In vitro activity of daptomycin against methicillin-resistant Staphylococcus aureus, including heterogeneously glycopeptide-resistant strains

Cell-Free Systems: Ideal Platforms for Accelerating the Discovery and Production of Peptide-Based Antibiotics

Peptide-based antibiotics (PBAs), including antimicrobial peptides (AMPs) and their synthetic mimics, have received significant interest due to their diverse and unique bioactivities. The integration of high-throughput sequencing and bioinformatics tools has dramatically enhanced the discovery of enzymes, allowing researchers to identify specific genes and metabolic pathways responsible for producing novel PBAs more precisely. Cell-free systems (CFSs) that allow precise control over transcription and translation in vitro are being adapted, which accelerate the identification, characterization, selection, and production of novel PBAs. Furthermore, these platforms offer an ideal solution for overcoming the limitations of small-molecule antibiotics, which often lack efficacy against a broad spectrum of pathogens and contribute to the development of antibiotic resistance. In this review, we highlight recent examples of how CFSs streamline these processes while expanding our ability to access new antimicrobial agents that are effective against antibiotic-resistant infections.

Dual release of daptomycin and BMP-2 from a composite of β-TCP ceramic and ADA gelatin

BACKGROUND

Antibiotic-containing carrier systems are one option that offers the advantage of releasing active ingredients over a longer period of time. In vitro sustained drug release from a carrier system consisting of microporous β-TCP ceramic and alginate has been reported in previous works. Alginate dialdehyde (ADA) gelatin gel showed both better mechanical properties when loaded into a β-TCP ceramic and higher biodegradability than pure alginate.

METHODS

Dual release of daptomycin and BMP-2 was measured on days 1, 2, 3, 6, 9, 14, 21, and 28 by HPLC and ELISA. After release, the microbial efficacy of the daptomycin was verified and the biocompatibility of the composite was tested in cell culture.

RESULTS

Daptomycin and the model compound FITC protein A (n = 30) were released from the composite over 28 days. A Daptomycin release above the minimum inhibitory concentration (MIC) by day 9 and a burst release of 71.7 ± 5.9% were observed in the loaded ceramics. Low concentrations of BMP-2 were released from the loaded ceramics over 28 days.

Evaluation of the Antibacterial Effect of Aurone-Derived Triazoles on Staphylococcus aureus

Infections caused by antibiotic-resistant bacteria continue to pose a significant public health threat despite their overall decreasing numbers in the last two decades. One group of compounds fundamental to the search for new agents is low-cost natural products. In this study, we explored a group of newly synthesized novel aurone-derived triazole compounds to identify those with pharmaceutical potential as inhibitors of antibiotic-resistant Staphylococcus aureus. Using the broth microdilution method, antibacterial activities against methicillin-resistant S. aureus ATCC 43300 (MRSA) and methicillin-sensitive S. aureus ATCC 29213 (MSSA) were identified for four aurone-derived triazole compounds, AT106, AT116, AT125, and AT137, using the half-maximal inhibitory concentrations for the bacteria (IC50) and mammalian cell lines (CC50). Compounds AT125 and AT137 were identified to have pharmaceutical potential as the IC50 values against MRSA were 5.412 µM and 3.870 µM, whereas the CC50 values measured on HepG2 cells were 50.57 µM and 39.81 µM, respectively, resulting in selectivity indexes (SI) > 10. Compounds AT106 and AT116 were also selected for further study. IC50 values for these compounds were 5.439 µM and 3.178 µM, and the CC50 values were 60.33 µM and 50.87 µM, respectively; however, SI values > 10 were for MSSA only. Furthermore, none of the selected compounds showed significant hemolytic activity for human erythrocytes. We also tested the four compounds against S. aureus biofilms. Although AT116 and AT125 successfully disrupted MSSA biofilms, there was no measurable potency against MRSA biofilms. Checkerboard antibiotic assays to identify inhibitory mechanisms for these compounds indicated activity against bacterial cell membranes and cell walls, supporting the pharmaceutical potential for aurone-derived triazoles against antibiotic-resistant bacteria. Examining structure-activity relationships between the four compounds in this study and other aurone-derived triazoles in our library suggest that substitution with a halogen on either the salicyl ring or triazole aryl group along with triazoles having nitrile groups improves anti-Staphylococcal activity with the location of the functionality being very important.

Pharmacokinetics of culture-directed antibiotics for the treatment of peritonitis in automated peritoneal dialysis: A systematic narrative review

The objectives of this study were to provide a summary of the pharmacokinetic data of some intraperitoneal (IP) antibiotics that could be used for both empirical and culture-directed therapy, as per the ISPD recommendations, and examine factors to consider when using IP antibiotics for the management of automated peritoneal dialysis (APD)-associated peritonitis. A literature search of PubMed, EMBASE, Scopus, MEDLINE and Google Scholar for articles published between 1998 and 2020 was conducted. To be eligible, articles had to describe the use of antibiotics via the IP route in adult patients ≥18 years old on APD in the context of pharmacokinetic studies or case reports/series. Articles describing the use of IP antibiotics that had been recently reviewed (cefazolin, vancomycin, gentamicin and ceftazidime) or administered for non-APD-associated peritonitis were excluded. A total of 1119 articles were identified, of which 983 abstracts were screened. Seventy-three full-text articles were assessed for eligibility. Eight records were included in the final study. Three reports had pharmacokinetic data in patients on APD without peritonitis. Each of cefepime 15 mg/kg IP, meropenem 0.5 g IP and fosfomycin 4 g IP given in single doses achieved drug plasma concentrations above the minimum inhibitory concentration for treating the susceptible organisms. The remaining five records were case series or reports in patients on APD with peritonitis. While pharmacokinetic data support intermittent cefepime 15 mg/kg IP daily, only meropenem 0.5 g IP and fosfomycin 4 g IP are likely to be effective if given in APD exchanges with dwell times of 15 h. Higher doses may be required in APD with shorter dwell times. Information on therapeutic efficacy was derived from case reports/series in individual patients and without therapeutic drug monitoring. Until more pharmacokinetic data are available on these antibiotics, it would be prudent to shift patients who develop peritonitis on APD to continuous ambulatory peritoneal dialysis, where pharmacokinetic information is more readily available.

Highly efficient antimicrobial agents based on sulfur-enriched, hydrophilic molybdenum disulfide nano/microparticles and coatings functionalized with palladium nanoparticles

In this research the molybdenum disulfide (MoS₂)-based nano/microparticles and coatings were synthesized through a simple, one-step hydrothermal approach without any other additives. Composition, structure, and morphology of the synthesized MoS₂-based materials were investigated using ultraviolet-visible spectroscopy (UV-Vis), inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) techniques. The fabricated materials exhibited relatively small (Δθ = 18.7 ± 2.5⁰) contact angle and prominent hydrophilic properties, which are attributable to sulfur-enriched MoS₂ composite as evidenced by simultaneous thermal analysis (STA) coupled with mass spectrometric (MS) analysis of evolving gaseous species (TG/DTA-MS) analysis. Such nanostructures exhibit a better adhesion of biomolecules, thus facilitating the interaction between them, as confirmed by highly effective antimicrobial action. The present study examines antimicrobial properties of hydrophilic, sulfur-enriched MoS₂ nano/microparticles as well as MoS₂-based coatings against various humans' pathogenic bacteria such as Salmonella enterica, Pseudomonas aeruginosa, Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), Micrococcus luteus, and two Candida yeast strains (C. parapsilosis, C. krusei). The MoS₂-ns (40 μg mL^-1) showed over 90% killing efficiency against S. aureus MRSA bacteria and both Candida yeast when exposed for 24 h. Petal-like MoS₂ microstructures and heterostructured MoS₂/Ti and Pd/MoS₂/Ti coatings also possessed high antimicrobial potential and are considered as a promising antimicrobial agent. The MoS₂-induced production of intracellular reactive oxygen species (ROS) was evidenced by measuring the standard DCF dye fluorescence.

Interaction of the antimicrobial peptide ∆M3 with the Staphylococcus aureus membrane and molecular models

Staphylococcus aureus is one of the most pathogenic bacteria; infections with it are associated with significant morbidity and mortality in health care facilities. Antimicrobial peptides are a promising next generation antibiotic with great potential against bacterial infections. In this study, evidence is presented of the biological and biophysical properties of the novel synthetic peptide ΔM3. Its antimicrobial activity against the ATCC 25923 and methicillin-resistant S. aureus strains was evaluated. The results showed that ΔM3 has activity in the same μM range as vancomycin. Biophysical studies were performed with palmitoyloleoylphosphatidylglycerol and cardiolipin liposomes loaded with calcein and used to follow the lytic activity of the peptide by fluorescence spectroscopy. On the other hand, ΔM3 was induced to interact with molecular models of the erythrocyte membrane buil-up of dimiristoylphosphatidylcholine and dimyristoylphosphatidylethanolamine, representative lipids of the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of ΔM3 to interact with the bacteria and erythrocyte model membranes was also evaluated by X-ray diffraction and differential scanning calorimetry. The morphological changes induced by the peptide to human erythrocytes were observed by scanning electron microscopy. Results with these techniques indicated that ΔM3 interacted with the inner monolayer of the erythrocyte membrane, which is rich in anionic lipids. Additionally, the cytotoxic effects of ΔM3 on red blood cells were evaluated by monitoring the hemoglobin release from erythrocytes. The results obtained from these different approaches showed ΔM3 to be a non-cytotoxic peptide with antibacterial activity.

Catechin isolated from cashew nut shell exhibits antibacterial activity against clinical isolates of MRSA through ROS-mediated oxidative stress

Staphylococcus aureus causes severe infections and among all methicillin-resistant S. aureus (MRSA) remains a great challenge in spite of decade research of antibacterial compounds. Even though some synthetic antibiotics have been developed, they are not effective against MRSA, and hence, there is a search for natural, alternative and plant-based antibacterial compound. In this connection, catechin isolated from cashew nut shell was investigated for its antibacterial potential against MRSA. Catechin exhibited zone of inhibition (ZOI) and minimum inhibitory concentration (MIC) in a range of 15.1-19.5 mm and 78.1-156.2 μg/ml, respectively, against ATCC and clinical isolates of MRSA. Among all clinical isolates, clinical isolate-3 exhibited highest sensitivity to catechin. Catechin has arrested the growth of MRSA strains and also caused toxicity by membrane disruption which was illustrated by AO/EB fluorescence staining. Increased nucleic acid leakage (1.58-28.6-fold) and protein leakage (1.40-23.50-fold) was noticed in MRSA due to catechin treatment when compared to methicillin. Bacteria treated with catechin at its MIC showed 1.52-, 1.87- and 1.74-fold increase of ROS production in methicillin susceptible S. aureus (MSSA), MRSA and clinical isolate-3 strains, respectively, as compared to control. Superoxide dismutase (5.31-9.63 U/mg protein) and catalase (1573-3930 U/mg protein) were significantly decreased as compared to control in catechin-treated S. aureus. Thus, catechin exhibited antibacterial activity through oxidative stress by increased production of ROS and decreased antioxidant enzymes. Altogether results suggest that catechin is a promising lead compound with antibacterial potential against MRSA. KEY POINTS: • Catechin was isolated and identified as active compound in cashew nut shell. • Catechin exhibited antimicrobial activity against clinical isolates of MRSA. • Bacterial cell wall damage was caused by catechin in MRSA strains. • Catechin increased the oxidative stress in MRSA by intracellular ROS production.

Vancomycin, linezolid and daptomycin susceptibility pattern among clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) from Sub- Himalyan Center

INTRODUCTION:

The efficacy of vancomycin, drug of choice for methicillin-resistant Staphylococcus aureus (MRSA), has become questionable due to the emergence of MRSA isolates with reduced susceptibility. The present study was conducted to determine the vancomycin, linezolid, and daptomycin susceptibility pattern in clinical isolates of MRSA and to observe minimum inhibitory concentration (MIC) creep over 2 years if any.

MATERIALS AND METHODS:

MIC of vancomycin, linezolid, and daptomycin were determined by E-test in 198 MRSA isolates and their MIC 50, MIC 90, and geometric mean MIC were calculated.

RESULTS:

While all isolates were sensitive to vancomycin, linezolid, and daptomycin, MIC 90 of vancomycin increased from 1.5 μg/ml in 2015 to 2 μg/ml in 2016. The percentage of isolates with vancomycin MIC >2 μg/ml doubled in 2016 (12.9%) as compared to 2015 (6.1%). MIC 90 for linezolid remained steady as 3 μg/ml, but geometric mean MIC increased from 2.20 μg/ml in 2015 to 2.29 μg/ml in 2016, and more than 40% isolates showed MIC 3 μg/ml. MIC 90 and geometric mean MIC of daptomycin decreased from 0.75 μg/ml to 0.5 μg/ml and 0.50 μg/ml to 0.36 μg/ml in 2015 and 2016, respectively.

CONCLUSION:

MIC creep was observed with vancomycin. Although linezolid MIC was within the susceptible zone, more than 40% strains showing MIC 3 μg/ml may herald the future development of either resistant or heteroresistant. Daptomycin showed good sensitivity against MRSA isolates. Therefore, it could be considered as an alternative agent for the treatment of infections caused by MRSA. However, it should be reserved where this class has a clear therapeutic advantage over other anti-MRSA drugs.

Hydrophobic interactions modulate antimicrobial peptoid selectivity towards anionic lipid membranes

Hydrophobic interactions govern specificity for natural antimicrobial peptides. No such relationship has been established for synthetic peptoids that mimic antimicrobial peptides. Peptoid macrocycles synthesized with five different aromatic groups are investigated by minimum inhibitory and hemolytic concentration assays, epifluorescence microscopy, atomic force microscopy, and X-ray reflectivity. Peptoid hydrophobicity is determined using high performance liquid chromatography. Disruption of bacterial but not eukaryotic lipid membranes is demonstrated on the solid supported lipid bilayers and Langmuir monolayers. X-ray reflectivity studies demonstrate that intercalation of peptoids with zwitterionic or negatively charged lipid membranes is found to be regulated by hydrophobicity. Critical levels of peptoid selectivity are demonstrated and found to be modulated by their hydrophobic groups. It is suggested that peptoids may follow different optimization schemes as compared to their natural analogues.

Activity of antimicrobial peptides and conventional antibiotics against superantigen positive Staphylococcus aureus isolated from patients with atopic dermatitis

Introduction

Staphylococcus aureus causes a diverse array of diseases, ranging from relatively harmless localized skin infections to life-threatening systemic conditions. It secretes toxins directly associated with particular disease symptoms.

Aim

To determine the prevalence of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) colonization among patients with atopic dermatitis and to assess the antimicrobial susceptibility to conventional antibiotics and selected antimicrobial peptides among toxin-producing strains and nonproducing strains.

Material and methods

One hundred patients with atopic dermatitis and 50 healthy people were microbiologically assessed for the carriage of S. aureus. Antimicrobial susceptibility tests were performed using the broth microdilution method for conventional antibiotics and antimicrobial peptides (CAMEL, Citropin 1.1, LL-37, Temporin A). Detection of genes lukS/lukF-PV, tst, sea-sed, eta and etb by multiplex PCR was performed.

Results

Staphylococcus aureus strains were isolated from the majority of patients, from either the skin (75%) or the anterior nares (73%). Among the conventional antibiotics tested, the highest rates of resistance were observed for ampicillin, daptomycin, lincomycin and erythromycin. Antimicrobial peptides did not show significant diversity in activity. Among MSSA strains greater differentiation of secreted toxins was observed (sec, eta, pvl, tsst, etb, seb), while in the group of MRSA strains secretion of 3 toxins (pvl, eta, seb) was noted.

Conclusions

Antimicrobial resistance continues to evolve. It is important to monitor S. aureus infections. The profile of toxins produced by S. aureus strains is an important consideration in the selection of an antimicrobial agent to treat infections.

High Antibacterial Activity of Functionalized Chemically Exfoliated MoS2

In view of the implications of inherent resistance of pathogenic bacteria, especially ESKAPE pathogens toward most of the commercially available antibiotics and the importance of these bacteria-induced biofilm formation leading to chronic infection, it is important to develop new-generation synthetic materials with greater efficacy toward antibacterial property. In addressing this issue, this paper reports a proof-of-principle study to evaluate the potential of functionalized two-dimensional chemically exfoliated MoS₂ (ce-MoS₂) toward inhibitory and bactericidal property against two representative ESKAPE pathogenic strain-a Gram-positive Staphylococcus aureus (MRSA) and a Gram-negative Pseudomonas aeruginosa. More significantly, the mechanistic study establishes a different extent of oxidative stress together with rapid membrane depolarization in contact with ce-MoS₂ having ligands of varied charge and hydrophobicity. The implication of our results is discussed in the light of the lack of survivability of planktonic bacteria and biofilm destruction in vitro. A comparison with widely used small molecules and other nanomaterial-based therapeutics conclusively establishes a better efficacy of 2D ce-MoS₂ as a new class of antibiotics.

Staphylococcus aureus inactivates daptomycin by releasing membrane phospholipids

Daptomycin is a bactericidal antibiotic of last resort for serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA)^1,2. Although resistance is rare, treatment failure can occur in more than 20% of cases^3,4 and so there is a pressing need to identify and mitigate factors that contribute to poor therapeutic outcomes. Here, we show that loss of the Agr quorum-sensing system, which frequently occurs in clinical isolates, enhances S. aureus survival during daptomycin treatment. Wild-type S. aureus was killed rapidly by daptomycin, but Agr-defective mutants survived antibiotic exposure by releasing membrane phospholipids, which bound and inactivated the antibiotic. Although wild-type bacteria also released phospholipid in response to daptomycin, Agr-triggered secretion of small cytolytic toxins, known as phenol soluble modulins, prevented antibiotic inactivation. Phospholipid shedding by S. aureus occurred via an active process and was inhibited by the β-lactam antibiotic oxacillin, which slowed inactivation of daptomycin and enhanced bacterial killing. In conclusion, S. aureus possesses a transient defence mechanism that protects against daptomycin, which can be compromised by Agr-triggered toxin production or an existing therapeutic antibiotic.

Daptomycin: an evidence-based review of its role in the treatment of Gram-positive infections

Infections caused by Gram-positive pathogens remain a major public health burden and are associated with high morbidity and mortality. Increasing rates of infection with Gram-positive bacteria and the emergence of resistance to commonly used antibiotics have led to the need for novel antibiotics. Daptomycin, a cyclic lipopeptide with rapid bactericidal activity against a wide range of Gram-positive bacteria including methicillin-resistant Staphylococcus aureus, has been shown to be effective and has a good safety profile for the approved indications of complicated skin and soft tissue infections (4 mg/kg/day), right-sided infective endocarditis caused by S. aureus, and bacteremia associated with complicated skin and soft tissue infections or right-sided infective endocarditis (6 mg/kg/day). Based on its pharmacokinetic profile and concentration-dependent bactericidal activity, high-dose (>6 mg/kg/day) daptomycin is considered an important treatment option in the management of various difficult-to-treat Gram-positive infections. Although daptomycin resistance has been documented, it remains uncommon despite the increasing use of daptomycin. To enhance activity and to minimize resistance, daptomycin in combination with other antibiotics has also been explored and found to be beneficial in certain severe infections. The availability of daptomycin via a 2-minute intravenous bolus facilitates its outpatient administration, providing an opportunity to reduce risk of health care-associated infections, improve patient satisfaction, and minimize health care costs. Daptomycin, not currently approved for use in the pediatric population, has been shown to be widely used for treating Gram-positive infections in children.

Study of Antibiotic Resistance Pattern in Methicillin Resistant Staphylococcus Aureus with Special Reference to Newer Antibiotic

The worldwide epidemic of antibiotic resistance is in danger of ending the golden age of antibiotic therapy. Resistance impacts on all areas of medicine, and is making successful empirical therapy much more difficult to achieve. Staphylococcus aureus demonstrates a unique ability to quickly respond to each new antibiotic with the development of a resistance mechanism, starting with penicillin, until the most recent, linezolid and daptomycin. Methicillin resistant S. aureus (MRSA) has become endemic today in hospitals worldwide. Resistance to the newer antimicrobial-agents — linezolid, vancomycin, teicoplanin, and daptomycin are been reported and also the fear of pandrug-resistance. This study was carried out to know the antimicrobial resistant pattern of MRSA to newer antibiotic, to know any isolates are extensively-drug resistant (XDR)/pandrug resistant (PDR), inducible macrolide-lincosamide streptogramin B (iMLSB), and mupirocin resistance. Thirty-six MRSA isolates resistant to the routinely tested antibiotic were further tested for list of antibiotic by a group of international experts. Isolates were tested for iMLSB and mupirocin resistance by the disk diffusion method. Of 385 MRSA, 36 (9.35%) isolates of MRSA were resistant to the routinely tested antibiotic. Among these 36 MRSA isolates, none of our isolates were XDR/PDR or showed resistant to anti-MRSA cephalosporins (ceftaroline), phosphonic acids, glycopeptides, glycylcyclines, and fucidanes. Lower resistance was seen in oxazolidinones (2.78%), streptogramins (5.56%), lipopeptide (5.56%). Thirty-four (94.44%) isolates showed constitutive MLSB (cMLSB) resistance and two (5.56%) iMLSB phenotypes. High- and low-level mupirocin resistance were seen in 13 (36.11%) and six (16.67%), respectively. In our study, none of our isolates were XDR or PDR. No resistance was observed to ceftaroline, telavancin, teicoplanin, and vancomycin; but the presence of linezolid resistance (1, 2.28%) and daptomycin resistance (2, 5.56%) in our rural set-up is a cause of concern.

In vitro activity of daptomycin & linezolid against methicillin resistant Staphylococcus aureus & vancomycin resistant enterococci isolated from hospitalized cases in Central India

BACKGROUND & OBJECTIVES

Growing incidence of methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant enteroccoci (VRE) is posing a therapeutic problem due to limited drug options. Therefore, the present study was undertaken to check susceptibility of MRSA and VRE isolates against new antimicrobials such as daptomycin and linezolid.

METHODS

A total of 586 Gram-positive isolates comprising 442 S. aureus and 144 enterococci isolated from hospitalized cases included in the study, were subjected to in vitro antimicrobial susceptibility testing by disc diffusion method. One hundred twenty four enterococci obtained from rectal swabs of neonates were also included. Minimum inhibitory concentration (MIC) was determined for daptomycin, linezolid, vancomycin and teicoplanin against 50 each isolates of MRSA and VRE by E strip.

RESULTS

Among the staphylococci, 326 (73.85%) isolates were MRSA. MIC for vancomycin and teicoplanin among MRSA was ≤ 3 μg/ml. MIC for daptomycin among MRSA was found to be in the range of 0.064-1.5 μg/ml. Percentage of VRE among clinical samples was 14.29 per cent while it was 47.06 per cent among enterococci from rectal swabs of neonates. MIC was >256 μg/ml for vancomycin among VRE and was associated with van A genotype. MIC range for daptomycin among VRE was 0.38-3 μg/ml. MIC for linezolid among MRSA and VRE was in the range of 0.25 to 1 and 0.38 -1.5 μg/ml, respectively.

INTERPRETATION & CONCLUSIONS

The present study showed a rise in MIC to vancomycin for sizable number of MRSA and growing percentage of VRE at our centre. Daptomycin and linezolid showed 100 per cent activity against MRSA and VRE.

Activity of daptomycin against multiresistant clinical isolates of Staphylococcus aureus and Streptococcus agalactiae

The activity of daptomycin against 141 Staphylococcus aureus and 63 Streptococcus agalactiae isolates was assessed. The isolates were previously characterized and showed resistance to the antibiotics normally used against gram-positive cocci. Daptomycin was active against 100% of the isolates (minimum inhibitory concentration [MIC(90)] = 0.5 microg/ml, for both species). This antibiotic shows good in vitro activity; therefore, it is an excellent therapeutic alternative against these isolates.

The efficacy and safety of daptomycin vs. vancomycin for the treatment of cellulitis and erysipelas

BACKGROUND

Results from previous trials suggest that daptomycin may result in faster clinical improvement than penicillinase-resistant penicillins or vancomycin for patients with complicated skin and skin structure infections.

OBJECTIVE

The objective was to evaluate whether daptomycin treatment of cellulitis or erysipelas would result in faster resolution compared with vancomycin.

DESIGN

The study was a prospective, evaluator-blinded, multi-centre trial. Patients were randomised to receive daptomycin 4 mg/kg once daily or vancomycin according to standard of care for 7-14 days.

PATIENTS

Adults diagnosed with cellulitis or erysipelas requiring hospitalisation and intravenous antibiotic therapy were eligible for enrolment.

RESULTS

The clinical success rates were 94.0% for daptomycin and 90.2% for vancomycin (95% confidence interval for the difference, -6.7%, 14.3%). There were no statistically significant differences between treatment arms in the time to resolution or improvement in any of the predefined clinical end-points. Both daptomycin and vancomycin were well tolerated.

CONCLUSIONS

There was no difference in the rate of resolution of cellulitis or erysipelas among patients treated with daptomycin or vancomycin. Daptomycin 4 mg/kg once daily appeared to be effective and safe for treating cellulitis or erysipelas.

Daptomycin in endocarditis and bacteraemia: a British perspective

Assessment of the place of daptomycin in the treatment of endocarditis and bacteraemia requires assimilation of data from one open-label randomized comparative clinical trial sized for equivalence, from registry data and from case reports. Selected relevant animal models and in vitro data are also considered in an effort to produce an integrated assessment of the current place of daptomycin in treatment. The evidence for the use of daptomycin is best in Staphylococcus aureus bacteraemia and endocarditis, but also includes some data on infections due to Enterococcus spp., especially if vancomycin-resistant. The emergence of resistance in a minority of patients on current dose regimens may mean that trials have to be repeated with higher doses, or the drug used in a combined therapy where rifampicin may be the best choice. In general, equivalence to comparator antibiotic regimens and a correlation for in vitro and in vivo findings have been demonstrated, but there are important gaps in the clinical data including a comparative equivalence trial in streptococcal and enterococcal endocarditis. Clinical benefit might be anticipated, but has not been proved, over aminoglycoside-containing regimens, and economic assessments are critical in the decision as to when and how daptomycin is deployed.

Single-dose pharmacokinetics of daptomycin in children with suspected or proved gram-positive infections

BACKGROUND

New antimicrobials such as daptomycin fill a void in the growing need for antibiotics effective against resistant Gram-positive pathogens. Although the pharmacokinetics of daptomycin have been well characterized in adults, no studies have evaluated the pharmacokinetics and tolerability in a pediatric population.

METHODS

Twenty-five children (12-17 years, n = 8; 7-11 years, n = 8; 2-6 years, n = 9) were enrolled in this multicenter, open-label study. Daptomycin was administered as a single 4-mg/kg intravenous dose followed by repeated blood sampling for 24 hours. Daptomycin was quantitated from plasma using a validated high performance liquid chromatography method and pharmacokinetic variables determined using a model-dependent approach.

RESULTS

Daptomycin systemic exposure decreased with decreasing age, reflecting more rapid rates of clearance in younger children. Total body exposure estimates in adolescents were approximately 1.7x those observed in children <6 years of age (374.4 versus 215.3 microg*h/L), they were comparable to those observed in adult historic controls. Estimates of apparent elimination half-life averaged 6.7 hours in adolescents, 5.6 hours in children 7-11 years of age, and 5.3 hours in children <6 years of age. One child had an adverse event (infusion site reaction) considered to be related to study drug.

CONCLUSIONS

Systemic drug exposure after a single weight-adjusted daptomycin dose is reduced in younger children compared with adolescents and adults consequent to an apparent age-associated change in total plasma clearance.

Daptomycin

There has been a steady rise in the prevalence of resistant Gram-positive pathogens and concerns about the clinical effectiveness of glycopeptides in treating infections due to Staphylococcus aureus. Daptomycin is a novel lipopeptide antimicrobial agent with activity against Gram-positive organisms, including multi-resistant strains. It is licensed in the USA and Europe for the treatment of complicated skin and soft tissue infections caused by Gram-positive organisms at a dose of 4mg/kg once daily. It has also been licensed in the USA for the treatment of S. aureus bacteraemia and right-sided endocarditis at 6mg/kg once daily. It is a safe and well-tolerated antibiotic, particularly at the current dosing regimen. Antimicrobial resistance, whilst being increasingly reported, still remains relatively rare. Further studies are required to determine the role of daptomycin for the treatment of osteomyelitis and septic arthritis, as well as its use in combination therapy.

Daptomycin: a rapidly bactericidal lipopeptide for the treatment of Gram-positive infections

Antimicrobial resistance among Gram-positive organisms continues to increase and has reached epidemic proportions in a number of countries and within medical centers worldwide. Daptomycin is a new lipopeptide antibiotic with rapid bactericidal activity against Staphylococcus aureus. It is also active against coagulase-negative staphylococci, enterococci and streptococci. It exerts its effect through cell membrane disruption that results in dissipation of the membrane potential. Daptomycin exhibits a prolonged postantibiotic effect and is well tolerated. In Phase III clinical trials, daptomycin was found to be similar in efficacy to standard therapy in complicated skin and skin structure infections. More recently, it was approved for the treatment of S. aureus bacteremia and right-sided endocarditis. Daptomycin is not indicated for pulmonary infections. Preliminary data suggest that daptomycin may be effective in urinary tract, bone and joint infections. However, randomized clinical trials are needed to confirm these findings. Daptomycin is an effective antimicrobial agent for the treatment of various serious Gram-positive infections, especially those caused by methicillin-resistant S. aureus.

Antimicrobial susceptibility of Gram-positive bacterial isolates from the Asia-Pacific region and an in vitro evaluation of the bactericidal activity of daptomycin, vancomycin, and teicoplanin: a SENTRY Program Report (2003-2004)

Medical centres in eight countries in the Asia-Pacific region provided 2391 isolates for the SENTRY Antimicrobial Surveillance Program during 2003-2004 to determine their susceptibility to several antimicrobial classes, including daptomycin. Daptomycin, vancomycin and teicoplanin minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined for 120 isolates of Staphylococcus aureus, which included wild-type (WT) methicillin-resistant S. aureus (MRSA) and strains with decreased susceptibility to vancomycin (hetero-vancomycin-intermediate S. aureus (hVISA)). Oxacillin-resistant staphylococcal isolates were much less susceptible to the other tested agents compared with oxacillin-susceptible strains. Vancomycin resistance was higher among Enterococcus faecium (10.3%) than Enterococcus faecalis (0.4%), and macrolide resistance was high both for beta-haemolytic (17.7%) and viridans group (48.7%) streptococci. Daptomycin (MIC for 90% of the organisms (MIC(90))=0.5-1mg/L) was two-fold more potent than vancomycin, with >99% susceptibility when tested against staphylococci. All tested isolates of E. faecalis (MIC(90)=2mg/L) and beta-haemolytic streptococci (MIC(90)=0.5mg/L) were susceptible to daptomycin. Daptomycin MIC and MBC values were slightly higher for the hVISA isolates compared with WT-MRSA, with MBC/MIC ratios of only 1-2 for both groups. The MBC/MIC ratio for vancomycin was often greater when tested against these strains, particularly hVISA. In contrast, teicoplanin MBC/MIC ratios were significantly higher, with many of the strains showing values consistent with tolerance (>or=32). Daptomycin was demonstrated to have excellent in vitro activity when tested against Gram-positive isolates collected from Asia-Pacific countries, including hVISA strains.