Long-term Mortality After Rapid Screening and Decolonization of Staphylococcus Aureus Carriers: Observational Follow-up Study of a Randomized, Placebo-controlled Trial

European Society of Clinical Microbiology and Infectious Diseases/European Committee on infection control clinical guidelines on pre-operative decolonization and targeted prophylaxis in patients colonized by multidrug-resistant Gram-positive bacteria before surgery

SCOPE

The aim of these guidelines is to provide recommendations for decolonization and perioperative antibiotic prophylaxis (PAP) in multidrug-resistant Gram-positive bacteria (MDR-GPB) adult carriers before inpatient surgery.

METHODS

These European Society of Clinical Microbiology and Infectious Diseases/European Committee on Infection Control guidelines were developed following a systematic review of published studies targeting methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci, methicillin-resistant coagulase-negative Staphylococci, and pan-drug-resistant-GPB. Critical outcomes were the occurrence of surgical site infections (SSIs) caused by the colonizing MDR-GPB and SSIs-attributable mortality. Important outcomes included the occurrence of SSIs caused by any pathogen, hospital-acquired infections, all-cause mortality, and adverse events associated with the interventions, including resistance development to the agents used and the incidence of Clostridioides difficile infections. The last search of all databases was performed on 1 November 2023. The level of evidence and the strength of each recommendation were defined according to the Grading of Recommendations Assessment, Development, and Evaluation approach. Consensus of a multidisciplinary expert panel was reached for the final list of recommendations. Antimicrobial stewardship considerations were included.

RECOMMENDATIONS

The guideline panel reviewed the impact of decolonization, targeted PAP, and combined interventions (e.g. decolonization and targeted PAP) on the risk of SSIs and other outcomes in MDR-GPB carriers, according to the type of bacteria and type of surgery. We recommend screening for S. aureus before high-risk operations, such as cardiothoracic and orthopaedic surgery. Decolonization with intranasal mupirocin with or without a chlorhexidine bath is recommended in patients colonized with S. aureus before cardiothoracic and orthopaedic surgery and suggested in other surgeries. The addition of vancomycin to standard prophylaxis is suggested for MRSA carriers in cardiothoracic surgery, orthopaedic surgery, and neurosurgery. Combined interventions (e.g. decolonization and targeted prophylaxis) are suggested for MRSA carriers undergoing cardiothoracic and orthopaedic surgery. No recommendation could be made regarding screening, decolonization and targeted prophylaxis for vancomycin-resistant enterococci because of the lack of data. No evidence was retrieved for methicillin-resistant coagulase-negative Staphylococci and pan-drug-resistant-GPB. Careful consideration of the laboratory workload and involvement of antimicrobial stewardship and infection control teams are warranted before implementing screening procedures or performing changes in PAP policy. Future research should focus on novel decolonizing techniques, on the monitoring of resistance to decolonizing agents and PAP regimens, and on standardized combined interventions in high-quality studies.

Eradication of community-onset Methicillin-resistant Staphylococcus aureus carriage: a narrative review

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) colonization increases infection risk in both patients and healthy individuals. Decolonization therapy has been proven to reduce S. aureus infections, but data on the effectiveness of individual decolonization strategies in community-onset MRSA carriage are scarce.

OBJECTIVES

The aim of this narrative review was to summarize the evidence on strategies for the elimination of MRSA colonization in community-onset MRSA carriers.

SOURCES

PubMed database was searched for studies on MRSA eradication, from inception to July 2023.

CONTENT

Topical therapy is proven to be effective in nasal-only carriage and in temporary load reduction. Mupirocin nasal ointment in combination with chlorhexidine body wash is highly effective in nasal-only MRSA carriers in the community as well. In patients with extra-nasal colonization, addition of orally administered antibiotics likely increases success rates compared with topical therapy alone. Studies on systemic treatment of extra-nasal MRSA decolonization are subject to a high heterogeneity of antimicrobial agents, treatment duration, and control groups. The majority of evidence supports the use of a combination of topical therapy with rifampin and another antimicrobial agent. Decolonization treatment with probiotics is a promising novel non-antibiotic strategy. However, achieving long-term decolonization is more likely in countries with low MRSA prevalence, given the risk of recolonization in a context of high MRSA prevalence.

IMPLICATIONS

The decision to pursue community-onset MRSA eradication treatment in the individual patient should be based on the combination of the treatment objective (short-term bacterial load reduction in health care settings vs. long-term eradication in community settings), and the likelihood of successful decolonization. The latter is influenced by both individual risk factors for treatment failure, and the risk of recolonization. The addition of a combination of systemic antibiotics is rational for extra-nasal long-term decolonization. To determine the most effective systemic antimicrobial agents in MRSA decolonization, more research is needed.

Strategies to prevent surgical site infections in acute-care hospitals: 2022 Update

The intent of this document is to highlight practical recommendations in a concise format designed to assist acute-care hospitals in implementing and prioritizing their surgical-site infection (SSI) prevention efforts. This document updates the Strategies to Prevent Surgical Site Infections in Acute Care Hospitals published in 2014. This expert guidance document is sponsored by the Society for Healthcare Epidemiology of America (SHEA). It is the product of a collaborative effort led by SHEA, the Infectious Diseases Society of America (IDSA), the Association for Professionals in Infection Control and Epidemiology (APIC), the American Hospital Association (AHA), and The Joint Commission, with major contributions from representatives of a number of organizations and societies with content expertise.

Prevention, Diagnosis and Management of Post-Surgical Mediastinitis in Adults Consensus Guidelines of the Spanish Society of Cardiovascular Infections (SEICAV), the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) and the Biomedical Research Centre Network for Respiratory Diseases (CIBERES)

This is a consensus document of the Spanish Society of Cardiovascular Infections (SEICAV), the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) and the Biomedical Research Centre Network for Respiratory Diseases (CIBERES). These three entities have brought together a multidisciplinary group of experts that includes anaesthesiologists, cardiac and cardiothoracic surgeons, clinical microbiologists, infectious diseases and intensive care specialists, internal medicine doctors and radiologists. Despite the clinical and economic consequences of sternal wound infections, to date, there are no specific guidelines for the prevention, diagnosis and management of mediastinitis based on a multidisciplinary consensus. The purpose of the present document is to provide evidence-based guidance on the most effective diagnosis and management of patients who have experienced or are at risk of developing a post-surgical mediastinitis infection in order to optimise patient outcomes and the process of care. The intended users of the document are health care providers who help patients make decisions regarding their treatment, aiming to optimise the benefits and minimise any harm as well as the workload.

Prevalence of Staphylococcus aureus nasal carriage and surgical site infection rate among patients undergoing elective cardiac surgery

BACKGROUND

Nasal carriers of Staphylococcus aureus are at increased risk of postoperative surgical site infection. Nasal decolonization with mupirocin is recommended in patients undergoing cardiac surgery to reduce surgical site infection. These data are still lacking in Thailand. Therefore, the aim of this study was to determine the prevalence of S. aureus nasal carriage in Thai patients undergoing elective cardiac surgery. The association of surgical site infection and S. aureus nasal carriage was also examined.

METHODS

This was a prospective cohort study of 352 patients who planned to undergo elective cardiac surgery. Nasal swab culture was performed in all patients preoperatively.

RESULTS

Of 352 patients, 46 (13.1%) had a positive nasal swab culture for methicillin-sensitive S. aureus (MSSA) and one patient (0.3%) harbored a methicillin-resistant S. aureus (MRSA) strain. The incidence of superficial and deep surgical site infection was 1.3% and 0.3%, respectively. After multivariate analysis, S. aureus nasal carriage was independently associated with superficial surgical site infection (odds ratio 13.04, 95% confidence interval 1.28-133.27; P=0.03).

CONCLUSIONS

The prevalence of MSSA and MRSA nasal carriage in Thai patients undergoing elective cardiac surgery was low. The incidence of surgical site infection was also very low in the population studied. Nevertheless, it was found that S. aureus nasal carriage increased the risk of superficial surgical site infection.

Screening and topical decolonization of preoperative nasal Staphylococcus aureus carriers to reduce the incidence of postoperative infections after lung cancer surgery: a propensity matched study

OBJECTIVES

Health care-associated infections (HAIs) are serious issues following lung cancer surgery, leading to an increased risk of morbidity and hospital cost burden. The aim of this study was to evaluate the impact on postoperative outcomes of a preoperative screening and decolonization strategy of nasal carriers for Staphylococcus aureus prior to lung cancer surgery.

METHODS

We performed a retrospective study comparing 2 cohorts of patients undergoing major lung resection: a control group of patients from the placebo arm of the randomized Clinical Study to Evaluate the Efficacy of Chlorhexidine Mouthwashes operated on between July 2012 and April 2015 without any nasopharyngeal screening (N = 224); an experimental group, with preoperative screening for S. aureus of nasal carriers and selective 5-day decolonization in positive carriers using mupirocin ointment between January 2017 and December 2017 (N = 310). The 2 groups were matched according to a propensity score analysis with 1:1 matching. The primary outcome was the rate of postoperative HAIs, and the secondary outcome was the need for postoperative mechanical ventilation after surgery.

RESULTS

After matching, 2 similar groups of 108 patients each were obtained. In the experimental group, 26 patients had positive results for nasal carriage, and a significant decrease was observed in the rate of overall postoperative HAIs [control n = 19, 17.6%; experimental group n = 9, 8.3%; P = 0.043; relative risk 0.47 (0.22-1)] and in the rate of postoperative mechanical ventilation [control n = 12, 11.1%; experimental group n = 4, 3.7%; P = 0.038; relative risk 0.33 (0.11-1)]. After logistic regression and multivariable analysis, screening of S. aureus nasal carriers reduced the rate of HAIs [odds ratio (OR) 0.29, 95% confidence interval (CI) 0.11-0.76; P = 0.01] and reduced the risk of the need for postoperative mechanical ventilation (OR 0.19, 95% CI 0.05-0.74; P = 0.02). There was no significant statistical difference between the 2 groups regarding the rate of postoperative S. aureus-associated infection (control group n = 6, 5.6%; experimental group n = 2, 1.9%; P = 0.28).

CONCLUSIONS

Identification of nasal carriers of S. aureus and selective decontamination using mupirocin appeared to have a beneficial effect on postoperative infectious events after lung resection surgery.

Nasal decolonization of Staphylococcus aureus and the risk of surgical site infection after surgery: a meta-analysis

Aim

To assess the effects of nasal decontamination on preventing surgical site infections (SSIs) in people who are Staphylococcus aureus carriers undergoing different types of surgeries and diverse measures of decolonization.

Methods

Relevant randomized controlled trials (RCTs) were identified through systematic searches of the PubMed, Embase, Web of science, and the Cochrane Library databases. The risk ratios (RRs) and 95% confidence intervals (CIs) were calculated and the effects model was chosen according to the heterogeneity. Subgroup analyses were performed according to different types of surgeries and measures of decolonization that Staphylococcus aureus carriers were applied.

Results

Twenty RCTs published between 1996 and 2019 involving 10,526 patients were included. Pooled results showed that the overall SSIs and pulmonary surgery SSIs presented with a statistical difference in measures of nasal decontamination (RR = 0.59 and 0.47, respectively, both p < 0.01). However, the associations between nasal decolonization and increased risks of SSIs in orthopedics surgery or cardiovascular surgery remained insignificant in studies. As for the diverse measures of nasal decontamination, 50% used mupirocin, 15% used chlorhexidine, 30% used different types of antimicrobial drugs, and 5% use others. The SSIs rate were decreased after chlorhexidine (RR = 0.474, 95% CI 0.259–0.864), while no significant difference was shown in the use of mupirocin (RR = 0.871, 95% CI 0.544–1.394).

Conclusion

It seems that nasal decolonization of Staphylococcus aureus may be associated with a reduction of SSIs in these patients, especially in patients who have been administered by pulmonary surgeries or treated with chlorhexidine.

Do Surgical Site Infections in Open Aortoiliac Surgery Differ Between Occlusive and Aneurysmal Arterial Disease?

Background:

Surgical site infections (SSI) are frequently seen after aortoiliac vascular surgery (2%-14%). Deep SSIs are associated with graft infection, sepsis, and mortality. This study evaluates the difference in incidence and nature of SSI following open aortoiliac surgery for aneurysmal disease compared to occlusive arterial disease.

Methods:

A retrospective cohort study was conducted, including all consecutive patients who underwent open aortoiliac vascular surgery between January 2005 and December 2016 in the Amphia Hospital, Breda, the Netherlands. Patients were grouped by disease type, either aneurysmal or occlusive arterial disease. Data were gathered, including patient characteristics, potential risk factors, and development of SSI. Surgical site infections were defined in accordance with the criteria of the Centers for Disease Control.

Results:

Between January 2005 and December 2016, a total of 756 patients underwent open aortoiliac surgery of which 517 had aortoiliac aneurysms and 225 had aortoiliac occlusive disease. The group with occlusive disease was younger, predominantly male, and had more smokers. After exclusion of 228 patients undergoing acute surgery, the SSI rate after elective surgery was 6.2%, with 10 of 301 SSIs in the aneurysmal group (3.0%) and 22 of 213 SSIs in the group with occlusive disease (10.3%, P < .001). Also, infection-related readmission and reintervention were higher after occlusive surgery, 6.6% versus 0.9% ( P < .001) and 4.2% versus 0.9% ( P = .003), respectively. Staphylococcus aureus was found as the most common pathogen, causing 64% of SSI in occlusive disease versus 10% in aneurysmal disease ( P = .005). Logistic regression showed occlusive arterial disease and chronic renal disease were associated with SSI.

Conclusion:

Our study presents evidence for a higher rate of SSI in patients with aortoiliac occlusive disease compared to aortoiliac aneurysmal disease, in part due to inherent use of inguinal incision in patients with occlusive disease. All precautions to prevent SSI should be taken in patients undergoing vascular surgery for arterial occlusive disease.

Diagnostic Accuracy of Presurgical Staphylococcus aureus PCR Assay Compared with Culture and Post-PCR Implementation Surgical Site Infection Rates

Nasal colonization with Staphylococcus aureus is a well-referenced risk factor for postoperative surgical site infections (SSIs). Our health care system that performs >40,000 surgeries per year assessed both the diagnostic accuracy of the BD MAX StaphSR assay (MAX StaphSR), a PCR-based test that detects and differentiates S. aureus and methicillin-resistant S. aureus (MRSA), compared with our standard of care culture and the subsequent clinical impact on SSIs 1 year after implementation. In addition, residual specimens were tested by broth-enriched culture. Performance parameters for all methods were determined using latent class analysis. Direct culture was the least sensitive for S. aureus (85.1%) and MRSA (76.7%), whereas the MAX StaphSR assay and broth-enriched culture had similar sensitivities (96.7%) for MRSA. Prospective assessment using MAX StaphSR during a 1-year, postimplementation period revealed a lower rate of SSIs per 100 targeted surgeries (0.3) compared with MRSA-only screening (1.10) and no screening (2.28) (P < 0.05 for StaphSR versus MRSA-only screening and StaphSR versus no testing). MRSA and methicillin-sensitive S. aureus SSIs occurred equally (n = 14 each). The MAX StaphSR assay provided accurate detection of both S. aureus and MRSA nasal colonization in presurgical patients, allowing infection prevention measures, including presurgical prophylaxis, to be implemented in a timely and consistent manner to avoid SSIs.

Antimicrobial approaches in the prevention of Staphylococcus aureus infections: a review

Background

The prophylactic application of antimicrobials that are active against Staphylococcus aureus can prevent infections. However, implementation in clinical practice is limited. We have reviewed antimicrobial approaches for the prevention of S. aureus infections.

Methods

We searched the Cochrane Central Register of Controlled Trials, PubMed/MEDLINE and EMBASE databases and trial registries using synonyms for S. aureus, infections and prevention as search terms. We included randomized controlled trials and systematic reviews only.

Results

Most studies were conducted with mupirocin. Mupirocin is effective in preventing S. aureus infections in patients receiving dialysis treatment and in surgical patients, particularly if the patients are carriers of S. aureus. The combination of mupirocin and chlorhexidine, but not chlorhexidine alone, is also effective against S. aureus infections. So far, vaccines have not proven successful in protecting against S. aureus infections. Regarding prophylactic povidone-iodine and systemic antibiotics, there is limited evidence supporting their effectiveness against S. aureus infections. Antimicrobial honey has not been proven to be more effective or non-inferior to mupirocin in protecting against S. aureus infections.

Conclusions

The current evidence supports the use of mupirocin as prophylaxis for preventing infections with S. aureus, particularly in carriers and in the surgical setting or in patients receiving dialysis treatment. Other antimicrobial agents have not been sufficiently proven to be effective so far, or have been proven ineffective. New trials with vaccines and anti-staphylococcal peptides are currently underway and may lead to new preventive strategies in the future.

Vaccination with the Staphylococcus aureus secreted proteins EapH1 and EapH2 impacts both S. aureus carriage and invasive disease

INTRODUCTION

There is a need for an efficacious vaccine reducing infections due to Staphylococcus aureus, a common cause of community and hospital infection. Infecting organisms originate from S. aureus populations colonising the nares and bowel. Antimicrobials are widely used to transiently reduce S. aureus colonisation prior to surgery, a practice which is selecting for resistant S. aureus isolates. S. aureus secretes multiple proteins, including the protease inhibitors extracellular adhesion protein homologue 1 and 2 (EapH1 and EapH2).

METHODS

Mice were vaccinated intramuscularly or intranasally with Adenovirus serotype 5 and Modified Vaccinia Ankara viral vectors expressing EapH1 and EapH2 proteins, or with control viruses. Using murine S. aureus colonisation models, we monitored S. aureus colonisation by sequential stool sampling. Monitoring of S. aureus invasive disease after intravenous challenge was performed using bacterial load and abscess numbers in the kidney.

RESULTS

Intramuscular vaccination with Adenovirus serotype 5 and Modified Vaccinia Ankara viral vectors expressing EapH1 and EapH2 proteins significantly reduces bacterial recovery in the murine renal abscess model of infection, but the magnitude of the effect is small. A single intranasal vaccination with an adenoviral vaccine expressing these proteins reduced S. aureus gastrointestinal (GI) tract colonisation.

CONCLUSION

Vaccination against EapH1 / EapH2 proteins may offer an antibiotic independent way to reduce S. aureus colonisation, as well as contributing to protection against S. aureus invasive disease.

Peri-Operative Nasal Eradication Therapy Prevents Staphylococcus aureus Surgical Site Infections in Aortoiliac Surgery

BACKGROUND

Surgical site infections (SSIs) cause considerable morbidity and deaths among patients undergoing vascular surgery. Pre-operative screening and subsequent treatment of nasal Staphylococcus aureus carriers with mupirocin and chlorhexidine reduces the risk of SSIs in cardiothoracic and orthopedic surgery. The aim of this study was to investigate the effect of this screen-and-treat strategy on the development of SSI in patients undergoing aortoiliac surgery.

METHODS

A prospective study was performed that enrolled an intervention cohort comprising all patients undergoing aortoiliac surgery from February 2013 to December 2016. Before surgery, patients were screened for S. aureus nasal carriage and, if positive, were treated with mupirocin nasal ointment and chlorhexidine body washes. The presence of SSI was recorded on the basis of the criteria of the U.S. Centers for Disease Control and Prevention. A historic control group was used, consisting of aortoiliac surgery patients in 2010 who tested positive for S. aureus but received no treatment.

RESULTS

A total of 374 patients in the study cohort were screened of whom 75 (20.1%) tested positive for S. aureus. Of these patients, 68 were given eradication therapy. In the 2010 cohort, 22 patients (15.7%) were positive. The incidence of S. aureus infection was 0 of 75 in the treatment group versus 3 of 22 (13.6%) in the control group (p = 0.021). Both the 30-day mortality rate (1.3% vs. 13.6%; p = 0.035) and the rate of re-interventions (12.0% vs. 31.8%) were significantly lower in the treated group.

CONCLUSION

We conclude that S. aureus nasal screening and eradication with mupirocin and chlorhexidine reduces S. aureus SSI and its complications after aortoiliac surgery.

Hand Hygiene Practices and Microbial Investigation of Hand Contact Swab among Physiotherapists in an Ebola Endemic Region: Implications for Public Health

BACKGROUND

Hand hygiene practices (HHP), as a critical component of infection prevention/control, were investigated among physiotherapists in an Ebola endemic region.

METHOD

A standardized instrument was administered to 44 randomly selected physiotherapists (23 males and 21 females), from three tertiary hospitals in Enugu, Nigeria. Fifteen participants (aged 22-59 years) participated in focus group discussions (FGDs) and comprised 19 participants in a subsequent laboratory study. After treatment, the palms/fingers of physiotherapists were swabbed and cultured, then incubated aerobically overnight at 37°C, and examined for microbial growths. An antibiogram of the bacterial isolates was obtained.

RESULTS

The majority (34/77.3%) of physiotherapists were aware of the HHP protocol, yet only 15/44.1% rated self-compliance at 71-100%. FGDs identified forgetfulness/inadequate HHP materials/infrastructure as the major barriers to HHP. Staphylococcus aureus were the most prevalent organisms, prior to (8/53.33%) and after (4/26.67%) HPP, while Pseudomonas spp. were acquired thereafter. E. coli were the most antibiotic resistant microbes but were completely removed after HHP. Ciprofloxacin and streptomycin were the most effective antibiotics.

CONCLUSION

Poor implementation of HPP was observed due to inadequate materials/infrastructure/poor behavioral orientation. Possibly, some HPP materials were contaminated; hence, new microbes were acquired. Since HPP removed the most antibiotic resistant microbes, it might be more effective in infection control than antibiotic medication.

Why does total elbow arthroplasty fail today? A systematic review of recent literature

BACKGROUND

Total elbow arthroplasty is a relatively uncommon type of arthroplasty, which has undergone several design changes in the past four decades. However, research on improvement requires knowledge of failure mechanisms that can be addressed. Therefore, we conducted a systematic review on modes of failure of total elbow arthroplasty.

METHODS

We conducted searches on PubMed/Medline, Embase and Cochrane databases to identify studies describing modes of failure of primary total elbow arthroplasties. The results were coupled per type of total elbow arthroplasty and individual arthroplasty models.

RESULTS

A total of 70 articles were included in this systematic review. 9308 individual total elbow arthroplasties were identified with 1253 revisions (13.5%). Aseptic loosening was the most prevalent reason for revision (38%), followed by deep infection (19%) and periprosthetic fractures (12%).

CONCLUSION

Revision rates have been found similar to a systematic review published in 2003. The revision percentage of total elbow arthroplasty for rheumatoid arthritis is significantly higher than for trauma and post-traumatic osteoarthritis. Aseptic loosening was seen less in linked implants. Infections and periprosthetic fractures did not differ between linkage design groups. Aseptic loosening remains the most frequent cause for revision of primary total elbow arthroplasty. Therefore, more research on the occurrence, progression and risk factors of aseptic loosening should be performed and lead to higher implant survival.

Evaluation of Staphylococcus aureus Eradication Therapy in Vascular Surgery

INTRODUCTION

Surgical site infections (SSI) are a serious complication in vascular surgery which may lead to severe morbidity and mortality. Staphylococcus aureus nasal carriage is associated with increased risk for development of SSIs in central vascular surgery. The risk for SSI can be reduced by perioperative eradication of S. aureus carriage in cardiothoracic and orthopedic surgery. This study analyzes the relation between S. aureus eradication therapy and SSI in a vascular surgery population.

METHODS

A prospective cohort study was performed, including all patients undergoing vascular surgery between February 2013 and April 2015. Patients were screened for S. aureus nasal carriage and, when tested positive, were subsequently treated with eradication therapy. The presence of SSI was recorded based on criteria of the CDC. The control group consisted of a cohort of vascular surgery patients in 2010, who were screened, but received no treatment.

RESULTS

A total of 444 patients were screened. 104 nasal swabs were positive for S. aureus, these patients were included in the intervention group. 204 patients were screened in the 2010 cohort. 51 tested positive and were included in the control group. The incidence of S. aureus infection was 5 out of 51 (9.8%) in the control group versus 3 out of 104 in the eradication group (2.2%; 95% confidence interval 0.02-1.39; P = 0.13). A subgroup analysis showed that the incidence of S. aureus infection was 3 out of 23 (13.0%) in the control group in central reconstructive surgery versus 0 out of 44 in the intervention group (P = 0.074). The reduction of infection pressure by S. aureus was stronger than the reduction of infection pressure by other pathogens (exact maximum likelihood estimation; OR = 0.0724; 95% CI: 0.001-0.98; p = 0.0475).

CONCLUSION

S. aureus eradication therapy reduces the infection pressure of S. aureus, resulting in a reduction of SSIs caused by S. aureus.