The Impact of Methicillin Resistance on the Outcome of Poststernotomy Mediastinitis Due toStaphylococcus aureus

Antibiotic therapy in reconstructive surgery of deep sternal wound infections

BACKGROUND

The choice of antibiotics and length of administration in the treatment of deep sternal wound infections (DSWI) is unclear. The reason for this is the lack of studies and local differences in resistance. An increase in resistance can be observed in gram-positive cocci, which are the most frequently detected in deep sternal infections. The duration of administration is often 2- 6 weeks or longer, although the benefit of prolonged antibiotic administration has not been confirmed by studies. We evaluated the antibiotic treatment during surgical treatment, consisting of surgical wound debridement and plastic chest reconstruction.

METHODS

Retrospective analysis of patients (n = 260) who underwent reconstructive surgery in the Department of Plastic Surgery at Leipzig University Hospital from 01.05.2012 - 31.12.2020. The duration of intake, results of microbiological swabs and resistance were investigated.

RESULTS

At the time of discharge, closed wound conditions were noted in 177 of 260 cases (68.1%). The largest proportion of patients (n = 238) was treated with a latissimus dorsi flap (91.5%).Antibiotic treatment was conducted in 206 of 260 cases (79.2%). The mean duration of antibiotic administration was 21.4 days (±17.6). Prolonged treatment over 14 days did not alter outcome (p = 0.226), in contrast, the number of multidrug resistances (p < 0.001). There was no prove of resistance against linezolid which is effective against the most common found infectious agents Staphylococcus epidermidis (n = 93; 24.0 %) & Staphylococcus aureus (n = 47; 12.1 %).

CONCLUSION

There is no evidence of benefit from antibiotic therapy over 14 days, whereas multidrug resistance increases with prolonged antibiotic use. In the absence of infectious agents or clinical signs of inflammation, surgical treatment without additional antibiotic treatment is effective.Linezolid is a suitable antibiotic in the treatment of gram-positive infections which are the most frequent in DSWI.

[Negative pressure wound therapy for deep sternal wound infections: microbiological characteristics and antibiotic resistance]

OBJECTIVE

To evaluate bacterial flora in patients with deep sternal wound infection and the effect of negative pressure wound therapy on eradication of the pathogen.

MATERIAL AND METHODS

There were 102 patients with deep wound infection after cardiac surgery. Mean age was 66.9±9.9 years. Diabetes mellitus was detected in 21 (20.5%) cases, chronic obstructive pulmonary disease - in 15 (14.7%). Wound debridement via daily dressings was performed in 64 patients; vacuum-assisted dressings were applied in 38 patients. Bacteriological analysis of discharge was carried out every week.

Results. Mixed infection was observed in 38 (37.3%) patients. S.aureus was the most common pathogen (n=51, 50%), Gram negative bacteria were found in 36 (35.3%) patients. Negative pressure wound therapy ensured eradication of S.aureus within 3 weeks while dressings were associated with only 40% decrease of the incidence of positive analyses (p<0.05). Effectiveness of the method was not obtained for Gram negative bacteria.

CONCLUSION

Negative pressure wound therapy accelerates eradication of Gram positive pathogens but does not affect eradication of Gram negative microbes.

Current perspectives on diagnosis and management of sternal wound infections

Deep sternal wound infection (DSWI), also known as mediastinitis, is a serious and potentially fatal condition. The diagnosis and treatment of DSWI are challenging. In this current narrative review, the epidemiology, risk factors, diagnosis, and surgical and antimicrobial management of DSWI are discussed. Ideally, the management of DSWI requires early and sufficient surgical debridement and appropriate antibiotic therapy. When foreign material is present, biofilm-active antibiotic therapy is also needed. Because DSWI is often complex, the management requires the involvement of a multidisciplinary team consisting of cardiothoracic surgeons, plastic surgeons, intensivists, infectious disease specialists, and clinical microbiologists.

Deep sternal wound infection after cardiac surgery: a comparison of three different wound infection types and an analysis of antibiotic resistance

Background

Deep sternal wound infection (DSWI) is a severe complication following cardiac surgery. We compared epidemiology, clinical features, and microbiology of three types of DSWI and examined the antibiotic resistance in DSWI patients.

Methods

From 2011 to 2015, 170 adult post-cardiac surgery DSWI patients were recruited for this study and underwent the pectoralis major muscle flap transposition in our department.

Results

Of 170 adult patients with DSWI (mean age of 54 years), the majority (99 patients, 58.2%) had type II DSWI. The three types of DSWI patients showed significant differences in terms of gender, smoking history, chronic obstructive pulmonary disease (COPD), length of intensive care unit (ICU) stay, and hospitalization cost (P<0.05). The most common symptoms of DSWI patients were fever and wound dehiscence accompanied by purulent secretions. Types I and II DSWI were more frequently associated with hypoproteinemia and high leucocyte count (P<0.05). Microbiological diagnosis was available for 77 of 170 patients (45.3%). Of 157 pathogens detected, 87 (55.4%) species of gram negative bacilli were identified and most commonly were Pseudomonas aeruginosa (25.5%) and methicillin-susceptible Staphylococcus aureus (20.4%). However, no statistically significant microbiological differences among the three DSWI types were observed (P>0.05). Notably, P. aeruginosa isolates showed 100% resistance to cefazolin and cefuroxime. Meanwhile, the resistance rate of Acinetobacter baumannii isolates to commonly used antibiotics was greater than 70%, while resistance rates of staphylococcus to penicillin-G were 100% and to clindamycin were over 70%. No isolates were resistant to vancomycin, linezolid, and tigecycline.

Conclusions

Three types of DSWI exhibit differences in epidemiology and clinical features. P. aeruginosa and S. aureus are the most common pathogens in DSWI patients and antibiotic resistance is a serious concern in these patients. Therefore, prevention and treatment of DSWI should be closely tailored to clinical features, local microbiological characteristics, and resistance patterns of commonly encountered pathogens.

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.

Diagnostic value of ⁹⁹mTc-HMPAO-labeled leukocytes scintigraphy in suspicion of post-sternotomy mediastinitis relapse

BACKGROUND

The diagnostic value of radiolabeled white blood cells (WBCs) scintigraphy in mediastinitis is well established, but data in the specific context of relapse are lacking. The present study aimed at evaluation of the diagnostic value of WBCs scintigraphy in suspicion of mediastinitis relapse after prior surgical revision.

METHODS AND RESULTS

Multiple planar incidences of the chest were acquired 4 and 20 hours after injection of labeled WBC in 43 patients. In case of non-conclusive scintigraphy, a second scan was performed 2-3 weeks after the first one. The diagnosis of infection was based on positive bacteriological results; otherwise patients were followed up for at least 1 year. Out of 39 analyzable patients, 17 (44%) were diagnosed with mediastinitis relapse. After the first scan, 32 of 39 were correctly classified, 2 were false positive, and 5 were not conclusive. After completion of an additional scan in the latter 5 patients, 36 of 39 were correctly classified and 3 were false positive (100% sensitivity, 86% specificity, 85% positive predictive value, and 100% negative predictive value).

CONCLUSIONS

In the specific context of suspicion of mediastinitis relapse, the optimal diagnostic value was achieved by repeating the scan when the first one was not conclusive. In this context, a negative WBC scintigraphy was able to rule out infection, with potential major impact on therapeutic management in patients with poor clinical status.

Combined Therapy of Teicoplanin and Caffeic Acid Phenethyl Ester (CAPE) in the Treatment of Experimental Mediastinitis in the Rat

Post-sternotomy mediastinitis affects 1-3% of patients undergoing cardiac surgery and is lethal in 10-47% of these patients. We investigated the effect of an antioxidant/anti-inflammatory agent, caffeic acid phenethyl ester (CAPE), in the attenuation of inflammatory response induced by methicillin-resistant Staphylococcus aureus (MRSA) infection in a rat experimental mediastinitis model. Rats, divided into six equal groups, received MRSA precolonized stainless steel wire pieces implanted into their mediastinal spaces. Control group and CAPE control group received saline and CAPE 10 micromol/kg.day(-1 )respectively, where Group A received a single dose of teicoplanin 24 mg/kg i.m. for the first day and then 12 mg/kg.day(-1) . Group B received teicoplanin as in Group A plus CAPE 10 micromol/kg. day(-1 )intra-peritoneally. Group C received teicoplanin 60 mg/kg i.m. for the first day and then 30 mg/kg.day(-1 )and Group D received teicoplanin as in Group C plus CAPE 10 micromol/kg.day(-1) . By the end of 14 days rats were sacrificed and serum malondialdehyde (MDA), myeloperoxidase (MPO), nitric oxide (NO), urea and creatinine levels were evaluated. Mediastinal organ tissues were collected for histopathological analysis. Infection rates in all the drug-treated groups were lower than the control groups ( P=0.002) but statistical significance was attained only between the groups A and D ( P=0.018). In connective tissues and the peribronchial area polymorphonuclear leukocytic (PNL) infiltration in the treatment groups, although becoming very close, did not reach statistical significance (P =0.053, P=0.075, respectively). PNL infiltration especially in the peribronchial tissues of the Group B animals was found to be significantly less than the Control and CAPE Control groups with P values of 0.013 and 0.010, respectively. MDA and MPO levels were significantly lower in the treatment groups ( P<0.001 and P<0.001 respectively). Levels of the degradation products of NO were lower in treatment groups compared to two control groups (P=0.003, P= 0.005). NO levels in Group D were lowest among all treatment groups ( P=0.001). It has been demonstrated that although bacterial colonization can be controlled in mediastinitis, the inflammatory response persists. The combination of an antioxidant / anti-inflammatory agent, CAPE, added to standard antibiotic therapy might be effective in the treatment of post-sternotomy mediastinitis due to MRSA.

Nosocomial infections in adult cardiogenic shock patients supported by venoarterial extracorporeal membrane oxygenation

BACKGROUND

Incidence and impact on adult patients' outcomes of nosocomial infections (NIs) occurring during venoarterial extracorporeal membrane oxygenation (VA-ECMO) support for refractory cardiogenic shock have rarely been described.

METHODS

We retrospectively reviewed the charts of a large series of patients who received VA-ECMO in our intensive care unit (ICU) from January 2003 through December 2009. Incidence, types, risk factors, and impact on outcomes of NIs occurring during ECMO support were analyzed.

RESULTS

Among 220 patients (49 ± 16 years old, simplified acute physiology score (SAPS) II 61 ± 20) who underwent ECMO support for >48 hours for a total of 2942 ECMO days, 142 (64%) developed NIs. Ventilator-associated pneumonia (VAP), bloodstream infections, cannula infections, and mediastinitis infections occurred in 55%, 18%, 10% and 11% of the patients, respectively. More critical condition at ICU admission, but not antibiotics at the time of ECMO cannulation, was associated with subsequently developing NIs (hazard ratio, 0.73; 95% confidence interval [CI], .50-1.05; P = .09). Infected patients had longer durations of mechanical ventilation, ECMO support, and hospital stays. Independent predictors of death were infection with severe sepsis or septic shock (odds ratio, 1.93; 95% CI, 1.26-2.94; P = .002) and SAPS II, whereas immunosuppression and myocarditis as the reason for ECMO support were associated with better outcomes.

CONCLUSIONS

Cardiogenic shock patients who received the latest generation VA-ECMO still had a high risk of developing NIs, particularly VAP. Strategies aimed at preventing these infections may improve the outcomes of these critically ill patients.

Inadequate antibiotic therapy in solid organ transplant recipients is associated with a higher mortality rate

BACKGROUND

Inadequate antibiotic therapy and failure to administer antibiotics in a timely fashion have been associated with substantial mortality rates in patients in the intensive care unit (ICU). We analyzed the infection pattern in solid organ transplant recipients as well as the impact of antibiotic resistance and inadequate antibiotic treatment on mortality rates and morbidity outcomes.

METHODS

Charts of adult solid organ transplant recipients in 2006 from a single institution were reviewed. Data on patients with bacterial and fungal infections acquired within one year after transplantation were compared with the primary outcome of death within 28 days. Statistical analysis included nonparametric tests (Wilcoxon rank sum, Fisher exact, and chi-square) and multivariable logistic regression with p < 0.05 considered significant.

RESULTS

Of the 366 patients, 114 (31%) had a total of 208 bacterial or fungal infections, and 44 of them (39%) were admitted to the ICU. Our primary endpoint, the 28-day mortality rate, was 8% overall, whereas the six-month mortality rate was 11%. Patients treated inadequately with antibiotics had a significantly higher mortality rate. The leading causes of infection were multiple organisms, coagulase-negative Staphylococcus, and E. coli, of which 76% were resistant to antibiotics. Antibiotic-resistant infections were associated with longer hospital stays (p = 0.04), intravenous antibiotic use prior to infection (p = 0.04), nucleotide synthesis inhibitor use (p = 0.02), ICU admission (p < 0.01), and respiratory failure (p = 0.03). Most infections were treated inadequately initially (69%) but treated adequately at 24 h (56%). Inadequate antibiotic treatment was significantly associated with younger age (p = 0.04), prior intravenous antibiotic use (p = 0.04), longer stay prior to infection (p = 0.05), and cardiovascular shock (p = 0.014). Inadequate antibiotic therapy at 24 h was associated with a higher mortality rate (14% vs. 2%; p = 0.03) and a trend toward longer ICU and in-hospital stays.

CONCLUSIONS

Most bacterial and fungal infections were resistant to antibiotics and were treated inadequately initially. Prior intravenous antibiotic use and longer stay prior to infection were associated with antibiotic resistance and inadequate antibiotic therapy. Failure to provide adequate antibiotic treatment within 24 h had a significant impact on the 28-day mortality rate and was associated with other detrimental clinical outcomes.

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.

Endogenous endophthalmitis caused by methicillin-resistant Staphylococcus aureus (MRSA)

PURPOSE

To report clinical features, diagnostic features, and outcome in three patients presenting with fulminant endogenous endophthalmitis caused by methicillin-resistant Staphylococcus aureus.

METHODS

Retrospective review of clinical data and microbiological findings in three cases.

RESULTS

All three patients had predisposing conditions for endogenous endophthalmitis (B-cell lymphoma, diabetes mellitus, steroid therapy, or gastrointestinal symptoms, such as vomiting and diarrhea). Two patients were colonized by methicillin-resistant Staphylococcus aureus in typical sites (nose, groin, throat, and conjunctiva), whereas one patient who developed phlebitis at the infusion puncture site followed by bacteremia presented no typical colonization. Despite adequate therapy, two patients lost visual function in the infected eye, one of which had to be enucleated. The other patient's eye regained adequate function.

CONCLUSION

Endogenous endophthalmitis by methicillin-resistant Staphylococcus aureus is a rare but serious condition. Early and specific therapy based on reliable detection of the underlying microorganism may help in preventing loss of visual function.

Community-associated methicillin-resistant Staphylococcus aureus mediastinitis

Community-associated methicillin (meticillin)-resistant Staphylococcus aureus (CA-MRSA) continues to emerge as a cause of serious infections, chiefly of the skin and soft tissues. We present the first documented case of CA-MRSA mediastinitis in an adult. Blood and mediastinal isolates were characterized as CA-MRSA by pulsed-field gel electrophoresis and susceptibility testing.

Risk factors for infective endocarditis and outcome of patients with Staphylococcus aureus bacteremia

OBJECTIVE

To investigate the risk factors for Staphylococcus aureus infective endocarditis (SAIE) and 6-month mortality in patients with S aureus bacteremia (SAB).

PATIENTS AND METHODS

This study consisted of patients who were diagnosed as having nosocomial or community-acquired SAB or SAIE between June 1, 2000, and December 31, 2005. Clinical characteristics of patients with SAB were compared with those of patients with SAIE, and predictors of mortality in patients with SAB were analyzed.

RESULTS

The median age of the 132 randomly selected patients with SAB and the 66 patients with SAIE was 66 and 68 years, respectively. Univariable analysis showed that unknown origin of SAB, a valvular prosthesis, a pacemaker, persistent fever, and persistent bacteremia were significantly associated with SAIE. In multivariable analysis, unknown origin of SAB (odds ratio [OR], 4.2; 95% confidence interval [CI], 1.9-9.3; P=.001), a valvular prosthesis (OR, 9.2; 95% CI, 3.2-26.2; P<.001), persistent fever (OR, 3.1; 95% CI, 1.0-9.0; P=.04), and persistent bacteremia (OR, 6.8; 95% CI, 2.3-20.2- P=.001) were independently associated with SAIE. Six- month mortality was 8% in patients with SAB vs 35% in patients with SAIE (OR, 6.5; 95% CI, 2.9- 14.8; P<.001). In univariable analysis, methicillin- resistant S aureus (OR, 7.2; 95% CI, 1.7 - 29.4; P=.005) was significantly associated with 6-month mortality in patients with SAB.

CONCLUSION

Unknown origin of SAB, a valvular prosthesis, persistent fever, and persistent bacteremia were independently associated with SAIE in patients with SAB. In univariable analysis, methicillin-resistant S aureus was associated with 6-month mortality in patients with SAB. S aureus infective endocarditis had a significantly higher mortality than SAB. The optimal management of SAB and SAIE deserves further study.

Staphylococcus aureus poststernotomy mediastinitis: description of two distinct acquisition pathways with different potential preventive approaches

OBJECTIVE

Determining the acquisition routes of infection is crucial to designing specific preventive approaches against Staphylococcus aureus poststernotomy mediastinitis.

METHODS

From 2002 to 2004, a nasal sample was obtained from patients before cardiac surgery. We collected clinical and microbiologic data of all episodes of S aureus poststernotomy mediastinitis. A case-control study (3:1) was performed to confirm the role of previous preoperative nasal colonization by S aureus as a risk factor for S aureus poststernotomy mediastinitis. Pulsed field gel electrophoresis molecular analysis of nasal and surgical site S aureus isolates was performed to analyze their relatedness in each patient with poststernotomy mediastinitis and with other patients of the study cohort.

RESULTS

S aureus nasal cultures were positive in 228 (15.9%) of 1432 patients: methicillin-susceptible S aureus in 222 (15.5%) and meticillin-resistant S aureus in 6 (0.4%). S aureus poststernotomy mediastinitis was diagnosed in 17 (1.2%) of 1432 patients: 9 (3.95%) of 228 in colonized patients versus 8 (0.66%) of 1204 in noncolonized patients (P < .0001). Seven of 9 patients (1.2%) with methicillin-susceptible S aureus had an identical isolate by pulsed field gel electrophoresis in preoperative nasal and surgical-site cultures, but no clonal relatedness was shown among the isolates from these 9 patients. None of the 8 patients with methicillin-resistant S aureus poststernotomy mediastinitis had an identical isolate by pulsed field gel electrophoresis in preoperative nasal and surgical-site cultures, and the same clone of methicillin-resistant S aureus was responsible for all these cases.

CONCLUSIONS

Endogenous [corrected] nasal colonization often precedes methicillin-resistant S aureus poststernotomy mediastinitis, which suggests that preoperative [corrected] decontamination is adequate for preventing methicillin-susceptible [corrected] S aureus poststernotomy mediastinitis, whereas hospital infection control measures seem to be the major factor for preventing methicillin-resistant S aureus poststernotomy mediastinitis.

[Staphylococcus aureus nosocomial infections in critically ill patients admitted in intensive care units]

BACKGROUND AND OBJECTIVE

To investigate the frequency of nosocomial infections caused by Staphylococcus aureus in critically ill patients admitted to Spanish intensive care units (ICUs) and to describe the characteristics and outcome of patients in whom this pathogen was isolated.

PATIENTS AND METHOD

Prospective, observational, and multicenter study. All patients admitted during one or 2 months to the participating ICUs in the National Nosocomial Infection Surveillance Study (ENVIN) between 1997 and 2003 were included. Patients were classified as infected by S. aureus, infected by other microorganisms, and without nosocomial infection.

RESULTS

A total of 34,914 patients were controlled of whom 3,450 (9.9%) had acquired a nosocomial infection during his/her ICU stay (16.0 infections per 100 patients). In 682 (19.8%) patients, a total of 775 infectious episodes in which one of the microorganisms isolated was S. aureus were documented (cumulative incidence 2.2 episodes of S. aureus infection per 100 patients). There was a predominance of S. aureus infection in patients with pneumonia associated with mechanical ventilation (21.4%) and in patients with catheter-related bacteremia (13%). Independent variables associated with S. aureus infection were male sex (odds ratio [OR] = 1.25; 95% confidence interval [CI], 1.03-1.52) and underlying trauma pathology (OR = 1.72, 95%; 95%CI, 1.26-2.35), whereas an older age has been a protective factor (OR = 0.90; 95%CI, 0.84-0.96). Mortality in patients with S. aureus infection was significantly higher than in infections caused by other microorganisms, and in both cases higher than in patients without infection (34.5%, 30.3%, and 10.7%, respectively). In 208 (30.5%) patients, infections due to methicillin-resistant S. aureus were diagnosed, which in turn had increased significantly over the years (p = 0.001). Mortality in patients with methicillin-resistant S. aureus infection was 35.1% compared with 34.2% in patients with methicillin sensitive S. aureus infections (p = NS).

CONCLUSIONS

S. aureus was isolated in 19.8% of patients with ICU-acquired infection, particularly in relation to pneumonia in mechanically ventilated patients. Mortality in patients with S. aureus infection was higher than that in patients with infections due to other microorganisms and patients without infection. In contrast, differences in the outcome of patients with infections caused by methicillin-sensitive or methicillin-resistant S. aureus were not found.

Selective Digestive Tract Decontamination—Will It Prevent Infection with Multidrug-Resistant Gram-Negative Pathogens but Still Be Applicable in Institutions where Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococci Are Endemic?

The purposes of selective decontamination of the digestive tract are to treat infections that may be incubating at the time a patient is admitted to an intensive care unit (ICU), by intravenous administration of antibiotics during the first days of a stay in the ICU, and to prevent ICU-acquired infections, by topical application of antibiotics in the oropharynx and the gastrointestinal tract. Despite multiple trials in which a considerable reduction in the incidence of ventilator-associated pneumonia was demonstrated, major objections against the routine use of selective decontamination of the digestive tract have included a lack of demonstrated reductions in mortality rates and in length of stay (in individual trials), a lack of cost-efficacy data, and the threat of selection of multidrug-resistant bacteria. Recently, 2 controlled, randomized studies reported significant reductions in mortality rates among patients in ICUs who underwent selective decontamination of the digestive tract in combination with reduced selection of antibiotic-resistant pathogens. However, those studies were performed in settings where levels of antibiotic resistance are low, and some methodological issues remain unresolved. If these beneficial results are confirmed, the question of how to balance these benefits against the expected enhanced selection of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and, possibly, multidrug-resistant gram-negative bacteria will emerge.

Gram-positive cocci infections in intensive care: guide to antibacterial selection

The incidence of multiresistance in Gram-positive cocci causing infections in critically ill patients admitted to the intensive care unit (ICU) has increased notably in recent years. Thus, therapeutic proposals have been modified according to the emergence of multiresistant cocci and adapted to epidemiological markers of individual infectious processes, geographical variations of these markers, the availability of new antibacterials, and advances in the knowledge of pharmacokinetic and pharmacodynamic aspects of their use. The current management of critically ill patients should consider new therapeutic approaches, such as the "de-escalating strategy", which includes the administration of empirical antibacterials active against multiresistant pathogens followed by directed treatment based on unequivocal data from antibacterial-susceptibility testing. Optimisation of antibacterial treatment should be viewed in the context of the need to determine plasma drug concentrations, pharmacoeconomic considerations and control of drug-related adverse events. Therapeutic proposals should be developed within the framework of the antibacterial policy of each hospital. The present review is focused on the description of the therapeutic strategies for the main infectious processes caused by Gram-positive cocci in severely ill patients admitted to the ICU according to a review of the pertinent literature and the clinical experience of the authors.

[Staphylococcus aureus infections: new challenges from an old pathogen]

Staphylococcus aureus is a versatile organism with several virulent characteristics and resistance mechanisms at its disposal. It is also a significant cause of a wide range of infectious diseases in humans. S. aureus often causes life-threatening deep seated infections like bacteremia, endocarditis and pneumonia. While traditionally confined mostly to the hospital setting, methicillin-resistant S. aureus (MRSA) is now rapidly becoming rampant in the community. Community-acquired MRSA is particularly significant because of its potential for unchecked spread within households and its propensity for causing serious skin and pulmonary infections. Because of the unfavorable outcome of many MRSA infections with the standard glycopeptide therapy, new antimicrobial agents belonging to various classes have been introduced and have been evaluated in clinical trials for their efficacy in treating resistant staphylococcal infections. A number of preventive strategies have also been suggested to contain the spread of such infections. In this review, we address the recent changes in the epidemiology of S. aureus and their impact on the clinical manifestations and management of serious infections. We also discuss new treatment modalities for MRSA infections and emphasize the importance of preventive approaches.

Is Methicillin Resistance Associated with a Worse Prognosis in Staphylococcus aureus Ventilator-Associated Pneumonia?

BACKGROUND

Excess mortality associated with methicillin resistance in patients with Staphylococcus aureus ventilator-associated pneumonia (SA-VAP), taking into account such confounders as treatment adequacy and time in the intensive care unit (ICU), have not been adequately estimated.

METHODS

One hundred thirty-four episodes of SA-VAP entered in the Outcomerea database were studied. Patients from whom methicillin-resistant S. aureus (MRSA) was recovered were compared with those from whom methicillin-susceptible S. aureus (MSSA) was recovered, stratified for duration of stay in the ICU at the time of VAP diagnosis and adjusted for confounders (severity at admission, characteristics at VAP diagnosis, and treatment adequacy).

RESULTS

Treatment was adequate within 24 h after VAP diagnosis for 86% of the 65 MSSA-infected patients and 77% of the 69 MRSA-infected patients (P = .2). Polymicrobial VAP was more commonly associated with MSSA than with MRSA (49.2% vs. 25.7%; P = .01). MRSA infection was associated with a lower prevalence of coma at hospital admission and a higher rate of use of central venous lines and fluoroquinolones during the first 48 h of the ICU stay. The rates of shock, recurrence, and superinfection were similar in both groups. The crude hospital mortality rate was higher for MRSA-infected patients than for MSSA-infected patients (59.4% vs. 40%; P = .024). This difference disappeared after controlling for time in the ICU before VAP and parameters imbalanced at ICU admission (odds ratio [OR], 1.23; 95% confidence interval [CI], 0.49-3.12; P = .7) and remained unchanged after further adjustments for initial treatment adequacy and polymicrobial VAP (OR, 0.98; 95% CI, 0.36-2.66).

CONCLUSIONS

Differences in patient characteristics, initial ICU treatment, and time in the ICU confounded estimates of excess death due to MRSA VAP. After careful adjustment, methicillin resistance did not affect ICU or hospital mortality rates.

Staphylococcal post-sternotomy mediastinitis: five year audit

BACKGROUND

The reported rate of post-sternotomy mediastinitis is between 0.8 and 2.3%, with up to 79% of cases caused by staphylococci. Mediastinitis is associated with significant morbidity and mortality. Obesity and diabetes are the only risk factors consistently identified. The aims of the present study were to determine the incidence and risk factors for staphylococci post-sternotomy mediastinitis and to audit its management.

METHODS

The clinical records of patients with staphylococcal post-sternotomy mediastinitis between 1 January 1998 and 31 May 2003 were retrospectively reviewed. Information collected included patient demographics, comorbidities, operation type, microbiology findings, surgical and medical management, and outcome. Data collected on cases were compared with data collected in a prospective database of all patients undergoing cardiac surgery.

RESULTS

The incidence of staphylococcal post-sternotomy mediastinitis was 1.2% (60 cases in 5176 median sternotomies). Staphylococcus aureus was isolated in 49 (82%) cases and coagulase-negative staphylococci in 11 (18%) cases. Eight (16%) S. aureus isolates were methicillin-resistant. Risk factors associated with mediastinitis were ethnicity, diabetes mellitus, emergency surgery, ejection fraction and length of preoperative hospital stay. In-hospital mortality was 15%. Eighteen per cent of cases were not cured by initial therapy.

CONCLUSION

Staphylococcal mediastinitis is a serious complication with significant rates of relapse and mortality. This audit has lead to an evaluation of our clinical pathways to ensure that prevention and management of surgical site infection is optimized.

BLOOD NEUTROPHIL BACTERICIDAL ACTIVITY AGAINST METHICILLIN-RESISTANT AND METHICILLIN-SENSITIVE STAPHYLOCOCCUS AUREUS DURING CARDIAC SURGERY

Whether methicillin-resistant Staphylococcus aureus (MRSA) constitutes per se an independent risk factor for morbidity and mortality after surgery as compared with methicillin-sensitive Staphylococcus aureus (MSSA) remains a subject of debate. The aim of this study was to assess whether innate defenses against MRSA and MSSA strains are similarly impaired after cardiac surgery. Both intracellular (isolated neutrophil functions) and extracellular (plasma) defenses of 12 patients undergoing scheduled cardiac surgery were evaluated preoperatively (day 0) and postoperatively (day 3) against two MSSA strains with a low level of catalase secretion and two MRSA strains with a high level of catalase secretion, inasmuch as SA killing by neutrophils relies on oxygen-dependent mechanisms. After surgery, an increase in plasma concentration of IL-10, an anti-inflammatory cytokine able to inhibit reactive oxygen species secretion and bactericidal activity of neutrophils, was evidenced. Despite the fact that univariate analysis suggested a specific impairment of neutrophil functions against MRSA strains, two-way repeated-measures ANOVA failed to demonstrate that the effect of S. aureus phenotype was significant. On the other hand, an increase in type-II secretory phospholipase A2 activity, a circulating enzyme involved in SA lysis, was evidenced and was associated with an enhancement of extracellular defenses (bactericidal activity of plasma) against MRSA. Overall, cardiac surgery and S. aureus phenotype had a significant effect on plasma bactericidal activity. Cardiac surgery was characterized by enhanced antibacterial defenses of plasma, whereas neutrophil killing properties were reduced. The overall effect of S. aureus phenotype on neutrophil functions did not seem significant.

Estudio comparativo de la meningitis posquirúrgica por Staphylococcus aureus sensible y resistente a meticilina

BACKGROUND AND OBJECTIVE

In recent years, meningitis caused by methicillin-resistant S. aureus has increased. This study was undertaken to compare the clinical characteristics and prognosis of methicillin-resistant S. aureus (MRSA) postneurosurgical meningitis and methicillin-sensible S. aureus (MSSA) postneurosurgical meningitis.

PATIENTS AND METHODS

Twenty-five episodes of postneurosurgical meningitis due to S. aureus (13 methicillin-resistant strains) seen during a ten-year period were retrospectively reviewed.

RESULTS

Most common underlying diseases were: intracerebral hemorrhage (50% of MRSA patients and 46% of MSSA patients) and neoplasm (53% of MRSA patients and 33% of MSSA patients). Eleven patients (6 of them with MRSA infection) had received antibiotic treatment previously. Thirteen patients were carriers of intraventricular catheters (8 with MRSA infection), 5 wore a ventriculoperitoneal shunt (4 with infections by MSSA), 5 cases had a CSF leakage (4 with infections by MRSA), and one patient with infection by MSSA wore an epidural catheter. Fifteen patients were cured (7 with MRSA infection), and 8 died due to the infection (27% with MSSA infection and 38% with MRSA infection).

CONCLUSIONS

The prognosis of postneurosurgical meningitis by S. aureus does not depend on the presence of resistance to methicillin. Nowadays, the intravenous administration of vancomycin is the treatment of choice in MRSA meningitis.

Impact of Methicillin Resistance on Outcome ofStaphylococcus aureusVentilator-associated Pneumonia

The impact of methicillin resistance on morbidity and mortality of patients suffering from severe Staphylococcus aureus infections remains highly controversial. We analyzed a retrospective cohort of 97 patients with methicillin-susceptible and 74 patients with methicillin-resistant Staphylococcus aureus ventilator-associated pneumonia (VAP). Initial empiric antibiotic therapy was appropriate for every patient. Patients with methicillin-resistant Staphylococcus aureus VAP were older, had higher disease-severity scores, and had been on mechanical ventilation longer at onset of VAP. Factors associated with 28-day mortality retained by multivariate logistic regression analysis were: age (odds ratio [OR] = 1.05, 95% confidence interval [CI], 1.02-1.08, p = 0.001) and Day 1 organ dysfunctions or infection (ODIN) score (OR = 1.90, 95% CI, 1.31-2.78, p = 0.001), but not methicillin resistance (OR = 1.72, 95% CI, 0.73-4.05, p = 0.22). The percentages of infection relapse or superinfection did not differ significantly between the two patient groups. In conclusion, after controlling for clinical and physiologic heterogeneity between groups, methicillin resistance did not significantly affect 28-day mortality of patients with Staphylococcus aureus VAP receiving appropriate antibiotics.

Epidemiology and control of antibiotic resistance in the intensive care unit

PURPOSE OF REVIEW

Resistance to antibiotics is very high in the intensive care units of many countries, although there are several exceptions. Some infections are becoming extremely difficult to treat. The risk of cross-transmission of those strains is very high. This review focuses on recent data (2003 to the present) that may help understanding and dealing with this serious public health problem.

RECENT FINDINGS

Intensive care units can be considered as 'factories' for creating, disseminating and amplifying resistance to antibiotics, for many reasons: importation of resistant microorganisms at admission, selection of resistant strains with an extensive use of broad-spectrum antibiotics, cross-transmission of resistant strains via the hands or the environment. Some national programs can be considered as failures, as in the UK and the USA. Other countries have been able to maintain a low level of resistance (Scandinavian countries, Netherlands, Switzerland, Germany, Canada). There is clearly an 'inoculum effect' above which preventive measures become poorly efficient. Several preventive measures have been proposed including preventive isolation, systematic screening at admission, local, national or international antibiotic guidelines, antibiotic prescriptions advice by infectious-disease teams, antibiotic prevention with selective digestive decontamination, antibiotic strategies such as 'cycling', or rather, for some authors, the use of an 'à la carte' antibiotic strategy which could be considered as a 'patient-to-patient antibiotic rotation'.

SUMMARY

There is obviously an international concern regarding the level of resistance to antibiotics in the intensive-care-unit setting. A strong program including prevention of cross-transmission and better usage of antibiotics seems to be needed in order to be successful. We do not know if this kind of program will enable countries with a very high endemic level of resistance to decrease the level in future years.