiac surgery alone, there was no difference in the rate of complex S aureus surgical-site infection between the two periods.

Table. Complex S aureus Surgical-Site Infections

Procedure Preintervention, n Intervention, n Rate Ratio (95% Confidence Interval) P- value
Hip or knee arthroplasty 20,642 11,059 0.48 (0.29 - 0.80) .005
Cardiac surgery 7576 3257 0.86 (0.47 - 1.57) .63
All 28,218 14,316 0.58 (0.37 - 0.92) .02


The best outcomes were achieved when healthcare workers and patients were fully adherent to all the elements of the bundle, with a rate ratio of 0.26 (P = .002). If the surgeon carried out at least some elements, the rate ratio was 0.54 (P = .01). For scheduled operations, the rate ratio was 0.55 (P = .009). There was no change in the rate of surgical-site infection caused by Gram-negative pathogens (rate ratio, 0.86; P = .67).

"Implementation of this bundle was associated with significantly lower rates of complex Staph aureus surgical-site infections in the total cohort and in the hip and knee arthroplasty group," said Dr Herwaldt. "It was not associated with an increase in Gram-negative infections."

Session moderator Michael Kurilla, MD, from the US National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, said, "The researchers clearly demonstrated that a combination of multiple factors can be brought to bear to significantly reduce the incidence of these complications."

With complicated algorithms for different kinds of patients, such as those with different S aureus status, checklists can help make sure that every element of a bundle is adhered to, "to ensure that the best possible care is being delivered in a systematic and reproducible manner," he told Medscape Medical News.

This study is "really important," said Deborah Yokoe, MD, from Brigham and Women's Hospital in Boston. She said that, to her knowledge, this is the first multicenter study to look specifically at "screening patients for Staph aureus carriage and then decolonizing Staph aureus carriers to prevent surgical-site infection." Previously, only single-center studies and meta- analyses have been done.

Cardiac operations and joint replacement procedures are associated with very serious surgical-site infections, she noted, so "these results have very important implications." Individual elements of the bundle may work synergistically, and therefore have the greatest impact when applied together, she explained. These study results are "compelling evidence" to get hospitals to begin to think about implementing the strategies.

Dr Herwaldt, Dr Kurilla, and Dr Yokoe have disclosed no relevant financial relationships.

IDWeek 2014: Abstract LB-9. Presented October 11, 2014.


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