Poststernotomy mediastinitis due to Staphylococcus aureus: comparison of methicillin-resistant and methicillin-susceptible cases

Current and emerging pharmacotherapy for the treatment of infections following open-heart surgery

INTRODUCTION

Patients undergoing open-heart surgery may suffer from postoperative complications, including severe infections. Antimicrobials to treat infectious complications in this population should be selected thoughtfully, taking into account three different and fundamental issues: (i) the site of infection; (ii) the suspected or proven causative agent and its susceptibility pattern; and (iii) the risk of suboptimal pharmacokinetic characteristics and potential toxicity of the chosen drug/s.

AREAS COVERED

The present narrative review summarizes the current and future antimicrobial options for the treatment of infections developing after open-heart surgery.

EXPERT OPINION

The pharmacological treatment of infections developing in cardiac surgery patients poses peculiar challenges, including the need for an active empirical therapy for severe events such as bloodstream infections, deep sternal wound infections, or early-onset postoperative prosthetic endocarditis. In addition, the risk for multidrug-resistant pathogens should also be taken into account in endemic areas. A multidisciplinary evaluation on a patient-by-patient basis, deeply involving infectious diseases specialists and cardiothoracic surgeons, remains essential for appropriately balancing both short-term and long-term risks and benefits of any possible surgical reintervention in combination with adequate pharmacotherapy.

Comparing Negative Pressure Wound Therapy with Instillation and Conventional Dressings for Sternal Wound Reconstructions

Background:

Muscle flap reconstruction has become a mainstay of therapy following treatment of sternal wound complications; however, success depends on removing wound exudate and infectious material from the wound before reconstruction and closure. Importantly, time to closure is a key factor affecting morbidity/mortality and cost-to-treat for this wound type.

Methods:

A retrospective analysis of 30 patients who were treated for sternal wound complications between June 2015 and October 2017 was performed. After surgical debridement, group 1 patients (n = 15) received negative pressure wound therapy (NPWT) with instillation and dwell time (NPWTi-d), instilling 1/8-strength Dakin’s solution with a 20-minute dwell time followed by 2 hours of NPWT (-125 mm Hg); group 2 patients (n = 15) were treated with wet-to-moist dressings soaked in 1/8-strength Dakin’s solution. After muscle flap reconstruction and closure with sutures, group 1 patients received closed incision negative pressure therapy, and group 2 patients received Benzoin and wound closure strips. Data collected included time to closure, therapy duration, number of debridements/dressing changes, drain duration, and complications.

Results:

There was a significantly shorter time to closure (P < 0.0001) for group 1 when compared with group 2. In addition, there were fewer therapy days (P = 0.0041), fewer debridements/dressing changes (P = 0.0011), and shorter drain duration (P = 0.0001) for group 1 when compared with group 2.

Conclusions:

We describe a novel regimen consisting of adjunctive NPWTi-d, along with debridement and systemic antibiotics, followed by closed incision negative pressure therapy after muscle flap reconstruction and closure, to help manage preexisting sternal wounds that had failed to close following a previous cardiac procedure.

Management of acute bacterial skin and skin structure infections with a focus on patients at high risk of treatment failure

Over the last 25 years, the terminology of skin and soft tissue infections, as well as their classification for optimal management of patients, has changed. The so-called and recently introduced term 'acute bacterial skin and skin structure infections' (ABSSSIs), a cluster of fairly common types of infection, including abscesses, cellulitis, and wound infections, require an immediate effective antibacterial treatment as part of a timely and cautious management. The extreme level of resistance globally to many antibiotic drugs in the prevalent causative pathogens, the presence of risk factors of treatment failure, and the high epidemic of comorbidities (e.g. diabetes and obesity) make the appropriate selection of the antibiotic for physicians highly challenging. The selection of antibiotics is primarily empirical for ABSSSI patients which subsequently can be adjusted based on culture results, although rarely available in outpatient management. There is substantial evidence suggesting that inappropriate antibiotic treatment is given to approximately 20-25% of patients, potentially prolonging their hospital stay and increasing the risk of morbidity and mortality. The current review paper discusses the concerns related to the management of ABSSSI and the patient types who are most vulnerable to poor outcomes. It also highlights the key management time-points that treating physicians and surgeons must be aware of in order to achieve clinical success and to discharge patients from the hospital as early as possible.

European Association for Cardio-Thoracic Surgery expert consensus statement on the prevention and management of mediastinitis

Mediastinitis continues to be an important and life-threatening complication after median sternotomy despite advances in prevention and treatment strategies, with an incidence of 0.25-5%. It can also occur as extension of infection from adjacent structures such as the oesophagus, airways and lungs, or as descending necrotizing infection from the head and neck. In addition, there is a chronic form of 'chronic fibrosing mediastinitis' usually caused by granulomatous infections. In this expert consensus, the evidence for strategies for treatment and prevention of mediatinitis is reviewed in detail aiming at reducing the incidence and optimizing the management of this serious condition.

Proper use of antibiotics: situation of linezolid at the intensive care unit of the Tunisian Military Hospital

Linezolid was introduced in clinical practice in the early 2000s. It was considered to be an ideal reserve drug for treatment of vancomycin-resistant Enterococcus spp. (VRE) and vancomycin-resistant Staphylococcus aureus (VRSA). The aim of our study was to describe and evaluate the use of linezolid in clinical practice at the intensive care unit (ICU) of the Tunisian military hospital. This is a thirty-month retrospective study including patients treated with linezolid at the ICU of the Tunisian military hospital. Data collection was realized using the patients' medical files and prescriptions. A pharmacist conducted an extended medication history and checked if an advice from an infectious disease-physician and a microbiological documentation were requested. A total of 80 patients were included. Forty-one per cent of indications were outside the Marketing Authorization (MA) criteria, and were mainly sepsis and postoperative mediastinitis (32% and 4% of total prescriptions, respectively). This antibiotic was used as a first-line therapy in 58% of cases. The advice from an infectious-disease physician was requested for 33% of prescriptions. Only 20% of infections were documented microbiologically, of which 35% were caused by methicillin resistant coagulase-negative Staphylococcus. Linezolid is an interesting therapeutic alternative in case of infections due to multi-resistant bacteria and/or complex clinical situations. Therefore, its prescription must be rationalized in order to slow down the emergence of resistance to this antibiotic. The high frequency of its use outside the MA criteria shows the importance of carrying out more clinical trials to evaluate its effectiveness and safety for new indications.

Nosocomial MRSA Infection in Vascular Surgery Patients: Impact on Patient Outcome

Although methicillin-resistant Staphylococcus aureus(MRSA) infection is a worldwide problem, data on its significance among vascular surgery patients remain scant and conflicting. This study was designed to evaluate the association between nosocomial MRSA infection and patient outcome following vascular surgery procedures. Outcomes among patients with MRSA infection were also compared to those infected with methicillin-sensitive Staphylococcus aureus(MSSA). All patients admitted to a tertiary care Vascular Surgery ward during the year 2002 were included in this retrospective review. In addition to information on demographic and comorbid conditions, data on surgical interventions, nosocomial infection incidence rates as defined by the Center for Disease Control guidelines, and MRSA screening results were collected. Primary outcome was in-hospital death. Secondary outcomes measures included length of hospital stay, readmissions, or repeat surgeries, and ICU admissions. Of a total of 408 subjects, 110 were documented with a nosocomial infection (27.0%). Of these, 16 patients (3.9%) were colonized with MRSA on screening at time of admission, 22 (5.4%) had acquired MRSA infection during hospitalization, and 15 (3.7%) had MSSA infection. Patients with MRSA, MSSA, and non-MRSA infection had similar baseline characteristics except for hypertension and tobacco use. Age and MRSA infection were significant risk factors for in-hospital deaths (OR 1.07, 95% CI 1.01–1.13, p = 0.01 and OR 7.44, 95% CI 1.63–33.9, p = 0.01, respectively). Adjusted for the effects of age, MRSA infection remained a significant independent risk factor associated with in-hospital deaths (OR 4.38, 95% CI 1.09–17.7, p = 0.04). After adjustment for baseline risk factors, MRSA infection was also independently associated with secondary outcome measures. Although risks of non-MRSA infections were also associated with adverse outcomes in the multivariate analyses, MRSA posed higher risks, as reflected by higher odds ratio in all instances. The 22 patients with documented MRSA infection had significantly longer hospital stays than those with MSSA infection (median 24 days vs 8 days, p = 0.02). However, no significant differences were noted between the 2 groups in terms of secondary outcome. These results show that MRSA infection is a significant risk factor for adverse clinical outcomes among patients undergoing vascular surgery procedures. Infection with MRSA results in a greater risk of these outcomes when compared with non-MRSA infection. However, despite concerns regarding the virulence of this strain of staphylococcus, patients infected with MRSA had no higher rates of morbidity or mortality except for increased length of hospital stay when compared to patients with MSSA.

Does percutaneous dilatational tracheostomy increase the incidence of sternal wound infection - a single center retrospective of 4100 cases

BACKGROUND

The impact of percutaneous dilatational tracheostomy (PDT) on the development of post-median sternotomy wound infection (SWI) and mediastinitis is still controversial. We aimed to investigate the frequency of cross-infection and incidence of SWI after PDT.

METHODS

In a retrospective design, out of a total of 4100 procedures, all patients who had undergone median sternotomy and postoperative PDT were included from January 2010 to May 2013. For comparison of the pathogens isolated from SWIs, data from all patients who developed an SWI without a PDT during the aforementioned period were also analyzed. Demographical, pre-, peri- and post-operative data were compared. Microbiologic analysis from cultures of sternal and tracheal wounds was performed. Day and duration of tracheostomy were correlated to SWI occurrence.

RESULTS

Of the 265 patients who underwent a PDT, 25 (9.4 %) developed an SWI. In this cohort, identical pathogens were isolated from the tracheostomy and SWI in 36 % (9/25) of the patients. Of the pathogens isolated from the SWIs from the PDT + SWI group, 60 % were gram-positive bacteria, 20 % gram-negative bacteria and 20 % Candida spp. In the cross-infection group, the patients developed the following types of SWIs: 11.1 % CDC I, 55.6 % CDC II and 33.3 % mediastinitis (CDC III). The incidence of SWI in the group SWI + PDT was 9.4 % (9.4 % vs. 3.4 %, PDT + SWI and SWI w/oPDT , respectively, p = 0.0001). In group SWI w/oPDT , only 1.5 % (2/131 vs. 5/25; p = 0.001) Candida spp were isolated from SWI. The infection-related in-hospital mortality was high in groups PDT + SWI vs. SWI w/oPDT (20 % vs. 0 %, respectively; p = 0.0001). The statistical analysis did not demonstrate any correlation between time of performing PDT and occurrence of SWI.

CONCLUSIONS

There was a high incidence of microbial cross-infection from the PDTs to the sternal wounds in our study. We did not detect any correlation between the time of performing PDT and occurrence of SWI. According to our data, PDT seems to increase the incidence of SWI, especially caused by Candida spp., after cardiac surgery, which results in a prolonged hospital stay. Therefore, early antifungal prophylaxis after a PDT might be reasonable in high-risk patients on long-term mechanical ventilation if there is an impending SWI.

Impact of Methicillin-Resistant Staphylococcus aureus Prevalence among S. aureus Isolates on Surgical Site Infection Risk after Coronary Artery Bypass Surgery

Objective.

Cephalosporins are recommended for antibiotic prophylaxis to prevent cardiothoracic surgical site infections (SSIs) except in patients withβ-lactam allergy or in settings with a “high” prevalence of methicillin-resistantStaphylococcus aureus(MRSA) among S.aureusisolates (hereafter, “MRSA prevalence”); however, “high” remains undefined. We sought to identify the MRSA prevalence at which glycopeptide prophylaxis would minimize SSIs relative toβ-lactam prophylaxis.

Methods.

We developed a decision analysis model to estimate SSI likelihood when either glycopeptides orβ-lactams were used for prophylaxis in cardiothoracic surgery. Event probabilities were derived from a systematic literature review. A similar cost-minimization model was also developed.

Results.

At 0% MRSA prevalence, SSI probability was 3.64% with glycopeptide prophylaxis and 3.49% withβ-lactam prophylaxis. At MRSA prevalences of 10%, 20%, 30%, or 40%, SSI probabilities with glycopeptide prophylaxis did not change, but they were 3.98%, 4.48%, 4.97%, and 5.47% withβ-lactam prophylaxis. The threshold of MRSA prevalence at which glycopeptide prophylaxis minimized SSI probability and cost was 3%. In sensitivity analyses, variations in most model estimates only modestly affected the threshold.

Conclusion.

Glycopeptide prophylaxis minimizes the risk of SSIs and cost when MRSA prevalence exceeds 3%. At very low MRSA prevalence (between 3% and 10%), the SSI minimization provided by glycopeptide prophylaxis is small and may be within the error of the model. Given the current MRSA prevalence in most community and healthcare settings, clinicians should consider routine prophylaxis with vancomycin. Our findings may have important policy implications, as benefits in cardiothoracic surgery antibiotic prophylaxis must be weighed against the limitations of increased glycopeptide use.

Use of incisional negative pressure wound therapy on closed median sternal incisions after cardiothoracic surgery: clinical evidence and consensus recommendations

Negative pressure wound therapy is a concept introduced initially to assist in the treatment of chronic open wounds. Recently, there has been growing interest in using the technique on closed incisions after surgery to prevent potentially severe surgical site infections and other wound complications in high-risk patients. Negative pressure wound therapy uses a negative pressure unit and specific dressings that help to hold the incision edges together, redistribute lateral tension, reduce edema, stimulate perfusion, and protect the surgical site from external infectious sources. Randomized, controlled studies of negative pressure wound therapy for closed incisions in orthopedic settings (which also is a clean surgical procedure in absence of an open fracture) have shown the technology can reduce the risk of wound infection, wound dehiscence, and seroma, and there is accumulating evidence that it also improves wound outcomes after cardiothoracic surgery. Identifying at-risk individuals for whom prophylactic use of negative pressure wound therapy would be most cost-effective remains a challenge; however, several risk-stratification systems have been proposed and should be evaluated more fully. The recent availability of a single-use, closed incision management system offers surgeons a convenient and practical means of delivering negative pressure wound therapy to their high-risk patients, with excellent wound outcomes reported to date. Although larger, randomized, controlled studies will help to clarify the precise role and benefits of such a system in cardiothoracic surgery, limited initial evidence from clinical studies and from the authors' own experiences appears promising. In light of the growing interest in this technology among cardiothoracic surgeons, a consensus meeting, which was attended by a group of international experts, was held to review existing evidence for negative pressure wound therapy in the prevention of wound complications after surgery and to provide recommendations on the optimal use of negative pressure wound therapy on closed median sternal incisions after cardiothoracic surgery.

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.

Closed incision management with negative pressure wound therapy

Post-sternotomy mediastinitis is the most severe surgical site infection after sternotomy with an incidence between 1-4% related to the patient co-morbidity. This complication will increase morbidity and mortality and may also have an economic impact. There are guidelines to prevent surgical site infections; however, age and co-morbidities increase and therefore it is important to develop new tools to improve wound healing. This manuscript will give an overview of a new concept using negative pressure wound therapy over a closed incision (so-called, closed incision management) after surgery and will include the principles of negative pressure wound therapy and the positively applied mechanical forces as a permutation of Wolff's law. The use and indication of this therapy is supported by experimental studies divided into physiological and biomechanical property studies. Finally, an overview of clinical studies is given based on the evidence rating scale for therapeutic studies.

Daptomycin and Its Immunomodulatory Effect: Consequences for Antibiotic Treatment of Methicillin-Resistant Staphylococcus aureus Wound Infections after Heart Surgery

Infections by methicillin-resistant Staphylococcus aureus (MRSA) play an increasing role in the postoperative course. Although wound infections after cardiac surgery are rare, the outcome is limited by the prolonged treatment with high mortality. Not only surgical debridement is crucial, but also antibiotic support. Next to vancomycin and linezolid, daptomycin gains increasing importance. Although clinical evidence is limited, daptomycin has immunomodulatory properties, resulting in the suppression of cytokine expression after host immune response stimulation by MRSA. Experimental studies showed an improved efficacy of daptomycin in combination with administration of vitamin E before infecting wounds by MRSA.

Methicillin-resistant Staphylococcus aureus infection: an independent risk factor for mortality in patients with poststernotomy mediastinitis

OBJECTIVE

The mortality rate of patients with poststernotomy mediastinitis remains very high. The aim of this study was to identify the risk factors associated with mortality in these patients.

SUBJECTS AND METHODS

Surveillance of sternal surgical-site infections including mediastinitis was carried out for adult patients undergoing a sternotomy between 2004 and 2012. Criteria from the US Centers for Disease Control and Prevention were used to make the diagnosis. All data on patients with a diagnosis of mediastinitis who were included in the study and on mortality risk factors were obtained from the hospital database and then analyzed using SPPS 16.0 for Windows.

RESULTS

Of the 19,767 patients undergoing open heart surgery, 117 (0.39%) had poststernotomy mediastinitis; 32% of these 117 died. The independent risk factors for mortality were methicillin-resistant Staphylococcus aureus (MRSA) [odds ratio (OR) 12.11 and 95% confidence interval (CI) 3.15-46.47], intensive-care unit stays >48 h after the first operation (OR 11.21 and 95% CI 3.24-38.84) and surgery that included valve replacement (OR 6.2 and 95% CI 1.44-27.13). The mortality rate decreased significantly, dropping from 38% (34/89) between 2004 and 2008 to 14% (4/28) between 2009 and 2012 (p = 0.018).

CONCLUSION

In this study, elimination of MRSA from the hospital setting decreased the rate of mortality in patients with poststernotomy mediastinitis.

[Post-operative mediastinitis in a heart hospital of Recife: contributions for nursing care]

The objective of this study was to determine the prevalence of post-operative mediastinitis with the purpose to contribute to nursing care knowledge. To do this, an analysis was performed on 896 medical records of patients who underwent heart surgery involving sternotomy at the Cardiology Emergency Room of Recife-PE, in the period between June 2007 and June 2009. The following variables were considered: gender, age, type of surgery, personal history, length of stay, use of antibiotics, and culture of the surgical wound. A high death rate from mediastinitis was observed (33.3%). Several risk factors were identified, including: systemic arterial hypertension (80.9%); smoking (61.9%); diabetes mellitus (42.8%); and obesity (33.3%), most of which (76.2%) were identified in patients who underwent surgery for myocardial revascularization. It is concluded that mediastinitis is a serious infection that needs continuous nursing supervision and preventive measures to assure an early diagnosis and, thus, reduce mortality.

Impact of methicillin-resistant Staphylococcus aureus prevalence among S. aureus isolates on surgical site infection risk after coronary artery bypass surgery

OBJECTIVE

Cephalosporins are recommended for antibiotic prophylaxis to prevent cardiothoracic surgical site infections (SSIs) except in patients with β-lactam allergy or in settings with a "high" prevalence of methicillin-resistant Staphylococcus aureus (MRSA) among S. aureus isolates (hereafter, "MRSA prevalence"); however, "high" remains undefined. We sought to identify the MRSA prevalence at which glycopeptide prophylaxis would minimize SSIs relative to β-lactam prophylaxis.

METHODS

We developed a decision analysis model to estimate SSI likelihood when either glycopeptides or β-lactams were used for prophylaxis in cardiothoracic surgery. Event probabilities were derived from a systematic literature review. A similar cost-minimization model was also developed.

RESULTS

At 0% MRSA prevalence, SSI probability was 3.64% with glycopeptide prophylaxis and 3.49% with β-lactam prophylaxis. At MRSA prevalences of 10%, 20%, 30%, or 40%, SSI probabilities with glycopeptide prophylaxis did not change, but they were 3.98%, 4.48%, 4.97%, and 5.47% with β-lactam prophylaxis. The threshold of MRSA prevalence at which glycopeptide prophylaxis minimized SSI probability and cost was 3%. In sensitivity analyses, variations in most model estimates only modestly affected the threshold.

CONCLUSION

Glycopeptide prophylaxis minimizes the risk of SSIs and cost when MRSA prevalence exceeds 3%. At very low MRSA prevalence (between 3% and 10%), the SSI minimization provided by glycopeptide prophylaxis is small and may be within the error of the model. Given the current MRSA prevalence in most community and healthcare settings, clinicians should consider routine prophylaxis with vancomycin. Our findings may have important policy implications, as benefits in cardiothoracic surgery antibiotic prophylaxis must be weighed against the limitations of increased glycopeptide use.

Evaluation of risk factors for hospital mortality and current treatment for poststernotomy mediastinitis

PURPOSE

Poststernotomy mediastinitis (PSM) following cardiovascular surgery remains an intractable complication associated with considerable mortality. It is therefore necessary to assess the risk factors associated with hospital mortality and evaluate the surgical treatment options for PSM.

METHODS

We identified 59 (2.2%) patients who developed PSM after cardiovascular surgery between January 1991 and January 2010. PSM was defined as deep sternal wound infection requiring surgical treatment. In all, 31 patients were infected with methicillin-resistant Staphylococcus aureus (MRSA); and 14 patients died in hospital from PSM. A total of 51 patients were treated by simple closure or tissue flap reconstruction after débridement (traditional treatment), and 8 underwent closure or reconstruction after negative-pressure wound therapy (NPWT). The risk factors for in-hospital mortality due to PSM were analyzed by comparing the characteristics of survivors and nonsurvivors. The available surgical treatments for mediastinitis were also assessed.

RESULTS

Univariate analysis identified age, sex, pulmonary disease, MRSA infection, prolonged mechanical ventilation and prolonged intensive care unit stay as risk factors for in-hospital mortality (P < 0.05). Multiple logistic regression analysis identified MRSA infection (odds ratio 20.263, 95% confidence interval 1.580-259.814; P = 0.0208) as an independent risk factor for hospital mortality. NPWT was associated with significantly less surgical failure than traditional treatment (P = 0.0204). There were no deaths as a result of PSM in patients who underwent NPWT irrespective of the presence of MRSA infection.

CONCLUSION

MRSA infection was an independent risk factor for PSM-related in-hospital mortality. NPWT may improve the prognosis for patients with MRSA mediastinitis.

Mediastinitis in pediatric cardiac surgery: Prevention, diagnosis and treatment

In spite of advances in the management of mediastinitis following sternotomy, mediastinitis is still associated with significant morbidity. The prognosis is much better in pediatric surgery compared to adult surgery, but the prolonged hospital stays with intravenous therapy and frequent required dressing changes that occur with several therapeutic approaches are poorly tolerated. Prevention includes nasal decontamination, skin preparation, antibioprophylaxis and air filtration in the operating theater. The expertise of the surgical team is an additional factor that is difficult to assess precisely. Diagnosis is often very simple, being made on the basis of a septic state with wound modification, while retrosternal puncture and CT scan are rarely useful. Treatment of mediastinitis following sternotomy is always a combination of surgical debridement and antibiotic therapy. Continued use of numerous surgical techniques demonstrates that there is no consensus and the best treatment has yet to be determined. However, we suggest that a primary sternal closure is the best surgical option for pediatric patients. We propose a simple technique with high-vacuum Redon's catheter drainage that allows early mobilization and short term antibiotherapy, which thus decreases physiological and psychological trauma for patients and families. We have demonstrated the efficiency of this technique, which is also cost-effective by decreasing intensive care and hospital stay durations, in a large group of patients.

Methicillin and Vancomycin Resistant S. aureus in Hospitalized Patients

S. aureus is the major bacterial cause of skin, soft tissue and bone infections, and one of the commonest causes of healthcare-associated bacteremia. Hospital-associated methicillin-resistant S. aureus (MRSA) carriage is associated with an increased risk of infection, morbidity and mortality. Screening of high-risk patients at the time of hospital admission and decolonization has proved to be an important factor in an effort to reduce nosocomial transmission. The electronic database Pub Med was searched for all the articles on "Establishment of MRSA and the emergence of vancomycin-resistant S. aureus (VRSA)." The search included case reports, case series and reviews. All the articles were cross-referenced to search for any more available articles. A total of 88 references were obtained. The studies showed a steady increase in the number of vancomycin-intermediate and vancomycin-resistant S. aureus. Extensive use of vancomycin creates a selective pressure that favors the outgrowth of rare, vancomycin-resistant clones leading to heterogenous vancomycin intermediate S. aureus hVISA clones, and eventually, with continued exposure, to a uniform population of vancomycin-intermediate S. aureus (VISA) clones. However, the criteria for identifying hVISA strains have not been standardized, complicating any determination of their clinical significance and role in treatment failures. The spread of MRSA from the hospital to the community, coupled with the emergence of VISA and VRSA, has become major concern among healthcare providers. Infection-control measures, reliable laboratory screening for resistance, appropriate antibiotic prescribing practices and avoidance of blanket treatment can prevent long-term emergence of resistance.

Characteristics and outcomes of methicillin-resistant Staphylococcus aureus surgical-site infections in patients with cancer: a case-control study

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) infections remain a significant cause of morbidity and mortality. We experienced an increased incidence of MRSA surgical-site infections (MRSA SSIs) at our institution. However, to our knowledge, no studies have evaluated the risk factors and outcomes of MRSA SSIs in cancer patients.

METHODS

We conducted a case-control study and identified all patients who had developed MRSA SSIs at our institution from July 1, 2002 to July 30, 2003, and all patients who had undergone surgery by the same surgical team during the same time period but who had not developed MRSA SSIs. Cases and controls were age-matched at 1:2 ratio.

RESULTS

The study included 29 cases and 58 controls. Mean interval between surgery and MRSA SSI onset was 17.8 days (range 3-75 days). Cases were more likely than controls to have progressive cancer (72 versus 38%), have received antibiotics (mainly quinolones) within 24 h of surgery (17 versus 2%), have had ongoing infection (10 versus 0%), and have had longer hospital and intensive care unit stays (11.0 versus 7.8 days and 3.4 versus 1.5 days) (all P < 0.05). In a multivariate logistic regression analysis, significant predictors of MRSA SSI in cancer patients were antibiotics use <24 h of surgery and progressive cancer. No surgical factors (i.e., procedure time or timing of perioperative antibiotics) were associated with increased risk of MRSA SSI.

CONCLUSIONS

Several clinical and postoperative factors were associated with increased risk of MRSA SSI in cancer patients, but antibiotic use before surgery (especially quinolones) and progressive cancer were the only independent predictors.

Clinical and financial outcomes due to methicillin resistant Staphylococcus aureus surgical site infection: a multi-center matched outcomes study

BACKGROUND

The clinical and financial outcomes of SSIs directly attributable to MRSA and methicillin-resistance are largely uncharacterized. Previously published data have provided conflicting conclusions.

METHODOLOGY

We conducted a multi-center matched outcomes study of 659 surgical patients. Patients with SSI due to MRSA were compared with two groups: matched uninfected control patients and patients with SSI due to MSSA. Four outcomes were analyzed for the 90-day period following diagnosis of the SSI: mortality, readmission, duration of hospitalization, and hospital charges. Attributable outcomes were determined by logistic and linear regression.

PRINCIPAL FINDINGS

In total, 150 patients with SSI due to MRSA were compared to 231 uninfected controls and 128 patients with SSI due to MSSA. SSI due to MRSA was independently predictive of readmission within 90 days (OR = 35.0, 95% CI 17.3-70.7), death within 90 days (OR = 7.27, 95% CI 2.83-18.7), and led to 23 days (95% CI 19.7-26.3) of additional hospitalization and $61,681 (95% 23,352-100,011) of additional charges compared with uninfected controls. Methicillin-resistance was not independently associated with increased mortality (OR = 1.72, 95% CI 0.70-4.20) nor likelihood of readmission (OR = 0.43, 95% CI 0.21-0.89) but was associated with 5.5 days (95% CI 1.97-9.11) of additional hospitalization and $24,113 (95% 4,521-43,704) of additional charges.

CONCLUSIONS/SIGNIFICANCE

The attributable impact of S. aureus and methicillin-resistance on outcomes of surgical patients is substantial. Preventing a single case of SSI due to MRSA can save hospitals as much as $60,000.

Treatments for skin and soft-tissue and surgical site infections due to MDR Gram-positive bacteria

Gram-positive aerobes are the most common organisms in hospitalized patients with skin and soft-tissue infections (SSTIs). Staphylococcus aureus is the most common Gram-positive aerobe among these infections with methicillin-resistant S. aureus (MRSA) the most common pathogen. The increased prevalence of MRSA has been noted in the hospital as well in the community setting. In choosing antimicrobial therapy, assessment of the infection and patient characteristics, such as animal exposure, travel history, underlying diseases, recent trauma, bites, burns, and water exposure, must be considered. Community-acquired MRSA strains are showing resistance to more antimicrobial classes, and b-lactam antibiotics can no longer be considered first-line therapy for community-acquired SSTIs. For more serious infections, there are several new antimicrobial options with good MRSA coverage, including linezolid, daptomycin, and tigecycline. Several agents are currently under clinical investigation or are being considered for approval by the US Food and Drug Administration, including ceftobiprole, dalbavancin, iclaprim, oritavancin, and telavancin.

Update: Methicillin-resistant Staphylococcus aureus screening and decolonization in cardiac surgery

Methicillin-resistant Staphylococcus aureus (MRSA) has become a concerning multidrug-resistant organism, expanding further outside the hospital setting. Cardiothoracic surgery patients are at an increased risk for mediastinitis and other surgical site infections, which may be further complicated by MRSA. To reduce MRSA surgical site infections, multidisciplinary active surveillance should be implemented in at least high-risk patients, incorporating basic infection control practices, appropriate antibiotic prophylaxis, and decolonization. This article will review the various guidelines, addressing the role of MRSA active surveillance in cardiothoracic surgery, and provide guidance for cardiothoracic surgeons.

Epidemiology of deep sternal wound infection in cardiac surgery

OBJECTIVES

The aim of this study was to investigate the incidence and predictors of deep sternal wound infection (DSWI) in a contemporary cohort of patients undergoing cardiac surgery. The early and late outcomes of patients with this complication also were analyzed.

DESIGN

A retrospective study of consecutive patients undergoing cardiac surgery using a computerized database based on the New York State Department of Health registry. Data collection was performed prospectively.

SETTING

A university hospital (single institution).

PARTICIPANTS

Five thousand seven hundred ninety-eight patients who underwent cardiac surgery between January 1998 and December 2005 including isolated coronary artery bypass graft (CABG) (n = 2,749, 47%), single- or multiple-valve surgery (n = 1,280, 22%), combined valve and CABG procedures (n = 934, 16%), and surgery involving the ascending aorta or the aortic arch (n = 835, 15%).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The overall incidence of DSWI was 1.8% (n = 106). The highest rate of DSWI occurred after combined valve/CABG surgery (2.4%, n = 22) and aortic procedures (2.4%, n = 19). Multivariate analysis revealed 11 predictors of DSWI: obesity (odds ratio [OR] = 2.2), previous myocardial infarction (OR = 2.1), diabetes (OR = 1.7), chronic obstructive pulmonary disease (OR = 2.3), preoperative length of stay >3 days (OR = 1.9), aortic calcification (OR = 2.7), aortic surgery (OR = 2.4), combined valve/CABG procedures (OR = 1.9), cardiopulmonary bypass time (OR = 1.8), re-exploration for bleeding (OR = 6.3), and respiratory failure (OR = 3.2). The mortality rate was 14.2% (n = 15) versus 3.6% (n = 205) in the control group (p < 0.001). One- and 5-year survival after DSWI were significantly decreased (72.4% +/- 4.4% and 55.8% +/- 5.6% v 93.8% +/- 0.3% and 82.0% +/- 0.6%, p < 0.001).

CONCLUSION

DSWI remains a rare but devastating complication and is associated with significant comorbidity, increased hospital mortality, and reduced long-term survival.

Staphylococcal surgical site infections

Staphylococcus aureus is the leading cause of surgical site infections (SSI) in the United States. In particular, SSI caused by methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a devastating complication, leading to increased mortality rates, increased length of hospitalization, and increased costs. Proven strategies for prevention of SSI caused by S aureus include addressing modifiable risk factors and correct choice and timing of antimicrobial prophylaxis. Other strategies, including decolonization and the use of vancomycin, remain controversial.

Overcrowding and understaffing in modern health-care systems: key determinants in meticillin-resistant Staphylococcus aureus transmission

Recent decades have seen the global emergence of meticillin-resistant Staphylococcus aureus (MRSA), causing substantial health and economic burdens on patients and health-care systems. This epidemic has occurred at the same time that policies promoting higher patient throughput in hospitals have led to many services operating at, or near, full capacity. A result has been limited ability to scale services according to fluctuations in patient admissions and available staff, and hospital overcrowding and understaffing. Overcrowding and understaffing lead to failure of MRSA control programmes via decreased health-care worker hand-hygiene compliance, increased movement of patients and staff between hospital wards, decreased levels of cohorting, and overburdening of screening and isolation facilities. In turn, a high MRSA incidence leads to increased inpatient length of stay and bed blocking, exacerbating overcrowding and leading to a vicious cycle characterised by further infection control failure. Future decision making should use epidemiological and economic evidence to evaluate the effect of systems changes on the incidence of MRSA infection and other adverse events.

Pharmacoeconomic analysis of microbiologic techniques for differentiating staphylococci directly from blood culture bottles

Differentiating staphylococci in blood cultures is a critical issue, particularly when only one of two cultures is positive by Gram staining for staphylococci. New tests for the identification of Staphylococcus aureus allow faster results and definitive treatment compared to the tube coagulase test interpreted at 24 h (TCT24). These newer tests, peptide nucleic acid fluorescence in situ hybridization (PNA-FISH) and real-time PCR (RT-PCR), offer improved sensitivity at higher cost. Data suggest that the tube coagulase test may be interpreted at 4 h (TCT4) with little loss of sensitivity. The impact of variability in turnaround time, sensitivity, specificity, and cost on comparative cost-effectiveness is unknown. Our aim was to establish the cost-effectiveness of TCT24, PNA-FISH, RT-PCR, and TCT4 for direct identification of staphylococci in blood cultures. Decision analysis comparing these strategies was done from the institutional perspective. Besides test variables, other variables included patient risk factors, empirical treatment, and follow-up cultures. Probability and cost estimates came from the literature and institutional data. Base case estimates were derived from institutional rates of 73% contamination when coagulase-negative staphylococci were identified, 67.6% prevalence of risk factors, and 12.4% prevalence of S. aureus when one of two cultures yielded staphylococci. Sensitivity analysis was done across a range of probabilities and costs. In the base case, TCT4 and TCT24 were more cost-effective than RT-PCR and PNA-FISH ($78 versus $120 versus $165 per patient, respectively). The advantage of TCT4 and TCT24 remained robust upon sensitivity analysis. TCT4 should be further evaluated as a rapid, cost-effective means for identification of S. aureus in blood cultures.

Pectoralis major-rectus abdominis bipedicled muscle flap in the treatment of poststernotomy mediastinitis

OBJECTIVES

Although the incidence of infected sternotomy wounds after median sternotomy for cardiovascular surgery is relatively low (0.5% to 5%), it is associated with significant morbidity and a long period of treatment. Today, muscle flaps, such as the pectoralis major or the rectus abdominis, are widely accepted as a mainstay of reconstructive options. Each method carries unavoidable limitations and setbacks of its own. To overcome the disadvantages of the pectoralis muscle and rectus abdominis muscle flaps, we designed and performed a pectoralis major-rectus abdominis muscle bipedicled flap for the coverage of sternal defects.

METHODS

The pectoralis major-rectus abdominis bipedicled flap was elevated as a single unit, preserving the thoracoepigastric fascia in continuity with the rectus muscle and its anterior fascia. The method was used in 27 patients with postoperative mediastinitis during a 5-year period.

RESULTS

The bipedicled flap could fill the defect with sufficient volume, not only in the upper two thirds but also in the lower one third of the sternum. Recurrent uncontrolled infection developed in 11% of all cases, and upper abdominal fascial attenuation was observed in 1 patient. There were no surgical intervention-related complications or deaths.

CONCLUSIONS

We conclude that pectoralis major-rectus abdominis bipedicled flap is a practical and efficacious method in the reconstruction of the anterior chest wall defect caused by poststernotomy mediastinitis. It not only provides sufficient volume to fill the entire mediastinum but also affords resolution of the infected wound with favorable outcomes comparable with those of other methods.

Are there better methods of monitoring MRSA control than bacteraemia surveillance? An observational database study

BACKGROUND

Despite a substantial burden of non-bacteraemic methicillin resistant Staphylococcus aureus (MRSA) disease, most MRSA surveillance schemes are based on bacteraemias. Using bacteraemia as an outcome, trends at hospital level are difficult to discern, due to random variation. We investigated rates of nosocomial bacteraemic and non-bacteraemic MRSA infection as surveillance outcomes.

METHODS AND FINDINGS

We used microbiology and patient administration system data from an Oxford hospital to estimate monthly rates of first nosocomial MRSA bacteraemia, and nosocomial MRSA isolation from blood/respiratory/sterile site specimens ("sterile sites") or all clinical samples (screens excluded) in all patients admitted from the community for at least 2 days between April 1998 and June 2006. During this period there were 441 nosocomial MRSA bacteraemias, 1464 MRSA isolations from sterile sites, and 3450 isolations from clinical specimens (8% blood, 15% sterile site, 10% respiratory, 59% surface swabs, 8% urine) in over 2.6 million patient-days. The ratio of bacteraemias to sterile site and all clinical isolations was similar over this period (around 3 and 8-fold lower respectively), during which rates of nosocomial MRSA bacteraemia increased by 27% per year to July 2003 before decreasing by 18% per year thereafter (heterogeneity p<0.001). Trends in sterile site and all clinical isolations were similar. Notably, a change in rate of all clinical MRSA isolations in December 2002 could first be detected with conventional statistical significance by August 2003 (p = 0.03). In contrast, when monitoring MRSA bacteraemia, identification of probable changes in trend took longer, first achieving p<0.05 in July 2004.

CONCLUSIONS

MRSA isolation from all sites of suspected infection, including bacteraemic and non-bacteraemic isolation, is a potential new surveillance method for MRSA control. It occurs about 8 times more frequently than bacteraemia, allowing robust statistical determination of changing rates over substantially shorter times or smaller areas than using bacteraemia as an outcome.

Interrupted time series analysis of vancomycin compared to cefuroxime for surgical prophylaxis in patients undergoing cardiac surgery

The increased incidence of methicillin-resistant Staphylococcus aureus (MRSA), the emergence of community-acquired MRSA, and the continued high incidence of methicillin-resistant Staphylococcus epidermidis have required that certain institutions choose vancomycin for surgical prophylaxis. However, the data supporting the use of vancomycin for surgical prophylaxis are controversial. The purpose of this project was to assess the effect of the change from cefuroxime to vancomycin for surgical site infection (SSI) rates in patients undergoing coronary artery bypass graft (CABG) surgery. The monthly rates of SSIs from 2001 to 2005 were analyzed before and after a change from cefuroxime to vancomycin antibiotic prophylaxis in patients undergoing CABG by using an interrupted time series analysis. Patients who underwent cardiac valve replacement surgery and who had received vancomycin during the entire study period were used as a comparator group. A total of 6,465 patients underwent CABG surgery (n = 4,239) or valve replacement surgery (n = 2,226) during the study period. On average, the monthly SSI incidence rate in patients undergoing CABG surgery decreased by 2.1 cases per 100 surgeries after the switch from cefuroxime to vancomycin (P = 0.042) when patients undergoing valve replacement were used as a comparator group. The change in SSI rates was associated with a decrease in the incidence of infections caused by coagulase-negative Staphylococcus and MRSA isolates, with little change in the incidence of SSIs due to other gram-positive organisms or gram-negative organisms. In institutions with a high incidence of methicillin-resistant Staphylococcus species, this study provides evidence for the clinical efficacy of vancomycin prophylaxis for the prevention of postoperative SSIs in patients undergoing CABG surgery.

Vancomycin for treatment of invasive, multi-drug resistant Staphylococcus aureus infections

Staphylococcus aureus is a bacterial pathogen responsible for a variety of serious infections and is a frequent cause of nosocomial disease. During the last 60 years, S. aureus has developed increasing in vitro resistance to virtually all antimicrobials. In contrast, vancomycin has maintained a high degree of activity in vitro against this pathogen, although slight changes with in vitro activity could vastly change clinical activity. As a result, vancomycin has become the mainstay of therapy for invasive infections due to methicillin-resistant strains. However, clinical strains of S. aureus with intermediate resistance to vancomycin were reported in 1996, followed in 2002 with reports of isolates that were fully resistant. Although many authorities believe vancomycin remains the drug of choice for most staphylococcal-resistant infections, important issues surrounding its clinical application remain. These include the need for multiple daily dosing, intravenous administration, requirements for serum concentration monitoring, increasing resistance in vitro, modest efficacy rates and (less frequently) treatment-limiting adverse effects. This review addresses these important topics.

Increase in the rate of sternal surgical site infection after coronary artery bypass graft: a marker of higher severity of illness

OBJECTIVE

To evaluate factors related to a gradual rise in sternal surgical site infection (SSI) rates.

DESIGN

Retrospective cohort study.

SETTING

A 608-bed, tertiary care teaching hospital.

PATIENTS

All patients who underwent coronary artery bypass graft (CABG) from January 2000 through September 2004.

RESULTS

Of 3,578 patients who underwent CABG, 144 (4%) had sternal SSI. There was an increase in infection rate, with a marked reduction in the number of operations per year. The percentage of patients with peripheral vascular disease increased from 12% to 24.3% (P<.001), and the percentage with congestive heart failure increased from 17% to 22% (P<.001). Between 2002 and 2004, the mean duration of surgery increased from 233 to 290 minutes (P<.001), the percentage of patients with a National Nosocomial Infections Surveillance System (NNIS) risk index of 2 increased from 14.3% to 38% (P<.001), and the percentage of patients with a postoperative stay in the intensive care unit of greater than 72 hours increased from 29% to 40.6% (P<.001). Multivariate analysis showed diabetes mellitus, peripheral vascular disease, obesity, duration of surgery, and postoperative stay in the intensive care unit of greater than 72 hours to be independently associated with infection.

CONCLUSIONS

An increase in infection in the CABG population not associated with an outbreak may be a reflection of a change in the severity of illness. Preoperative, intraoperative, and postoperative markers for increased infection risk may be used, in addition to the NNIS risk index, to assess the patient population risk.

Risk factors for 1-year mortality after postoperative mediastinitis

OBJECTIVE

Postoperative mediastinitis after median sternotomy is associated with disability and mortality. The aim of this study was to identify risk factors for mortality 1 year after postoperative mediastinitis diagnosis.

METHODS

Postoperative mediastinitis was defined as an organ-space infection involving the mediastinum and necessitating debridement. A total of 183 cases of postoperative mediastinitis were prospectively identified from infection control databases. By using univariate and multivariate analysis, clinical risk factors for 1-year mortality were identified.

RESULTS

Of 183 patients, 36 (19.7%) died within 3 months of the initial operation. Overall, 51 (33%) died during the study period (the median time to death from the date of diagnosis was 37 days [interquartile range, 11,139 days]). In multivariate analysis, independent predictors of 1-year mortality were a greater than 3-day delay in sternal closure after debridement (hazard ratio, 6.27; P < .001), age greater than 65 years (hazard ratio, 2.29; P = .015), serum creatinine level greater than 2 mg/dL before debridement (hazard ratio, 2.52; P = .019), stay in an intensive care unit before sternal debridement (hazard ratio, 5.56; P < .001), and postoperative mediastinitis due to methicillin-resistant Staphylococcus aureus (hazard ratio, 2.13; P = .02). Treatment with antibiotics with in vitro activity against the infecting pathogen within 7 days of initial debridement was associated with a decreased risk for mortality (hazard ratio, 0.40; P = .03).

CONCLUSIONS

Our data suggest that, to improve long-term survival, patients with postoperative mediastinitis should undergo sternal closure within 72 hours after sternal debridement and should receive effective antimicrobial therapy based on operative culture results.

Dalbavancin: A Novel Lipoglycopeptide Antibacterial

Dalbavancin is a new lipoglycopeptide antibacterial possessing in vitro activity against a variety of gram-positive pathogens. Against methicillin-susceptible and methicillin-resistant Staphylococcus aureus, it has demonstrated favorable minimum inhibitory concentration ranges compared with those of currently available agents. Dalbavancin is highly protein bound (> 90%), which may contribute to its prolonged half-life of 149-300 hours. Because of this long half-life, once-weekly dosing strategies have been used in clinical trials. Efficacy and tolerability have been demonstrated in a wide variety of animal infection models. Clinical success and safety have been shown in phase II and III trials for skin and soft-tissue infections and a phase II trial for catheter-related bloodstream infections. In these trials with vancomycin, linezolid, and various beta-lactams as comparators, comparable results have been reported. The results of further phase III trials are anxiously awaited and will more clearly define the clinical role of this novel agent.