Daptomycin for Complicated Skin Infections: A Randomized Trial

Antibiotics daptomycin interacts with S protein of SARS-CoV-2 to promote cell invasion of Omicron (B1.1.529) pseudovirus

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has posed enormous challenges to global public health. The use of antibiotics has greatly increased during the SARS-CoV-2 epidemic owing to the presence of bacterial co-infection and secondary bacterial infections. The antibiotics daptomycin (DAP) is widely used in the treatment of infectious diseases caused by gram-positive bacteria owing to its highly efficient antibacterial activity. It is pivotal to study the antibiotics usage options for patients of coronavirus infectious disease (COVID-19) with pneumonia those need admission to receive antibiotics treatment for bacterial co-infection in managing COVID-19 disease. Herein, we have revealed the interactions of DAP with the S protein of SARS-CoV-2 and the variant Omicron (B1.1.529) using the molecular docking approach and Omicron (B1.1.529) pseudovirus (PsV) mimic invasion. Molecular docking analysis shows that DAP has a certain degree of binding ability to the S protein of SARS-CoV-2 and several derived virus variants, and co-incubation of 1-100 μM DAP with cells promotes the entry of the PsV into human angiotensin-converting enzyme 2 (hACE2)-expressing HEK-293T cells (HEK-293T-hACE2), and this effect is related to the concentration of extracellular calcium ions (Ca2+). The PsV invasion rate in the HEK-293T-hACE2 cells concurrently with DAP incubation was 1.7 times of PsV infection alone. In general, our findings demonstrate that DAP promotes the infection of PsV into cells, which provides certain reference of antibiotics selection and usage optimization for clinicians to treat bacterial coinfection or secondary infection during SARS-CoV-2 infection.

Daptomycin Dose Optimization in Pediatric Staphylococcus aureus Bacteremia: A Pharmacokinetic/Pharmacodynamic Investigation

Daptomycin is an antibiotic with Gram-positive activity, including methicillin-resistant Staphylococcus aureus, for which optimal pediatric dosing is unknown. This study aimed to evaluate daptomycin exposures achieved with package label dosing and to identify dosing regimens necessary to enhance efficacy and minimize toxicity in children with S. aureus bacteremia. Monte Carlo simulations were performed to determine probability of target attainment (PTA) for six pediatric age cohorts. Area under the curve to minimum inhibitory concentration ratio (AUC0-24:MIC) ≥666 was used to determine the PTA for efficacy (PTAE). Minimum concentration (Cmin) ≥24.3 mg/L determined the PTA for toxicity (PTAT). Acceptable dosing regimens were those which achieved the combined target of ≥90% PTAE and ≤5% PTAT. Package label dosing of daptomycin yielded insufficient efficacy with only 26.3% PTAE in children 13-24 months, 39.5% PTAE in children 2-6 years, 30.1% PTAE in children 7-11 years, and 50.1% PTAE in adolescents ≥12 years. To achieve the combined efficacy and safety target, doses of 18-24 mg/kg in children 3-12 months, 20-24 mg/kg in children 13-24 months, 19-24 mg/kg in children 2-6 years, 17-19 mg/kg in children 7-11 years, and 10-14 mg/kg in adolescents ≥12 years are necessary. Package label dosing resulted in suboptimal exposure for the majority of pediatric patients in all age groups evaluated. If targeting validated efficacy and safety endpoints, daily daptomycin doses of at least 20 mg/kg in children ≤6 years, 17 mg/kg in children 7-11 years, and 10 mg/kg in adolescents ≥12 years are necessary. Clinical studies evaluating these higher doses are needed.

Acute bacterial skin and skin structure infections in pediatric patients: potential role of dalbavancin

INTRODUCTION

Acute bacterial skin and skin structure infections (ABSSSIs) are a subtype of skin and soft tissue infections (SSTI), usually sustained by Gram-positive bacteria, whose incidence is high among children. ABSSSIs are responsible for a considerable number of hospitalizations. Moreover, as multidrug resistant (MDR) pathogens become widespread, the pediatric category seems burdened with an increased risk of resistance and treatment failure.

AREAS COVERED

To obtain a view on the status of the field, we describe the clinical, epidemiological, and microbiological aspects of ABSSSI in children. Old and new treatment options were critically revised with a focus on the pharmacological characteristics of dalbavancin. Evidence on the use of dalbavancin in children was collected, analyzed, and summarized.

EXPERT OPINION

Many of the therapeutic options available at the moment are characterized by the need for hospitalization or repeated intravenous infusions, safety issues, possible drug-drug interactions, and reduced efficacy on MDRs. Dalbavancin, the first long-acting molecule with strong activity against methicillin-resistant and also many vancomycin-resistant pathogens represents a game changer for adult ABSSSI. In pediatric settings, the available literature is still limited, but a growing body of evidence supports dalbavancin use in children with ABSSSI, demonstrating this drug to be safe and highly efficacious.

Pharmacokinetics of intravenous daptomycin in Japanese pediatric patients: Pharmacokinetic comparisons supporting dosing recommendations in Japanese pediatric patients

INTRODUCTION

The pharmacokinetics (PK) of daptomycin has not been previously characterized in Japanese pediatric patients with complicated skin and soft tissue infections (cSSTI) or bacteremia. An aim of the study includes evaluation of PK of daptomycin in Japanese pediatric patients and an appropriateness of the age-specific, weight-based dosing regimens in Japanese pediatric patients based on PK comparison with Japanese adult patients.

METHODS

The phase 2 trial enrolled Japanese pediatric patients (age 1-17 years) with cSSTI (n = 14) or bacteremia (n = 4) caused by gram-positive cocci in order to evaluate safety, efficacy and PK. The Phase 3 trial in Japanese adult patients (SSTI n = 65, septicemia/right-sided infective endocarditis (RIE) n = 7) was referred to for PK comparison between adult and pediatric. Daptomycin concentrations in plasma were analyzed by reverse-phase high-performance liquid chromatography (HPLC). PK parameters were determined using non-compartmental analysis in Japanese pediatric and Japanese adult patients. The exposures in Japanese pediatric patients were graphically compared with those in Japanese adult patients. The relationship between daptomycin exposures and creatine phosphokinase (CPK) elevation was explored visually.

RESULTS

Following administration of the age-specific, weight-based dosing regimens, daptomycin exposures were overlapping across age groups in pediatric patients with cSSTI with similar observations based on clearance. The distribution of individual exposure in Japanese pediatric patients was overlapping with that in Japanese adult patients. No apparent relationship between daptomycin exposures and CPK elevation in Japanese pediatric patients was observed.

CONCLUSIONS

The results suggested that the age-specific, weight-based dosing regimens are considered to be appropriate in Japanese pediatric patients.

Therapeutic Options and Outcomes for the Treatment of Children with Gram-Positive Bacteria with Resistances of Concern: A Systematic Review

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant coagulase-negative Staphylococci (MR-CoNS), and vancomycin-resistant Enterococci (VRE) are increasing worldwide and represent a threat for the limited treatment options in pediatric patients and neonates compared to adults. Recommendations in pediatrics are mainly extrapolated from adults' studies.

METHODS

A literature search for the treatment of these pathogens in children (<18 years old) was conducted in Embase, MEDLINE, and Cochrane Library. Studies reporting data on single-patient-level outcomes related to a specific antibiotic treatment for multidrug resistant (MDR) Gram-positive bacterial infection in children were included. Studies reporting data from adults and children were included if single-pediatric-level information could be identified (PROSPERO registration: CRD42022383867).

RESULTS

The search identified 11,740 studies (since January 2000), of which 48 fulfilled both the inclusion and the exclusion criteria and were included in the analysis: 29 for MRSA, 20 for VRE, and seven for MR-CoNS. Most studies were retrospective studies. Vancomycin was mainly used as a comparator, while linezolid and daptomycin were the most studied antimicrobials showing good efficacy.

CONCLUSIONS

Linezolid showed a safety and efficacy profile in a neonatal setting; daptomycin is increasingly used for MRSA, but the evidence is scarce for VRE.

MRSA and Skin Infections in Psoriatic Patients: Therapeutic Options and New Perspectives

Psoriatic patients present various infectious risk factors, but there are few studies in the literature evaluating the actual impact of psoriasis in severe staphylococcal skin infections. Our narrative review of the literature suggests that psoriatic patients are at increased risk of both colonization and severe infection, during hospitalization, by S. aureus. The latter also appears to play a role in the pathogenesis of psoriasis through the production of exotoxins. Hospitalized psoriatic patients are also at increased risk of MRSA skin infections. For this reason, new molecules are needed that could both overcome bacterial resistance and inhibit exotoxin production. In our opinion, in the near future, topical quorum sensing inhibitors in combination with current anti-MRSA therapies will be able to overcome the increasing resistance and block exotoxin production. Supplementation with Vitamin E (VE) or derivatives could also enhance the effect of anti-MRSA antibiotics, considering that psoriatic patients with metabolic comorbidities show a low intake of VE and low serum levels, making VE supplementation an interesting new perspective.

Role of Daptomycin in Cutaneous Wound Healing: A Narrative Review

Daptomycin is active against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and the on-label indications for its use include complicated skin and skin structure infections (cSSSI). We performed a narrative review of the literature with the aim to evaluate the role of daptomycin in the skin wound healing process, proposing our point of view on the possible association with other molecules that could improve the skin healing process. Daptomycin may improve wound healing in MRSA-infected burns, surgical wounds, and diabetic feet, but further studies in humans with histological examination are needed. In the future, the combination of daptomycin with other molecules with synergistic action, such as vitamin E and derivates, IB-367, RNA III-inhibiting peptide (RIP), and palladium nanoflowers, may help to improve wound healing and overcome forms of antibiotic resistance.

Pharmacokinetics and pharmacodynamics of peptide antibiotics

Antimicrobial resistance is a major global health challenge. As few new efficacious antibiotics will become available in the near future, peptide antibiotics continue to be major therapeutic options for treating infections caused by multidrug-resistant pathogens. Rational use of antibiotics requires optimisation of the pharmacokinetics and pharmacodynamics for the treatment of different types of infections. Toxicodynamics must also be considered to improve the safety of antibiotic use and, where appropriate, to guide therapeutic drug monitoring. This review focuses on the pharmacokinetics/pharmacodynamics/toxicodynamics of peptide antibiotics against multidrug-resistant Gram-negative and Gram-positive pathogens. Optimising antibiotic exposure at the infection site is essential for improving their efficacy and minimising emergence of resistance.

A case of acute focal bacterial nephritis caused by methicillin-resistant Staphylococcus saprophyticus in a 13-year-old adolescent girl treated with daptomycin

Staphylococcus saprophyticus is a gram-positive, coagulase-negative member of the Staphylococcus genus and is second only to Escherichia coli as a cause of urinary tract infections in the young female population. S. saprophyticus usually has good susceptibility to drugs commonly used to treat urinary tract infections, but it is often methicillin-resistant. Here we report a case of acute focal bacterial nephritis in a 13-year-old female patient caused by methicillin-resistant S. saprophyticus and treated with daptomycin (DAP). The patient had a history of unilateral hearing loss and presented to her previous physician with a 3-day history of fever, right-sided abdominal pain, and diarrhea. Cefotaxime antimicrobial chemotherapy was initiated as an empiric therapy targeting E. coli, the most frequent cause of community-onset pyelonephritis. Vancomycin (VCM) was started for acute focal bacterial nephritis caused by methicillin-resistant S. saprophyticus but was stopped due to allergy and replaced with DAP. After 13 days of treatment with DAP, the patient received 17 days of treatment with sulfamethoxazole-trimethoprim combination therapy. The patient experienced no adverse events and did not relapse. DAP is a relatively new anti-methicillin-resistant Staphylococcus aureus drug used to treat gram-positive cocci infections. It is primarily excreted by the kidneys, which may be desirable in treating urinary tract infections. For children who cannot receive VCM for any reason, DAP may be a viable alternative.

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S. saprophyticus is a common cause of urinary tract infections in young women.

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The use of daptomycin for urinary tract infections in children is rare.

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Vancomycin (VCM) is usually used to treat methicillin-resistant S. saprophyticus.

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If VCM is unavailable, daptomycin can used to treat urinary tract infections in such cases.

Efficacy and safety of daptomycin in Japanese pediatric participants with complicated skin and soft tissue infections or bacteremia caused by gram-positive cocci

INTRODUCTION

Complicated skin and soft tissue infections (cSSTIs) and bacteremia caused by Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), are common causes of infection for children worldwide. Here, the safety and efficacy of daptomycin in Japanese pediatric participants are reported.

METHODS

This open-label, single-arm phase 2 study (NCT03643952) enrolled Japanese pediatric participants (age 1-17 years) with cSSTI or bacteremia caused by gram-positive cocci. Participants received age-adjusted doses of intravenous daptomycin for 5 to up to 14 days (cSSTI) or 5 to up to 42 days (bacteremia). The primary objective was safety and tolerability; efficacy among participants with infections caused by MRSA was a secondary objective.

RESULTS

A total of 18 participants (cSSTI, n = 14; bacteremia, n = 4) were enrolled across 12 study sites in Japan. The most common pathogen was S. aureus (15/18 [83.3%]), including methicillin-susceptible and -resistant isolates. Adverse events (AE) were reported in 42.9% (6/14) of participants with cSSTI and 100% (4/4) of participants with bacteremia. No deaths, serious AEs, discontinuations of study medication due to an AE, or events of clinical interest occurred in the study. In participants with infections caused by MRSA, 87.5% [7/8] achieved favorable clinical response at test of cure (TOC) visit (cSSTI, 85.7% [6/7]; bacteremia, 100% [1/1]). In this population, favorable microbiological response at TOC was achieved by 71.4% (5/7) of participants with cSSTI and 100% (1/1) of participants with bacteremia.

CONCLUSIONS

Daptomycin was well tolerated, exhibited a favorable safety profile, and was effective for the treatment of cSSTI or bacteremia in Japanese children.

Antibacterial Activity and Amphidinol Profiling of the Marine Dinoflagellate Amphidinium carterae (Subclade III)

Microalgae have received growing interest for their capacity to produce bioactive metabolites. This study aimed at characterising the antimicrobial potential of the marine dinoflagellate Amphidinium carterae strain LACW11, isolated from the west of Ireland. Amphidinolides have been identified as cytotoxic polyoxygenated polyketides produced by several Amphidinium species. Phylogenetic inference assigned our strain to Amphidinium carterae subclade III, along with isolates interspersed in different geographic regions. A two-stage extraction and fractionation process of the biomass was carried out. Extracts obtained after stage-1 were tested for bioactivity against bacterial ATCC strains of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa. The stage-2 solid phase extraction provided 16 fractions, which were tested against S. aureus and E. faecalis. Fractions I, J and K yielded minimum inhibitory concentrations between 16 μg/mL and 256 μg/mL for both Gram-positive. A targeted metabolomic approach using UHPLC-HRMS/MS analysis applied on fractions G to J evidenced the presence of amphidinol type compounds AM-A, AM-B, AM-22 and a new derivative dehydroAM-A, with characteristic masses of m/z 1361, 1463, 1667 and 1343, respectively. Combining the results of the biological assays with the targeted metabolomic approach, we could conclude that AM-A and the new derivative dehydroAM-A are responsible for the detected antimicrobial bioactivity.

Antimicrobial prescribing for treatment of serious infections caused by Staphylococcus aureus and methicillin-resistant Staphylococcus aureus in pediatrics: an expert review

Introduction: Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), remains a significant pathogen in children. Despite evidence of decreasing prevalence, MRSA bacteremia has been closely associated with complications, including certain infections (i.e. musculoskeletal and endovascular) linked to increased treatment failures.Areas covered: This expert review summarized recent published literature on the role of treatment, dosing and administration of antibiotics used to combat serious S. aureus infections in children. The pertinent antibiotics presented were vancomycin, oxazolidinones, semi-synthetic glycopeptides, daptomycin, tigecycline, novel cephalosporins, fosfomycin and lefamulin. Vancomycin has been the most commonly used antibiotic in empiric therapy for serious MRSA infection, with new key recommendations emphasizing a different approach to dosing and therapeutic monitoring. For other antibiotics, data remain limited or clinical trials are underway.Expert opinion: MRSA remains a significant pathogen in the pediatric population. As numerous therapeutic agents are available, many agents have limited data on usage in pediatric patients. Future studies require pharmacokinetic, safety and efficacy studies in pediatric patients to ensure appropriate therapeutic treatment and outcomes. Phage therapy has been used to treat deep-seated MRSA infections and is an emerging investigational treatment option.

Daptomycin for Pediatric Gram-Positive Acute Hematogenous Osteomyelitis

BACKGROUND

We prospectively evaluated efficacy and safety of daptomycin versus active comparator in children with acute hematogenous osteomyelitis (AHO).

METHODS

Randomized, controlled, double-blind, global, multicenter, phase 3 trial. Patients 1-17 years of age with suspected/confirmed AHO requiring hospitalization and intravenous therapy were randomized 1:1 to intravenous daptomycin (once-daily, age-adjusted doses) or comparator (vancomycin, nafcillin or equivalent) ≥4 days, followed by oral therapy (14-42 days total). Primary endpoint: protocol-defined clinical improvement by Day 5 in the modified intention-to-treat (MITT) population (confirmed AHO, ≥1 dose of study treatment); differences between study arms were evaluated using a prespecified 15% noninferiority margin for daptomycin.

RESULTS

Seventy-three patients per arm received treatment. Pathogens were isolated from 62% of patients (83% methicillin-susceptible Staphylococcus aureus, 9% methicillin-resistant S. aureus [MRSA]). Clinical improvement by Day 5 was observed in 55/71 (78%) daptomycin- and 58/70 (83%) comparator-treated MITT patients (95% confidence interval [CI]: -19.4, 7.4). This difference was not statistically significant; however, daptomycin did not meet the prespecified 15% noninferiority margin, since the lower bound of the 95% CI extended below 15%. Overall, 82% of daptomycin and 87% of comparator patients achieved clinical cure at the test-of-cure visit (secondary endpoint). More comparator patients had treatment-emergent (63% vs. 46%) and treatment-related (18% vs. 7%) adverse events.

CONCLUSIONS

Differences between daptomycin and comparator for the primary endpoint were not statistically significant; however, prespecified noninferiority criteria for daptomycin were not met. With insufficient cases of confirmed MRSA, we could not evaluate daptomycin for MRSA AHO. Our nonvalidated protocol design yields valuable information for implementing future trials in AHO (ClinicalTrials.gov NCT01922011).

Lifesaving Treatment of Aortic Valve Staphylococcus aureus Endocarditis: Daptomycin and Early Surgical Therapy

Infective endocarditis (IE) is an uncommon infection in children. The recommended treatment for native valve endocarditis secondary to methicillin-susceptible Staphylococcus aureus infection is antistaphylococcal penicillins such as nafcillin or oxacillin. If the initial therapy fails in IE, it can lead to catastrophic results. Nowadays, daptomycin is the best alternative antimicrobial agent to treat children with severe infections, when standard antimicrobial therapy does not yield a result. Herein, in this article, we described a case of a 16-year-old boy who had aortic valve S. aureus endocarditis with septic embolization and stroke. The patient was successfully treated only with daptomycin as well as surgical therapy in the early phase of the infection.

Considerations and Caveats in Combating ESKAPE Pathogens against Nosocomial Infections

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are among the most common opportunistic pathogens in nosocomial infections. ESKAPE pathogens distinguish themselves from normal ones by developing a high level of antibiotic resistance that involves multiple mechanisms. Contemporary therapeutic strategies which are potential options in combating ESKAPE bacteria need further investigation. Herein, a broad overview of the antimicrobial research on ESKAPE pathogens over the past five years is provided with prospective clinical applications.

One Size Fits All? Application of Susceptible-Dose-Dependent Breakpoints to Pediatric Patients and Laboratory Reporting

The Clinical and Laboratory Standards Institute antimicrobial and antifungal standards define a susceptible-dose-dependent (SDD) category for certain organisms and drug combinations. Reporting MICs within the SDD category suggests that treatment success is likely with increased drug exposure. These breakpoints are based on pharmacokinetic, pharmacodynamic, and clinical outcome data from adults and not pediatric patients. This commentary aims to discuss the implications of reporting SDD interpretations for pediatric patients and recommends laboratory reporting comments.

Common Community-acquired Bacterial Skin and Soft-tissue Infections in Children: an Intersociety Consensus on Impetigo, Abscess, and Cellulitis Treatment

PURPOSE

The main objective of this article was to offer practical suggestions, given the existing evidence, for identifying and managing bacterial impetigo, abscess, and cellulitis in ambulatory and hospital settings.

METHODS

Five Italian pediatric societies appointed a core working group. In selected conditions, specially trained personnel evaluated quality assessment of treatment strategies according to the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Only randomized controlled trials (RCTs) and observational studies were included for quality assessment according to the GRADE methodology. MEDLINE, Ovid MEDLINE, EMBASE, and Cochrane Library databases were searched with a strategy combining MeSH and free text terms.

FINDINGS

The literature review included 364 articles focusing on impetigo, skin abscess, and cellulitis/orbital cellulitis. The articles included for quality assessment according to the GRADE methodology for impetigo comprised 5 RCTs and 1 observational study; for skin abscess, 10 RCTs and 3 observational studies were included; for cellulitis and erysipelas, 5 RCTs and 5 observational studies were included; and for orbital cellulitis, 8 observational studies were included. Recommendations were formulated according to 4 grades of strength for each specific topic (impetigo, skin abscesses, cellulitis, and orbital cellulitis). Where controversies arose and expert opinion was considered fundamental due to lack of evidence, agreement according to Delphi consensus recommendations was included.

IMPLICATIONS

Based on a literature review and on local epidemiology, this article offers practical suggestions for use in both ambulatory and hospital settings for managing the most common bacterial SSTIs.

Efficacy and safety of daptomycin: systematic review and meta-analysis

Background:

The aim of this study was to assess whether daptomycin is safer and more efficacious than comparators for the treatment of serious infection caused by gram-positive microorganisms.

Methods:

Electronic databases (Medline, EMBASE, the Cochrane Central Register of Controlled Trials and clinical registered trials) were searched to identify randomized controlled trials (RCTs) that assessed the efficacy and safety of daptomycin versus therapy with any other antibiotic comparator. Two reviewers independently applied selection criteria, performed a quality assessment and extracted the data. Heterogeneity was assessed, and a random-effects or fixed-effects model, when appropriate, was used for estimates of risk ratio (RR). The primary outcome assessed was the risk of clinical treatment failure among the intention-to-treat population and the presence of any treatment related adverse event (AEs).

Results:

A total of seven trials fulfilled the inclusion criteria. Daptomycin treatment failure rates were no different to comparator regimens (RR = 0.96; CI 95% 0.86–1.06). No significantly different treatment related AEs were identified when comparing groups (RR = 0.91; CI 95% 0.83–1.01).

Conclusions:

No significant differences in treatment failure rates and safety were found using daptomycin or any of the comparators treatment.

Infectious Diseases Clinician's Variation in the Management of Pediatric Staphylococcus aureus Bacteraemia and Equipoise for Clinical Trials

Background: Pediatric Staphylococcus aureus bacteraemia is one of the leading causes of community-acquired blood-stream infection in the developed world; however, our understanding of management practices by treating clinicians is limited. Methods: The authors designed a web-based clinician survey with support from the Australian and New Zealand Pediatric Infectious Diseases group, of the Australasian Society of Infectious Diseases. Clinicians were presented with three pediatric cases of varying severity. Antibiotic choice, durations of intravenous and oral therapy and research priorities for pediatric S. aureus bacteraemia trials were gauged. Results and Conclusion: Large variation in antibiotic prescribing amongst clinicians is demonstrated and increased, corresponding with escalating case complexity and persisting MRSA bacteraemia. Most clinicians chose defining optimal duration of therapy for S. aureus bacteraemia as their top clinical trial priority. These findings highlight the importance of prioritizing pediatric S. aureus bacteraemia clinical trials, to inform guidelines and best practice management.

Randomized Multicenter Study Comparing Safety and Efficacy of Daptomycin Versus Standard-of-care in Pediatric Patients With Staphylococcal Bacteremia

BACKGROUND

Staphylococcus aureus, including community-associated methicillin-resistant S. aureus, is an important cause of pediatric bacteremia. Daptomycin is a well-established treatment option for Gram-positive bacteremia in adults, but its safety and efficacy in children require confirmation.

METHODS

This was a randomized (2:1), evaluator-blinded, multicenter, phase 4 clinical trial comparing intravenous daptomycin with standard-of-care (SOC) for treatment of S. aureus bacteremia in 1- to 17-year-old patients (Clinicaltrials.gov: NCT01728376). Total treatment duration (intravenous followed by oral step-down therapy) was 5-42 days. Daptomycin was dosed once daily by patient age: 12-17 years, 7 mg/kg; 7-11 years, 9 mg/kg and 1-6 years, 12 mg/kg. The primary objective was to evaluate daptomycin safety in children who received ≥1 dose; secondary objectives included comparing daptomycin efficacy with SOC (the trial was not designed to confirm noninferiority) and pharmacokinetic analysis.

RESULTS

Fifty-five children were randomized to daptomycin and 27 to SOC (primarily vancomycin or cefazolin); 90% had S. aureus. In both groups, 15% of patients had drug-related adverse events, primarily diarrhea (4% daptomycin, 8% SOC) and increased creatine phosphokinase (4% daptomycin, 0% SOC). Clinical success (blinded evaluator-assessed complete/partial resolution of bacteremia signs and symptoms 7-14 days after end-of-treatment) rates were similar for daptomycin (88%) and SOC (77%; 95% confidence interval for difference: -9% to 31%). Daptomycin plasma levels across age groups were comparable with those in adults receiving daptomycin at 6 mg/kg.

CONCLUSIONS

Once-daily, age-appropriate daptomycin was well tolerated in children with staphylococcal bacteremia; efficacy was comparable with SOC. Daptomycin in age-adjusted doses is a safe treatment alternative in this setting.

Pharmacokinetics of Daptomycin in Critically Ill Pediatric Patients

The pharmacokinetics of daptomycin (10 mg/kg once daily) was studied in 4 critically ill pediatric patients aged 8 to 14 yrs. The area under the concentration-time curve from time zero to infinity (AUC_0-∞) of plasma concentrations on day 1 ranged between 123.8 to 663.9 μg · h/ml, with lower values observed in septic and burn patients; clearance ranged from 15.1 to 80.7 ml/h/kg. Higher-than-recommended doses of daptomycin may be needed in septic children to ensure optimal drug exposure. Interpatient variability may suggest a role for therapeutic drug monitoring.

New Antimicrobial Agents for the Treatment of Staphylococcal Infections in Children

Several new antimicrobial agents-daptomycin, ceftaroline, telavancin, dalbavancin, and-tedizolid have been approved for the treatment of staphylococcal infections, including methicillin-resistant Staphylococcus aureus (MRSA), in adults. Ceftaroline and daptomycin have been approved by the US Food and Drug Administration for use in children. Ceftaroline, a beta-lactam antibiotic with activity against MRSA, has been approved for treatment of community-acquired bacterial pneumonia and complicated skin and skin structure infections. Daptomycin has been approved for treatment of complicated skin and skin structure infections. In this article, we review the pharmacokinetics and pharmacodynamics of these antibiotics and available data on use in children.

Community-Acquired MRSA Pericarditis and Mediastinitis in a Previously Healthy Infant

Invasive community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections disproportionately affect children, but there are few pediatric reports of pericarditis and mediastinitis caused by CA-MRSA in previously healthy children. Here we report a severe case of CA-MRSA pericarditis with extension to the mediastinum and carotid sheath in a previously healthy 8-month-old infant who was successfully treated with surgical interventions and with a combination of daptomycin and vancomycin. The relatively indolent clinical course in this patient was notable given the significant extent of infection. This case highlights the potential virulence of CA-MRSA in previously healthy children and the importance of early diagnosis, prompt drainage, and appropriate antibiotic coverage.

On the quest for the elusive mechanism of action of daptomycin: Binding, fusion, and oligomerization

Daptomycin, sold under the trade name CUBICIN, is the first lipopeptide antibiotic to be approved for use against Gram-positive organisms, including a number of highly resistant species. Over the last few decades, a number of studies have tried to pinpoint the mechanism of action of daptomycin. These proposed modes of action often have points in common (e.g. the requirement for Ca²⁺ and lipid membranes containing a high proportion of phosphatidylglycerol (PG) headgroups), but also points of divergence (e.g. oligomerization in solution and in membranes, membrane perturbation vs. inhibition of cell envelope synthesis). In this study, we investigate how concentration effects may have an impact on the interpretation of the biophysical data used to support a given mechanism of action. Results obtained from small angle neutron scattering (SANS) experiments and molecular dynamics (MD) simulations show that daptomycin oligomerizes at high concentrations (both with and without Ca²⁺) in solution, but that this oligomer readily falls apart. Photon correlation spectroscopy (PCS) experiments demonstrate that daptomycin causes fusion more readily in DMPC/PG membranes than in POPC/PG, suggesting that the latter may be a better model system. Finally, fluorescence and Förster resonance energy transfer (FRET) experiments reveal that daptomycin binds strongly to the lipid membrane and that oligomerization occurs in a concentration-dependent manner. The combined experiments provide an improved framework for more general and rigorous biophysical studies toward understanding the elusive mechanism of action of daptomycin. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman.