Single or combination therapy of staphylococcal endocarditis in intravenous drug abusers

The Effectiveness of Combination Therapy for Treating Methicillin-Susceptible Staphylococcus aureus Bacteremia: A Systematic Literature Review and a Meta-Analysis

Background: This meta-analysis aims to evaluate the effectiveness of combination therapy for treating MSSA bacteremia. Methods: We searched Ovid MEDLINE, EMBASE, Cochrane CENTRAL, and clinicaltrials.gov for studies including adults with MSSA bacteremia. The monotherapy group used a first-line antibiotic active against MSSA and the combination group used a first-line antibiotic plus additional antibiotic/s. The primary outcome was all-cause mortality. Secondary outcomes included persistent bacteremia, duration of bacteremia, relapse, and adverse events. Random-effects models with inverse variance weighting were used to estimate pooled risk ratios (pRR). Heterogeneity was assessed using the I² value and the Cochrane’s Q statistic. Results: A total of 12 studies (6 randomized controlled trials [RCTs]) were included. Combination therapy did not significantly reduce 30-day mortality (pRR 0.92, 95% CI, 0.70–1.20), 90-day mortality (pRR 0.89, 95% CI, 0.74–1.06), or any-time mortality (pRR 0.91, 95% CI, 0.76–1.08). Among patients with deep-seated infections, adjunctive rifampicin may reduce 90-day mortality (3 studies with moderate-high risk of bias; pRR 0.62, 95% CI, 0.42–0.92). For secondary outcomes, combination therapy decreased the risk of relapse (pRR 0.38, 95% CI, 0.22–0.66), but this benefit was not maintained when pooling RCTs (pRR 0.54, 95% CI, 0.12–2.51). Combination therapy was associated with an increased risk of adverse events (pRR 1.74, 95% CI, 1.31–2.31). Conclusions: Combination therapy not only did not decrease mortality in patients with MSSA bacteremia, but also increased the risk of adverse events. Combination therapy may reduce the risk of relapse, but additional high-quality studies are needed.

The Effect of Combination Therapy on Mortality and Adverse Events in Patients with Staphylococcus aureus Bacteraemia: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Introduction

The findings of randomized controlled trials (RCTs), observational studies, and meta-analyses vary regarding the effectiveness and safety of combination therapy for patients with Staphylococcus aureus bacteraemia (SAB). We aimed to identify the effectiveness and safety of combination therapy in patients with SAB compared with those of monotherapy.

Methods

We performed a systematic review and meta-analysis to compare combination therapy versus monotherapy in patients with SAB. Two authors independently searched PubMed, Embase, and the Cochrane Library of clinical trials until 17 February 2021. Any RCT comparing mortality or adverse events (AEs) of combination therapy versus monotherapy for patients with SAB was eligible. Summary risk ratios (RRs) and 95% confidence intervals (CIs) were evaluated using a random-effects model. The primary outcome was all-cause mortality at any time point. This meta-analysis is registered with the PROSPERO database (CRD42020188176) and reported according to PRISMA guidelines.

Results

In total, 1906 articles were identified and screened, and 14 studies (2367 patients) were included in the meta-analysis. There was no significant difference in the risk of all-cause mortality between the two groups (RR = 1.00; 95% CI 0.83–1.20; P = 0.99; I² = 0%). Similar results were obtained by subgroup analysis of mortality recording time, endocarditis, pathogen resistance, article publication time, number of patients, and adjuvant antibiotics. Notably, combination treatment might significantly increase the risk of drug-related AEs (RR = 1.68; 95% CI 1.06–2.66; P = 0.03; I² = 67%) and nephrotoxicity (RR = 2.30; 95% CI 1.68–3.16; P < 0.00001; I² = 0%), although the occurrences of AEs leading to treatment discontinuation and serious AEs were not significantly different between the two groups.

Conclusions

The meta-analysis suggested that combination therapy could not reduce mortality but might increase the risk of drug-related AEs and nephrotoxicity and should be applied very cautiously. Future studies on combined drug therapy for SAB need careful and rigorous design for specific antibiotic combinations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00539-y.

A comparison of different antibiotic regimens for the treatment of infective endocarditis

BACKGROUND

Infective endocarditis is a microbial infection of the endocardial surface of the heart. Antibiotics are the cornerstone of treatment, but due to the differences in presentation, populations affected, and the wide variety of micro-organisms that can be responsible, their use is not standardised. This is an update of a review previously published in 2016.

OBJECTIVES

To assess the existing evidence about the clinical benefits and harms of different antibiotics regimens used to treat people with infective endocarditis.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase Classic and Embase, LILACS, CINAHL, and the Conference Proceedings Citation Index - Science on 6 January 2020. We also searched three trials registers and handsearched the reference lists of included papers. We applied no language restrictions.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) assessing the effects of antibiotic regimens for treating definitive infective endocarditis diagnosed according to modified Duke's criteria. We considered all-cause mortality, cure rates, and adverse events as the primary outcomes. We excluded people with possible infective endocarditis and pregnant women.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, 'Risk of bias' assessment, and data extraction in duplicate. We constructed 'Summary of findings' tables and used GRADE methodology to assess the quality of the evidence. We described the included studies narratively.

MAIN RESULTS

Six small RCTs involving 1143 allocated/632 analysed participants met the inclusion criteria of this first update. The included trials had a high risk of bias. Three trials were sponsored by drug companies. Due to heterogeneity in outcome definitions and different antibiotics used data could not be pooled. The included trials compared miscellaneous antibiotic schedules having uncertain effects for all of the prespecified outcomes in this review. Evidence was either low or very low quality due to high risk of bias and very low number of events and small sample size. The results for all-cause mortality were as follows: one trial compared quinolone (levofloxacin) plus standard treatment (antistaphylococcal penicillin (cloxacillin or dicloxacillin), aminoglycoside (tobramycin or netilmicin), and rifampicin) versus standard treatment alone and reported 8/31 (26%) with levofloxacin plus standard treatment versus 9/39 (23%) with standard treatment alone; risk ratio (RR) 1.12, 95% confidence interval (CI) 0.49 to 2.56. One trial compared fosfomycin plus imipenem 3/4 (75%) versus vancomycin 0/4 (0%) (RR 7.00, 95% CI 0.47 to 103.27), and one trial compared partial oral treatment 7/201 (3.5%) versus conventional intravenous treatment 13/199 (6.53%) (RR 0.53, 95% CI 0.22 to 1.31). The results for rates of cure with or without surgery were as follows: one trial compared daptomycin versus low-dose gentamicin plus an antistaphylococcal penicillin (nafcillin, oxacillin, or flucloxacillin) or vancomycin and reported 9/28 (32.1%) with daptomycin versus 9/25 (36%) with low-dose gentamicin plus antistaphylococcal penicillin or vancomycin; RR 0.89, 95% CI 0.42 to 1.89. One trial compared glycopeptide (vancomycin or teicoplanin) plus gentamicin with cloxacillin plus gentamicin (13/23 (56%) versus 11/11 (100%); RR 0.59, 95% CI 0.40 to 0.85). One trial compared ceftriaxone plus gentamicin versus ceftriaxone alone (15/34 (44%) versus 21/33 (64%); RR 0.69, 95% CI 0.44 to 1.10), and one trial compared fosfomycin plus imipenem versus vancomycin (1/4 (25%) versus 2/4 (50%); RR 0.50, 95% CI 0.07 to 3.55). The included trials reported adverse events, the need for cardiac surgical interventions, and rates of uncontrolled infection, congestive heart failure, relapse of endocarditis, and septic emboli, and found no conclusive differences between groups (very low-quality evidence). No trials assessed quality of life.

AUTHORS' CONCLUSIONS

This first update confirms the findings of the original version of the review. Limited and low to very low-quality evidence suggests that the comparative effects of different antibiotic regimens in terms of cure rates or other relevant clinical outcomes are uncertain. The conclusions of this updated Cochrane Review were based on few RCTs with a high risk of bias. Accordingly, current evidence does not support or reject any regimen of antibiotic therapy for the treatment of infective endocarditis.

Aminoglycosides for infective endocarditis: time to say goodbye?

BACKGROUND

Based on experimental studies showing synergism with β-lactams and glycopeptides, aminoglycosides have long been considered essential in the treatment of infective endocarditis (IE). However, their use is associated with a high risk of renal failure, especially in elderly patients.

AIMS

The aim of this narrative review was to summarize the evidence to support reducing or even avoiding the use of aminoglycosides for the treatment of IE. We also analysed data supporting the use of aminoglycosides in specific subgroup of IE patients.

SOURCES

PubMed database was searched up to July 2019 to identify relevant studies.

CONTENTS

Recent European Guidelines reduced the use of aminoglycosides in IE, no longer recommended in Staphylococcus aureus native-valve IE, and shortened to 2 weeks for IE related to Enterococcus faecalis and streptococci with penicillin MIC >0.125 μg/mL. In addition, an alternative regimen without aminoglycosides (ampicillin or amoxicillin plus ceftriaxone) is proposed for E. faecalis. Observational studies suggested that gentamicin would not be necessary in the case of staphylococcal prosthetic valve IE as long as rifampicin is maintained. Recent clinical studies showed that for streptococcal IE, gentamicin could be restricted to isolates with penicillin MIC >0.5 μg/mL. For the empirical and definitive treatment of E. faecalis IE, amoxicillin or ampicillin plus ceftriaxone may be considered, irrespective of high-level of aminoglycoside resistance.

IMPLICATIONS

In a scenario of progressive increase in the age and frailty of IE patients, the use of aminoglycosides can be reduced or avoided in ~90% cases. This should result in reduced incidence of renal failure, an important prognostic factor in IE.

Management of endocarditis among persons who inject drugs: A narrative review of surgical and psychiatric approaches and controversies

BACKGROUND

People who inject drugs (PWID) represent a high-risk subgroup of endocarditis patients. This is highlighted by poorer post-operative outcomes in injection drug use-related infective endocarditis (IDU-IE), which is largely attributable to the increased vulnerability of prosthetic valves to re-infection. Consequently, many centres do not perform valve replacement on these patients. A parallel, but often underrecognized, component of care is the role of multidisciplinary management for individuals with IDU-IE, including perioperative addictions and psychiatric care. Consequently, surgical management options in IDU-IE remain a controversial topic.

OBJECTIVES

To determine the characteristics of optimal surgical and psychiatric care for individuals with IDU-IE.

METHODS

We conducted a narrative synthesis of the findings of literature retrieved from searches of computerized databases, hand searches, and authoritative text, organizing the findings into several key themes: clinical characteristics and factors associated with mortality in IDU-IE, alternative surgical management options, perioperative risk stratification techniques, principles of psychiatric and addictions management in IDU-IE, ethical considerations and controversies, and future research directions.

RESULTS/CONCLUSIONS

Managing IDU-IE involves the treatment of two comorbidities: the intra-cardiac infection and the underlying substance use disorder. Cardiac surgery represents a high-intensity intervention with appreciable risk, and the benefit it is not always clear. As patients often present acutely, it is not feasible to use drug abstinence as a prerequisite to surgery. Involvement of inpatient psychiatry and addictions teams, however, appears to be an evidence-based approach that can bridge IDU-IE patients with opioid agonist therapy in hospital and adequate outpatient treatment options for their underlying addiction upon their discharge from hospital. It is likely that a majority of these patients are not receiving optimal psychiatric management despite increasing recognition of efficacy. Further interdisciplinary studies are needed to elucidate optimal surgical and multidisciplinary protocols.

BACKGROUND

Infective endocarditis (IE) is an infection of the innermost lining of the heart often affecting the heart valves. Over the last few decades, the epidemiology of IE has shifted in the developed world and while it continues to be a significant cause of morbidity and mortality, there has been a significant increased incidence among persons who inject drugs (PWID). To date, well-conducted epidemiologic studies of IE among PWID have been sparse, which has limited our ability to fully characterize this disease phenomenon. To address this knowledge deficit, we conducted a narrative synthesis of the findings of literature retrieved from searches of computerized databases, hand searches, and authoritative text, and organized our findings into six key themes: clinical characteristics and factors associated with mortality in IDU-IE, alternative surgical management options, perioperative risk stratification techniques, principles of psychiatric and addictions management in IDU-IE, ethical considerations and controversies, and future research directions.

Gentamicin may have no effect on mortality of staphylococcal prosthetic valve endocarditis

PURPOSE

To analyze the influence of adding gentamicin to a regimen consisting of β-lactam or vancomycin plus rifampicin on survival in patients suffering from Staphylococcal prosthetic valve endocarditis (SPVE).

METHODS

From January 2008 to September 2016, 334 patients with definite SPVE were attended in the participating hospitals. Ninety-four patients (28.1%) received treatment based on β-lactam or vancomycin plus rifampicin and were included in the study. Variables were analyzed which related to patient survival during admission, including having received treatment with gentamicin.

RESULTS

Seventy-seven (81.9%) were treated with cloxacillin (or vancomycin) plus rifampicin plus gentamicin, and 17 patients (18.1%) received the same regimen without gentamicin. The causative microorganism was Staphylococcus aureus in 40 cases (42.6%) and coagulase-negative staphylococci in 54 cases (57.4%). Overall, 40 patients (42.6%) died during hospital admission, 33 patients (42.9%) in the group receiving gentamicin and 7 patients in the group that did not (41.2%, P = 0.899). Worsening renal function was observed in 42 patients (54.5%) who received gentamicin and in 9 patients (52.9%) who did not (p = 0.904). Heart failure as a complication of endocarditis (OR: 4.58; CI 95%: 1.84-11.42) and not performing surgery when indicated (OR: 2.68; CI 95%: 1.03-6.94) increased mortality. Gentamicin administration remained unrelated to mortality (OR: 1.001; CI 95%: 0.29-3.38) in the multivariable analysis.

CONCLUSIONS

The addition of gentamicin to a regimen containing vancomycin or cloxacillin plus rifampicin in SPVE was not associated to better outcome.

Proposal for shorter antibiotic therapies

OBJECTIVES

Reducing antibiotic consumption has now become a major public health priority. Reducing treatment duration is one of the means to achieve this objective. Guidelines on the therapeutic management of the most frequent infections recommend ranges of treatment duration in the ratio of one to two. The Recommendation Group of the French Infectious Diseases Society (SPILF) was asked to collect literature data to then recommend the shortest treatment durations possible for various infections.

METHODS

Analysis of the literature focused on guidelines published in French and English, supported by a systematic search on PubMed. Articles dating from one year before the guidelines publication to August 31, 2015 were searched on the website.

RESULTS

The shortest treatment durations based on the relevant clinical data were suggested for upper and lower respiratory tract infections, central venous catheter-related and uncomplicated primary bacteremia, infective endocarditis, bacterial meningitis, intra-abdominal, urinary tract, upper reproductive tract, bone and joint, skin and soft tissue infections, and febrile neutropenia. Details of analyzed articles were shown in tables.

CONCLUSION

This work stresses the need for new well-conducted studies evaluating treatment durations for some common infections. Following the above-mentioned work focusing on existing literature data, the Recommendation Group of the SPILF suggests specific study proposals.

Right-Sided Infective Endocarditis and Pulmonary Infiltrates: An Update

Sixty years after its initial description, right-sided infective endocarditis (RSIE) still poses a challenge to all medical practitioners. Epidemiological data reveal a rising incidence attributable to the global surge in the number of intravenous drug users and the increased use of central vascular catheters and implantable cardiac devices. RSIE differs from left-sided infective endocarditis in more than just the location of the involved cardiac valve. They have different clinical presentations, diagnostic findings, and prognoses; hence, they require different management strategies. Cardiac murmurs and systemic emboli are usually absent in RSIE, whereas pulmonary embolism and its related complications dominate the clinical picture. Diagnostic delay of RSIE is secondary to the similarity in its initial presentation to other entities. Complications may ensue as a result of this delay. Diagnosis can be initially confirmed by using transthoracic echocardiography, except in patients with implanted cardioverter defibrillator, where a transesophageal echocardiogram is necessary. Various factors may increase mortality and morbidity in RSIE such as tricuspid valve vegetation size, fungal etiology, and low CD4 cell count in HIV patients. Oxacillin and vancomycin had been the traditionally used agents for the treatment of methicillin-susceptible and methicillin-resistant Staphylococcus aureus, respectively. More recently, daptomycin has shown promising results, which has led to its Food and Drug Administration (FDA) approval for the treatment of S. aureus bacteremia and associated RSIE. The aim of this article is to provide a comprehensive update on RSIE including epidemiology, pathogenesis, microbiology, diagnosis, management, and prognosis.

A comparison of different antibiotic regimens for the treatment of infective endocarditis

BACKGROUND

Infective endocarditis is a microbial infection of the endocardial surface of the heart. Antibiotics are the cornerstone of treatment, but their use is not standardised, due to the differences in presentation, populations affected and the wide variety of micro-organisms that can be responsible.

OBJECTIVES

To assess the existing evidence about the clinical benefits and harms of different antibiotics regimens used to treat people with infective endocarditis.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE Classic and EMBASE, LILACS, CINAHL and the Conference Proceedings Citation Index on 30 April 2015. We also searched three trials registers and handsearched the reference lists of included papers. We applied no language restrictions.

SELECTION CRITERIA

We included randomised controlled trials assessing the effects of antibiotic regimens for treating possible infective endocarditis diagnosed according to modified Duke's criteria. We considered all-cause mortality, cure rates and adverse events as the primary outcomes. We excluded people with possible infective endocarditis and pregnant women.

DATA COLLECTION AND ANALYSIS

Three review authors independently performed study selection, 'Risk of bias' assessment and data extraction in duplicate. We constructed 'Summary of findings' tables and used GRADE methodology to assess the quality of studies. We described the included studies narratively.

MAIN RESULTS

Four small randomised controlled trials involving 728 allocated/224 analysed participants met our inclusion criteria. These trials had a high risk of bias. Drug companies sponsored two of the trials. We were unable to pool the data due to the heterogeneity in outcome definitions and the different antibiotics used.The included trials compared the following antibiotic schedules. The first trial compared quinolone (levofloxacin) plus standard treatment (anti-staphylococcal penicillin (cloxacillin or dicloxacillin), aminoglycoside (tobramycin or netilmicin) and rifampicin) versus standard treatment alone reporting uncertain effects on all-cause mortality (8/31 (26%) with levofloxacin plus standard treatment versus 9/39 (23%) with standard treatment alone; RR 1.12, 95% CI 0.49 to 2.56, very low quality evidence). The second trial compared daptomycin versus low-dose gentamicin plus an anti-staphylococcal penicillin (nafcillin, oxacillin or flucloxacillin) or vancomycin. This showed uncertain effects in terms of cure rates (9/28 (32.1%) with daptomycin versus 9/25 (36%) with low-dose gentamicin plus anti-staphylococcal penicillin or vancomycin, RR 0.89 95% CI 0.42 to 1.89; very low quality evidence). The third trial compared cloxacillin plus gentamicin with a glycopeptide (vancomycin or teicoplanin) plus gentamicin. In participants receiving gentamycin plus glycopeptide only 13/23 (56%) were cured versus 11/11 (100%) receiving cloxacillin plus gentamicin (RR 0.59, 95% CI 0.40 to 0.85; very low quality evidence). The fourth trial compared ceftriaxone plus gentamicin versus ceftriaxone alone and found no conclusive differences in terms of cure (15/34 (44%) with ceftriaxone plus gentamicin versus 21/33 (64%) with ceftriaxone alone, RR 0.69, 95% CI 0.44 to 1.10; very low quality evidence).The trials reported adverse events, need for cardiac surgical interventions, uncontrolled infection and relapse of endocarditis and found no conclusive differences between comparison groups (very low quality evidence). No trials assessed septic emboli or quality of life.

AUTHORS' CONCLUSIONS

Limited and very low quality evidence suggested that there were no conclusive differences between antibiotic regimens in terms of cure rates or other relevant clinical outcomes. However, because of the very low quality evidence, this needs confirmation. The conclusion of this Cochrane review was based on randomised controlled trials with high risk of bias. Accordingly, current evidence does not support or reject any regimen of antibiotic therapy for treatment of infective endocarditis.

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta lactam antibiotic with an aminoglycoside antibiotic may provide certain advantages over beta lactam monotherapy.

OBJECTIVES

Our objectives were to compare beta lactam monotherapy versus beta lactam-aminoglycoside combination therapy in patients with sepsis and to estimate the rate of adverse effects with each treatment regimen, including the development of bacterial resistance to antibiotics.

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 11); MEDLINE (1966 to 4 November 2013); EMBASE (1980 to November 2013); LILACS (1982 to November 2013); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2013). We scanned citations of all identified studies and contacted all corresponding authors. In our previous review, we searched the databases to July 2004.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta lactam monotherapy versus any combination of a beta lactam with an aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause mortality. Secondary outcomes included treatment failure, superinfections and adverse events. Two review authors independently collected data. We pooled risk ratios (RRs) with 95% confidence intervals (CIs) using the fixed-effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 69 trials that randomly assigned 7863 participants. Twenty-two trials compared the same beta lactam in both study arms, while the remaining trials compared different beta lactams using a broader-spectrum beta lactam in the monotherapy arm. In trials comparing the same beta lactam, we observed no difference between study groups with regard to all-cause mortality (RR 0.97, 95% CI 0.73 to 1.30) and clinical failure (RR 1.11, 95% CI 0.95 to 1.29). In studies comparing different beta lactams, we observed a trend for benefit with monotherapy for all-cause mortality (RR 0.85, 95% CI 0.71 to 1.01) and a significant advantage for clinical failure (RR 0.75, 95% CI 0.67 to 0.84). No significant disparities emerged from subgroup and sensitivity analyses, including assessment of participants with Gram-negative infection. The subgroup of Pseudomonas aeruginosa infections was underpowered to examine effects. Results for mortality were classified as low quality of evidence mainly as the result of imprecision. Results for failure were classified as very low quality of evidence because of indirectness of the outcome and possible detection bias in non-blinded trials. We detected no differences in the rate of development of resistance. Nephrotoxicity was significantly less frequent with monotherapy (RR 0.30, 95% CI 0.23 to 0.39). We found no heterogeneity for all these comparisons.We included a small subset of studies addressing participants with Gram-positive infection, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta lactams for sepsis should be discouraged. All-cause mortality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Native valve right sided infective endocarditis

Right-sided infective endocarditis (RSIE) accounts for 5-10% of all cases of infective endocarditis (IE), and is predominantly encountered in the injecting drug user (IDU) population, where HIV and HCV coinfections often coexist. Staphylococcus aureus is the most common pathogen. The pathogenesis of RSIE is still not well understood. RSIE usually presents as a persistent fever with respiratory symptoms whilst signs of systemic embolisation as seen in left-sided IE are notably absent. The prompt diagnosis of RSIE thus requires a high index of suspicion. Transthoracic echocardiography (TTE) can detect the majority of RSIE, whilst transoesophageal echocardiography (TOE) can increase sensitivity. Virulence of the causative organism and vegetation size are the major determinants of prognosis. Most cases of RSIE resolve with appropriate antibiotic administration.

Management of infective endocarditis: challenges and perspectives

Despite improvements in medical and surgical therapies, infective endocarditis is associated with poor prognosis and remains a therapeutic challenge. Many factors affect the outcome of this serious disease, including virulence of the microorganism, characteristics of the patients, presence of underlying disease, delays in diagnosis and treatment, surgical indications, and timing of surgery. We review the strengths and limitations of present therapeutic strategies and propose future directions for better management of endocarditis according to the most recent research. Novel perspectives on the management of endocarditis are emerging and offer hope for decreasing the rate of residual deaths by accelerating the process of diagnosis and risk stratification, reducing delays in starting antimicrobial therapy, rapid transfer of high-risk patients to specialised medico-surgical centres, development of new surgical methods, and close long-term follow-up.

Combination therapy with an aminoglycoside for Staphylococcus aureus endocarditis and/or persistent bacteremia is associated with a decreased rate of recurrent bacteremia: a cohort study

PURPOSE

Although limited data exist on the efficacy and potential risk of synergistic aminoglycoside therapy for persistent Staphylococcus aureus bacteremia and endocarditis, aminoglycosides are frequently used in clinical practice.

METHODS

As our study population, we included subjects fulfilling the modified Duke criteria for S. aureus endocarditis and/or having greater than 72 h of S. aureus bacteremia. Among these subjects, we compared patients who did and did not receive aminoglycoside therapy for their S. aureus bloodstream infection. These groups were compared for the primary outcome of recurrent bacteremia, as well as for the duration of bacteremia, mortality, complication rate, and incident renal failure.

RESULTS

Eighty-seven subjects fulfilled the inclusion criteria. Of these, 49 received aminoglycoside therapy, whereas 38 did not. There were no significant differences in the baseline characteristics when comparing groups who did or did not receive aminoglycoside therapy. Four (8.2%) subjects treated with aminoglycoside therapy experienced recurrent bacteremia versus nine (23.7%) who did not receive aminoglycoside therapy [relative risk and 95% confidence interval [RR (95%CI)] = 0.51 (0.22-1.17), p = 0.04]. In multivariable analyses, aminoglycoside use remained significantly associated with a decrease in recurrent bacteremia [adjusted odds ratio (OR) (95%CI) = 0.26 (0.07-0.98), p = 0.046]. No significant differences were seen between groups treated with and without an aminoglycoside in terms of the 6-month all-cause mortality (51.0 vs. 42.1%, p = 0.41), complication rate (71.4 vs. 73.7%, p = 0.82), or incident renal failure (54.5 vs. 46.9%, p = 0.54).

CONCLUSIONS

The use of combination therapy with an aminoglycoside in persistent S. aureus bacteremia and/or endocarditis may be associated with a lower rate of recurrent bacteremia without significant differences in the incident renal failure.

Antimicrobial therapy of sepsis and septic shock--when are two drugs better than one?

In clinical practice, physicians frequently use combination therapy despite the conflicting evidence for its effectiveness. The results of recent studies have contributed to our understanding of this important issue. In this article, we examine the evidence for, or against, the use of combination drug therapy compared with monotherapy in the management of serious infections, sepsis, and septic shock.

Clinical management of Staphylococcus aureus bacteraemia

Staphylococcus aureus bacteraemia is one of the most common serious bacterial infections worldwide. In the UK alone, around 12,500 cases each year are reported, with an associated mortality of about 30%, yet the evidence guiding optimum management is poor. To date, fewer than 1500 patients with S aureus bacteraemia have been recruited to 16 controlled trials of antimicrobial therapy. Consequently, clinical practice is driven by the results of observational studies and anecdote. Here, we propose and review ten unanswered clinical questions commonly posed by those managing S aureus bacteraemia. Our findings define the major areas of uncertainty in the management of S aureus bacteraemia and highlight just two key principles. First, all infective foci must be identified and removed as soon as possible. Second, long-term antimicrobial therapy is required for those with persistent bacteraemia or a deep, irremovable focus. Beyond this, the best drugs, dose, mode of delivery, and duration of therapy are uncertain, a situation compounded by emerging S aureus strains that are resistant to old and new antibiotics. We discuss the consequences on clinical practice, and how these findings define the agenda for future clinical research.

A European survey of antibiotic management of methicillin-resistant Staphylococcus aureus infection: current clinical opinion and practice

Although the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) varies across Europe, healthcare-associated MRSA infections are common in many countries. Despite several national guidelines, the approach to treatment of MRSA infections varies across the continent, and there are multiple areas of management uncertainty for which there is little clinical evidence to guide practice. A faculty, convened to explore some of these areas, devised a survey that was used to compare the perspectives of infection specialists from across Europe on the management of MRSA infections with those of the faculty specialists. The survey instrument, a web-based questionnaire, was sent to 3840 registered delegates of the 19th European Congress of Clinical Microbiology and Infectious Diseases, held in April 2009. Of the 501 (13%) respondents to the survey, 84% were infection/microbiology specialists and 80% were from Europe. This article reports the survey results from European respondents, and shows a broad range of opinion and practice on a variety of issues pertaining to the management of minor and serious MRSA infections, such as pneumonia, bacteraemia, and skin and soft tissue infections. The issues include changing epidemiology, when and when not to treat, choice of treatment, and duration and route of treatment. The survey identified areas where practice can be improved and where further research is needed, and also identified areas of pan-European consensus of opinion that could be applied to European guidelines for the management of MRSA infection.

New therapeutic choices for infections caused by methicillin-resistant Staphylococcus aureus

In recent years, a marked increase in the incidence of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) has occurred in many countries. This review addresses the effectiveness and limitations of drugs classically used for the treatment of MRSA, e.g. vancomycin, and also newer anti-MRSA antimicrobials, e.g. second-generation glycolipopeptides, tigecycline, and beta-lactams.

Antibiotic treatment of Staphylococcus aureus endocarditis. A review of 119 cases

Clinical and bacteriological information of Staphylococcus aureus endocarditis was reviewed in 119 cases from all over Denmark. Overall mortality was 71%. Survival correlated with antistaphylococcal treatment, short duration from onset of infection to start of treatment, and long duration of treatment. In spite of relevant treatment, mortality was significantly lower in cases infected with penicillin-susceptible strains than when penicillin-resistant strains were isolated. There were no differences in the effect of various anti-staphylococcal treatment regimens; in particular, there were no differences in mortality with regard to beta-lactam antibiotics alone as compared to beta-lactam antibiotics in combination with aminoglycosides. However, embolic manifestations occurred more often after start of treatment with combination therapy than with beta-lactam antibiotics alone.

Endocarditis caused by Staphylococcus aureus: A reappraisal of the epidemiologic, clinical, and pathologic manifestations with analysis of factors determining outcome

Staphylococcus aureus is the leading cause of infectious endocarditis and its mortality has remained high despite better diagnostic and therapeutic procedures over time. We conducted a retrospective review of 133 cases of definite S. aureus endocarditis seen at a single tertiary care hospital over 22 years to assess changes in the epidemiology and incidence of the infection, manifestations, outcome, risk factors for mortality, and impact of cardiac surgery on prognosis.Patients were classified into 2 groups: 1) right-sided endocarditis (64 patients) and 2) left-sided endocarditis (69 patients). While the number of cases of left-sided endocarditis remained steady at 1-3 cases per 10,000 admissions, the incidence of right-sided endocarditis, after a peak in the early 1990s, declined to almost disappear in 2001. Among the cases of right-sided endocarditis, we found 2 subsets of patients with different clinical features and prognosis: the first subset comprised 53 intravenous drug abusers, and the second subset comprised 11 patients with catheter-associated S. aureus bacteremia and endocarditis. Fifty-one patients were human immunodeficiency virus (HIV)-positive drug abusers, most of whom (80.3%) had right-sided endocarditis. We did not find differences in mortality between HIV-positive and HIV-negative individuals; mortality seemed to depend more on the site of the heart involved than on HIV status.Among the cases of left-sided endocarditis, the mitral valve was more commonly involved than the aortic valve (61% vs. 30%). Overall, 74% of patients with left-sided endocarditis developed 1 or more cardiac or extracardiac complication. In comparison, only 23.4% of patients with right-sided endocarditis developed complications.Prosthetic valve endocarditis (PVE) was hospital-acquired more frequently than native valve endocarditis (NVE). Patients with PVE had a shorter duration of symptoms until diagnosis and presented with or developed cardiac murmurs less frequently than patients with NVE. Cardiac failure (49%), renal failure (43%) and central nervous system (CNS) events (35%) were frequently observed in patients with both PVE and NVE. Valve replacement was more frequently needed and more rapidly performed in patients with PVE than in their counterparts with NVE.The overall mortality of patients with right-sided endocarditis was 17%. While the mortality of right-sided endocarditis in injection drug users was 3.7%, the mortality of patients with right-sided endocarditis associated with infected intravenous catheters was 82% (odds ratio [OR], 0.01; 95% confidence interval [CI], 0.001-0.07). For left-sided endocarditis mortality was 38% and was not significantly different in patients with NVE or PVE (OR, 0.65; 95% CI, 0.23-1.87). CNS complications were associated with mortality in both NVE (OR, 6.55; 95% CI, 1.78-24.04) and PVE (OR, 32; 95% CI, 2.63-465.40). Development of 2 or 3 complications was associated with an increased risk of mortality (OR, 5.59; 95% CI, 1.08-28.80 and OR, 9.25; 95% CI, 1.36-62.72 for 2 vs. 1 complication and for 3 vs. 2 complications, respectively).Surgical treatment did not significantly influence mortality in cases of NVE, (OR, 3.19; 95% CI, 0.76-13.38) but significantly improved the prognosis of patients with PVE (OR, 69; 95% CI, 2.89-1647.18).S. aureus endocarditis is an aggressive, often fatal, infection. The results of the current study suggest that valve replacement will improve the outcome of infection, particularly in patients with PVE.

The role of aminoglycosides in combination with a beta-lactam for the treatment of bacterial endocarditis: a meta-analysis of comparative trials

BACKGROUND

The addition of an aminoglycoside to a beta-lactam for the treatment of patients with infective endocarditis has been supported by data from laboratory and animal studies.

PURPOSE

We sought to review the evidence from the available comparative clinical trials regarding the role of aminoglycosides in combination with a beta-lactam for the treatment of bacterial endocarditis caused by Gram-positive cocci.

DATA SOURCES

The studies for our meta-analysis were retrieved from searches of the PubMed and Cochrane Central Register of Controlled Trials databases, as well as from the references cited in relevant articles. No limits were set regarding the language and date of publication of the studies.

STUDY SELECTION

Included studies were prospective studies that provided comparative data regarding the effectiveness of the treatment and/or mortality in patients receiving monotherapy with a beta-lactam or beta-lactam/aminoglycoside combination therapy.

DATA EXTRACTION

Two independent reviewers performed the literature search, study selection and extraction of data from relevant studies.

DATA SYNTHESIS

No clinical trial comparing beta-lactam monotherapy with beta-lactam/aminoglycoside combination therapy for the treatment of enterococcal endocarditis was found. We performed a meta-analysis of five available comparative trials [four randomized controlled trials (RCTs) and one comparative prospective trial], which included 261 patients with bacterial endocarditis in native valves due to Staphylococcus aureus (four studies) or streptococci of the viridans group (one study). There was no statistically significant difference between beta-lactam monotherapy and beta-lactam/aminoglycoside combination therapy regarding mortality [odds ratio (OR) = 0.59, 95% confidence interval (95% CI) = 0.21-1.66], treatment success (OR = 1.25, 95% CI = 0.49-3.05), treatment success without surgery (OR = 1.66, 95% CI = 0.64-4.30) or relapse of endocarditis (OR = 0.79, 95% CI = 0.15-4.29). Nephrotoxicity was less common in the beta-lactam monotherapy arm than in the beta-lactam/aminoglycoside combination therapy arm (OR = 0.38, 95% CI = 0.16-0.88, P = 0.024). No difference between the two treatment arms was found in subanalyses of the four studies that included only patients with staphylococcal infections in terms of mortality (OR = 0.69, 95% CI = 0.26-1.86, fixed effects model), treatment success (OR = 1.27, 95% CI = 0.47-3.43, fixed effects model) or relapse (OR = 0.76, 95% CI = 0.12-4.92, fixed effects model).

LIMITATIONS

The relatively small number of available comparative trials was the major limitation of this meta-analysis.

CONCLUSIONS

The limited evidence from the available prospective comparative studies does not offer support for the addition of an aminoglycoside to beta-lactam treatment of patients with endocarditis caused by Gram-positive cocci. A large multicentre RCT is necessary to reach a definitive conclusion on this issue.

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta-lactam antibiotic with an aminoglycoside antibiotic may have certain advantages over beta-lactam monotherapy.

OBJECTIVES

We compared clinical outcomes for beta lactam-aminoglycoside combination therapy versus beta lactam monotherapy for sepsis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library, Issue 3, 2004); MEDLINE (1966 to July 2004); EMBASE (1980 to March 2003); LILACS (1982 to July 2004); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2003). We scanned citations of all identified studies and contacted all corresponding authors.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta-lactam monotherapy to any combination of one beta-lactam and one aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause fatality. Secondary outcomes included treatment failure, superinfections, colonization, and adverse events. Two authors independently collected data. We pooled relative risks (RR) with their 95% confidence intervals (CI) using the fixed effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 64 trials, randomizing 7586 patients. Twenty trials compared the same beta-lactam in both study arms, while the remaining compared different beta-lactams using a broader spectrum beta-lactam in the monotherapy arm. In studies comparing the same beta-lactam, we observed no difference between study groups with regard to all-cause fatality, RR 1.01 (95% CI 0.75-1.35) and clinical failure, RR 1.11 (95% CI 0.95-1.29). In studies comparing different beta-lactams, we observed an advantage to monotherapy: all cause fatality RR 0.85 (95% CI 0.71-1.01), clinical failure RR 0.77 (95% CI 0.69-0.86). No significant disparities emerged from subgroup and sensitivity analyses, including the assessment of patients with Gram-negative and Pseudomonas aeruginosa infections. We detected no differences in the rate of resistance development. Adverse events rates did not differ significantly between the study groups overall, although nephrotoxicity was significantly more frequent with combination therapy, RR 0.30 (95% CI 0.23-0.39). We found no heterogeneity for all comparisons. We included a small subset of studies addressing patients with Gram-positive infections, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta-lactams for sepsis should be discouraged. All-cause fatality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Short-course gentamicin in combination with daptomycin or vancomycin against Staphylococcus aureus in an in vitro pharmacodynamic model with simulated endocardial vegetations

The ability to maximize bactericidal activity while minimizing toxicity is a therapeutic goal in the treatment of infective endocarditis. We evaluated the impact of administering short-course regimens of gentamicin in combination with daptomycin or vancomycin against one methicillin-susceptible (MSSA 1199) and one methicillin-resistant (MRSA 494) Staphylococcus aureus isolate using an in vitro pharmacodynamic model with simulated endocardial vegetations over 96 h. Human therapeutic dosing regimens for daptomycin (6 and 8 mg/kg of body weight), vancomycin, and gentamicin were simulated. Short-course combination regimens involving gentamicin were administered either as a single 5-mg/kg dose or three 1-mg/kg doses for only the first 24 h and compared to the regimens administered for the full 96-h duration. For all experiments, physiologic conditions of albumin, calcium, and pH were simulated. Both regimens of daptomycin achieved 99.9% kill by 32 h and maintained bactericidal activity against both isolates, which was significantly different from vancomycin, which displayed bacteriostatic activity (P < 0.05). The effects of all short-course regimens of gentamicin were equal to those of the full-duration regimens in combination with daptomycin. Adding three doses of gentamicin (1 mg/kg) to daptomycin resulted in enhancement and bactericidal activity at 24 h against both MRSA and MSSA. The addition of a single dose of gentamicin (5 mg/kg) enhanced or improved the activity of daptomycin and resulted in early bactericidal activity at 4 h against both isolates. The addition of three doses of gentamicin (1 mg/kg) did not improve the activity of vancomycin. However, the addition of a single 5-mg/kg dose of gentamicin to vancomycin resulted in early enhancement at 4 h and 99.9% kill at 32 h for MRSA. These results suggest that a single high dose of gentamicin in combination with daptomycin or vancomycin may be of utility to maximize synergistic and bactericidal activity and minimize toxicity. Further investigation is warranted.

Infective endocarditis: a review of the best treatment options

Despite significant advances in antimicrobial therapy and an enhanced ability to diagnose and treat complications, infective endocarditis is still associated with substantial morbidity and mortality today, and its incidence has not decreased over the past decades. This apparent paradox may be explained by a progressive change in risk factors, leading to an evolution in its epidemiological and clinical features. In fact, new risk factors for endocarditis have emerged, such as intravenous drug abuse, diffusion of heart surgery procedures and prosthetic valve implantation, atherosclerotic valve disease in elderly patients, and nosocomial disease. Recently identified microorganisms (including Bartonella spp., Abiotrophia defectiva, and the HACEK group of bacteria [including Haemophilus spp., Actinobacillus spp., Cardiobacterium hominis, Eikenella corrodens and Kingella kingae]) are sometimes the cause of culture-negative endocarditis, and emerging resistant bacteria (such as methicillin- or vancomycin-resistant Staphylococci and vancomycin-resistant Enterococci) are becoming a new challenge for conventional antibiotic therapy. New therapeutic approaches need to be developed for the treatment of infective endocarditis caused by drug-resistant Gram-positive cocci, and some antimicrobial compounds recently introduced in clinical practice (such as streptogramins and oxazolidinones) may be an effective alternative, but further clinical studies are needed in order to confirm their effectiveness and safety. This review should help redefine the best therapeutic and preventive strategies against infective endocarditis.

Guidelines for the antibiotic treatment of endocarditis in adults: report of the Working Party of the British Society for Antimicrobial Chemotherapy

The BSAC Guidelines on Endocarditis were last published in 1998. The Guidelines presented here have been updated and extended to reflect changes in both the antibiotic resistance characteristics of causative organisms and the availability of new antibiotics. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking, and therefore a consensus approach has again been adopted. The Guidelines cover diagnosis and laboratory testing, suitable antibiotic regimens and causative organisms. Special emphasis is placed on common causes of endocarditis, such as streptococci and staphylococci, however, other bacterial causes (such as enterococci, HACEK organisms, Coxiella and Bartonella) and fungi are considered. The special circumstances of prosthetic endocarditis are discussed.

Methicillin-resistant Staphylococcus aureus infections in ICU patients

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in patients admitted to the intensive care unit has dramatically increased in recent years, with an associated increase in morbidity and mortality and the costs of caring for patients with MRSA infections. Although indiscriminate and inappropriate use of antibiotics has contributed to this phenomenon, horizontal transmission of MRSA between patients and health care providers is the principal cause of this observed increase. This article discusses the pathogenesis, epidemiology, treatment, and prevention of MRSA infections in critically ill patients.

Beta lactam monotherapy versus beta lactam-aminoglycoside combination therapy for sepsis in immunocompetent patients: systematic review and meta-analysis of randomised trials

OBJECTIVE

To compare beta lactam monotherapy with beta lactam-aminoglycoside combination therapy for severe infections.

DATA SOURCES

Medline, Embase, Lilacs, Cochrane Library, and conference proceedings, to 2003; references of included studies; contact with all authors. No restrictions, such as language, year of publication, or publication status.

STUDY SELECTION

All randomised trials of beta lactam monotherapy compared with beta lactam-aminoglycoside combination therapy for patients without neutropenia who fulfilled criteria for sepsis.

DATA SELECTION

Two reviewers independently applied selection criteria, performed quality assessment, and extracted the data. The primary outcome assessed was all cause fatality by intention to treat. Relative risks were pooled with the random effect model (relative risk < 1 favours monotherapy).

RESULTS

64 trials with 7586 patients were included. There was no difference in all cause fatality (relative risk 0.90, 95% confidence interval 0.77 to 1.06). 12 studies compared the same beta lactam (1.02, 0.76 to 1.38), and 31 studies compared different beta lactams (0.85, 0.69 to 1.05). Clinical failure was more common with combination treatment overall (0.87, 0.78 to 0.97) and among studies comparing different beta lactams (0.76, 0.68 to 0.86). There was no advantage to combination therapy among patients with Gram negative infections (1835 patients) or Pseudomonas aeruginosa infections (426 patients). There was no difference in the rate of development of resistance. Nephrotoxicity was significantly more common with combination therapy (0.36, 0.28 to 0.47). Heterogeneity was not significant for these comparisons.

CONCLUSIONS

In the treatment of sepsis the addition of an aminoglycoside to beta lactams should be discouraged. Fatality remains unchanged, while the risk for adverse events is increased.

Combination antibiotic therapy for infective endocarditis

Despite the availability of new and potent antibiotics, modern echocardiography, and advanced surgical techniques, infective endocarditis (IE) is still associated with high morbidity and mortality rates. Use of synergistic antibiotic combinations is an appealing way to optimize therapy for IE. This review focuses on evidence-based recommendations for combination antimicrobial therapy for IE due to the most common etiologic pathogens. Few proven synergistic approaches for the treatment of IE have been globally demonstrated via in vitro models, experimental IE models, and human clinical trials, except for IE due to enterococci. Novel approaches, such as short-course aminoglycoside therapy and double-beta-lactam combination therapy, appear to be promising for treatment of enterococcal IE. Short-course combination therapy involving agents with activity against the cell wall (CWAs) and aminoglycosides is highly effective for IE caused by viridans group streptococci. Although synergistic combination therapy with CWAs-aminoglycosides remains widely used by clinicians for Staphylococcus aureus IE, few definitive human data exist that demonstrate the clinical benefit of such an approach.

[Antibiotic combinations in Staphylococcus aureus infections: arguments against]

In a case of severe infection due to Staphylococcus aureus, generally accepted practice involves the use of a combination of antibiotics. This article examines the type and quality of the experimental and clinical data which has been collected in this context. Published findings suggest that the arguments in favour of combinations are usually theoretical, and that a demonstration of the superiority of combinations has never been made by comparative, randomised studies.

Monotherapy versus combination therapy for bacterial infections

The authors discuss the latest findings regarding the use of one or more antimicrobial drugs for a variety of infections. They offer suggestions for treatment based on a host of considerations, including the synergy and antagonism of specific drugs, type of infection, potential toxicities, and cost.

Right-sided endocarditis caused by Staphylococcus aureus in drug abusers

A prospective, open, and randomized study of right-sided endocarditis caused by Staphylococcus aureus in drug abuse patients is reported. The following parenteral treatments were compared. Group A patients were treated with 2 g of cloxacillin every 4 h and 1.5 mg of gentamicin per kg of body weight every 8 h for 2 weeks. Group B patients were treated with teicoplanin at 10 mg/kg/12 h on the 1st to 3rd days, 6 mg/kg/12 h on the 4th to 7th days, and 7 mg/kg/24 h on the 8th days. Drug abusers with bacteremia caused by S. aureus and suggestive signs of endocarditis were included. Clinical failures were observed in one patient in group A and in four of six patients in group B. Three patients in group B developed breakthrough bacteremia with teicoplanin-susceptible strains on days +6, +14, and +19. Serum teicoplanin levels and serum bactericidal titers showed a decrease in the 2nd week, when dosages received were 7 mg/kg/day. In conclusion, in treatment of right-sided endocarditis caused by S. aureus in drug abusers with teicoplanin, the use of dosages of 7 mg/kg/day is not recommended even if patients have received dosages of 12 mg/kg/day during the 1st week.

Endocarditis in the emergency department

Clinical presentations and pathogeneses of endocarditis and aspects of its diagnosis and management relevant to emergency department practice are reviewed. Guidelines for admission, laboratory evaluation, and decisions regarding the initiation of therapy in the ED are offered. Also discussed are the role of the emergency physician in the prevention of iatrogenic infection and current recommendations regarding administration of prophylactic antibiotics for ED procedures.

Comparison of the effectiveness of various antibiotics in the treatment of methicillin-susceptible Staphylococcus aureus experimental infective endocarditis

The effectiveness of various antibiotics was tested in the eradication of a strain of methicillin-susceptible Staphylococcus aureus (MSSA) of cardiac vegetations, in an experimental model of endocarditis in rabbits. Twelve animals comprised the control group and 48 the treated ones. After inducing the experimental endocarditis, the animals were treated for three days; then mortality, blood cultures at 48 and 72 hours and the title of the colony forming units per gram of vegetation (CFU/g) were evaluated. Imipenem and the cloxacillin-gentamicin association were found to be as effective as cloxacillin in eradicating the microorganisms of the vegetation. Clindamycin in high doses was shown to be a valid alternative. Vancomycin, teicoplanin, rifampin and ciprofloxacin were less effective than cloxacillin. The experimental model seems to be an effective method for evaluating antimicrobial treatments in staphylococcal endocarditis.

Vancomycin for Staphylococcus aureus endocarditis in intravenous drug users

The clinical courses of 13 consecutive intravenous drug users with Staphylococcus aureus endocarditis treated principally with vancomycin were reviewed. Two patients, one with only right-sided endocarditis and the other with tricuspid and mitral valve endocarditis, had recurrences of positive blood cultures 2 days after completing a 4-week course of vancomycin. Two patients, both of whom eventually were cured, had modifications of therapy because of bacteremia persisting 7 and 16 days into therapy. One patient required an operation for recurrent fevers, and the resected vegetation showed evidence of active infection. Time-kill studies performed with nafcillin and vancomycin for 10 isolates of S. aureus showed that vancomycin was less rapidly bactericidal than nafcillin. Although vancomycin is used as an alternative to penicillinase-resistant penicillins for treatment of staphylococcal endocarditis, these findings raise the question of whether it is equivalent to these drugs in efficacy.

Oxygen-dependent up-regulation of mucoid exopolysaccharide (alginate) production in Pseudomonas aeruginosa

We previously showed substantial differences in Pseudomonas aeruginosa exopolysaccharide production in vitro at oxygen tensions reflective of the right versus left cardiac circuits in vivo (40 versus 80 mm Hg, respectively; A. S. Bayer, T. O'Brien, D. C. Norman, and C. C. Nast, J. Antimicrob. Chemother. 23:21-35, 1989). However, those studies did not specifically confirm this exopolysaccharide to be the characteristic P. aeruginosa mucoid alginate seen in patients with cystic fibrosis. With a murine monoclonal antibody prepared against P. aeruginosa alginate, strongly positive immunofluorescence (IF) staining of a nonmucoid P. aeruginosa strain (PA-96) was seen after its exposure in vitro to oxygen tensions (pO2) of approximately 80 mm Hg; the intensity of the IF staining under these conditions was similar to that observed with a phenotypically mucoid P. aeruginosa strain (C1712M) from a cystic fibrosis patient. In contrast, the same nonmucoid strain (PA-96), after exposure to pO2 of approximately 40 mm Hg, showed little IF staining for alginate. Following enzyme treatment with alginase, PA-96 cells previously exposed to the higher pO2 and exhibiting enhanced alginate production, as determined by IF staining, now showed no IF staining. Moreover, treatment of the oxygen-up-regulated PA-96 cells with alginase released amounts of unsaturated alginate breakdown products (uronic acids) quantitatively similar to those released by typically mucoid strains treated with the same enzyme. These data indicated that the P. aeruginosa exopolysaccharide in our studies was, indeed, mucoid alginate and that variations in oxygen tensions represent one of the trigger mechanisms for the up-regulation of mucoid exopolysaccharide production.

Repeated echocardiography: essential in the management of Staphylococcus aureus endocarditis

Staphylococcus aureus endocarditis in a previously healthy 25 year old man is described. Repeated echocardiography recorded rapid progression of aortic root and interventricular septal involvement and, even though the patient was clinically stable, early surgery was advised with a satisfactory outcome. This case report clearly demonstrates the vital role of repeated cross-sectional echocardiography in the management of such cases.

Evaluation of teicoplanin for treatment of endocarditis caused by gram-positive cocci in 20 patients

Teicoplanin, a new glycopeptide antibiotic similar to vancomycin, was evaluated for the treatment of bacterial endocarditis in an open multicenter study from May 1985 to August 1987. A total of 20 patients with positive blood culture endocarditis received teicoplanin once daily as a mean intravenous injection of 7.3 mg/kg of body weight (range, 4.8 to 10.6 mg/kg); in 17 patients, teicoplanin was combined with another antibiotic, usually an aminoglycoside. The mean duration of therapy was 28 days (range, 7 to 66 days). The diagnosis of endocarditis was confirmed by echocardiography or anatomical findings in 15 patients and established on the basis of clinical manifestations plus positive blood cultures in 5 patients. The tricuspid valve was involved in 11 of the 20 patients. Isolates from blood were 12 Staphylococcus aureus, 1 Staphylococcus hominis, 1 Micrococcus sedentarius, 1 Enterococcus faecalis, 3 Streptococcus bovis, and 2 nongroupable Streptococcus sp. At the end of therapy, bacterial eradication was achieved in 17 of 20 patients (85%), and a favorable clinical outcome had occurred in 14 of 17 evaluable patients (82%). Of these 14 patients, one relapsed 4 months after the end of treatment. Thus, teicoplanin was effective in 13 of 17 patients (76%). Mean peak levels of teicoplanin in serum were lower, 23.1 +/- 2.9 micrograms/ml, in patients who failed than in those who were cured (45.8 +/- 8.4 micrograms/ml). Side effects occurred in 7 of 20 patients (35%), and required premature discontinuation of teicoplanin in 3 patients. These side effects were fever in three patients, rash in three patients, hearing loss in two patients, and increased serum transaminase levels in two patients. This study demonstrates the efficacy of teicoplanin in the treatment of endocarditis and the need for achieving peak levels in serum close to 40 micrograms/ml. Teicoplanin should now be further evaluated in endocarditis caused by gram-positive cocci means of controlled comparative study with standard therapy.

Ciprofloxacin therapy of experimental endocarditis caused by methicillin-susceptible or methicillin-resistant Staphylococcus aureus

Ciprofloxacin was more effective (P less than 0.01) than either imipenem or nafcillin therapy of experimental methicillin-susceptible Staphylococcus aureus endocarditis in rabbits after 2 or 3 days of treatment. There was no significant difference between results of treatment of methicillin-susceptible S. aureus experimental endocarditis with ciprofloxacin and results with the combination of nafcillin and gentamicin. Ciprofloxacin was more effective (P less than 0.01) than vancomycin therapy of experimental methicillin-resistant S. aureus endocarditis after 3 days of treatment. After 5 days of treatment, there was no significant difference between the results of treatment of experimental methicillin-resistant S. aureus endocarditis with ciprofloxacin and results with vancomycin.