Surgical site infections in cardiac surgery: an 11-year perspective

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.

Role of targeted and universal mupirocin-based decolonization for preventing surgical-site infections in patients undergoing cardiothoracic surgery: A systematic review and meta-analysis

The purpose of the present study was to provide a systematic literature review and pool evidence on the efficacy of mupirocin-based decolonization protocol in reducing surgical-site infections (SSIs) in patients undergoing cardiothoracic (CT) surgery based on their Staphylococcus (S.) aureus carrier state. The PubMed, Embase, Ovid, BioMed Central, Cochrane Central Register of Controlled Trials and Google Scholar databases were searched for studies comparing mupirocin-based decolonization with controls for reducing SSIs in patients following CT surgery. Studies were grouped based on the targeted population of intervention, i.e. carriers or all patients. A total of 17 studies were included. Of these, 8 studies used targeted mupirocin-based decolonization, while universal decolonization was performed in 9 studies. The results were conflicting for studies performing targeted decolonization and it was not possible to perform a meta-analysis due to non-homogenous studies. Pooled analysis of 34,859 patients indicated that universal mupirocin-based decolonization significantly reduced the risk of all SSIs [risk ratio (RR): 0.54; 95% CI: 0.40,0.75; I²=73.35%]. The intervention significantly reduced the risk of superficial SSIs (RR: 0.37; 95% CI: 0.25,0.55; I²=0%) but not of deep SSIs (RR: 0.45; 95% CI: 0.19,1.09; I²=80.67%). The results indicated a significantly reduced risk of S. aureus SSIs (SA-SSIs) with mupirocin-based decolonization (RR: 0.44; 95% CI: 0.32,0.61; I²=0%) but not for methicillin-resistant S. aureus (MRSA-SSIs; RR: 0.25; 95% CI: 0.05,1.28; I²=79.07%). Evidence on the role of targeted mupirocin-based decolonization to reduce SSIs after CT surgery was non-coherent and inconclusive. Analysis of low-quality retrospective studies suggested that universal mupirocin-based decolonization may reduce all SSIs, superficial SSIs and SA-SSIs, but not deep SSIs or MRSA-SSIs in patients after CT surgery.

Reduction of Postoperative Infections Through Routine Preoperative Universal Decolonization of Advanced Heart Failure Patients With Chlorhexidine and Mupirocin Before Left Ventricular Assist Device Implantation: A Single-Center Observational Study

BACKGROUND

Left ventricular assist devices (LVADs) are increasingly being used in patients with advanced heart failure as bridge to transplant, bridge to decision, or destination therapy. Infections are a major complication associated with LVADs. Staphylococcus aureus is one of the common causative organisms associated with LVAD infections. Methicillin resistant staphylococcus aureus (MRSA)-colonized patients are at an increased risk for developing MRSA-associated infections. Various studies have demonstrated decolonization of skin with topical chlorhexidine and nares with 2% intranasal mupirocin ointment is effective in reducing MRSA-associated infections.

OBJECTIVE

The objective of this observational study was to examine the impact of a universal decolonization protocol using topical chlorhexidine and intranasal mupirocin ointment for 5 days before LVAD implantation on postoperative infections (30, 60, and 90 days) and 30-day infection-related rehospitalization.

METHODS

A preoperative universal decolonization with 4% chlorhexidine daily whole-body bath and 2% intranasal mupirocin ointment twice a day for 5 days was implemented for patients undergoing elective LVAD implantation. Using an observational study design, we included a convenience sample of 84 subjects who were established patients in an accredited advanced heart failure program. Thirty-seven patients served in the standard protocol group, and 47 in the universal decolonization protocol group participated in the observational study.

RESULTS

In the standard protocol group, there were 4 MRSA infections with none in the universal decolonization group (χ = 5.34, P = .03). In total, there were 8 surgical site infections in the standard protocol group and 1 in the universal decolonization group (χ = 5.95, P = .01).

CONCLUSION

A 5-day universal decolonization protocol before LVAD implantation was effective in reducing total infections as well as MRSA-specific infections.

Systematic review of a patient care bundle in reducing staphylococcal infections in cardiac and orthopaedic surgery

Surgical site infections (SSIs) are serious adverse events hindering surgical patients' recovery. In Australia and New Zealand, SSIs are a huge burden to patients and healthcare systems. A bundled approach, including pre-theatre nasal and/or skin decolonization has been used to reduce the risk of staphylococcal infection. The aim of this review is to assess the effectiveness of the bundle in preventing SSIs for cardiac and orthopaedic surgeries. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Published literature was searched in PubMed, Embase and Cochrane Library of Systematic reviews. Identified articles were selected and extracted based on a priori defined Population-Intervention-Comparator-Outcome and eligibility criteria. Data of randomized controlled trials (RCTs) and comparative observational studies were synthesized by meta-analyses. Quality appraisal tools were used to assess the evidence quality. The review included six RCTs and 19 observational studies. The bundled treatment regimens varied substantially across all studies. RCTs showed a trend of Staphylococcus aureus SSIs reduction due to the bundle (relative risk = 0.59, 95% confidence interval (CI) = 0.33, 1.06) with moderate heterogeneity. Observational studies showed statistically significant reduction in all-cause and S. aureus SSIs, with 51% (95% CI = 0.41, 0.59) and 47% (95% CI = 0.35, 0.65), respectively. No publication biases were detected. SSIs in major cardiac and orthopaedic surgeries can be effectively reduced by approximately 50% with a pre-theatre patient care bundle approach.

Influence of a 5-year serial infection control and antibiotic stewardship intervention on cardiac surgical site infections

BACKGROUND

Surgical site infections (SSIs) complicate surgery, resulting in higher morbidity and mortality. Infection control bundles and antibiotic stewardship can be effective at reducing SSIs. The influence of long-term serial interventions is unclear.

OBJECTIVE

The goal of this retrospective quasiexperimental study was to assess the influence of a 5-year serial infection control and antibiotic stewardship intervention on SSIs.

METHODS

The multidisciplinary program actively implemented pre-, intra-, and postoperative strategies over a 5-year period from 2009-2014 for all patients undergoing coronary artery bypass graft (CABG), valve replacement, or both at a tertiary care public institution. Outcomes are compared with a 2-year preinterventions period (2007-2009) and 1-year postinterventions period (2014-2015).

RESULTS

A total of 6,518 procedures were included. After interventions, the overall combined infection rate for CABG, CABG and valve, and valve procedures decreased by 66.3%, from 11.9%-4.0% (odds ratio, 0.34; 95% confidence interval, 0.23-0.49; P < .001). A significant decrease of >50% (P < .001) relative rate was observed in overall, sternum, leg, CABG, and combined CABG and valve infection rates when comparing pre- and postinterventions groups. The antibiotic stewardship intervention increased overall conformity to the internal surgical prophylaxis protocol by 46.8%, from 39.8%-86.6% (95% confidence interval, 41.0-52.4; P < .001).

CONCLUSION

Long-term, serial comprehensive infection control and antibiotic stewardship interventions decrease overall SSIs in patients undergoing CABG and valve replacement procedures.

Effect of Preoperative Antibiotic Prophylaxis on Surgical Site Infections Complicating Cardiac Surgery

Objective.

To evaluate the effect of an optimized policy for antibiotic prophylaxis on surgical site infection (SSI) rates in cardiac surgery.

Design.

Prospective cohort study.

Setting.

Tertiary medical center in Israel.

Methods.

SSIs were recorded during a 10-year study period and ascertained through routine surveillance using the National Healthcare Safety Network (NHSN) methodology. Multivariable analyses were conducted to determine which significant covariates, including the administration of preoperative prophylaxis, affected these outcomes.

Results.

A total of 2,637 of 3,170 evaluated patients were included, and the overall SSI rate was 8.4%. A greater than 50% reduction in SSI rates was observed in the last 4 years of the study. Overall and site-specific infection rates were similar for patients receiving cefazolin or vancomycin. SSIs developed in 206 (8.1%) of the 2,536 patients who received preoperative prophylaxis (within 2 hours of the first incision) compared with 14 (13.9%) of 101 patients who received antibiotic prophylaxis at a different time (P= .04; odds ratio [OR], 1.8; 95% confidence interval [CI], 1.0–3.3). After accounting for covariates, preoperative hospital stay (5 days or more), an NHSN risk category (2 or 3), age (60 years or more), surgeon's role, and the period of measurement were significantly associated with SSIs. Emergency surgery, age, surgeon's role, and nonpreoperative prophylaxis were found to be independent predictors of superficial SSI.

Conclusions.

We observed a progressive and significant decrease in SSI rates after the implementation of an infection control program that included an optimized policy of preoperative prophylaxis in cardiac surgery.

Epidemiological Surveillance of Surgical Site Infection and its Risk Factors in Cardiac Surgery: A Prospective Cohort Study

INTRODUCTION AND OBJECTIVES

Surgical site infection in cardiac surgery is uncommon. The aim of the present study was to examine the incidence of this infection, compare it with national and international data, and evaluate its risk factors.

METHODS

This prospective cohort study included patients who underwent valve surgery or coronary revascularization during a 6-year period. The incidence of surgical site infection was studied. Associations between risk factors and infection were evaluated using odds ratios (OR). The infection rate was compared with Spanish and American data using the standardized infection ratio.

RESULTS

A total of 1557 patients were included. The overall cumulative incidence of infection was 4% (95% confidence interval [95%CI], 3.6%-5.6%), 3.6% in valve surgery (95%CI, 2.5%-4.7%) and 4.3% in coronary revascularization (95%CI, 2.3%-6.3%). Risk factors for surgical site infection in valve surgery were diabetes mellitus (OR=2.8; P<.05) and obesity (OR=6.6; P<.05). Risk factors for surgical site infection in coronary revascularization were diabetes mellitus (OR=2.9; P<.05) and reoperation for bleeding (OR=8.8; P<.05).

CONCLUSIONS

Diabetes mellitus and obesity favor surgical site infection in valve surgery, whereas diabetes mellitus and reoperation for bleeding favor surgical site infection in coronary revascularization. Infection surveillance and control programs permit evaluation and comparison of infection rates in cardiac surgery.

Effect of perioperative mupirocin and antiseptic body wash on infection rate and causative pathogens in patients undergoing cardiac surgery

INTRODUCTION

Preoperative nasal mupirocin has been shown to reduce surgical site infections (SSIs) in patients undergoing cardiac surgery. We analyzed the effect of mupirocin plus antiseptic body wash on SSI rate and etiology.

METHODS

Prospective SSI surveillance was done for patients undergoing cardiac surgery before and after implementation of mupirocin nasal ointment and chlorhexidine/octenidine body wash.

RESULTS

Overall SSI rate was 8.6% (81 out of 945) for the control and 6.9% (58 out of 842) for the intervention cohort (P = .19). In multivariable analysis, the study protocol was associated with an odds ratio of 0.61 (95% confidence interval, 0.41-0.91; P = .015) with regard to any SSI. This effect was exclusively due to a reduction in superficial SSIs and was observed both in patients with preoperative and postoperative treatment initiation. Coagulase-negative staphylococci (CoNS), the most commonly isolated pathogen, were found in 37% and 48% (P = .19) of patients in the control and the intervention cohort, respectively. CoNS were methicillin resistant in 69% of cases.

CONCLUSIONS

Mupirocin and antiseptic body wash reduced the rate of superficial but not deep or organ/space SSIs. Postoperative patient treatment may be critical in reducing the risk for superficial SSI, presumably due to a reduction of bacterial skin load. A high proportion of SSI was due to methicillin-resistant CoNS and thus not covered by routine perioperative antimicrobial prophylaxis.

Continuous Intraoperative Cefazolin Infusion May Reduce Surgical Site Infections During Cardiac Surgical Procedures: A Propensity-Matched Analysis

OBJECTIVES

The authors sought to determine whether an institutional transition from intermittent to continuous dosing of intraoperative antibiotics in cardiac surgery affected surgical site infection (SSI) outcomes.

DESIGN

A retrospective chart review utilizing propensity matching.

SETTING

A single academic, tertiary care hospital.

PARTICIPANTS

One thousand one hundred seventy-nine patients undergoing coronary artery bypass grafting (CABG) and/or cardiac valvular surgery between April 2013 and November 2014 who received perioperative cefazolin.

INTERVENTIONS

By method of cefazolin administration, patients were divided into an "intermittent-dosing" (ID) group and a "continuous-infusion" (CI) group.

MEASUREMENTS AND MAIN RESULTS

Of the 1,179 patients who underwent cardiac surgery during the study period, 1:1 propensity score matching yielded 399 patients in each group. Rates of diabetes (33.6% ID v 33.8% CI, p = 0.94), coronary artery bypass (62.3% v 61.4%, p = 0.66), and bilateral internal mammary artery harvesting (6.0% v 8.3%, p = 0.22) were similar between groups. SSIs occurred in more ID patients than CI patients (2.3% v 0.5%, p = 0.03). This difference was driven by decreases in extremity and conduit harvest site SSIs (1.8% v 0.3%, p = 0.03), as there were no episodes of mediastinitis, and superficial sternal SSI rates did not differ (0.5% v 0.3%, p = 0.56). There also were significantly fewer episodes of pneumonia in the CI group (6.0% v 2.3%, p = 0.008). Intensive care unit and total lengths of stay did not differ. Thirty-day mortality was 2.8% in both groups (p = 1.00).

CONCLUSIONS

As compared to ID regimens, CI cefazolin infusion may reduce post-cardiac surgery infectious complications. Further study in larger patient populations is needed.

Care bundle to prevent methicillin-resistant Staphylococcus aureus sternal wound infection after off-pump coronary artery bypass

Methicillin-resistant Staphylococcus aureus (MRSA) sternal wound infection (SWI) after cardiac surgery is endemic in our hospital. An infection control care bundle with preoperative chlorhexidine showering and povidone iodine paint before bathing was introduced in 2006. From 2001 to 2012, 23 (2.3%) of 1,010 patients undergoing off-pump coronary artery bypass had SWIs. SWI significantly decreased after 2006 (1.4% vs 3.4%, respectively; P = .03). Care bundle was more protective against MRSA infection (2.3% vs 0.5%, respectively; P = .021). SWI remained a common complication after off-pump coronary artery bypass. MRSA infection was most common, and the mortality was high. Care bundle can effectively decrease the incidence of SWI, especially infection caused by MRSA.

Effectiveness of a bundled intervention of decolonization and prophylaxis to decrease Gram positive surgical site infections after cardiac or orthopedic surgery: systematic review and meta-analysis

OBJECTIVE

To evaluate studies assessing the effectiveness of a bundle of nasal decolonization and glycopeptide prophylaxis for preventing surgical site infections caused by Gram positive bacteria among patients undergoing cardiac operations or total joint replacement procedures.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed (1995 to 2011), the Cochrane database of systematic reviews, CINAHL, Embase, and clinicaltrials.gov were searched to identify relevant studies. Pertinent journals and conference abstracts were hand searched. Study authors were contacted if more data were needed.

ELIGIBILITY CRITERIA

Randomized controlled trials, quasi-experimental studies, and cohort studies that assessed nasal decolonization or glycopeptide prophylaxis, or both, for preventing Gram positive surgical site infections compared with standard care.

PARTICIPANTS

Patients undergoing cardiac operations or total joint replacement procedures. DATA EXTRACTION AND STUDY APPRAISAL: Two authors independently extracted data from each paper and a random effects model was used to obtain summary estimates. Risk of bias was assessed using the Downs and Black or the Cochrane scales. Heterogeneity was assessed using the Cochran Q and I(2) statistics.

RESULTS

39 studies were included. Pooled effects of 17 studies showed that nasal decolonization had a significantly protective effect against surgical site infections associated with Staphylococcus aureus (pooled relative risk 0.39, 95% confidence interval 0.31 to 0.50) when all patients underwent decolonization (0.40, 0.29 to 0.55) and when only S aureus carriers underwent decolonization (0.36, 0.22 to 0.57). Pooled effects of 15 prophylaxis studies showed that glycopeptide prophylaxis was significantly protective against surgical site infections related to methicillin (meticillin) resistant S aureus (MRSA) compared with prophylaxis using β lactam antibiotics (0.40, 0.20 to 0.80), and a non-significant risk factor for methicillin susceptible S aureus infections (1.47, 0.91 to 2.38). Seven studies assessed a bundle including decolonization and glycopeptide prophylaxis for only patients colonized with MRSA and found a significantly protective effect against surgical site infections with Gram positive bacteria (0.41, 0.30 to 0.56).

CONCLUSIONS

Surgical programs that implement a bundled intervention including both nasal decolonization and glycopeptide prophylaxis for MRSA carriers may decrease rates of surgical site infections caused by S aureus or other Gram positive bacteria.

National surveillance of surgical site infections after coronary artery bypass grafting in Norway: incidence and risk factors

OBJECTIVE

A mandatory national surveillance system for surgical site infections (SSIs) following certain surgical procedures, including coronary artery bypass grafting (CABG), was introduced in Norway in 2005. The objectives of this study were to measure national baseline incidence rates of SSIs after CABG, describe the characteristics of the patients and procedures, and identify possible risk factors for infection.

METHODS

In 2005-2009, all hospitals that performed CABG were invited to assess all patients undergoing CABG surgery in 3-month periods for SSIs. The hospitals evaluated infection status at discharge and 30 days after surgery by sending post-discharge questionnaires to all patients. We calculated incidence proportions and risk ratios for different risk factors. We applied the National Nosocomial Infection Surveillance (NNIS) risk index to the data.

RESULTS

In total, 2440 patients were included. Altogether, 124 sternal and 217 harvest site infections were registered, giving incidence proportions of 5.1% and 8.9%, respectively. Over 95% of infections occurred post-discharge from the hospital. No risk factors were identified. Incidence did not significantly increase with higher NNIS risk index; however, 93% of the patients fell into the same risk category.

CONCLUSIONS

We have provided a baseline rate for SSIs after CABG procedures in Norway. The results show the importance of post-hospital discharge follow-up. The NNIS risk index did not adequately stratify CABG patients. We recommend that more potential risk variables should be included in the surveillance, such as the European System for Cardiac Operative Risk Evaluation (EuroSCORE), height, weight, and diabetes.

Harvest surgical site infection following coronary artery bypass grafting: risk factors, microbiology, and outcomes

BACKGROUND

Our goals were to evaluate the risk factors predisposing to saphenous vein harvest surgical site infection (HSSI), the microbiology implicated, associated outcomes including 30-day mortality, and identify opportunities for prevention of infection.

METHODS

All patients undergoing coronary artery bypass grafting (CABG) procedures from January 2000 through September 2004 were included. Data were collected on preoperative, intraoperative, and postoperative factors, in addition to microbiology and outcomes.

RESULTS

Eighty-six of 3578 (2.4%) patients developed HSSI; 28 (32.6%) of them were classified as deep. The median time to detection was 17 (range, 4-51) days. An organism was identified in 64 (74.4%) cases; of them, a single pathogen was implicated in 50 (78%) cases. Staphylococcus aureus was the most frequently isolated pathogen: 19 (38% [methicillin-susceptible S aureus (MSSA) = 12, methicillin-resistant S aureus (MRSA) = 7]). Gram-negative organisms were recovered in 50% of cases, with Pseudomonas aeruginosa predominating in 11 (22%) because of a single pathogen. Multiple pathogens were identified in 14 (22%) cases. The 30-day mortality was not significantly different in patients with or without HSSI. Multivariate analysis showed age, diabetes mellitus, obesity, congestive heart failure, renal insufficiency, and duration of surgery to be associated with increased risk.

CONCLUSION

Diabetes mellitus, obesity, congestive heart failure, renal insufficiency, and duration of surgery were associated with increased risk for HSSI. S aureus was the most frequently isolated pathogen.

Nosocomial infections after pediatric cardiac surgery

BACKGROUND

This study examined the rate of nosocomial infection (NI) in children who underwent cardiac surgery, and also investigated the impact of postdischarge infection surveillance. Risk factors for surgical site infections (SSIs) also were evaluated.

METHODS

All patients who underwent open-heart cardiac surgery in the Hospital for Children and Adolescents, Helsinki University Central Hospital, Finland, between January 2000 and December 2002 were included. Data were collected retrospectively from hospital registries. A prospective postdischarge survey was conducted to detect SSIs arising within 30 days after surgery, as well as respiratory and gastrointestinal infections with onset within 3 days after discharge.

RESULTS

The study included 614 procedures performed in 511 patients. A total of 80 NIs were found (overall NI rate, 6.3 per 1000 patient days), including 21 superficial and 6 deep SSIs. Multivariable analysis identified preoperative hospitalization > 48 hours and high American Society of Anesthesiologists (ASA) score as risk factors for SSI. The postdischarge study revealed 7 additional superficial SSIs, 29 respiratory infections, and 29 gastrointestinal infections; 12 patients required rehospitalization.

CONCLUSIONS

Almost 25% of the patients had at least 1 NI. All severe NIs were detected during the postoperative hospital stay. Respiratory and gastrointestinal infections were common and often led to rehospitalization, thus increasing costs.

Surgical site infections in cardiac surgery after a hospital catastrophe

On 2 November 1999, one of the main hospital façades adjoining cardiovascular surgery collapsed in a 900-bed teaching hospital in Santander, Spain. The purpose of this study was to determine whether the accident affected the safety of patients by increasing the risk for nosocomial and surgical site infections (SSI). Measures for the prevention of nosocomial infections were immediately reinforced. A total of 217 consecutive patients were operated on before 2 November 1999, with another 296 after this date. Patients in both study periods showed similar severity of illness, complexity of surgical procedure and length of hospital stay. The overall rate of nosocomial infection before and after the accident was 28.1% and 24.7%, respectively (P=0.381). The rates of respiratory infection, urinary infection and bacteraemia were also similar. A statistically significant reduction in the SSI rate in the second period was observed (14.8% vs 4.4%, P=0.008). The collapse of the façade was not associated with any increase in nosocomial infection rates, but there was a significant reduction of SSI rates in relation to intensive infection control measures implemented after the collapse.

Postoperative surveillance, registration and classification of wound infection in cardiac surgery--experiences from Great Britain

Wound infection in cardiac surgery is a continuing problem despite improvements in surgical technique. The risk factors for, and appearance of, the infected wound differ from operations in other specialties. A robust definition is required for successful surveillance but many are open to different interpretations. At UCLH, comparison between UK and US definitions shows marked differences in patients defined as infected. Surveillance with feedback is effective if conducted over several years, but a high proportion of infected wounds are only identified during post-discharge follow-up. Deteriorating performance of an individual surgeon can be detected and interventions focused on improving faults identified during data collection. Often highlighting the problem is sufficient to reverse the trend, but the process of audit and control is becoming more important as accountability and performance is demanded by primary care providers and patients.

An alternative scoring system to predict risk for surgical site infection complicating coronary artery bypass graft surgery

OBJECTIVE

To analyze the risk factors for surgical site infection (SSI) complicating coronary artery bypass graft (CABG) surgery and to create an alternative SSI risk score based on the results of multivariate analysis.

METHODS

A prospective cohort study involving inpatient and laboratory-based surveillance of patients who underwent CABG surgery over a 27-month period from January 1, 2003 through March 31, 2005. Data were obtained from 6 acute care hospitals in Victoria, Australia, that contributed surveillance data for SSI complicating CABG surgery to the Victorian Hospital Acquired Infection Surveillance System Coordinating Centre and the Australasian Society of Cardiac and Thoracic Surgeons, also in Victoria.

RESULTS

A total of 4,633 (93%) of the 4,987 patients who underwent CABG surgery during this period were matched in the 2 systems databases. There were 286 SSIs and 62 deep or organ space sternal SSIs (deep or organ space sternal SSI rate, 1.33%). Univariate analysis revealed that diabetes mellitus, body mass index (BMI) greater than 35, and receipt of blood transfusion were risk factors for all types of SSI complicating CABG surgery. Six multivariate analysis models were created to examine either preoperative factors alone or preoperative factors combined with operative factors. All models revealed diabetes and BMI of 30 or greater as risk factors for SSI complicating CABG surgery. A new preoperative scoring system was devised to predict sternal SSI, which assigned 1 point for diabetes, 1 point for BMI of 30 or greater but less than 35, and 2 points for BMI of 35 or greater. Each point in the scoring system represented approximately a doubling of risk of SSI. The new scoring system performed better than the National Nosocomial Infections Surveillance System (NNIS) risk index at predicting SSI.

CONCLUSION

A new weighted scoring system based on preoperative risk factors was created to predict sternal SSI risk following CABG surgery. The new scoring system outperformed the NNIS risk index. Future studies are needed to validate this scoring system.

Post-discharge surgical site surveillance: does patient education improve reliability of diagnosis?

Post-discharge surgical infection surveillance by patients remains an integral part of many infection control programmes despite proven unreliability. We attempted to improve the validity of patient recognition of signs and symptoms of wound infection and post-discharge postal questionnaire responses through specific education prior to discharge. In total, 588 patients were studied after random assignment into two intervention groups, one of which received relevant education. Both groups were followed for four weeks post-operatively, with features of infection assessed weekly by experienced infection control nurses (ICNs) and by patient responses to routine postal questionnaires. Those patients who received education demonstrated a significantly poorer correlation with ICN diagnosis compared to the non-educated group (Kappa 0.69 and 0.81 respectively, P=0.05). Both patient groups achieved the same sensitivity for recall (83.3%), with high specificity demonstrated by both groups [educated (93.7%); non-educated (98.1%)]. The positive predictive value was 65.2% for the educated group and 83.3% for the non-educated patient group. When infected wounds identified by patients were examined for the proportion that were overdiagnosed, the excess of SSI identified by the educated patient group was 44.4% and by the non-educated group 16.7%. These results suggest that pre-discharge education causes patients to overdiagnose clinical features of wound infection and fails to improve the validity of diagnosis. This outcome further questions the value of post-discharge infection rates obtained by patient self-assessment as a measure of quality of performance.

Staphylococcus aureus, the major pathogen in orthopaedic and cardiac surgical site infections: a literature review

Due to the increasing number of orthopaedic and cardiac procedures, these units are considered as high-risk areas because of the potentially serious consequences of surgical site infections (SSI), primarily caused by Staphylococcus aureus. The goal of this review was to evaluate the impact of S. aureus on the incidence of SSI in these high risk wards. Studies were identified by a search on the MEDLINE literature using the following mesh terms: S. aureus, cardiac, orthopaedic, surgery, SSI. Beside, data from different surveillance systems were also included. Overall, biological investigation was performed only on a small proportion of identified SSIs. Of those identified, S. aureus represented the most common pathogen accounting for approximately 20% of all SSIs. Of the 59,274 hip prostheses reported from the HELICS surveillance network, S. aureus formed 48.6% of the pathogens (416 bacteria isolated). Similarly, it represented 43.7% of pathogens after coronary artery bypass grafting. Although S. aureus turned out to be the major pathogen, this work identifies the relative lack of knowledge on the overall incidence of S. aureus infections and on the impact of this pathogenic agent when taking into consideration the degree of wound contamination and category of SSI. There is a need for more detailed information on the role of S. aureus in the burden of surgical site infections and consequently how to establish multiple approach prevention programs.

An enhanced benchmark for prosthetic joint replacement infection rates

BACKGROUND

The National Nosocomial Infection Surveillance System (NNIS) has historically provided the infection control community with the most accurate benchmark for healthcare-associated infections. However, NNIS does not require postdischarge surveillance. For medical centers where comprehensive postdischarge surveillance is possible, the efficiency of surgical site infection (SSI) detection is enhanced and rates may be higher than those provided by NNIS.

METHODS

From 1999 to 2004, a large integrated healthcare system (IHCS) used a standard surveillance methodology inclusive of the postdischarge period. This article compares IHCS and NNIS SSI data.

RESULTS

IHCS infection rates, stratified and weighted average (hip, 1.7; knee, 2.1) for the study period are higher than the corresponding NNIS rates (hip, 1.4; knee, 1.2) (hip, P = .006; knee, P = .012) when infections detected by the IHCS during the postdischarge period are included.

CONCLUSIONS

The data from the study period show that when comprehensive postdischarge surveillance is used by the IHCS, SSI rates are higher than those reflected in the NNIS database.

Reduction of surgical site infections after Caesarean delivery using surveillance

Since 1997, the Krankenhaus Infektions Surveillance System (KISS) has collected data on surgical site infections (SSIs) following Caesarean delivery (CD). The aim of this study was to determine whether surveillance and feedback of healthcare-associated infections (HAIs) could reduce the infection rate after CD. Only departments that had participated in KISS for at least three years were included in the analysis. The CD infection rates of the first, second and third years of KISS participation were compared for significant differences. The relative risk was calculated for the first and the third year of KISS participation. Multi-variate logistic regression analysis was performed to detect significant risk factors for SSI after CD using the third year of participation as one parameter. Twenty-six of 52 obstetric and gynaecology departments met the study's inclusion criteria. In those 26 departments, 17,405 CD procedures were performed and 331 SSIs were recorded (1.9%). The SSI rate after CD procedures was significantly reduced in the third year of KISS participation (1.6%) compared with the first year of KISS participation (2.4%), with a relative risk of 0.63 [95% confidence interval (CI) 0.48-0.82]. Logistic regression analysis confirmed that KISS participation over three years was an independent factor for the reduction of SSI rate (odds ratio 0.64; 95% CI 0.49-0.83). As shown previously for other types of HAI, this study demonstrated that continuous surveillance and comparison with stratified reference data could reduce SSI infection rates after CD.

Surveillance for mupirocin resistance following introduction of routine peri-operative prophylaxis with nasal mupirocin

The authors have previously described the successful use of a five-day peri-operative prophylaxis regimen using nasal mupirocin and topical triclosan (PPNMTT) to prevent methicillin-resistant Staphylococcus aureus (MRSA) infection. The present article describes the results of repeated point-prevalence surveillance for four years to determine whether mupirocin resistance has emerged in surgical units using empirical, short-term, peri-operative prophylaxis with nasal mupirocin. Before starting PPNMTT and every six months thereafter for four years, point-prevalence surveillance was performed for nasal S. aureus carriage in all patients on five orthopaedic surgery wards, one vascular surgery ward and one elderly medicine control ward. S. aureus screening and clinical isolates (surgical patients) were undertaken for low- [minimum inhibitory concentration (MIC) 8-128 mg/L] and high-level (MIC > 128 mg/L) mupirocin resistance. All isolates were phage typed to determine whether there was evidence of the spread of clonal mupirocin-resistant strains. Of 593, 139 and 206 nasal screening swabs (taken after the regimen had started) from orthopaedic, vascular and control patients, 28%, 24% and 48% (orthopaedic/vascular surgery vs elderly medicine, P < 0.001) yielded S. aureus isolates, respectively, and 12%, 11% and 30% (P < 0.001) were MRSA positive, respectively. Of the S. aureus nasal screen isolates from orthopaedic/vascular surgery and control patients, 5% and 4%, respectively, were low-level mupirocin resistant (P > 0.1). Of 286 (orthopaedic/vascular surgery) and 68 (elderly medicine) clinical S. aureus isolates obtained after the regimen had started, 7% and 9% (P > 0.1), respectively, were low-level mupirocin resistant. No high-level mupirocin-resistant isolates were isolated from mupirocin (orthopaedic/vascular surgery) or elderly medicine control ward patients. There was no trend towards increasing prevalence of low-level mupirocin resistance during the four-year study period. The results of phage typing did not support the clonal spread of resistant strains. Long-term follow-up confirmed the efficacy of PPNMTT in reducing the prevalence of nasal carriage of S. aureus and MRSA in orthopaedic and vascular surgery patients. Despite four years of use of PPNMTT, there was no evidence of sustained emergence or spread of mupirocin resistance.

PREVENTING SURGICAL-SITE INFECTIONS After Coronary Artery Bypass Graft

Home health nurses play a key role in teaching, assessing, and caring for patients who are at risk for infection. The need for preventing surgical-site infections in patients after bypass is paramount. The incidence, impact, surveillance, and prevention of infection are discussed, along with guidelines to assist the home health nurse in practice.

Molecular epidemiology of microbial contamination in the operating room environment: Is there a risk for infection?

BACKGROUND

Modern operating rooms are considered to be aseptic environments. The use of surgical mask, frequent air exchanges, and architectural barriers are used to reduce airborne microbial populations. Breaks in surgical technique, host contamination, or hematogenous seeding are suggested as causal factors in these infections. This study implicates contamination of the operating room air as an additional etiology of infection.

METHODS

To investigate the potential sources of perioperative contamination, an innovative in situ air-sampling analysis was conducted during an 18-month period involving 70 separate vascular surgical procedures. Air-sample cultures were obtained from multiple points within the operating room, ranging from 0.5 to 4 m from the surgical wound. Selected microbial clonality was determined by pulse-field gel electrophoresis. In a separate series of studies microbial nasopharyngeal shedding was evaluated under controlled environmental conditions in the presence and absence of a surgical mask.

RESULTS

Coagulase-negative staphylococci were recovered from 86% of air samples, 51% from within 0.5 m of the surgical wound, whereas Staphylococcus aureus was recovered from 64% of air samples, 39% within 0.5 m from the wound. Anterior nares swabs were obtained from 11 members of the vascular team, clonality was observed between 8 strains of S epidermidis, and 2 strains of S aureus were recovered from selected team members and air-samples collected throughout the operating room environment. Miscellaneous Gram-negative isolates were recovered less frequently (<33%); however, 7 isolates expressed multiple patterns of antimicrobial resistance. The traditional surgical mask demonstrated limited effectiveness at curtailing microbial shedding, especially during symptomatic periods of rhinorrhea.

CONCLUSIONS

Gram-positive staphylococcal isolates were frequently isolated from air samples obtained throughout the operating room, including areas adjacent to the operative field. Nasopharyngeal shedding from person participating in the operation was identified as the source of many of these airborne contaminants. Failure of the traditional surgical mask to prevent microbial shedding is likely associated with an increased risk of perioperative contamination of biomedical implants, especially in procedures lasting longer than 90 minutes.

Multicenter experience: prevention and management of left ventricular assist device infections

Implantable left ventricular assist devices (LVADs) have demonstrated clinical success in both the bridge-to-transplantation and destination-therapy patient populations; however, infection remains one of the most common causes of mortality during mechanical circulatory support. Thus, serious LVAD infections may negate the benefits of LVAD implantation, resulting in decreased quality of life, increased morbidity and mortality, and increased costs associated with implantation. Prevention of device-related infection is crucial to the cost-effective use of mechanical circulatory support devices. Therefore, adherence to evidence-based infection control and prevention guidelines, meticulous surgical technique and optimal postoperative surgical site care form the foundation for LVAD associated infection prevention.

Surgical site infection rates following cardiac surgery: the impact of a 6-year infection control program

BACKGROUND

To evaluate the impact of an infection control program on surgical site infections (SSIs) complicating cardiac operations.

METHODS

Prospective cohort study of patients undergoing cardiac operations. Interventions included prospective surveillance, povidone-iodine scrub showers, depilation before surgery, administration of preoperative antibiotic prophylaxis in the operating room, and postdischarge follow-up. Logistic regression models were fitted to assess infection rates over time, adjusting for factors known to affect SSI rates.

RESULTS

The overall SSI rate for 2051 procedures was 10.4%. Rates of superficial and deep incisional SSIs remained unchanged over the study period. The rates of all organ/space infections, mediastinitis, and SSIs because of methicillin-resistant Staphylococcus aureus during the first 2 years were 3.25%, 2.22%, and 1.48%, respectively, and they decreased to 1.17%, 0.73%, and 0.73%, respectively, by the end of 2002 (P = .01, P = .01, and P = .09, respectively). The adjusted odds ratios for these 3 types of infection at the end of 2002 compared with December 31, 1998, were 0.19 (95% confidence interval [95% CI]: 0.07-0.48), 0.20 (95% CI: 0.06-0.66), and 0.28 (95% CI: 0.08-0.97), respectively.

CONCLUSION

We observed significant reductions in organ/space infection rates, particularly mediastinitis. These differences remained significant when adjusted for potential confounding variables.