Bacteremic pneumonia due to Staphylococcus aureus: A comparison of disease caused by methicillin-resistant and methicillin-susceptible organisms

[GEIPC-SEIMC (Study Group for Infections in the Critically Ill Patient of the Spanish Society for Infectious Diseases and Clinical Microbiology) and GTEI-SEMICYUC ( Working Group on Infectious Diseases of the Spanish Society of Intensive Medicine, Critical Care, and Coronary Units) recommendations for antibiotic treatment of gram-positive cocci infections in the critical patient]

In recent years, an increment of infections caused by gram-positive cocci has been documented in nosocomial and hospital-acquired-infections. In diverse countries, a rapid development of resistance to common antibiotics against gram-positive cocci has been observed. This situation is exceptional in Spain but our country might be affected in the near future. New antimicrobials active against these multi-drug resistant pathogens are nowadays available. It is essential to improve our current knowledge about pharmacokinetic properties of traditional and new antimicrobials to maximize its effectiveness and to minimize toxicity. These issues are even more important in critically ill patients because inadequate empirical therapy is associated with therapeutic failure and a poor outcome. Experts representing two scientific societies (Grupo de estudio de Infecciones en el Paciente Crítico de la SEIMC and Grupo de trabajo de Enfermedades Infecciosas de la SEMICYUC) have elaborated a consensus document based on the current scientific evidence to summarize recommendations for the treatment of serious infections caused by gram-positive cocci in critically ill patients.

Outcome of vancomycin treatment in patients with methicillin-susceptible Staphylococcus aureus bacteremia

Limited data on the clinical outcome of vancomycin treatment compared with that of beta-lactam treatment in patients with methicillin-susceptible Staphylococcus aureus bacteremia (MSSA-B) are available. We used different and complementary approaches: (i) a retrospective cohort study using a propensity score to adjust for confounding by treatment assignment and (ii) a matched case-control study. Of all patients with S. aureus bacteremia (SAB) in two university-affiliated hospitals over a 7-year period, 294 patients with MSSA-B were enrolled in the cohort study. The cases for the case-control study were defined as patients who received vancomycin treatment for MSSA-B; the controls, who were patients that received beta-lactam treatment for MSSA-B, were selected at a 1:2 (case:control) ratio according to the objective matching scoring system and the propensity score system. In the cohort study, SAB-related mortality in patients with vancomycin treatment (37%, 10/27) was significantly higher than that in those with beta-lactam treatment (18%, 47/267) (P = 0.02). In addition, multivariate analysis revealed that vancomycin treatment was associated with SAB-related mortality when independent predictors for SAB-related mortality and propensity score were considered (adjusted odds ratio of 3.3, 95% confidence interval of 1.2 to 9.5). In the case-control study using the objective matching scoring system and the propensity score system, SAB-related mortality in case patients was 37% (10/27) and in control patients 11% (6/54) (P < 0.01). Our data suggest that vancomycin is inferior to beta-lactam in the treatment of MSSA-B.

The modified APACHE II score outperforms Curb65 pneumonia severity score as a predictor of 30-day mortality in patients with methicillin-resistant Staphylococcus aureus pneumonia

OBJECTIVE

To compare the predictive accuracy for 30-day mortality of the CURB65 score adopted by the British Thoracic Society and the simpler CRB65 score to APACHE (acute physiology and chronic health evaluation) II in patients with methicillin-resistant Staphylococcus aureus (MRSA) pneumonia.

DESIGN

A retrospective, single-center, observational cohort study.

SETTING

Barnes-Jewish Hospital, a 1,200-bed urban teaching hospital.

PATIENTS

Adult patients requiring hospitalization identified to have MRSA pneumonia.

INTERVENTIONS

Retrospective data collection from automated hospital, microbiology, and pharmacy databases.

MEASUREMENTS AND MAIN RESULTS

Two hundred eighteen patients with MRSA pneumonia were identified over a 3-year period. Forty-four patients (20.2%) died during hospitalization. All three prediction rules had high negative predictive values but relatively low positive predictive values at most cut-off points examined. APACHE II had the greatest area under the receiver operating characteristic curve (0.805; 95% confidence interval [CI], 0.743 to 0.866) compared to CURB65 (0.634; 95% CI, 0.541 to 0.727) and CRB65 (0.643; 95% CI, 0.546 to 0.739) [p < 0.05 for both comparisons]. Similar results were obtained when the subgroups of community-acquired MRSA pneumonia and health-care-associated MRSA pneumonia were examined separately.

CONCLUSIONS

APACHE II outperformed CURB65 and CRB65 for initial prognostic assessment in MRSA pneumonia.

Limitations of Vancomycin in the Management of Resistant Staphylococcal Infections

Vancomycin is effective against methicillin-resistant Staphylococcus aureus and has been widely used in the past few years. However, several recent reports have highlighted the limitations of vancomycin, and its role in the management of serious infections is now being reconsidered. Vancomycin treatment failure rates are associated with an increase in the minimum inhibitory concentration as well as a decrease in the rate of bacterial killing. The intrinsic limitations of vancomycin also include poor tissue penetration, particularly in the lung; relatively slow bacterial killing; and the potential for toxicity. In addition, intermediate-level vancomycin resistance has emerged among staphylococci, as have rare cases of fully resistant strains. Because of these problems, when using vancomycin, it is probably prudent to carefully establish the diagnosis, test for antimicrobial susceptibility, and monitor serum trough concentrations to ensure adequate dosing.

Recomendaciones GEIPC-SEIMC y GTEI-SEMICYUC para el tratamiento antibiótico de infecciones por cocos grampositivos en el paciente crítico

In recent years, an increment of infections caused by gram-positive cocci has been documented in nosocomial and hospital-acquired infections. In diverse countries, a rapid development of resistance to common antibiotics against gram-positive cocci has been observed. This situation is exceptional in Spain but our country might be affected in the near future. New antimicrobials active against these multi-drug resistant pathogens are nowadays available. It is essential to improve our current knowledge about pharmacokinetic properties of traditional and new antimicrobials to maximize its effectiveness and to minimize toxicity. These issues are even more important in critically ill patients because inadequate empirical therapy is associated with therapeutic failure and a poor outcome. Experts representing two scientific societies (Grupo de estudio de Infecciones en el Paciente Critico de la SEIMC and Grupo de trabajo de Enfermedades Infecciosas de la SEMICYUC) have elaborated a consensus document based on the current scientific evidence to summarize recommendations for the treatment of serious infections caused by gram-positive cocci in critically ill patients.

Burden of methicillin-resistant Staphylococcus aureus: focus on clinical and economic outcomes

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major public concern. Hospital-acquired MRSA rates have steadily increased over the past 25 years, and the bacterial strain is making inroads to the community. The morbidity and mortality burden of MRSA infection is compounded by delayed or inappropriate antibiotic treatment, taking a toll on health care resources that are already stretched thin. Vancomycin has historically been the drug of choice for this pathogen because its broad spectrum can address the multidrug resistance of most MRSA infections. Despite its sustained in vitro microbiologic inhibitory activity, researchers are beginning to question the continued utility of vancomycin for MRSA infections. Evidence against vancomycin is most notable with regard to nosocomial pneumonia and skin and soft tissue infections. In addition, because vancomycin must be administered intravenously, patients typically require prolonged hospitalization, which further increases the cost of MRSA treatment and exposes patients to additional nosocomial infections. Recent studies have shown that antibiotics with good bioavailability, such as linezolid, can be given orally to facilitate early hospital discharge, thus alleviating the economic burden of MRSA infections. Several agents have been developed over the past decade that have excellent in vitro activity against MRSA. Further studies are needed to determine if these drugs can better eradicate MRSA than vancomycin and remedy the adverse outcomes frequently observed with this organism.

Role of superantigenic strains in the prognosis of community-acquired methicillin-susceptible Staphylococcus aureus bacteraemia

Methicillin-susceptible Staphylococcus aureus (MSSA) strains can produce superantigenic toxins that may trigger a massive release of pro-inflammatory cytokines, which are involved in the onset of septic shock. This 1-year prospective pilot study assessed the role of the production of superantigenic toxins in the outcome of immunocompetent patients hospitalised for community-acquired MSSA bacteraemia. Thirty-seven patients were enrolled, of whom 14 died in hospital. Fourteen patients had septic shock, and the mortality rate in this subgroup was 56%. Twenty-seven (73%) isolates produced at least one superantigenic toxin, but this did not influence the rate of occurrence of septic shock or death.

Impact of empirical-therapy selection on outcomes of intravenous drug users with infective endocarditis caused by methicillin-susceptible Staphylococcus aureus

This study compares beta-lactam and vancomycin among intravenous drug users with infective endocarditis caused by methicillin-susceptible Staphylococcus aureus. Patients who received vancomycin had higher infection-related mortality, even if they were switched to beta-lactam once culture results became available; this relationship persisted after logistic regression analysis controlling for clinical characteristics.

Early switch from vancomycin to oral linezolid for treatment of gram-positive heart valve endocarditis

BACKGROUND

Patients with complicated gram-positive endocarditis are usually treated with a combination of surgical procedure and long-term antibiotic therapy with intravenous vancomycin. However, oral linezolid offers the potential for an early switch from intravenous vancomycin to oral linezolid therapy.

METHODS

We conducted a retrospective study from February 2002 to August 2005 to determine the potential for early switch from intravenous vancomycin to oral linezolid in patients surgically treated for a left-sided active gram-positive endocarditis.

RESULTS

Fourteen patients were identified; average age was 52 +/- 16 years. There were 10 (85%) and 2 (15%) cases of native and prosthetic valve endocarditis, respectively. Patients were operated on 3 to 10 days after diagnosis. There were no cases of operative mortality. Mean follow-up was 20.8 +/- 7.0 months. Two (14%) patients died of noncardiac causes during follow-up. The mean intensive care unit length of stay was 3.1 +/- 2.3 days, and mean hospital length of stay was 10.5 +/- 3.4 days. No cases of recurrent endocarditis or periprosthetic leakage were observed.

CONCLUSIONS

The combination of aggressive surgical treatment and the early switch from intravenous vancomycin to oral linezolid for treatment of active gram-positive heart valve endocarditis is safe and effective, and reduces infection relapses, vancomycin use, hospital length of stay, and economic costs.

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.

Methicillin-resistant Staphylococcus aureus as a cause of community-acquired pneumonia

New pathogens have emerged that now complicate the management of community-acquired pneumonia (CAP). Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a potential cause of CAP, particularly complicated CAP. In this literature review, the incidence, invasiveness, and antimicrobial management of CA-MRSA is discussed. Based on existing data and the rising incidence of CA-MRSA, we recommend a change in antibiotic selection for complicated CAP.

Treatment of hospital-acquired pneumonia caused by methicillin-resistant Staphylococcus aureus

Nosocomial pneumonia and ventilator-assisted pneumonia may be polymicrobial and can be caused by a wide spectrum of pathogens. Potentially multidrug-resistant microorganisms often represent the 'core' pathogens of the most severe infections. Among Gram-positive pathogens, methicillin-resistant Staphylococcus aureus (MRSA) plays a key role, mainly in mechanically ventilated patients or in patients with specific risk factors. The mainstay of treatment for MRSA pneumonia has been glycopeptide antibiotics, i.e. vancomycin and, to a lesser extent, teicoplanin. However, owing to its insufficient penetration into lung compartments, vancomycin may result in therapeutic failure or slow clinical responses. Moreover, vancomycin serum levels must be monitored in order to minimise nephrotoxicity and to maximise the concentration in the lung. Finally, the emergence of staphylococci isolates with reduced susceptibility to vancomycin suggests that glycopeptides should no longer be considered as first-line antibacterial agents for Gram-positive lung infections. Among new therapeutic options, linezolid may be an appropriate choice for MRSA pulmonary infections owing to its good pharmacokinetic profile in the lung and its acceptable tolerability, especially in patients with renal insufficiency or in those receiving other nephrotoxic agents. However, to contain the increasing emergence of drug resistance among hospitalised patients, these novel antimicrobial agents should be used judiciously, restricting their use to patients not responsive to, or intolerant of, glycopeptides. Other new drugs under development appear to be promising and deserve further evaluation.

Vancomycin in vitro bactericidal activity and its relationship to efficacy in clearance of methicillin-resistant Staphylococcus aureus bacteremia

We examined the relationship between the time to clearance of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia while patients were receiving vancomycin therapy and the in vitro bactericidal activity of vancomycin. Vancomycin killing assays were performed with 34 MRSA bloodstream isolates (17 accessory gene regulator group II [agr-II] and 17 non-agr-II isolates) from 34 different patients with MRSA bacteremia for whom clinical and microbiological outcomes data were available. Vancomycin doses were prospectively adjusted to achieve peak plasma concentrations of 28 to 32 mug/ml and trough concentrations of 8 to 12 microg/ml. Bactericidal assays were performed over 24 h with approximately 10(7) to 10(8) CFU/ml in broth containing 16 microg/ml vancomycin. The median time to clearance of bacteremia was 6.5 days for patients with MRSA isolates demonstrating > or =2.5 reductions in log(10) CFU/ml at 24 h and >10.5 days for patients with MRSA isolates demonstrating <2.5 log(10) CFU/ml by 24 h (P = 0.025). The median time to clearance was significantly longer with MRSA isolates with vancomycin MICs of 2.0 microg/ml compared to that with MRSA isolates with MICs of < or =1.0 microg/ml (P = 0.019). The bacteremia caused by MRSA isolates with absent or severely reduced delta-hemolysin expression was of a longer duration of bacteremia (10 days and 6.5 days, respectively; P = 0.27) and had a decreased probability of eradication (44% and 78%, respectively; P = 0.086). We conclude that strain-specific microbiological features of MRSA, such as increased vancomycin MICs and decreased killing by vancomycin, appear to be predictive of prolonged MRSA bacteremia while patients are receiving vancomycin therapy. Prolonged bacteremia and decreased delta-hemolysin expression may also be related. Evaluation of these properties may be useful in the consideration of antimicrobial therapies that can be used as alternatives to vancomycin for the treatment of MRSA bacteremia.

Risk factors for death due to nosocomial infection in intensive care unit patients: findings from the Krankenhaus Infektions Surveillance System

OBJECTIVE

To determine risk factors for death among patients with nosocomial pneumonia and patients with primary bloodstream infections (BSI) in intensive care units (ICUs).

DESIGN

Prospective cohort study.

SETTING

Data collected from January 1997 through June 2003 from ICUs registered with the Krankenhaus Infektions Surveillance System in Germany.

PATIENTS

A total of 8,432 patients with nosocomial pneumonia from 202 ICUs and 2,759 patients with nosocomial primary BSI from 190 ICUs.

METHODS

The following risk factors were considered in the analysis: age, sex, time in the ICU before onset of infection, type of ICU, type and size of hospital, intubation, central venous catheter use, total parenteral nutrition, and type of pathogen.

RESULTS

A total of 750 patients (8.9%) with nosocomial pneumonia and 302 patients (10.9%) with nosocomial primary BSI died. Multiple logistic regression analysis identified treatment in a medical or surgical ICU (odds ratio [OR], 1.55 [95% confidence interval {CI}, 1.32-1.82]) or a hospital with more than 1,000 beds (OR, 2.14 [95% CI, 1.81-2.56]), age older than 65 years (OR, 1.54 [95% CI, 1.31-1.81]), and infection with methicillin-resistant Staphylococcus aureus (OR, 2.39 [95% CI, 1.81-3.12]) or multidrug-resistant Pseudomonas aeruginosa (OR, 3.00 [95% CI, 1.90-4.63]) as independent determinants of death from nosocomial pneumonia. Age older than the median of 63 years (OR, 1.44 [95% CI, 1.12-1.86]) and methicillin-resistant S. aureus as the causative agent (OR, 2.98 [95% CI, 1.81-5.82]) were both associated with increased mortality from primary BSI. The types of infecting pathogens, particularly those resistant to multiple drugs, were also strong outcome predictors among ICU patients.

CONCLUSIONS

The study results underline the need for further investigations of the role of antimicrobial resistance in the outcome of patients with nosocomial pneumonia and patients with primary BSI.

Bacteriemias por Staphylococcus aureus sensible a meticilina: epidemiología y factores pronósticos. Estudio prospectivo 2000-2003

BACKGROUND

Staphylococcus aureus bacteremia continues to be a major problem in hospitals due to its high prevalence, severity and treatment difficulties. This study aimed to evaluate epidemiological and clinical features, risk factors and influence of antibiotic choice in outcome and mortality in patients with methicillin susceptible S. aureus bacteremia (SAMSB).

PATIENTS AND METHODS

A prospective, observational study of inpatients with SAMSB (2000-3).

RESULTS

A total of 131 with SAMSB were included (mean age 56 years; 58% > or = 60 year-old); 56.5% were due to nosocomial bacteremia; 46% of all patients had an underlying condition (diabetes mellitus being the most frequent [28%]); a risk factor for bacteraemia was identified in 98% (intravenous catheter: 72%). Mortality rate was 16% (21/131). Comparative analysis according to nosocomial or community acquisition showed that the former was more frequent in Surgical Wards, patients with intravenous or urinary catheters, traumatic patients, dialysis and ICU patients. Initial severity and mortality were highest in community-acquired SAMSB. In multivariate analysis, risk factors associated with higher mortality were: presence of an ultimately or rapidly fatal underlying disease, acute severity of illness at onset and inadequate empirical treatment.

CONCLUSIONS

SAMSB is a clinically severe infection that occurs in patients with baseline disease, especially diabetics, that is almost always related to predisposing risk factors (mainly intravenous catheters). In the presence of a serious baseline disease, the initial critical clinical condition and inadequate empirical treatment are the main prognostic factors associated to greater mortality.

Use of Vancomycin or First-Generation Cephalosporins for the Treatment of Hemodialysis-Dependent Patients with Methicillin-Susceptible Staphylococcus aureus Bacteremia

BACKGROUND

Because of its ease of dosing, vancomycin is commonly used to treat methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia in patients undergoing long-term hemodialysis. Clinical outcomes resulting from such a therapeutic strategy have not been well defined.

METHODS

We prospectively identified patients undergoing long-term hemodialysis who received a diagnosis of MSSA bacteremia. Clinical outcomes were grouped according to the predominant antibiotic received during their therapy (vancomycin or a first-generation cephalosporin [cefazolin]). Treatment failure (defined as death or recurrent infection) was determined at 12 weeks after the initial positive blood culture results. A multivariable analysis was used to adjust for confounders.

RESULTS

During an 84-month period, 123 hemodialysis-dependent patients with MSSA bacteremia were identified. Patients receiving vancomycin (n=77) tended to be younger (51 vs. 57 years; P=.06) and had a lower rates of metastatic complications at presentation (11.7% vs. 36.7%; P=.001) than did those receiving cefazolin (n=46). The 2 groups were similar with regard to Acute Physiology and Chronic Health Evaluation II scores, comorbidities, source of infection, type of hemodialysis access, and access removal rates. Treatment failure was more common among patients receiving vancomycin (31.2% vs. 13%; P=.02). In the multivariable analysis, factors independently associated with treatment failure included vancomycin use (odds ratio, 3.53; 95% confidence interval, 1.15-13.45) and retention of the hemodialysis access (odds ratio, 4.99; 95% confidence interval, 1.89-13.76).

CONCLUSIONS

Hemodialysis-dependent patients with MSSA bacteremia treated with vancomycin are at a higher risk of experiencing treatment failure than are those receiving cefazolin. In the absence of patient specific circumstances (e.g., allergy to beta-lactams), vancomycin should not be continued beyond empirical therapy for hemodialysis-dependent patients with MSSA bacteremia.

The risk factors for mortality of community-acquired pneumonia in Japan

Community-acquired pneumonia remains one of the most important diseases associated with mortality. The aim of this study was to identify the risk factors for mortality in patients with community-acquired pneumonia in Japan. This prospective study was carried out at the Social Insurance Tagawa Hospital, Fukuoka, Japan. All patients were managed according to the 1993 American Thoracic Society guidelines for community-acquired pneumonia, after an evaluation of the risk class by the pneumonia Patient Outcome Research Team (PORT) study. A comparison of several factors, including demographic findings, clinical signs, underlying diseases, results of medical examinations, severity of diseases, and causative pathogens in both survival and fatal groups, was carried out from 227 episodes of community-acquired pneumonia in 208 hospitalized patients (128 men, mean age 67.7 years). The presence of a risk of aspiration, low systolic blood pressure, low PaO(2)/FIO(2) ratio, a high pneumonia score, and the presence of severe congestive heart failure were found to be independent risk factors for mortality from community-acquired pneumonia. The mortality in risk classes IV and V was 17.5% and 54.2%, respectively, and there was a significant correlation between risk classes. The risk factors we identify here are generally similar to those given in previous reports in Western countries. According to the prediction rule of the pneumonia PORT study, the risk classes were strongly associated with the mortality, and would be suitable and helpful for the management of patients with community-acquired pneumonia in Japan.

A review of the current place of glycopeptides in turkish medical practice

BACKGROUND

Glycopeptide antibiotics are considered by many investigators to be the last resort in the treatment of gram-positive bacterial infections.

OBJECTIVE

The aim of this review was to assess the place of glycopeptides in the treatment of common gram-positive bacteria in accordance with the current epidemiologic data in Turkey.

METHODS

A search of both the English- and Turkish-language literature indexed on MEDLINE, Ulakbim (Turkey), and Pleksus (Turkey) was performed using the terms: vancomycin, teicoplanin, and glycopeptides, or their Turkish-language counterparts. The complete texts of the articles found in these databases were obtained from the electronic library of Gulhane Medical Academy, Ankara, Turkey. Articles from regional journals, without the support of an electronic format, were obtained by direct communication. Articles of interest were those based on studies occurring in Turkish populations, with special consideration given to publications in press after 2002.

RESULTS

Staphylococci were the most frequent gram-positive pathogens encountered in Turkish hospitals. Studies have found that ∼74% of strains were Staphylococcus aureus and the remaining strains were coagulase-negative staphylococci (CoNS). Overall methicillin resistance in staphylococci was reported as ∼60%. In Turkey, S aureus was one of the most common infectious agents found inside hospitals and is deemed a growing threat in the community. While the rate of methicillin resistance in community-acquired isolates is ∼4%, the data from hospitals suggest that reduced resistance comprises most of the isolates. In the studies reviewed, older quinolones like ciprofloxacin and ofloxacin seem to be ineffective in nearly half of the S aureus isolates. Alternatives like rifampicin, gentamicin, tetracycline, trimethoprim/sulfamethoxazole (TMP/SMX), clindamycin, and erythromycin have had substantial resistance profiles in >50% of the strains. In recent Turkish studies, in vitro profiles of linezolid, quinupristin/dalfopristin (QD), and daptomycin have had positive results. As in the S aureus isolates, resistance trends have been observed in the CoNS group of pathogens. The possible use of β-lactams seems restricted, and alternative approaches have become necessary. Quinolones, gentamicin, tetracycline, TMP/SMX, clindamycin, and erythromycin have resistance profiles of >50%. Although glycopeptide resistance was not detected, the frequency of heterogenous vancomycin-intermediate S aureus, a precursor to future resistance, was 13% in 1 study. Current studies in Turkey have found that Enterococcus faecalis comprises three quarters of enterococci while the rest are comprised of Enterococcus faecium. Initial studies performed with linezolid, QD, and daptomycin suggest that these drugs might be effective alternatives for future enterococcal infections that may have high glycopeptide resistance. Approximately 8% of the Streptococcus pneumoniae strains had high-level resistance in Turkey. However, 10 million units of crystallized penicillin or 3 g of oral amoxicillin maintains the optimum treatment of pneumococcal infections outside the central nervous system (CNS). Resistance profiles in third-generation cephalosporins in Turkey range between 2% and 2.5%.

CONCLUSIONS

In Turkey, a review of the existing literature found that the current use of glycopeptides in pneumococcal infections is restricted to CNS infections facing therapeutic failure in due course. However, the belief that these drugs are the last resort, either in staphylococcal or enterococcal infections, is no longer valid. If a patient has a critical status due to probable gram-positive microorganisms, clinicians should consider the empiric use of glycopeptides. However, new molecules such as linezolid, QD, and daptomycin, offered for use in the treatment of gram-positive bacterial diseases, should be reserved for the future, when glycopeptides eventually become obsolete.

Community-acquired methicillin-resistant Staphylococcus aureus infections in children

Methicillin-resistant Staphylococcus aureus (MRSA) is now an established community pathogen in many areas of the United States as well as the world. Community-acquired MRSA (CA-MRSA) infections have changed several aspects of staphylococcal infections in children including the epidemiology, clinical manifestations, laboratory approach, antibiotic management, and prevention.

The relationship between antimicrobial resistance and patient outcomes: mortality, length of hospital stay, and health care costs

There is an association between the development of antimicrobial resistance in Staphylococcus aureus, enterococci, and gram-negative bacilli and increases in mortality, morbidity, length of hospitalization, and cost of health care. For many patients, inadequate or delayed therapy and severe underlying disease are primarily responsible for the adverse outcomes of infections caused by antimicrobial-resistant organisms. Patients with infections due to antimicrobial-resistant organisms have higher costs (approximately 6,000-30,000 dollars) than do patients with infections due to antimicrobial-susceptible organisms; the difference in cost is even greater when patients infected with antimicrobial-resistant organisms are compared with patients without infection. Strategies to prevent nosocomial emergence and spread of antimicrobial-resistant organisms are essential.

Active screening in high-risk units is an effective and cost-avoidant method to reduce the rate of methicillin-resistant Staphylococcus aureus infection in the hospital

OBJECTIVE

To evaluate the impact of active screening for methicillin-resistant Staphylococcus aureus (MRSA) on MRSA infection rates and cost avoidance in units where the risk of MRSA transmission is high.

METHODS

During a 15-month period, all patients admitted to our adult medical and surgical intensive care units (ICUs) were screened for MRSA nasal carriage on admission and weekly thereafter. The overall rates of all MRSA infections and of nosocomial MRSA infection in the 2 adult ICUs and the general wards were compared with rates during the 15-month period prior to the start of routine screening. The percentage of patients colonized or infected with MRSA on admission and the cost avoidance of the surveillance program were also assessed.

RESULTS

The overall rate of MRSA infections for all 3 areas combined decreased from 6.1 infections per 1,000 census-days in the preintervention period to 4.1 infections per 1,000 census-days in the postintervention period (P = .01). The decrease remained statistically significant when only nosocomial MRSA infections were examined (4.5 vs 2.8 infections per 1,000 census-days; P < .01), despite a corresponding increase during the postintervention period in the percentage of patients with onset of MRSA infection in the first 72 hours after admission to the general wards (46% to 81%; P < .005). A total of 3.7% of ICU patients were colonized or infected with MRSA on admission; MRSA would not have been detected in 91% of these patients if screening had not been performed. At a cost of Dollars 3,475/month for the program, we averted a mean of 2.5 MRSA infections/month for the ICUs combined, avoiding Dollars 19,714/month in excess cost in the ICUs.

CONCLUSIONS

Even in a setting of increasing community-associated MRSA, active MRSA screening as part of a multi-factorial intervention targeted to high-risk units may be an effective and cost-avoidant strategy for achieving a sustained decrease of MRSA infections throughout the hospital.

Economic consequences of antimicrobial resistance

BACKGROUND

In the past two decades, a dramatic increase in the frequency and prevalence of antimicrobial-resistant pathogens has challenged clinicians and researchers.

MATERIALS AND METHODS

A review of the literature was conducted. Available data identifying the costs and consequences of resistance are summarized while the issues and limitations of research assessing the economics of resistance are acknowledged.

RESULTS

Microbial resistance is a complex, multifactorial phenomenon, but the single most powerful influence is antimicrobial use. Treatment guidelines, clinical pathways, and other directives exert widespread influences on individual selection of antimicrobial agents. However, use of an empiric regimen that does not provide effective coverage, or a targeted regimen that is dosed too low to provide optimal therapy, will delay eradication of the pathogen, increase the potential for resistance to emerge, extend and increase morbidity, and expose the patient to an increased risk of mortality. Coincident with these untoward clinical events are economic consequences secondary to increased duration of treatment, and for some, an extended duration of hospitalization.

CONCLUSION

Resistant gram-negative and gram-positive bacteria have been associated with increased direct medical costs ranging from several thousand dollars to tens of thousands of dollars per patient.

Review of new guidelines for prophylaxis and treatment of MRSA infections

A joint working party has produced evidence-based guidelines for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the U.K. These guidelines will help clinicians choose appropriate therapy and point to areas where further research is needed. This review summarizes the main recommendations and discusses their implementation into clinical practice.

Review of new guidelines for prophylaxis and treatment of MRSA infections

A joint working party has produced evidence-based guidelines for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the UK. These guidelines will help clinicians choose appropriate therapy and point to areas where further research is needed. This review summarizes the main recommendations and discusses their implementation into clinical practice.

Hospital-acquired pneumonia in the 21st century: a review of existing treatment options and their impact on patient care

Hospital-acquired pneumonia is a common nosocomial infection, with significant morbidity and mortality, and represents a major therapeutic challenge to clinicians. The therapeutic approach must be patient-oriented and institution-specific. The specific risk factors of each patient, such as previous antibiotic exposure, underlying diseases, length of hospital stay and the local patterns of antimicrobial resistance, should guide physicians in their decision of the initial optimal empirical therapy. Delays in the initiation or inappropriate/inadequate initial therapy are related to increased mortality and worse outcomes. In responding patients, as soon as culture data are available, efforts should be made to change the initial broad spectrum antibiotic regimen to a more targeted one (de-escalation). The optimal duration of treatment is a matter of debate, but courses longer than 1 week are rarely justified.

The issue of antimicrobial resistance in human medicine

Antibiotics are used worldwide in human medicine and agriculture. In many cases the use of antibiotics is unnecessary or questionable. Consumption of antibiotics is linked to bacterial resistance. In hospitals, most common resistant bacteria include methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and Gram-negative rods including Enterobacteriaceae and Pseudomonas aeruginosa. Vancomycin intermediate and resistant S. aureus, described just recently, represent a new treatment challenge. In the community, penicillin and macrolide-resistant pneumococci developed several decades ago and are now present all over the world. More recently, community-acquired methicillin-resistant S. aureus has become a problem in several countries causing skin infections but also severe diseases. Resistance to co-trimoxazole in Escherichia coli has changed empirical treatment of urinary tract infections, one of the most common causes of the visit to the physician's office. Several reports and studies trying to limit the use of antibiotics have shown that antimicrobial resistance of bacteria can be reversed, but in general the problem is far from being solved. World Health Assembly and the European Community Council have recognized the problem of antibiotic resistance as a priority. The relationship between agricultural use of antimicrobials and antibacterial resistance in humans should be further investigated.

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.

[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.

Vancomycin: a history

Vancomycin became available for clinical use >50 years ago but was soon discarded in favor of other antibiotics that were deemed to be more efficacious and less toxic. The advent of pseudomembranous enterocolitis, coupled with the spread of methicillin-resistant Staphylococcus aureus, led to a resurgence in the use of vancomycin. Almost immediately, concerns arose with regard to its therapeutic utility. In addition, resistance to vancomycin developed, first in enterococci and later in staphylococci. Several types of resistance have now been identified, each with a unique effect on infections treated with vancomycin. Recent studies have rekindled interest in the best way to administer the antibiotic. The findings of future studies may result in a return to measuring levels of vancomycin in serum, to assure a successful therapeutic outcome.

Antibiotics for treatment of resistant gram-positive coccal infections

Vancomycin is considered the workhorse for the treatment of most drug-resistant gram-positive bacterial infections. However, concerns have been raised regarding the increasing rates of vancomycin-resistant enterococci and the clinical shortcomings of vancomycin in the treatment of invasive Staphylococcus aureus infections. Resources have been committed to the development of antimicrobial agents with activity against these organisms. This review will focus on the newer antibacterial agents that have been developed for the treatment of resistant gram-positive pathogens. Included in this review are the agents: quinupristin-dalfopristin, linezolid, daptomycin, telithromycin, and tigecycline.

Potential Impact of Vancomycin Pulmonary Distribution on Treatment Outcomes in Patients with Methicillin-ResistantStaphylococcus aureusPneumonia

Vancomycin as the drug of choice for treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia has been called into question on the basis of therapeutic failures. In patients with MRSA pneumonia, treatment failures are probably due to the complex interplay of variables affecting the host-antimicrobial-pathogen interrelationship. However, it has been suggested that decreased penetration of vancomycin into the lungs may contribute. This review explores physiochemical and physiologic variables that affect pulmonary penetration and describes methods used in quantifying pulmonary vancomycin concentrations. Most important, findings are evaluated in the clinical context of the chemotherapeutic options available for treatment of MRSA pneumonia. The possibility of increased serum vancomycin concentrations as a method to optimize current treatment outcomes is also explored.

Persistence in Staphylococcus aureus bacteremia: incidence, characteristics of patients and outcome

Staphylococcus aureus bacteremia often persists. The reasons for persistence and its outcome are poorly defined. We conducted a prospective-observational study among 245 consecutive S. aureus (MRSA: n=125; MSSA: n=120) bacteremias (>or=1 positive blood cultures (BC)) among 234 adults (18-103-y-old; median=59 y) hospitalized during 1 January 2002-31 December 2002 at a 600-bed teaching hospital. Measurements included bacteremia duration, complication-rate (metastatic infection, relapse or attributable mortality) and outcome. Bacteremia duration was measured based on follow-up BC among 193 patients and estimated based on symptoms resolution in the rest. Measured (1-59 d; median=2) and estimated (median=1 d) duration correlated (r=0.885) though positive follow-up BC was often detected without fever (57/105 patients, 54.3%). Persistence (defined as bacteremia for >or=3 d) was noted in 84 cases (38.4%). Complication-rate increased steadily with bacteremia duration (6.6%, 24.0% and 37.7% in bacteremia for 1-2, 3 and >or=4 d, respectively; p=0.05). Cox regression analysis revealed that bacteremia duration correlated positively with endovascular sources (p=0.006), vancomycin treatment (p=0.016), cardiovascular prosthesis (p=0.025), metastatic infections (p=0.025) and diabetes (p=0.038). It is concluded that persistent bacteremia is a feature of S. aureus infection, irrespective of oxacillin susceptibility, associated with worse outcome. Risk factors include endovascular sources, cardiovascular prosthesis, metastatic infections, vancomycin treatment and diabetes. Patients at risk may benefit from novel treatment strategies.

Daptomycin for the Treatment of Gram-Positive Bacteremia and Infective Endocarditis: A Retrospective Case Series of 31 Patients

STUDY OBJECTIVE

To evaluate the outcomes in patients with bacteremia and/or infective endocarditis who were treated with daptomycin.

DESIGN

Retrospective chart review.

SETTING

A university-affiliated medical center in Chicago, Illinois, and a regional hospital in Fountain Valley, California.

PATIENTS

Thirty-one inpatients treated with daptomycin for bacteremia and/or infective endocarditis.

MEASUREMENTS AND MAIN RESULTS

Patients were given daptomycin 4-6 mg/kg intravenously every 24-48 hours based on the practitioner's discretion and depending on the patient's clinical condition and presence of comorbidities. Primary end points were resolution of signs and symptoms of infection and discharge from the hospital. Methicillin-resistant Staphylococcus aureus ([MRSA] 11 patients) and vancomycin-resistant entercocci ([VRE] 11 patients) were the most common pathogens, whereas 7 patients had methicillin-sensitive S. aureus infection and 1 patient had coagulasenegative Staphylococcus infection. One patient with endocarditis had a negative culture result. Overall, 24 (77%) of the 31 patients achieved clinical resolution and were discharged, including all patients infected with MRSA; 7 patients died, 6 of whom had VRE infection. Duration of treatment for infective endocarditis lasted longer (typically 22-43 days) than that for bacteremia only (< or = 14 days), and no patients discontinued daptomycin because of adverse events.

CONCLUSION

In these patients, daptomycin was safe and well tolerated even for extended durations of treatment. Daptomycin may provide an effective option for treating drug-resistant gram-positive bloodstream infections and endocarditis.

Guidelines for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the UK

These evidence-based guidelines have been produced after a literature review of the treatment and prophylaxis of methicillin-resistant Staphylococcus aureus (MRSA) infection. The guidelines were further informed by antibiotic susceptibility data on MRSA from the UK. Recommendations are given for the treatment of common infections caused by MRSA, elimination of MRSA from carriage sites and prophylaxis of surgical site infection. There are several antibiotics currently available that are suitable for use in the management of this problem and potentially useful new agents are continuing to emerge.

Infective endocarditis: diagnosis, antimicrobial therapy, and management of complications: a statement for healthcare professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young, and the Councils on Clinical Cardiology, Stroke, and Cardiovascular Surgery and Anesthesia, American Heart Association: endorsed by the Infectious Diseases Society of America

BACKGROUND

Despite advances in medical, surgical, and critical care interventions, infective endocarditis remains a disease that is associated with considerable morbidity and mortality. The continuing evolution of antimicrobial resistance among common pathogens that cause infective endocarditis creates additional therapeutic issues for physicians to manage in this potentially life-threatening illness.

METHODS AND RESULTS

This work represents the third iteration of an infective endocarditis "treatment" document developed by the American Heart Association under the auspices of the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease of the Young. It updates recommendations for diagnosis, treatment, and management of complications of infective endocarditis. A multidisciplinary committee of experts drafted this document to assist physicians in the evolving care of patients with infective endocarditis in the new millennium. This extensive document is accompanied by an executive summary that covers the key points of the diagnosis, antimicrobial therapy, and management of infective endocarditis. For the first time, an evidence-based scoring system that is used by the American College of Cardiology and the American Heart Association was applied to treatment recommendations. Tables also have been included that provide input on the use of echocardiography during diagnosis and treatment of infective endocarditis, evaluation and treatment of culture-negative endocarditis, and short-term and long-term management of patients during and after completion of antimicrobial treatment. To assist physicians who care for children, pediatric dosing was added to each treatment regimen.

CONCLUSIONS

The recommendations outlined in this update should assist physicians in all aspects of patient care in the diagnosis, medical and surgical treatment, and follow-up of infective endocarditis, as well as management of associated complications. Clinical variability and complexity in infective endocarditis, however, dictate that these guidelines be used to support and not supplant physician-directed decisions in individual patient management.

Medical versus surgical management of Staphylococcus aureus prosthetic valve endocarditis

PURPOSE

The study's purpose was to identify prognostic factors associated with mortality in Staphylococcus aureus prosthetic valve endocarditis and to determine whether these factors influenced decisions to treat medically versus surgically. We also analyzed whether there was a subset of patients who were cured with medical therapy alone.

SUBJECTS AND METHODS

A retrospective review of patients with S aureus prosthetic valve endocarditis was performed. Demographic and clinical data were collected from existing medical records. Severity of illness was classified using American Society of Anesthesiologists (ASA) score. Impact of treatment on in-hospital mortality was assessed using multiple logistic regression analysis.

RESULTS

Fifty-five patients met the Duke criteria for definite S aureus prosthetic valve endocarditis. Twenty-three patients were treated medically, and 32 patients had surgical intervention. Overall mortality was 36% (28% in the surgical group and 48% in the medical group). ASA score IV (P < .001) and older age (P = .014) were significant risk factors of mortality. Patients with ASA score IV (P = .037) and multiple prosthetic valves (P = .013) were less likely to undergo surgery. Medically treated patients were older compared with those in the surgical group (median age 66 vs 55 years, P = .04). All 4 patients aged less than 50 years in the medically treated group survived.

CONCLUSION

Mortality was generally higher in the medically treated patients with S aureus prosthetic valve endocarditis. Multivariable analysis showed that ASA class IV and bioprosthetic valves were independent predictors of mortality. A subset of medically treated patients characterized by age less than 50 years, ASA score III, and without cardiac, central nervous system, or systemic complications were cured without surgical intervention.

Implications of methicillin-resistant Staphylococcus aureus as a community-acquired pathogen in pediatric patients

Methicillin-resistant Staphylococcus aureus is now an established community pathogen in many areas of the United States and the world. Community-acquired methicillin-resistant S aureus infections have changed several aspects of staphylococcal infections in children. This article discusses epidemiology, clinical manifestations, laboratory diagnosis, treatment, and prevention.

Early empirical glycopeptide therapy for patients with methicillin-resistant Staphylococcus aureus bacteraemia: impact on the outcome

OBJECTIVES

To evaluate whether appropriate early empirical glycopeptide therapy improves outcomes of patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia.

METHODS

We retrospectively collected the data for all adult patients with confirmed MRSA bacteraemia diagnosed and treated at National Taiwan University Hospital during the period 1 April 1997-31 March 2001, and followed their survival up to three years. The main outcome measures were MRSA-related death and all-cause mortality.

RESULTS

There were 77 MRSA-related deaths among 162 patients. There was no statistically significant difference in MRSA-related deaths between patients receiving glycopeptides before or within 48 h after blood culture (n = 43) (55%, 18/33, non-septic shock group; 90%, 9/10, septic shock group) or those whose glycopeptide therapy was begun more than 48 h after blood culture (n = 119) (37%, 40/107, non-septic shock group; 83%, 10/12, septic shock group) (P = 0.11 and 1.00, respectively). The outcome measure of all-cause mortality from 30 days to 3 years yields similar results. Multivariate logistic regression analysis and Cox analysis showed that the length of delay (daily increment) between blood culture sampling and start of glycopeptide therapy did not have a statistically significant impact on MRSA-related death or all-cause 30-day mortality after adjusting for the effect of other variables [adjusted odds ratio 0.99, 95% confidence interval (95% CI) 0.88-1.12; adjusted hazard ratio 0.87, 95% CI 0.74-1.02, respectively).

CONCLUSIONS

The hypothesis that earlier empirical use of glycopeptide therapy reduces mortality in patients with hospital-acquired MRSA bacteraemia was not supported.

Can β-lactams be re-engineered to beat MRSA?

Methicillin-resistant Staphylococcus aureus (MRSA) strains are important nosocomial pathogens worldwide and now are also of growing importance in community-acquired infection. Their resistance depends upon a supplementary peptidoglycan transpeptidase, PBP2' (PBP-2a), which continues to function when normal PBPs have been inactivated by beta-lactams. PBP2' is encoded by the mecA gene, which is carried by the staphylococcal cassette chromosome, a large and somewhat variable DNA insert of uncertain origin. PBP2' does not wholly lack affinity for beta-lactams, but its affinity for available analogues is very weak. In principle, it should be possible to re-engineer beta-lactams to bind PBP2' strongly, and the desirability of this approach is self-evident: no other antibiotic class has a record equal to the beta-lactams for safety and efficacy. Moreover, there is consensus that beta-lactams are inherently more efficacious than vancomycin against infections due to susceptible staphylococci. In practice, finding viable PBP2'-active beta-lactams has proved difficult and the catalogue of near-misses extends back to the 1980s. At last, however, one cephalosporin with high affinity for PBP2'--ceftobiprole--is entering phase III trials. Ceftobiprole inhibits MRSA at 1-2 mg/L under standard conditions. Even when mecA/PBP2' was induced strongly, ceftobiprole MICs for MRSA only reached 4 mg/L, a clinically attainable concentration. A phase II trial in skin and skin structure infection recorded cures by ceftobiprole in 4/4 MRSA infections, and results of the phase III trials are awaited with great interest.

Nosocomial pneumonia : rationalizing the approach to empirical therapy

Nosocomial pneumonia or hospital-acquired pneumonia (HAP) causes considerable morbidity and mortality. It is the second most common nosocomial infection and the leading cause of death from hospital-acquired infections. In 1996 the American Thoracic Society (ATS) published guidelines for empirical therapy of HAP. This review focuses on the literature that has appeared since the ATS statement. Early diagnosis of HAP and its etiology is crucial in guiding empirical therapy. Since 1996, it has become clear that differentiating mere colonization from etiologic pathogens infecting the lower respiratory tract is best achieved by employing bronchoalveolar lavage (BAL) or protected specimen brush (PSB) in combination with quantitative culture and detection of intracellular microorganisms. Endotracheal aspirate and non-bronchoscopic BAL/PSB in combination with quantitative culture provide a good alternative in patients suspected of ventilator-associated pneumonia. Since culture results take 2-3 days, initial therapy of HAP is by definition empirical. Epidemiologic studies have identified the most frequently involved pathogens: Enterobacteriaceae, Haemophilus influenzae, Streptococcus pneumoniae and Staphylococcus aureus ('core pathogens'). Empirical therapy covering only the 'core pathogens' will suffice in patients without risk factors for resistant microorganisms. Studies that have appeared since the ATS statement issued in 1996, demonstrate several new risk factors for HAP with multiresistant pathogens. In patients with risk factors, empirical therapy should consist of antibacterials with a broader spectrum. The most important risk factors for resistant microorganisms are late onset of HAP (>/=5 days after admission), recent use of antibacterial therapy, and mechanical ventilation. Multiresistant bacteria of specific interest are methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, Acinetobacter calcoaceticus-baumannii, Stenotrophomonas maltophilia and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae. Each of these organisms has its specific susceptibility pattern, demanding appropriate antibacterial treatment. To further improve outcomes, specific therapeutic options for multiresistant pathogens and pharmacological factors are discussed. Antibacterials developed since 1996 or antibacterials with renewed interest (linezolid, quinupristin/dalfopristin, teicoplanin, meropenem, new fluoroquinolones, and fourth-generation cephalosporins) are discussed in the light of developing resistance.Since the ATS statement, many reports have shown increasing incidences of resistant microorganisms. Therefore, one of the most important conclusions from this review is that empirical therapy for HAP should not be based on general guidelines alone, but that local epidemiology should be taken into account and used in the formulation of local guidelines.

The importance of the development of antibiotic resistance in Staphylococcus aureus

Hospital- and community-acquired Staphylococcus aureus infections pose a substantial burden in terms of morbidity, mortality and health care costs. The introduction of new antibiotics to counter this pathogen has frequently been closely followed by the emergence of resistant strains. Most significantly, S. aureus isolates resistant to beta-lactams have become common, and many of these are also resistant to beta-lactamase-resistant penicillins. The rapid spread of methicillin-resistant S. aureus (MRSA) clones across the world often results in hospital outbreaks, but implementation of appropriate control measures usually reduces prevalence to sporadic levels. However, the recent emergence of MRSA infections in the community, affecting patients with no established risk factors for MRSA acquisition, is likely to impact significantly on future strategies for control of nosocomial MRSA. In contrast to other antibiotic classes, S. aureus resistance to glycopeptides did not emerge until nearly 40 years after their clinical introduction, and as a result this drug class has remained the mainstay of treatment for MRSA infections. However, a number of vancomycin-intermediate S. aureus isolates have emerged worldwide and four fully resistant S. aureus isolates have been reported in the USA. This raises the concern that the current first-line treatment for MRSA infection may become ineffective in an increasing proportion of cases in the near future. New classes of antibiotic are urgently needed to treat infections with this growing population of multidrug-resistant S. aureus, and the recently introduced oxazolidinone linezolid and the cyclic lipopeptide daptomycin are welcome additions to the ever-narrowing range of therapies effective against this pathogen.

Prevention and control of antimicrobial-resistant infections in intensive care patients

OBJECTIVE

To review the literature summarizing important aspects of infection control in the critical care setting and to provide recommendations to reduce infections with resistant bacteria in the intensive care unit.

DATA SOURCE

Computer searches of MEDLINE, EMBASE, and the Cochrane Library.

DATA

The frequency of antibiotic-resistant, health care-associated infections has increased every year for the past 2 decades. Infections with antibiotic-resistant organisms have been linked to increases in morbidity, length of hospitalization, increased healthcare costs, and increased mortality. A comprehensive approach is necessary to prevent antimicrobial resistance in ICUs. This includes (1) preventing infections; (2) diagnosing and treating infections appropriately; (3) using antimicrobials wisely; and (4) preventing transmission.

CONCLUSIONS

The reservoirs for antibiotic-resistant organisms are colonized patients, and the vectors are often healthcare workers. This places an enormous responsibility on healthcare providers to protect their patients. Clinicians must recognize the importance of adhering to the recommendations in the Centers for Disease Control's Campaign to Prevent Antimicrobial Resistance in the healthcare setting.

Neumonía nosocomial causada por Staphylococcus aureus resistente a meticilina

Methicillin-resistant Staphylococcus aureus (MRSA) is an increasingly common cause of hospital acquired pneumonia (HAP) and the second most frequently isolated pathogen from patients who die from HAP. High-risk units for MRSA colonization such as intensive care (ICU's) are the most affected. Multiple risk factors for transmission of MRSA have been identified, including colonization pressure and severity of illness at ICU admission. On the other hand, the most important predisposing factor for MRSA infection is prolonged mechanical ventilation and/or previous antibiotic therapy. Controlling the spread of MRSA remains a major challenge for hospitals. Screening programs, together with contact precautions for cases with MRSA and judicious antimicrobial use are major factors for a successful control. Early appropriate initial therapy is of crucial importance and improves outcome. The standard therapy has been glycopeptides but, in spite of its in vitro activity, mortality in critically ill patients treated with glycopeptides has consistently been reported high, mainly due to their poor lung penetration. Linezolid shows better clinical cure and survival rates, but further studies are needed. As the treatment options for MRSA pneumonia are limited and inadequate, development of more effective drugs is mandatory.

Enfoque clínico del paciente con neumonía asociada a ventilación mecánica

Ventilator-associated pneumonia (VAP) is the most frequent infection in the intensive care unit. The importance of this entity lies not only in its high incidence but also in the significant mortality it produces. Therefore, a new episode of VAP should be clinically suspected when new or persistent radiological opacity, purulent respiratory secretions and other signs of sepsis (fever and leukocytosis) are present. In these patients, at the very least, tracheal aspirate samples with quantitative culture and direct staining should be immediately obtained, followed by prompt initiation of empirical broad-spectrum antibiotic therapy. The choice of initial antibiotic therapy should be patient-based, taking into account the risk factors associated especially with VAP caused by Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus, because of the high associated mortality. To evaluate resolution of VAP, we analyze various clinical variables (based mainly on resolution of fever and hypoxemia) and microbiologic information. Once the microorganism responsible for VAP has been isolated, antibiotic therapy can be adapted, based on de-escalation, to reduce the emergence of resistant bacteria. Recent studies suggest that shorter antibiotic regimens reduce the emergence of antibiotic-resistant pathogens, cost and adverse events.