Daptomycin versus linezolid for treatment of vancomycin-resistant enterococcal bacteremia: systematic review and meta-analysis

Treatment of Complicated Gram-Positive Bacteremia and Infective Endocarditis

The Gram-positive cocci Staphylococcus aureus, Streptococcus spp., and Enterococcus spp. are the most frequent causative organisms of bloodstream infections and infective endocarditis. "Complicated bacteremia" is a term used in S. aureus bloodstream infections and originally implied the presence of metastatic infectious foci (i.e. complications of S. aureus bacteremia). These complications demand longer antimicrobial treatment durations and, frequently, interventional source control. Several risk factors for the incidence of bacteremia complications have been identified and are often used for the definition of complicated bacteremia. Here, we discuss management and diagnostic approaches and treatment options for patients with complicated bacteremia, with particular focus on infective endocarditis. We also summarize the available evidence regarding imaging modalities and the choice of antimicrobial mono- or combination therapy according to resistance patterns for these pathogens as well as treatment durations and optimized application routes. Finally, we synopsize current and future areas of research in complicated bacteremia and infective endocarditis.

Bactericidal versus bacteriostatic antibacterials: clinical significance, differences and synergistic potential in clinical practice

Antibacterial activity can be classified as either bactericidal or bacteriostatic, using methods such as the MBC/MIC ratio and time-kill curves. However, such categorization has proven challenging in clinical practice, as these definitions only apply under specific laboratory conditions, which may differ from clinical settings. Several factors, such as the specific bacteria or infectious medium, can affect the action of antibiotics, with many antibacterials exerting both activities. These definitions have also led to the belief that bactericidal antibacterials are superior to bacteriostatic, especially in more severe cases, such as endocarditis, neutropenia and bacteraemia. Additionally, current dogma dictates against the combination of bactericidal and bacteriostatic antibacterials in clinical practice, due to potential antagonism. This review aimed to assess the differences in antibacterial activity of bactericidal and bacteriostatic antibacterials based on in vitro and in vivo studies and examine their antagonistic or synergistic effects. Our findings show that specific bacteriostatic agents, such as linezolid and tigecycline, are clinically non-inferior to bactericidals in multiple infections, including pneumonia, intra-abdominal infections, and skin and soft tissue infections. Studies also support using several bacteriostatic agents as salvage therapies in severe infections, such as neutropenic fever and endocarditis. Additionally, not all combinations of bacteriostatic and bactericidal agents appear to be antagonistic, with many combinations, such as linezolid and rifampicin, already being used. The findings should be interpreted with caution, as most evidence is from observational studies and there is a need for randomized controlled trials to assess their effectiveness and combinations, especially within the context of rising antimicrobial resistance.

Pharmacotherapies for multidrug-resistant gram-positive infections: current options and beyond

INTRODUCTION

Infections due to multidrug-resistant organisms (MDRO) are a serious concern for public health with high morbidity and mortality. Though many antibiotics have been introduced to manage these infections, there are remaining concerns regarding the optimal management of Gram-positive MDROs.

AREAS COVERED

A literature search on the PubMed/Medline database was conducted. We applied no language and time limits for the search strategy. In this narrative review, we discuss the current options for managing Gram-positive MDROs as well as non-traditional antibacterial agents in development.

EXPERT OPINION

Despite their introduction more than 70 years ago, glycopeptides are still the cornerstone in treating Gram-positive infections: all registrative studies of new antibiotics have glycopeptides as control; these studies are designed as not inferior studies, therefore it is almost impossible to give recommendations other than the use of glycopeptides in the treatment of Gram-positive infections. The best evidence on treatments different from glycopeptides comes from post-hoc analysis and meta-analysis. Non-traditional antibacterial agents are being studied to aid in short and effective antibiotic therapies. The use of non-traditional antibacterial agents is not restricted to replacing traditional antibacterial agents with alternative therapies; instead, they should be used in combination with antibiotic therapies.

New advances in management and treatment of cardiac implantable electronic devices infections

Cardiac implantable electronic devices (CIED) are increasingly used worldwide, and infection of these devices remains one of the most feared complications.CIED infections (CDIs) represent a challenge for physicians and the healthcare system in general as they require prolonged hospitalization and antibiotic treatment and are burdened by high mortality and high costs, so management of CDIs must be multidisciplinary.The exact incidence of CDIs is difficult to define, considering that it is influenced by various factors mainly represented by the implanted device and the type of procedure. Risk factors for CDIs could be divided into three categories: device related, patient related, and procedural related and the etiology is mainly sustained by Gram-positive bacteria; however, other etiologies cannot be underestimated. As a matter of fact, the two cornerstones in the treatment of these infections are device removal and antimicrobial treatment. Finally, therapeutic drug monitoring and PK/PD correlations should be encouraged in all patients with CDIs receiving antibiotic therapy and may result in a better clinical outcome and a reduction in antibiotic resistance and economic costs.In this narrative review, we look at what is new in the management of these difficult-to-treat infections.

Promiscuous, persistent and problematic: insights into current enterococcal genomics to guide therapeutic strategy

Vancomycin-resistant enterococci (VRE) are major opportunistic pathogens and the causative agents of serious diseases, such as urinary tract infections and endocarditis. VRE strains mainly include species of Enterococcus faecium and E. faecalis which can colonise the gastrointestinal tract (GIT) of patients and, following growth and persistence in the gut, can transfer to blood resulting in systemic dissemination in the body. Advancements in genomics have revealed that hospital-associated VRE strains are characterised by increased numbers of mobile genetic elements, higher numbers of antibiotic resistance genes and often lack active CRISPR-Cas systems. Additionally, comparative genomics have increased our understanding of dissemination routes among patients and healthcare workers. Since the efficiency of currently available antibiotics is rapidly declining, new measures to control infection and dissemination of these persistent pathogens are urgently needed. These approaches include combinatory administration of antibiotics, strengthening colonisation resistance of the gut microbiota to reduce VRE proliferation through commensals or probiotic bacteria, or switching to non-antibiotic bacterial killers, such as bacteriophages or bacteriocins. In this review, we discuss the current knowledge of the genomics of VRE isolates and state-of-the-art therapeutic advances against VRE infections.

Practical Lessons on Antimicrobial Therapy for Critically Ill Patients

Sepsis stands as a formidable global health challenge, with persistently elevated mortality rates in recent decades. Each year, sepsis not only contributes to heightened morbidity but also imposes substantial healthcare costs on survivors. This narrative review aims to highlight the targeted measures that can be instituted to alleviate the incidence and impact of sepsis in intensive care. Here we discuss measures to reduce nosocomial infections and the prevention of equipment and patient colonisation by resilient pathogens. The overarching global crisis of bacterial resistance to newly developed antimicrobial agents intensifies the imperative for antimicrobial stewardship and de-escalation. This urgency has been accentuated in recent years, notably during the COVID-19 pandemic, as high-dose steroids and opportunistic infections presented escalating challenges. Ongoing research into airway colonisation's role in influencing disease outcomes among critically ill patients underscores the importance of tailoring treatments to disease endotypes within heterogeneous populations, which are important lessons for intensivists in training. Looking ahead, the significance of novel antimicrobial delivery systems and drug monitoring is poised to increase. This narrative review delves into the multifaceted barriers and facilitators inherent in effectively treating critically ill patients vulnerable to nosocomial infections. The future trajectory of intensive care medicine hinges on the meticulous implementation of vigilant stewardship programs, robust infection control measures, and the continued exploration of innovative and efficient technological solutions within this demanding healthcare landscape.

A cost minimisation analysis comparing oral linezolid and intravenous daptomycin administered via an outpatient parenteral antibiotic therapy programme in patients requiring prolonged antibiotic courses

This study is an economic analysis seeking to examine cost savings that may be accrued from usage of oral linezolid in place of OPAT IV daptomycin in patients requiring prolonged courses of IV or highly bioavailable oral antibiotic therapy. In order to do so we conducted a literature review to establish the scenarios in which the agents could be considered equivalent. We then, using a decision-tree model, conducted a cost analysis to establish differences in cost between the approaches. Under the model base-case, the total cost of treatment with OPAT daptomycin was €3,496.84 and the total cost of treatment with oral linezolid was €772.01. Therefore the oral linezolid strategy would be projected to save the Irish health service €2,724.83 per patient. These results were robust to one-way deterministic sensitivity analyses and probabilistic sensitivity analysis. Our study suggests that significant savings could be safely accrued in the management of these patients.

Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Treatment decisions in VRE bacteraemia: a survey of infectious diseases pharmacists

Background

VRE infections increased in 2020. High-dose daptomycin (≥10 mg/kg) has shown mortality benefit over other regimens, though daptomycin resistance is increasing. Limited data exist on the practice patterns of ID pharmacists for VRE bloodstream infections (VRE BSIs).

Objectives

To describe practice patterns for VRE BSI in ID pharmacists.

Methods

A 22-question REDCap survey was distributed to ID pharmacist members of the American College of Clinical Pharmacy (ACCP) Infectious Diseases Practice and Research Network (ID PRN) via e-mail listserv. The survey was distributed on 7 April 2022 and remained open for 4 weeks.

Results

Sixty-eight pharmacists responded. All pharmacists completed additional training or certification in infectious diseases past their PharmD, and most (70.5%) had been practising for 10 years or less. Pharmacists at academic medical centres (80.0%) were more likely (P = 0.001) to have implemented the updated CLSI breakpoints than pharmacists at other types of institutions (55.2%). Daptomycin was the preferred drug for VRE BSI (92.6%), with 10 mg/kg (72.1%) being the preferred dose. Adjusted body weight was the most common weight (61.2%) used for obese patients. Fourteen days (76.1%) was the most common treatment duration for VRE BSI. Pharmacists defined persistent VRE BSI as 5 days (68.7%) after first blood culture.

Conclusions

ID pharmacists overwhelmingly selected high-dose daptomycin for VRE BSI. There were variations in practice and response rate when selecting combination therapy, managing persistent bacteraemia, and treating patients with high daptomycin MICs or previous exposure to daptomycin.

Daptomycin Pharmacokinetics in Blood and Wound Fluid in Critical Ill Patients with Left Ventricle Assist Devices

Daptomycin is a cyclic lipopeptide antibiotic with bactericidal effects against multidrug-resistant Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VRE). For critically ill patients, especially in the presence of implants, daptomycin is an important therapeutic option. Left ventricle assist devices (LVADs) can be utilized for intensive care patients with end-stage heart failure as a bridge to transplant. We conducted a single-center prospective trial with critically ill adults with LVAD who received prophylactic anti-infective therapy with daptomycin. Our study aimed to evaluate the pharmacokinetics of daptomycin in the blood serum and wound fluids after LVAD implantation. Daptomycin concentration were assessed over three days using high-performance liquid chromatography (HPLC). We detected a high correlation between blood serum and wound fluid daptomycin concentration at 12 h (IC95%: 0.64 to 0.95; r = 0.86; p < 0.001) and 24 h (IC95%: -0.38 to 0.92; r = 0.76; p < 0.001) after antibiotic administration. Our pilot clinical study provides new insights into the pharmacokinetics of daptomycin from the blood into wound fluids of critically ill patients with LVADs.

Risk factors for mortality after linezolid treatment of vancomycin-resistant Enterococcus bloodstream infection

OBJECTIVES

We analyzed the risk factors affecting linezolid treatment outcome in vancomycin-resistant Enterococcus (VRE) bloodstream infection (BSI).

METHODS

We conducted a multicenter observational study of patients who received linezolid 600 mg every 12 hours for VRE BSI. The primary outcome was 28-day mortality. The estimated area under the concentration-time curve and trough concentration were calculated. Multivariable logistic regression was used for the outcome analysis.

RESULTS

A total of 170 patients were included: 114 (67.1%) survived and 56 (32.9%) did not. A total of 26 (18.2%) isolates showed a linezolid minimum inhibitory concentration (MIC) of ≤1 mg/l, 113 (79.0%) of 2 mg/l, and 4 (2.8%) of 4 mg/l. The univariable analysis showed that the linezolid MIC and concentration-time curve/MIC were not associated with mortality (P = 0.95 and P = 0.42, respectively). After adjusting for underlying comorbidity and disease severity, the linezolid dose per body weight (LDBW), body height, and interaction between them were independent risks for mortality. Marginal analysis showed that increasing the LDBW was protective in patients with a body height <160 cm. A trough concentration of >12.2 mg/l was a risk factor for thrombocytopenia.

CONCLUSION

The LDBW and body height were interactively associated with clinical outcomes of linezolid treatment for VRE BSI.

The Combination of Daptomycin with Fosfomycin is More Effective than Daptomycin Alone in Reducing Mortality of Vancomycin-Resistant Enterococcal Bloodstream Infections: A Retrospective, Comparative Cohort Study

INTRODUCTION

High-dose daptomycin-based combinations are recommended for vancomycin-resistant Enterococcus (VRE) bloodstream infection (BSI). Preclinical data have shown a synergistic effect of daptomycin/fosfomycin combinations against VRE. However, clinical studies comparing daptomycin monotherapy with daptomycin/fosfomycin combinations are unavailable.

METHODS

An observational study of VRE-BSI was performed between 2010-2021 on patients receiving daptomycin monotherapy (≥ 8 mg/kg) or daptomycin combined with intravenous fosfomycin. Patients treated with concomitant β-lactam combinations were excluded. The primary outcome was in-hospital mortality. Outcomes were analyzed using multivariable logistic regression and augmented inverse probability weighting (AIPW) analyses.

RESULTS

Among 224 patients, 176 received daptomycin monotherapy, and 48 received fosfomycin combinations. The median daptomycin and fosfomycin doses were 9.8 mg/kg and 12 g/day, respectively. In-hospital mortality was 77.3% and 47.9% in the daptomycin monotherapy and fosfomycin combination groups (P < 0.001), respectively. Multivariable logistic regression analysis predicted lower mortality with fosfomycin combination treatment (adjusted odds ratio, 0.35; 95% confidence interval (CI), 0.17-0.73; P = 0.005). AIPW demonstrated a 17.8% reduced mortality with fosfomycin combinations (95% CI, - 30.6- - 4.9%; P = 0.007). The survival benefit was significant, especially among patients with a lower Pitt bacteremia score or fosfomycin minimum inhibitory concentration (MIC) ≤ 64 mg/l. Fosfomycin combination resulted in higher hypernatremia (10.4% vs. 2.8%, P = 0.04) and hypokalemia (33.3% vs. 15.3%, P = 0.009) compared to daptomycin monotherapy.

CONCLUSION

The combination of high-dose daptomycin with fosfomycin improved the survival rate of patients with VRE-BSI compared to daptomycin alone. The benefit of the combination was most pronounced for VRE with fosfomycin MIC ≤ 64 mg/l and for patients with a low Pitt bacteremia score.

Epidemiology, microbiological and clinical characteristics of Enterococcus species bloodstream infections: A 10-year retrospective cohort study from Qatar

Background and objective

Enterococcus species is one of the leading causes of community and healthcare-associated infections resulting in significant morbidity and mortality. In this study, we aim to evaluate the epidemiology, microbiological and clinical characteristics of Enterococcus Blood Stream Infections (BSIs) over 10 years period in a national secondary care setting.

Methods

A retrospective cohort study was conducted on verified cases of enterococcal BSIs in adults from January 2009–December 2018 from specialized care hospitals at Hamad Medical Corporation, Qatar. Epidemiological, microbiological and clinical data were reported and analyzed.

Results

A total of 263 enterococcus BSIs cases were identified, predominant were males (65%) with a median age of 63 (IQR 48–74). E. faecalis and E. faecium were predominate at 93.5% (73.38% and 20.15% respectively). Diabetes was the commonest premorbid condition (54.3%) followed by chronic kidney disease (36.5%). Central lines and genitourinary were the most common sources (18.25%, 14.83% respectively) while no identified source was reported in 45.25% of cases. Ampicillin susceptibility was 82.51% while vancomycin resistance was reported in 10.6% of isolates. Successful bacteremia clearance was achieved in 81.37% of cases at a mean of 4 days (Range 2–5 days) while metastatic complications occurred in 5.3% of cases. Univariate mortality risk analysis was associated with ICU admission, low level of consciousness, high bacteremia scores, and presence of catheters. The 30 days mortality was high at 66.54% with CKD and cancer patients at the highest mortality risks (OR 16.334 (CI 4.2–62.4) and 16 (CI 3–84) respectively.

Conclusion

Significant mortality was associated with enterococcus BSI despite low rates for ampicillin and vancomycin resistance necessitating early identification of susceptible patients to instigate suitable preventive measures.

•

Enterococcus bacteremia cases were enrolled retrospectively over a decade timeframe.

•

E. faecalis and E. faecium constitute the majority at 93.5%.

•

Significant mortality was associated with enterococcus bloodstream infection.

•

Low rates for ampicillin and vancomycin resistance.

•

Enterococcus bacteremia carries high mortality in CKD and cancer patients.

Relationship Between Linezolid Exposure and the Typical Clinical Laboratory Safety and Bacterial Clearance in Chinese Pediatric Patients

Objectives: There have been limited studies concerning the safety and efficacy of linezolid (LZD) in children. This study aimed to evaluate the association between LZD exposure and clinical safety and efficacy in Chinese pediatric patients.

Methods: This retrospective cross-sectional study included patients ≤18 years of age who received ≥3 days of LZD treatment between 31 January 2015, and 31 December 2020. Demographic characteristics, medication information, laboratory test information, and bacterial culture results were collected from the Hospital Information System (HIS). Exposure was defined as AUC₂₄ and calculated by the non-linear mixed-effects modeling program (NONMEM), version 7.2, based on two validated population pharmacokinetic models. Binary logistic regression analyses were performed to analyze the associations between AUC₂₄ and laboratory adverse events, and receiver operating characteristic curves were used to calculate the cut-off values. Efficacy was evaluated by bacterial clearance.

Results: A total of 413 paediatric patients were included, with an LZD median (interquartile range) dose, duration, clearance and AUC₂₄ of 30.0 (28.1-31.6) mg/kg/day, 8 (4‒15) days,1.31 (1.29-1.32) L/h and 81.1 (60.6-108.7) mg/L·h, respectively. Adverse events associated with TBil, AST, ALT, PLT, hemoglobin, WBC, and neutrophil count increased during and after LZD treatment when compared with before medication (p < 0.05), and the most common adverse events were thrombocytopaenia (71/399, 17.8%) and low hemoglobin (61/401, 15.2%) during the LZD treatment. Patients with AUC₂₄ higher than 120.69 mg/L h might be associated with low hemoglobin 1–7 days after the end of the LZD treatment, and those with an AUC₂₄ higher than 92.88 mg/L∙h might be associated with thrombocytopaenia 8–15 days after the end of the LZD treatment. A total of 136 patients underwent bacterial culture both before and after LZD treatment, and the infection was cleared in 92.6% (126/136) of the patients, of whom 69.8% (88/126) had AUC₂₄/MIC values greater than 80.

Conclusion: Hematological indicators should be carefully monitored during LZD treatment, especially thrombocytopaenia and low hemoglobin, and a continuous period of monitoring after LZD withdrawal is also necessary. Since the AUC₂₄ cut-off values for laboratory adverse events were relatively low, a trade-off is necessary between the level of drug exposure required for treatment and safety, and the exposure target (AUC₂₄/MIC) in pediatric patients should be further studied, especially for patients with complications and concomitant medications.

Recommendations and guidelines for the treatment of infections due to multidrug resistant organisms

Antimicrobial drug resistance is one of the major threats to global health. It has made common infections increasingly difficult or impossible to treat, and leads to higher medical costs, prolonged hospital stays and increased mortality. Infection rates due to multidrug-resistant organisms (MDRO) are increasing globally. Active agents against MDRO are limited despite an increased in the availability of novel antibiotics in recent years. This guideline aims to assist clinicians in the management of infections due to MDRO. The 2019 Guidelines Recommendations for Evidence-based Antimicrobial agents use in Taiwan (GREAT) working group, comprising of infectious disease specialists from 14 medical centers in Taiwan, reviewed current evidences and drafted recommendations for the treatment of infections due to MDRO. A nationwide expert panel reviewed the recommendations during a consensus meeting in Aug 2020, and the guideline was endorsed by the Infectious Diseases Society of Taiwan (IDST). This guideline includes recommendations for selecting antimicrobial therapy for infections caused by carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Enterobacterales, and vancomycin-resistant Enterococcus. The guideline takes into consideration the local epidemiology, and includes antimicrobial agents that may not yet be available in Taiwan. It is intended to serve as a clinical guide and not to supersede the clinical judgment of physicians in the management of individual patients.

Influence of daptomycin doses on the outcomes of VRE bloodstream infection treated with high-dose daptomycin

OBJECTIVES

The CLSI recommended high-dose daptomycin (8-12 mg/kg) for treating Enterococcus faecium bloodstream infections (BSI). The current study was designed to determine the safety and efficacy of increasing the daptomycin dose for VRE BSI patients receiving ≥8 mg/kg.

METHODS

We conducted a multicentre prospective observational study of patients who received a ≥8 mg/kg dose of daptomycin for treatment of VRE BSI. The primary outcome was 28 day mortality.

RESULTS

A total of 661 patients were included. The 28 day mortality rate was 45.1%. The survivors received higher doses of daptomycin than non-survivors (10.1 versus 9.8 mg/kg; P < 0.001). An increase in the daptomycin dose independently predicted lower mortality [adjusted OR (aOR) = 0.85; 95% CI = 0.73-0.99; P = 0.03]. Eighty-six survivors (23.7%) and 43 non-survivors (14.4%) received a ≥11 mg/kg dose of daptomycin (P = 0.003). The 8 to <11 and ≥11 mg/kg doses of daptomycin differed in the 28 day mortality in the higher MIC group (≥2 mg/L) (49.4% versus 33.3%; P = 0.004), but not in the lower MIC group (≤1 mg/L) (29.3% versus 29.4%; P = 0.99). A dose of ≥11 mg/kg was associated with a higher (3.9%) rate of highly elevated creatine kinase (>2000 U/L) compared with 1.1% with 8 to <11 mg/kg (P = 0.04).

CONCLUSIONS

The efficacy of daptomycin is dose dependent. A high daptomycin dose, especially at ≥11 mg/kg, improved survival in patients with VRE BSI, but was associated with highly elevated creatine kinase. We recommend a ≥11 mg/kg dose of daptomycin be considered for treatment of VRE BSI, particularly for isolates with higher MICs.

Overcoming Stenotrophomonas maltophilia Resistance for a More Rational Therapeutic Approach

Stenotrophomonas maltophilia is an underappreciated source of morbidity and mortality among gram-negative pathogens. Effective treatment options with acceptable toxicity profiles are limited. Phenotypic susceptibility testing via commercial automated test systems is problematic and no Food and Drug Administration breakpoints are approved for any of the first-line treatment options for S maltophilia. The lack of modern pharmacokinetic/pharmacodynamic data for many agents impedes dose optimization, and the lack of robust efficacy and safety data limits their clinical utility. Levofloxacin has demonstrated similar efficacy to trimethoprim-sulfamethoxazole, although rapid development of resistance is a concern. Minocycline demonstrates the highest rate of in vitro susceptibility, however, evidence to support its clinical use are scant. Novel agents such as cefiderocol have exhibited promising activity in preclinical investigations, though additional outcomes data are needed to determine its place in therapy for S maltophilia. Combination therapy is often employed despite the dearth of adequate supporting data.

Risk Factors Associated with Failure of Linezolid Therapy in Vancomycin-Resistant Enterococcus faecium Bacteremia: A Retrospective Cohort Study in a Referral Center in Mexico

We aimed to assess the factors associated with 30-day mortality in patients with vancomycin-resistant Enterococcus faecium (VREf) bloodstream infection (BSI) who received treatment with linezolid in an 11-year retrospective cohort of patients with VREf BSI. A univariate and stepwise multivariate logistic regression analysis was performed to determine 30-day mortality factors. Moreover, a Cox proportional hazards analysis of predictor covariates of mortality was performed. Eighty patients were included in the final analysis; 42 (53%) died and 38 (47%) survived 30 days after the index bacteremia. Thirteen patients of 42 (31%) died in the first 7 days. The Acute Physiology and Chronic Health Evaluation II (APACHE II) score was significantly associated with 30-day mortality (adjusted odds ratio [aOR], 1.46; 95% confidence interval [CI]: 1.22-1.76; p < 0.001) in the multivariate analysis. Moreover, VREf BSI persisting for more than 48 hours was a strong factor related to 30-day mortality (aOR, 19.6; 95% CI: 1.46-263; p = 0.01). Adequate control of infection source showed a trend to be protective without reaching significance in the multivariate analysis (aOR, 0.19; 95% CI: 0.04-1.0; p = 0.05). The Cox proportional hazards analysis confirmed the same significant mortality predictor besides linezolid treatment within the first 48 hours as a protective factor (hazard ratio 0.46; 95% CI: 0.23-0.92, p = 0.02). Severely ill patients with high APACHE II score and persistent bacteremia have a higher risk of failure with linezolid therapy.

Coagulation dysfunction events associated with tigecycline: a real-world study from FDA adverse event reporting system (FAERS) database

BACKGROUND

Tigecycline has broad-spectrum anti-bacterial activity and often used for critically ill patients with complicated infections. Only a few clinical studies have reported the coagulation disorder induced by tigecycline. The aim of this study was to investigate the association between tigecycline and coagulation dysfunction using the US Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHOD

Data from January 2005 to December 2020 in FAERS were retrieved. We investigated the clinical characteristics of the coagulation dysfunction events and conducted disproportionality analysis by using reporting odds ratios (ROR) to compare tigecycline with the full database and other antibiotics.

RESULTS

The total number of reports of coagulation dysfunction related to tigecycline as the primary suspect drug was 223. The median time to event of the coagulation dysfunction events was 10 (interquartile range [IQR] 6.75-13) days. 80.72% coagulation-related adverse events appeared within the first 14 days since the initiation of tigecycline administration. The overall ROR (95% CI) for coagulation-related adverse events was 3.55 (3.08, 4.09). The RORs (95% CI) for thrombocytopenia, hypofibrinogenaemia, coagulopathy, activated partial thromboplastin time prolonged, international normalized ratio increased, prothrombin time prolonged were 8.21 (6.34, 10.62), 705.41 (526.81, 944.54), 30.67 (21.92, 42.92), 42.98 (24.85, 74.31), 4.67 (2.51, 8.71), and 27.99 (15.01, 52.19), respectively. In analyses stratified on comparing tigecycline to vancomycin and daptomycin, significant coagulation dysfunction signals were found with the RORs (95% CI) 2.74 (2.34, 3.22) and 3.08 (2.57, 3.70).

CONCLUSIONS

We found a strong signal of high frequency of reporting coagulation dysfunction in tigecycline. Health professionals should be aware of the potential coagulation disorders risk and monitor coagulation parameters during anti-bacterial therapy with tigecycline, particularly the need to monitor fibrinogen levels.

Daptomycin-Resistant Enterococcus Bacteremia Is Associated with Prior Daptomycin Use and Increased Mortality after Liver Transplantation

Background

Risk factors for acquisition of vancomycin-resistant Enterococcus (VRE) include immunosuppression, antibiotic exposure, indwelling catheters, and manipulation of the gastrointestinal tract, all of which occur in liver transplant recipients. VRE infections are documented in liver transplantation (LT); however, only one single center study has assessed the impact of daptomycin-resistant Enterococcus (DRE) in this patient population.

Methods

We conducted a retrospective multicenter cohort study comparing liver transplant recipients with either VRE or DRE bacteremia. The primary outcome was death within 1 year of transplantation. Multivariable logistic regression analyses were performed to calculate adjusted odds ratios for outcomes of interest.

Results

We identified 139 cases of Enterococcus bacteremia following LT, of which 78% were VRE and 22% were DRE. When adjusted for total intensive care unit days in the first transplant year, liver-kidney transplantation, and calcineurin inhibitor use, patients with DRE bacteremia were 2.65 times more likely to die within 1 year of transplantation (adjusted odds ratio [aOR], 2.648; 95% CI, 1.025–6.840; P = .044). Prior daptomycin exposure was found to be an independent predictor of DRE bacteremia (aOR, 30.62; 95% CI, 10.087–92.955; P < .001).

Conclusions

In this multicenter study of LT recipients with Enterococcus bacteremia, DRE bacteremia was associated with higher 1-year mortality rates when compared with VRE bacteremia. Our data provide strong support for dedicated infection prevention and antimicrobial stewardship efforts for transplant patients. Further research is needed to support the development of better antibiotics for DRE and practical guidance focusing on identification and prevention of colonization and subsequent infection in liver transplant recipients at high risk for DRE bacteremia.

In vitro activities of thiazolidione derivatives combined with daptomycin against clinical Enterococcus faecium strains

Background

Previous reports have demonstrated two thiazolidione derivatives (H2-60 and H2-81) can robustly inhibit the planktonic growth and biofilm formation of S. epidermidis and S. aureus by targeting the histidine kinase YycG. Whereas the antibacterial and anti-biofilm activity of these two thiazolidione derivatives (H2-60 and H2-81) against Enterococcus faecium remains elusive. Here, the pET28a-YycG recombinant plasmid were in vitro expressed in E. coli competent cell BL21 (DE3) and induced to express YycG’ protein (conding HisKA and HATPase_c domain) by 0.5 mM IPTG and was purified by Ni – NTA agarose and then for the autophosphorylation test. Antimicrobial testing and time-killing assay were also be determined. Anti-biofilm activity of two derivatives with sub-MIC concentration towards positive biofilm producers of clinical E. faecium were detected using polystyrene microtiter plate and CLSM.

Results

The MICs of H2-60 and H2-81 in the clinical isolates of E. faecium were in the range from 3.125 mg/L to 25 mg/L. Moreover, either H2-60 or H2-81 showed the excellent bactericidal activity against E. faecium with monotherapy or its combination with daptomycin by time-killing assay. E. faecium planktonic cells can be decreased by H2-60 or H2-81 for more than 3 × log10 CFU/mL after 24 h treatment when combined with daptomycin. Furthermore, over 90% of E. faecium biofilm formation could markedly be inhibited by H2-60 and H2-81 at 1/4 × MIC value. In addition, the frequency of the eradicated viable cells embedded in mature biofilm were evaluated by the confocal laser microscopy, suggesting that of H2-60 combined with ampicillin or daptomycin was significantly high when compared with single treatment (78.17 and 74.48% vs. 41.59%, respectively, P < 0.01).

Conclusion

These two thiazolidione derivatives (H2-60 and H2-81) could directly impact the kinase phosphoration activity of YycG of E. faecium. H2-60 combined with daptomycin exhibit the excellent antibacterial and anti-biofilm activity against E. faecium by targeting YycG.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02423-8.

Alternatives to Fight Vancomycin-Resistant Staphylococci and Enterococci

Gram positive pathogens are a significant cause of healthcare-associated infections, with Staphylococci and Enterococci being the most prevalent ones. Vancomycin, a last resort glycopeptide, is used to fight these bacteria but the emergence of resistance against this drug leaves some patients with few therapeutic options. To counter this issue, new generations of antibiotics have been developed but resistance has already been reported. In this article, we review the strategies in place or in development to counter vancomycin-resistant pathogens. First, an overview of traditional antimicrobials already on the market or in the preclinical or clinical pipeline used individually or in combination is summarized. The second part focuses on the non-traditional antimicrobials, such as antimicrobial peptides, bacteriophages and nanoparticles. The conclusion is that there is hitherto no substitute equivalent to vancomycin. However, promising strategies based on drugs with multiple mechanisms of action and treatments based on bacteriophages possibly combined with conventional antibiotics are hoped to provide treatment options for vancomycin-resistant Gram-positive pathogens.

UPLC-MS/MS Determination of Linezolid and Heme in Plasma of Infected Patients and Correlation Analysis

Linezolid can cause serious haematological toxicity, such as thrombocytopenia and aneamia. Heme, composed of iron and porphyrin, is an important component of hemoglobin. In order to investigate the relationship between the concentration of linezolid and heme in the plasma of infected patients, a UPLC-MS/MS method that can determine the concentrations of linezolid and heme simultaneously was developed and validated. A total of 96 healthy subjects and 81 infected patients, who received blood routine blood tests, were included and determined by the UPLC-MS/MS method. The results showed that the concentration of linezolid was 5.08 ± 3.46 μg/mL in infected patients who were treated with linezolid. The heme in healthy subjects was 7.05 ± 8.68 μg/mL, and it was significantly decreased to 0.88 ± 0.79 μg/mL in infected patients (P < 0.01). Spearman correlation analysis showed that linezolid had a high negative correlation with platelet (PLT) (R = -0.309). Heme had a high positive correlation with hemoglobin (Hb) (R = 0.249) in healthy subjects and infected patients. The ROC analysis showed that heme had diagnostic value to distinguish low Hb (110 g/L). In conclusion, there was a positive correlation between heme and Hb, and this correlation was also observed in infected patients. A high concentration of linezolid was inclined to decrease PLT. Monitoring of heme and linezolid helps in the early diagnose of low Hb and PLT.

The Increasing Issue of Vancomycin-Resistant Enterococci and the Bacteriocin Solution

Enterococci are commensals of human and other animals’ gastrointestinal tracts. Only making up a small part of the microbiota, they have not played a significant role in research, until the 1980s. Although the exact year is variable according to different geographical areas, this was the decade when vancomycin-resistant enterococci (VRE) were discovered and since then their role as causative agents of human infections has increased. Enterococcus faecium is on the WHO’s list of “bacteria for which new antibiotics are urgently needed,” and with no new antibiotics in development, the situation is desperate. In this review, different aspects of VRE are outlined, including the mortality caused by VRE, antibiotic resistance profiles, animal-modeling efforts, and virulence. In addition, the limitations of current antibiotic treatments for VRE and prospective new treatments, such as bacteriocins, are reviewed.

Antimicrobial susceptibility of bacteremic vancomycin-resistant Enterococcus faecium to eravacycline, omadacycline, lipoglycopeptides, and other comparator antibiotics: Results from the 2019-2020 Nationwide Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART)

Multicenter surveillance of antimicrobial susceptibility was performed for 235 vancomycin-resistant Enterococcus faecium (VREfm) isolates from 18 Taiwanese hospitals. The minimum inhibitory concentrations (MICs) of eravacycline, omadacycline, lipoglycopeptides, and other comparator antibiotics were determined using the broth microdilution method. Nearly all isolates of VREfm were not susceptible to teicoplanin, dalbavancin, and telavancin, with susceptibility rates of 0.5%, 1.7% and 0.5%, respectively. Tigecycline and eravacycline were active against 93.2% and 89.7% of the VREfm isolates, respectively. Moreover, the susceptibility rates of quinupristin/dalfopristin, tedizolid, and linezolid were 59.1%, 84.2%, and 77.4%, respectively. Additionally, 94% of the VREfm isolates were classified as susceptible to daptomycin, and the MICs of omadacycline required to inhibit VREfm growth by 50% and 90% were 0.12 and 0.5 mg/L, respectively. Susceptibility rates of VREfm isolates to synthetic tetracyclines and daptomycin were slightly lower and to oxazolidinone-class antibiotics were much lower in Taiwan than those in other parts of the world. Continuous monitoring of VREfm resistance to novel antibiotics, including synthetic tetracyclines, oxazolidinone-class antibiotics, and daptomycin, is needed in Taiwan.

[Infections due to multidrug-resistant pathogens : Pathogens, resistance mechanisms and established treatment options]

The increase in resistant pathogens has long been a global problem. Complicated life-threatening infections due to multidrug-resistant pathogens (MRD) meanwhile occur regularly in intensive care medicine. An important and also potentially modifiable factor of the rapid spread of resistance is the irrational use of broad spectrum antibiotics in human medicine. In addition to many other resistance mechanisms, beta-lactamases play an important role in Gram-negative pathogens. They are not uncommonly the leading reason of difficult to treat infections and the failure of known routinely used broad spectrum antibiotics, such as cephalosporins, (acylamino)penicillins and carbapenems. Strategies for containment of MRDs primaríly target the rational use of antibiotics. In this respect interdisciplinary treatment teams, e.g. antibiotic stewardship (ABS) and infectious diseases stewardship (IDS) play a major role.

From Etest to Vitek 2: Impact of Enterococcal Linezolid Susceptibility Testing Methodology on Time to Active Therapy

Different linezolid antimicrobial susceptibility testing (AST) methodologies yield various results. In 2018, we transitioned our linezolid AST methodology from the Etest to Vitek 2. We sought to evaluate the impact of this change on antibiotic use among 181 inpatients with vancomycin-resistant enterococcal (VRE) infections. The transition from Etest to Vitek 2 resulted in an increase in linezolid susceptibility (38% versus 96%; P < 0.001) and a reduction in time to active antibiotic therapy (3 versus 2.6 days; P = 0.007).

cfr(B), cfr(C), and a New cfr-Like Gene, cfr(E), in Clostridium difficile Strains Recovered across Latin America

Cfr is a radical S-adenosyl-l-methionine (SAM) enzyme that confers cross-resistance to antibiotics targeting the 23S rRNA through hypermethylation of nucleotide A2503. Three cfr-like genes implicated in antibiotic resistance have been described, two of which, cfr(B) and cfr(C), have been sporadically detected in Clostridium difficile However, the methylase activity of Cfr(C) has not been confirmed. We found cfr(B), cfr(C), and a cfr-like gene that shows only 51 to 58% protein sequence identity to Cfr and Cfr-like enzymes in clinical C. difficile isolates recovered across nearly a decade in Mexico, Honduras, Costa Rica, and Chile. This new resistance gene was termed cfr(E). In agreement with the anticipated function of the cfr-like genes detected, all isolates exhibited high MIC values for several ribosome-targeting antibiotics. In addition, in vitro assays confirmed that Cfr(C) and Cfr(E) methylate Escherichia coli and, to a lesser extent, C. difficile 23S rRNA fragments at the expected positions. The analyzed isolates do not have mutations in 23S rRNA genes or genes encoding the ribosomal proteins L3 and L4 and lack poxtA, optrA, and pleuromutilin resistance genes. Moreover, these cfr-like genes were found in Tn6218-like transposons or integrative and conjugative elements (ICE) that could facilitate their transfer. These results indicate selection of potentially mobile cfr-like genes in C. difficile from Latin America and provide the first assessment of the methylation activity of Cfr(C) and Cfr(E), which belong to a cluster of Cfr-like proteins that does not include the functionally characterized enzymes Cfr, Cfr(B), and Cfr(D).

[S2k guidelines of the PEG on calculated parenteral initial treatment of bacterial diseases in adults : Focussed summary and supplementary information on antibiotic treatment of critically ill patients]

In January 2018 the recent revision of the S2k guidelines on calculated parenteral initial treatment of bacterial diseases in adults-update 2018 (Editor: Paul Ehrlich Society for Chemotherapy, PEG) was realized. It is a helpful tool for the complex infectious disease setting in an intensive care unit. The present summary of the guidelines focuses on the topics of anti-infective agents, including new substances, pharmacokinetics and pharmacodynamics as well as on microbiology, resistance development and recommendations for calculated drug therapy in septic patients. As in past revisions the recent resistance situation and results of new clinical studies are considered and anti-infective agents are summarized in a table.

Advances in the therapy of bacterial bloodstream infections

BACKGROUND

Advances in the diagnostic and therapeutic management of patients with bloodstream infections (BSIs) have been achieved in the last years, improving clinical outcome. However, mortality associated with some pathogens, such as Staphylococcus aureus and Enterococcus spp., is still high. In addition, the spread of antibiotic resistance, mainly among Gram-negative bacteria, reduces treatment options in some circumstances. Therefore, interest in new drugs, combination regimens and optimal dosing schedules is rising.

OBJECTIVES

Our aim is to summarize the current evidence on available antibiotic regimens for patients with bacterial BSI, focusing on drug choice, combination regimens and optimal dosing schedules. We selected bacteria that are difficult to manage because of virulence factors (i.e. methicillin-susceptible S. aureus), tolerance to antibiotic activity (i.e. Enterococcus faecalis), and/or susceptibility patterns (i.e. methicillin-resistant S. aureus, vancomycin-resistant enterococci, carbapenem-resistant Enterobacteriaceae, multidrug-resistant Pseudomonas aeruginosa and carbapenem-resistant Acinetobacter baumannii).

SOURCES

MEDLINE search with English language and publication in the last 5 years as limits.

CONTENT AND IMPLICATIONS

The literature gaps on the use of new drugs, the uncertainties regarding the use of combination regimens, and the need to optimize dosing schedules in some circumstances (e.g. augmented renal clearance, renal replacement therapy, high inoculum BSI sources, and isolation of bacteria showing high MICs) have been revised.

Linezolid use in German acute care hospitals: results from two consecutive national point prevalence surveys

Background

Linezolid belongs to a reserve group of antibiotics. In recent years, reports on linezolid resistance in gram-positive cocci have become more frequent. Overuse of linezolid is a relevant factor for resistance development. The objective of this study was to describe current prescription practices of linezolid in German hospitals and identify targets for antimicrobial stewardship interventions.

Methods

We analyzed all linezolid prescriptions from the datasets of the consecutive national point prevalence surveys performed in German hospitals in 2011 and 2016. In both surveys, data on healthcare-associated infections and antimicrobial use were collected following the methodology of the European Centre for Disease Prevention and Control.

Results

Overall, the percentage of linezolid among all documented antimicrobials increased significantly from 2011 to 2016 (p < 0.01). In 2011, 0.3% (119 of 41,539) patients received linezolid, in 2016 this proportion was significantly higher (0.4%; 255 of 64,412 patients; p < 0.01). In 2016, intensive care units (ICUs) were the wards most frequently prescribing linezolid. The largest proportion of patients receiving linezolid were non-ICU patients. Roughly 38% of linezolid prescriptions were for treatment of skin/soft tissue and respiratory tract infections. In 2016, linezolid was administered parenterally in 70% (n = 179) of cases. Multivariable analysis showed that the ward specialty ICU posed an independent risk factor, while Northern and Southwestern regions in Germany were independent protective factors for a high rate of linezolid prescriptions.

Conclusions

In conclusion, we detected potentials for improving linezolid prescription practices in German hospitals. Given the emergence of linezolid resistance, optimization of linezolid use must be a target of future antimicrobial stewardship activities.

Association of daptomycin dosing regimen and mortality in patients with VRE bacteraemia: a review

VRE are associated with ∼1300 deaths per year in the USA. Recent literature suggests that daptomycin, a cyclic lipopeptide antibiotic with concentration-dependent bactericidal activity, is the preferred treatment option for VRE bacteraemia, yet the optimal dosing strategy for this indication has not been established. In vitro evidence suggests that higher-than-labelled doses of daptomycin are required to optimally treat VRE bacteraemia and to inhibit the development of resistance. However, concern of dose-dependent toxicities, notably increases in creatine phosphokinase and the development of rhabdomyolysis, are a barrier to initiating high-dose schemes in clinical practice. Thus, the effectiveness and safety of high-dose daptomycin regimens in clinical practice have remained unclear. While early studies failed to identify differences in mortality, newer, larger investigations suggest high-dose (≥9 mg/kg) daptomycin is associated with reduced mortality in patients with VRE bacteraemia compared with standard (6 mg/kg) dosing regimens. Additionally, the high-dose regimens appear to be safe and may be associated with improved microbiological outcomes. The purpose of this review is to examine the published evidence on the effectiveness and safety of high-dose daptomycin compared with standard dosing regimens for VRE bacteraemia.

Linezolid vs glycopeptides in the treatment of glycopeptide-susceptible Enterococcus faecium bacteraemia: A propensity score matched comparative study

BACKGROUND

The incidence of ampicillin-resistant Enterococcus faecium bacteraemia is increasing. Vancomycin remains the first-line treatment in areas with a high prevalence of glycopeptide-susceptible isolates, but data comparing its clinical outcomes with other treatments are lacking. The objective of this study was to compare the effectiveness and safety of linezolid and glycopeptides for the treatment of glycopeptide-susceptible E. faecium bloodstream infection (GSEF-BSI).

METHODS

This retrospective observational cohort study was conducted from January 2006 to May 2018 at the Hospital del Mar, Barcelona, Spain, and compared the clinical outcomes and safety of linezolid and glycopeptides in adult patients with GSEF-BSI. The main outcomes included clinical cure at the end of therapy, 30-day mortality, microbiological eradication and attributable length of stay (LOS). Propensity score matching was performed to reduce potential confounders among groups.

RESULTS

In total, 105 patients with GSEF-BSI were included (linezolid, n=38; glycopeptides, n=67). After propensity score matched analysis, 56 (53.3%) patients, 28 in each cohort, entered the final analysis. No differences were observed in any of the main clinical outcomes among patients treated with linezolid or glycopeptides: clinical cure [16/28 (57.1%) vs 13/28 (46.4%), P=0.593], 30-day mortality [8/28 (28.6%) vs 12/28 (42.9%), P=0.403], microbiological eradication [22/28 (78.6%) vs 20/28 (71.4%), P=0.758] and median attributable LOS (18.0 vs 17.0 days, P=0.924). Adverse events were similar in both groups.

CONCLUSIONS

Linezolid and glycopeptides showed similar clinical effectiveness and safety in the treatment of GSEF-BSI. Linezolid could be an alternative to glycopeptides in the treatment of GSEF-BSI.

Novel Strategies for the Management of Vancomycin-Resistant Enterococcal Infections

PURPOSE OF REVIEW

Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens that commonly affect critically ill patients. VRE have a remarkable genetic plasticity allowing them to acquire genes associated with antimicrobial resistance. Therefore, the treatment of deep-seated infections due to VRE has become a challenge for the clinician. The purpose of this review is to assess the current and future strategies for the management of recalcitrant deep-seated VRE infections and efforts for infection control in the hospital setting.

RECENT FINDINGS

Preventing colonization and decolonization of multidrug-resistant bacteria are becoming the most promising novel strategies to control and eradicate VRE from the hospital environment. Fecal microbiota transplantation (FMT) has shown remarkable results on treating colonization and infection due to Clostridiodes difficille and VRE, as well as to recover the integrity of the gut microbiota under antibiotic pressure. Initial reports have shown the efficacy of FMT on reestablishing patient microbiota diversity in the gut and reducing the dominance of VRE in the gastrointestinal tract. In addition, the use of bacteriophages may be a promising strategy in eradicating VRE from the gut of patients. Until these strategies become widely available in the hospital setting, the implementation of infection control measures and stewardship programs are paramount for the control of this pathogen and each program should provide recommendations for the proper use of antibiotics and develop strategies that help to detect populations at risk of VRE colonization, prevent and control nosocomial transmission of VRE, and develop educational programs for all healthcare workers addressing the epidemiology of VRE and the potential impact of these pathogens on the cost and outcomes of patients. In terms of antibiotic strategies, daptomycin has become the standard of care for the management of deep-seated infections due to VRE. However, recent evidence indicates that the efficacy of this antibiotic is limited, and higher (10-12 mg/kg) doses and/or combination with β-lactams is needed for therapeutic success. Clinical data to support the best use of daptomycin against VRE are urgently needed. This review provides an overview of recent developments regarding the prevention, treatment, control, and eradication of VRE in the hospital setting. We aim to provide an update of the most recent therapeutic strategies to treat deep-seated infections due to VRE.

Comparison of linezolid and daptomycin for the treatment of vancomycin-resistant enterococcal bacteremia

Vancomycin-resistant enterococcal bacteremia (VRE-B) is a common nosocomial infection associated with significant morbidity and mortality. Daptomycin and linezolid are primary treatment options although definitive clinical data to assess comparative therapeutic effectiveness are lacking. This study assessed the outcomes of patients with VRE-B treated with linezolid or daptomycin. This was a single-center, retrospective cohort study evaluating adult patients with VRE-B treated with either daptomycin or linezolid admitted between January 2012 and August 2016 at a tertiary care, academic medical center. The primary outcome was clinical failure, a composite outcome defined as 14-day in-hospital mortality, microbiologic failure, or relapse of VRE-B. Secondary outcomes included 14-day in-hospital mortality, microbiologic failure, relapse of VRE-B, duration of VRE-B, and antibiotic failure. A multivariate logistic regression model was performed to adjust for potential confounding variables. A total of 93 patients were included (n = 62 for linezolid and n = 31 for daptomycin). All blood isolates were Enterococcus faecium. Overall clinical failure was 55.9% and 14-day in-hospital mortality was 21.5%. There was a significantly higher rate of clinical failure in the daptomycin group as compared with the linezolid-treated patients (74.2% versus 46.8%; p = 0.01; respectively). In multivariate logistic regression analysis, there was a significantly higher odds of clinical failure for patients treated with daptomycin as compared with linezolid (adjusted odds ratio 2.89; 95% confidence interval 1.08–7.75) after adjusting for confounders. Secondary outcomes were not statistically significantly different between study groups. Standard-dose (6 mg/kg) daptomycin treatment was associated with a higher rate of clinical failure as compared with linezolid treatment.

Updates on urinary tract infections in kidney transplantation

Urinary tract infection (UTI) represents the most common infection after kidney transplantation; it is associated with an increased risk for acute kidney rejection and impaired graft function in the early post-transplant period. Kidney transplant recipients with UTIs are often clinically asymptomatic due to the immunosuppressive therapy; however, asymptomatic bacteriuria may progress to acute pyelonephritis, bacteremia and urosepsis, particularly in the early post-transplant period, that are independent risk factors for short and long-term graft and patient survival. This article reviews the definitions, incidence, risk factors and the management of UTI in kidney transplant recipients; furthermore, the main controversial and still unanswered questions, regarding the causes of recurrent UTIs, adequate use of antibiotics to avoid antibiotic resistance, dosing and timing for prophylaxis and treatment of symptomatic infections, are also discussed. The emerging definition of urinary microbiota introduces new concepts in understanding the complexity of the disease and might represent the future target for therapeutic interventions.

Diagnosis and treatment of catheter-related bloodstream infection: Clinical guidelines of the Spanish Society of Infectious Diseases and Clinical Microbiology and (SEIMC) and the Spanish Society of Spanish Society of Intensive and Critical Care Medicine and Coronary Units (SEMICYUC)

Catheter-related bloodstream infections (CRBSI) constitute an important cause of hospital-acquired infection associated with morbidity, mortality, and cost. The aim of these guidelines is to provide updated recommendations for the diagnosis and management of CRBSI in adults. Prevention of CRBSI is excluded. Experts in the field were designated by the two participating Societies (the Spanish Society of Infectious Diseases and Clinical Microbiology and [SEIMC] and the Spanish Society of Spanish Society of Intensive and Critical Care Medicine and Coronary Units [SEMICYUC]). Short-term peripheral venous catheters, non-tunneled and long-term central venous catheters, tunneled catheters and hemodialysis catheters are covered by these guidelines. The panel identified 39 key topics that were formulated in accordance with the PICO format. The strength of the recommendations and quality of the evidence were graded in accordance with ESCMID guidelines. Recommendations are made for the diagnosis of CRBSI with and without catheter removal and of tunnel infection. The document establishes the clinical situations in which a conservative diagnosis of CRBSI (diagnosis without catheter removal) is feasible. Recommendations are also made regarding empirical therapy, pathogen-specific treatment (coagulase-negative staphylococci, Staphylococcus aureus, Enterococcus spp., Gram-negative bacilli, and Candida spp.), antibiotic lock therapy, diagnosis and management of suppurative thrombophlebitis and local complications.

Linezolid Inhibited Synthesis of ATP in Mitochondria: Based on GC-MS Metabolomics and HPLC Method

Linezolid has been widely used in serious infections for its effective inhibiting effect against multidrug-resistant gram-positive pathogens. However, linezolid caused severe adverse reactions, such as thrombocytopenia, anaemia, optic neuropathy, and near-fatal serotonin syndrome. In order to investigate the toxicity of linezolid, twenty-four Sprague-Dawley rats were randomly divided into: control group (n=7), low-group (n=8), and high-group (n=9). The rats of low-group and high-group were given by gavage with linezolid 60 and 120 mg/kg/day for 7 days, respectively. The serum concentration of linezolid was determined by high performance liquid chromatography (HPLC); blood metabolic change was analyzed by gas chromatography-mass spectrometer (GC-MS). Adenosine triphosphate (ATP) concentration in HepG2-C3A after being cultured with linezolid was determined by HPLC. The results showed that there were six metabolites and nine metabolites had statistical differences in low-group and high-group (P<0.05). The trimethyl phosphate was the most significant indicator in those changed metabolites. Except for d-glucose which was slightly increased in low-group, octadecanoic acid, cholest-5-ene, hexadecanoic acid, α-linolenic acid, eicosapentaenoic acid, 9,12-Octadecadienoic acid, and docosahexaenoic acid were all decreased in low-group and high-group. ATP concentration was decreased in HepG2-C3A after cultured with linezolid. In conclusion, the toxicity of linezolid is related to its serum concentration. Linezolid may inhibit the synthesis of ATP and fatty acid.

Whole-genome sequencing based characterization of antimicrobial resistance in Enterococcus

Whole-genome sequencing (WGS) has transformed our understanding of antimicrobial resistance, yielding new insights into the genetics underlying resistance. To date, most studies using WGS to study antimicrobial resistance have focused on gram-negative bacteria in the family Enterobacteriaceae, such as Salmonella spp. and Escherichia coli, which have well-defined resistance mechanisms. In contrast, relatively few studies have been performed on gram-positive organisms. We sequenced 197 strains of Enterococcus from various animal and food sources, including 100 Enterococcus faecium and 97 E. faecalis. From analyzing acquired resistance genes and known resistance-associated mutations, we found that resistance genotypes correlated with resistance phenotypes in 96.5% of cases for the 11 drugs investigated. Some resistances, such as those to tigecycline and daptomycin, could not be investigated due to a lack of knowledge of mechanisms underlying these phenotypes. This study showed the utility of WGS for predicting antimicrobial resistance based on genotype alone.

Influence of Inoculum Effect on the Efficacy of Daptomycin Monotherapy and in Combination with β-Lactams against Daptomycin-Susceptible Enterococcus faecium Harboring LiaSR Substitutions

Enterococcus faecium isolates that harbor LiaFSR substitutions but are phenotypically susceptible to daptomycin (DAP) by current breakpoints are problematic, since predisposition to resistance may lead to therapeutic failure. Using a simulated endocardial vegetation (SEV) pharmacokinetic/pharmacodynamic (PK/PD) model, we investigated DAP regimens (6, 8, and 10 mg/kg of body weight/day) as monotherapy and in combination with ampicillin (AMP), ceftaroline (CPT), or ertapenem (ERT) against E. faecium HOU503, a DAP-susceptible strain that harbors common LiaS and LiaR substitutions found in clinical isolates (T120S and W73C, respectively). Of interest, the efficacy of DAP monotherapy, at any dose regimen, was dependent on the size of the inoculum. At an inoculum of ∼10⁹ CFU/g, DAP doses of 6 to 8 mg/kg/day were not effective and led to significant regrowth with emergence of resistant derivatives. In contrast, at an inoculum of ∼10⁷ CFU/g, marked reductions in bacterial counts were observed with DAP at 6 mg/kg/day, with no resistance. The inoculum effect was confirmed in a rat model using humanized DAP exposures. Combinations of DAP with AMP, CPT, or ERT demonstrated enhanced eradication and reduced potential for resistance, allowing de-escalation of the DAP dose. Persistence of the LiaRS substitutions was identified in DAP-resistant isolates recovered from the SEV model and in DAP-resistant derivatives of an initially DAP-susceptible clinical isolate of E. faecium (HOU668) harboring LiaSR substitutions that was recovered from a patient with a recurrent bloodstream infection. Our results provide novel data for the use of DAP monotherapy and combinations for recalcitrant E. faecium infections and pave the way for testing these approaches in humans.

Linezolid: a review of its properties, function, and use in critical care

Linezolid can be considered as the first member of the class of oxazolidinone antibiotics. The compound is a synthetic antibiotic that inhibits bacterial protein synthesis through binding to rRNA. It also inhibits the creation of the initiation complex during protein synthesis which can reduce the length of the developed peptide chains, and decrease the rate of reaction of translation elongation. Linezolid has been approved for the treatment of infections caused by vancomycin-resistant Enterococcus faecium, hospital-acquired pneumonia caused by Staphylococcus aureus, complicated skin and skin structure infections (SSSIs), uncomplicated SSSIs caused by methicillin-susceptible S. aureus or Streptococcus pyogenes, and community-acquired pneumonia caused by Streptococcus pneumoniae. Analysis of high-resolution structures of linezolid has demonstrated that it binds a deep cleft of the 50S ribosomal subunit that is surrounded by 23S rRNA nucleotides. Mutation of 23S rRNA was shown to be a linezolid resistance mechanism. Besides, mutations in specific regions of ribosomal proteins uL3 and uL4 are increasingly associated with linezolid resistance. However, these proteins are located further away from the bound drug. The methicillin-resistant S. aureus and vancomycin-resistant enterococci are considered the most common Gram-positive bacteria found in intensive care units (ICUs), and linezolid, as an antimicrobial drug, is commonly utilized to treat infected ICU patients. The drug has favorable in vitro and in vivo activity against the mentioned organisms and is considered as a useful antibiotic to treat infections in the ICU.

A retrospective clinical comparison of daptomycin vs daptomycin and a beta-lactam antibiotic for treating vancomycin-resistant Enterococcus faecium bloodstream infections

There is limited clinical evidence to support the combination of daptomycin and beta-lactam antibiotics (DAP + BLA) for treatment of vancomycin-resistant enterococci (VRE) bloodstream infections (BSI). We conducted a prospective observational cohort study of VRE-BSI during 2010-2015. The primary endpoint was mortality at the end of treatment. We included 114 patients who received DAP for VRE-BSI. Of these 87 (76.3%) received DAP + BLA. There were no significant differences in mortality between the DAP and DAP + BLA groups on univariable analysis (10/27 vs. 34/87, P = 0.85). A subgroup analysis of patients with enterococcal DAP minimum inhibitory concentrations (MICs) ≤2 mg/L, revealed that those treated with DAP + BLA had a lower mortality (adjusted hazard ratio [aHR], 0.23; 95% confidence interval [CI], 0.06-0.93; P = 0.04) after adjustment for other significant predictors of mortality, including the DAP dose. In addition, patients receiving high-dose (≥9 mg/kg) DAP + BLA independently had a better survival than those receiving low-dose DAP alone (aHR = 5.16), low-dose DAP + BLA (aHR = 5.39), and high-dose DAP alone (aHR = 19.01) (P < 0.05 for all comparisons). For patients with VRE-BSIs, the DAP MIC of the isolate and the DAP dose influence the effect of DAP + BLA on outcome. A high-dose DAP + BLA might improve survival. These findings support the use of high-dose DAP + BLA for treatment of VRE-BSI.

Vancomycin-resistant enterococcus infection in the hematopoietic stem cell transplant recipient: an overview of epidemiology, management, and prevention

Vancomycin-resistant enterococcus (VRE) is now one of the leading causes of nosocomial infections in the United States. Hematopoietic stem cell transplantation (HSCT) recipients are at increased risk of VRE colonization and infection. VRE has emerged as a major cause of bacteremia in this population, raising important clinical questions regarding the role and impact of VRE colonization and infection in HSCT outcomes as well as the optimal means of prevention and treatment. We review here the published literature and scientific advances addressing these thorny issues and provide a rational framework for their approach.

Gram-Positive Bacterial Infections: Research Priorities, Accomplishments, and Future Directions of the Antibacterial Resistance Leadership Group

Antimicrobial resistance in gram-positive bacteria remains a challenge in infectious diseases. The mission of the Gram-Positive Committee of the Antibacterial Resistance Leadership Group (ARLG) is to advance knowledge in the prevention, management, and treatment of these challenging infections to improve patient outcomes. Our committee has prioritized projects involving methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) due to the scope of the medical threat posed by these pathogens. Approved ARLG projects involving gram-positive pathogens include (1) a pharmacokinetics/pharmacodynamics study to evaluate the impact of vancomycin dosing on patient outcome in MRSA bloodstream infection (BSI); (2) defining, testing, and validating innovative assessments of patient outcomes for clinical trials of MRSA-BSI; (3) testing new strategies for "step-down" antibiotic therapy for MRSA-BSI; (4) management of staphylococcal BSIs in neonatal intensive care units; and (5) defining the impact of VRE bacteremia and daptomycin susceptibility on patient outcomes. This article outlines accomplishments, priorities, and challenges for research of infections caused by gram-positive organisms.

Prevalence and Antimicrobial Resistance of Enterococci Isolated from Retail Meats in the United States, 2002 to 2014

Bacteria of the genus Enterococcus are important human pathogens that are frequently resistant to a number of clinically important antibiotics. They are also used as markers of animal fecal contamination of human foods and are employed as sentinel organisms for tracking trends in resistance to antimicrobials with Gram-positive activity. As part of the National Antimicrobial Resistance Monitoring System (NARMS), we evaluated several retail meat commodities for the presence of enterococci from 2002 to 2014, and we found 92.0% to be contaminated. The majority of isolates were either Enterococcus faecalis (64.0%) or Enterococcus faecium (28.6%), and the antimicrobial resistance of each isolate was assessed by broth microdilution. The resistance prevalences for several drugs, including erythromycin and gentamicin, were significantly higher among poultry isolates, compared to retail beef or pork isolates. None of the isolates was resistant to the clinically important human drug vancomycin, only 1 isolate was resistant to linezolid, and resistance to tigecycline was below 1%. In contrast, a majority of both E. faecalis (67.5%) and E. faecium (53.7%) isolates were resistant to tetracycline. Overall, the robust NARMS testing system employed consistent sampling practices and methods throughout the testing period, with the only significant trend in resistance prevalence being decreased E. faecium resistance to penicillin. These data provide excellent baseline levels of resistance that can be used to measure future changes in resistance prevalence that may result from alterations in the use of antimicrobials in food animal production.IMPORTANCE Enterococci, including E. faecalis and E. faecium, are present in the guts of food-producing animals and are used as a measure of fecal contamination of meat. We used the large consistent sampling methods of NARMS to assess the prevalence of Enterococcus strains isolated from retail meats, and we found over 90% of meats to be contaminated with enterococci. We also assessed the resistance of the Enterococcus strains, commonly used as a measure of resistance to agents with Gram-positive activity, in foods. Resistance prevalence was over 25% for some antimicrobials and sample sources but was less than 1% for several of the most important therapeutic agents used in human medicine.