Daptomycin

Probing the multitargeted potency of FDA-approved Amifostine against MRSA and control comparison with sulfamethoxazole to establish alternative medications

Methicillin-Resistant Staphylococcus aureus (MRSA) is a multidrug-resistant bacterial strain causing infections from mild skin conditions to life-threatening sepsis. It is classified into healthcare-associated (HA-MRSA) and community-associated (CA-MRSA), with significant healthcare and economic burdens. The rising prevalence and resistance to existing antibiotics highlight the urgent need for improved infection control, antibiotic stewardship, and research into multitargeted therapies to combat resistance and ensure effective treatment options. In this study, we performed a multitargeted docking study followed by pose filtering with MM/GBSA of an FDA-approved drug library. We identified Amifostine as a multitargeted inhibitor of transferases and hydrolases proteins involved in MRSA with docking scores ranging from -11.040 to -7.559 kcal/mol. We compared it with Sulfamethoxazole with docking scores -4.851 to -2.868 kcal/mol, which is an approved compound against MRSA, and found Amifostine a far better drug for MRSA instead just for its use to protect the kidneys of patients getting chemotherapy for the treatment of ovarian cancer. We also performed Interaction Fingerprints, pharmacokinetics, 5ns WaterMap and 100ns MD Simulation in water. We compared the results and extended the study with binding free energy and total energy of each MD simulation trajectory computations and found that Amifostine is a far better drug than Sulfamethoxazole-however, experimental validation is needed before its human use.

The Epiphyte Bacillus sp. G2112 Produces a Large Diversity of Nobilamide Peptides That Promote Biofilm Formation in Pseudomonads and Mycobacterium aurum

Bacillus sp. G2112, an isolate from cucumber plants that inhibited plant pathogens, produces not only surfactins, iturins, and fengycins common to many Bacillus spp., but also a large variety of N-acyl-(depsi)peptides related to A-3302-B and nobilamides. Four known and fourteen previously unreported nobilamide peptides were characterized using high-resolution mass spectrometry, tandem mass spectrometry, and NMR. The stereochemistry of the amino acids of nobilamide peptides was determined using Marfey's method. The diversity of nobilamide peptides from Bacillus sp. G2112 resulted from the incorporation of different acyl groups and amino acids in the sequence. The peptides occur in linear or cyclic form. In addition, a truncated N-acetylpentapeptide was produced. Agar diffusion assays with selected nobilamide peptides against plant pathogens and human pathogens revealed that A-3302-B and its N-acyl homologs, A-3302-A and nobilamide J, exhibited powerful antibiotic activity (at 5 µg/hole) against Lysinibacillus sphaericus that can cause severe sepsis and bacteremia in patients. Moreover, nobilamide peptides from Bacillus sp. G2112 strongly promoted biofilm formation in the Gram-positive Mycobacterium aurum and Gram-negative pseudomonads. Structurally diverse nobilamides from Bacillus sp. G2112, whether linear or cyclic, penta and heptapeptides, induced biofilm formation, suggesting that the common N-acetyl-D-Phe-D-Leu-L-Phe-D-allo-Thr-L-Val amino acid sequence motif is important for the biofilm-inducing activity.

Discovery and Optimization of Novel SaFabI Inhibitors as Specific Therapeutic Agents for MRSA Infection

As the rate-limiting enzyme in fatty acid biosynthesis, Staphylococcus aureus enoyl-acyl carrier protein reductase (SaFabI) emerges as a compelling target for combating methicillin-resistant S. aureus (MRSA) infections. Herein, compound 1, featuring a 4-(1H-benzo[d]imidazol-2-yl)pyrrolidin-2-one scaffold, was identified as a potent SaFabI inhibitor (IC50 = 976.8 nM) from an in-house library. Subsequent optimization yielded compound n31, with improved inhibitory efficacy on enzymatic activity (IC50 = 174.2 nM) and selective potency against S. aureus (MIC = 1-2 μg/mL). Mechanistically, n31 directly inhibited SaFabI in cellular contexts. Moreover, n31 exhibited favorable safety and pharmacokinetic profiles, and dose-dependently treated MRSA-induced skin infections, outperforming the approved drug, linezolid. The chiral separation of n31 resulted in (S)-n31, with superior activities (IC50 = 94.0 nM, MIC = 0.25-1 μg/mL) and in vivo therapeutic efficacy. In brief, our research proposes (S)-n31 as a promising candidate for SaFabI-targeted therapy, offering specific anti-S. aureus efficacy and potential for further development.

Gausemycin Antibiotic Family Acts via Ca2+-Dependent Membrane Targeting

We report the molecular mechanism of action of gausemycins and the isolation of new members of the family, gausemycins C (1c), D (1d), E (1e), and F (1f), the minor components of the mixture. To elucidate the mechanism of action of gausemycins, we investigated the antimicrobial activity of the most active compounds, gausemycins A and B, in the presence of Ca2+, other metal ions, and phosphate. Gausemycins require a significantly higher Ca2+ concentration for maximum activity than daptomycin but lower than that required for malacidine and cadasides. Species-specific antimicrobial activity was found upon testing against a wide panel of Gram-positive bacteria. Membranoactivity of gausemycins was demonstrated upon their interactions with model lipid bilayers and micelles. The pore-forming ability was found to be dramatically dependent on the Ca2+ concentration and the membrane lipid composition. An NMR study of gausemycin B in zwitterionic and anionic micelles suggested the putative structure of the gausemycin/membrane complex and revealed the binding of Ca2+ by the macrocyclic domain of the antibiotic.

Treatment of MRSA Infection: Where are We?

Staphylococcus aureus is a leading cause of septicemia, endocarditis, pneumonia, skin and soft tissue infections, bone and joint infections, and hospital-acquired infections. In particular, methicillin-resistant Staphylococcus aureus (MRSA) is associated with high morbidity and mortality, and continues to be a major public health problem. The emergence of multidrug-resistant MRSA strains along with the wide consumption of antibiotics has made anti-MRSA treatment a huge challenge. Novel treatment strategies (e.g., novel antimicrobials and new administrations) against MRSA are urgently needed. In the past decade, pharmaceutical companies have invested more in the research and development (R&D) of new antimicrobials and strategies, spurred by favorable policies. All research articles were collected from authentic online databases, including Google Scholar, PubMed, Scopus, and Web of Science, by using different combinations of keywords, including 'anti-MRSA', 'antibiotic', 'antimicrobial', 'clinical trial', 'clinical phase', clinical studies', and 'pipeline'. The information extracted from articles was compared to information provided on the drug manufacturer's website and Clinical Trials.gov (https://clinicaltrials.gov/) to confirm the latest development phase of anti-MRSA agents. The present review focuses on the current development status of new anti-MRSA strategies concerning chemistry, pharmacological target(s), indications, route of administration, efficacy and safety, pharmacokinetics, and pharmacodynamics, and aims to discuss the challenges and opportunities in developing drugs for anti-MRSA infections.

Intramolecular Hydrogen Bonding Enables a Zwitterionic Mechanism for Macrocyclic Peptide Formation: Computational Mechanistic Studies of CyClick Chemistry

Macrocyclic peptides have become increasingly important in the pharmaceutical industry. We present a detailed computational investigation of the reaction mechanism of the recently developed "CyClick" chemistry to selectively form imidazolidinone cyclic peptides from linear peptide aldehydes, without using catalysts or directing groups (Angew. Chem. Int. Ed. 2019, 58, 19073-19080). We conducted computational mechanistic to investigate the effects of intramolecular hydrogen bonds (IMHBs) in promoting a kinetically facile zwitterionic mechanism in "CyClick" of pentapeptide aldehyde AFGPA. Our DFT calculations highlighted the importance of IMHB in pre-organization of the resting state, stabilization of the zwitterion intermediate, and the control of the product stereoselectivity. Furthermore, we have also identified that the low ring strain energy promotes the "CyClick" of hexapeptide aldehyde AAGPFA to form a thermodynamically more stable 15+5 imidazolidinone cyclic peptide product. In contrast, large ring strain energy suppresses "CyClick" reactivity of tetra peptide aldehyde AFPA from forming the 9+5 imidazolidinone cyclic peptide product.

Re-evaluation of FDA-approved antibiotics with increased diagnostic accuracy for assessment of antimicrobial resistance

Accurate assessment of antibiotic susceptibility is critical for treatment of antimicrobial resistant (AMR) infections. Here, we examine whether antimicrobial susceptibility testing in media more physiologically representative of in vivo conditions improves prediction of clinical outcome relative to standard bacteriologic medium. This analysis reveals that ∼15% of minimum inhibitory concentration (MIC) values obtained in physiologic media predicted a change in susceptibility that crossed a clinical breakpoint used to categorize patient isolates as susceptible or resistant. The activities of antibiotics having discrepant results in different media were evaluated in murine sepsis models. Testing in cell culture medium improves the accuracy by which MIC assays predict in vivo efficacy. This analysis identifies several antibiotics for treatment of AMR infections that standard testing failed to identify and those that are ineffective despite indicated use by standard testing. Methods with increased diagnostic accuracy mitigate the AMR crisis via utilizing existing agents and optimizing drug discovery.

A review of recent advances in the treatment of adults with complicated urinary tract infection

INTRODUCTION

Complicated urinary tract infections (cUTIs) entail diverse clinical conditions that could be managed differently and not necessarily with premature empiric therapy. Since multidrug-resistant organisms (MDROs) are widely spreading worldwide, the possibility of encountering these resistant bacteria is inevitably part of the daily life of physicians who manage cUTIs.

AREAS COVERED

The advances in the management of cUTIs are explored, illustrating: 1) a proposed therapeutical approach to cUTIs within the antimicrobial stewardship context; 2) evidence regarding novel antibiotics targeting MDROs. Evidence research has been performed through MEDLINE/PubMed using appropriate keywords and terms regarding cUTIs published before June 2022.

EXPERT OPINION

Novel antimicrobial drugs are available in the clinicians' armamentarium. Selecting the optimal therapy for suitable patients may be challenging given the multifaceted group of cUTIs. Carbapenems use is widely increasing, the role of old β-lactam/β-lactamase inhibitors is constantly revised, and novel drugs lack real-life studies. Understanding the different ranges of the complexity of patients affected by cUTIs may help select the most suitable antibiotic for every single case. More multicentric observational studies targeting cUTIs are needed to elucidate the appropriate drug based on patient characteristics and presentations, providing stronger recommendations for cases encountered in everyday clinical practice.

Antimicrobial Peptide Mimics for Clinical Use: Does Size Matter?

The search for efficient antimicrobial therapies that can alleviate suffering caused by infections from resistant bacteria is more urgent than ever before. Infections caused by multi-resistant pathogens represent a significant and increasing burden to healthcare and society and researcher are investigating new classes of bioactive compounds to slow down this development. Antimicrobial peptides from the innate immune system represent one promising class that offers a potential solution to the antibiotic resistance problem due to their mode of action on the microbial membranes. However, challenges associated with pharmacokinetics, bioavailability and off-target toxicity are slowing down the advancement and use of innate defensive peptides. Improving the therapeutic properties of these peptides is a strategy for reducing the clinical limitations and synthetic mimics of antimicrobial peptides are emerging as a promising class of molecules for a variety of antimicrobial applications. These compounds can be made significantly shorter while maintaining, or even improving antimicrobial properties, and several downsized synthetic mimics are now in clinical development for a range of infectious diseases. A variety of strategies can be employed to prepare these small compounds and this review describes the different compounds developed to date by adhering to a minimum pharmacophore based on an amphiphilic balance between cationic charge and hydrophobicity. These compounds can be made as small as dipeptides, circumventing the need for large compounds with elaborate three-dimensional structures to generate simplified and potent antimicrobial mimics for a range of medical applications. This review highlight key and recent development in the field of small antimicrobial peptide mimics as a promising class of antimicrobials, illustrating just how small you can go.

Biotechnological Insights on the Expression and Production of Antimicrobial Peptides in Plants

The emergence of drug-resistant pathogens poses a serious critical threat to global public health and requires immediate action. Antimicrobial peptides (AMPs) are a class of short peptides ubiquitously found in all living forms, including plants, insects, mammals, microorganisms and play a significant role in host innate immune system. These peptides are considered as promising candidates to treat microbial infections due to its distinct advantages over conventional antibiotics. Given their potent broad spectrum of antimicrobial action, several AMPs are currently being evaluated in preclinical/clinical trials. However, large quantities of highly purified AMPs are vital for basic research and clinical settings which is still a major bottleneck hindering its application. This can be overcome by genetic engineering approaches to produce sufficient amount of diverse peptides in heterologous host systems. Recently plants are considered as potential alternatives to conventional protein production systems such as microbial and mammalian platforms due to their unique advantages such as rapidity, scalability and safety. In addition, AMPs can also be utilized for development of novel approaches for plant protection thereby increasing the crop yield. Hence, in order to provide a spotlight for the expression of AMP in plants for both clinical or agricultural use, the present review presents the importance of AMPs and efforts aimed at producing recombinant AMPs in plants for molecular farming and plant protection so far.

Systematical Characterization of Impurity Profiles in Daptomycin Raw Material by 2-Dimentional HPLC Tandem with MS Detector

Objective:

To systematically characterize the impurity profile in Daptomycin raw material by 2 Dimensional LC/MSn.

Method:

The target impurity was separated by first Dimensional HPLC and enriched by a 500μl loop, then desalted using the on-line second Dimensional HPLC and analyzed by MS detector in positive mode. Their structures were characterized based on the degradation mechanism and mass fragmentation regularity of the cyclic lipopeptide, as well as the molecular thermodynamic calculation.

Results:

A total of 12 impurities were characterized in the raw material, including 6 degradation products; 8 impurities are reported for the first time. The mass fragmentation regularities of 2 β-isomers of Asp residue were summarized.

Conclusion:

The structures of impurities in Daptomycin raw material, especially for β-isomer impurities, could be rapidly identified by on-line 2 Dimensional LC/MSn method together with the molecular thermodynamic calculation.

One Pathway, Two Cyclic Non-Ribosomal Pentapeptides: Heterologous Expression of BE-18257 Antibiotics and Pentaminomycins from Streptomyces cacaoi CA-170360

The strain Streptomyces cacaoi CA-170360 produces the cyclic pentapeptides pentaminomycins A-H and BE-18257 A-C, two families of cyclopeptides synthesized by two non-ribosomal peptide synthetases encoded in tandem within the same biosynthetic gene cluster. In this work, we have cloned and confirmed the heterologous expression of this biosynthetic gene cluster, demonstrating that each of the non-ribosomal peptide synthetases present in the cluster is involved in the biosynthesis of each group of cyclopeptides. In addition, we discuss the involvement of a stand-alone enzyme belonging to the Penicillin Binding Protein family in the release and macrocyclization of the peptides.

A New Era of Antibiotics: The Clinical Potential of Antimicrobial Peptides

Antimicrobial resistance is a multifaceted crisis, imposing a serious threat to global health. The traditional antibiotic pipeline has been exhausted, prompting research into alternate antimicrobial strategies. Inspired by nature, antimicrobial peptides are rapidly gaining attention for their clinical potential as they present distinct advantages over traditional antibiotics. Antimicrobial peptides are found in all forms of life and demonstrate a pivotal role in the innate immune system. Many antimicrobial peptides are evolutionarily conserved, with limited propensity for resistance. Additionally, chemical modifications to the peptide backbone can be used to improve biological activity and stability and reduce toxicity. This review details the therapeutic potential of peptide-based antimicrobials, as well as the challenges needed to overcome in order for clinical translation. We explore the proposed mechanisms of activity, design of synthetic biomimics, and how this novel class of antimicrobial compound may address the need for effective antibiotics. Finally, we discuss commercially available peptide-based antimicrobials and antimicrobial peptides in clinical trials.

A comparative assessment of clinical, pharmacological and antimicrobial profile of novel anti-methicillin-resistant Staphylococcus aureus agent levonadifloxacin: Therapeutic role in nosocomial and community infections

Staphylococcus aureus is of significant clinical concern in both community- and hospital-onset infections. The key to the success of S. aureus as a pathogen is its ability to swiftly develop antimicrobial resistance. Methicillin-resistant S. aureus (MRSA) is not only resistant to nearly all beta-lactams but also demonstrates resistance to several classes of antibiotics. A high prevalence of MRSA is seen across worldwide. For many decades, vancomycin remained as gold standard antibiotic for the treatment of MRSA infections. In the past decades, linezolid, daptomycin, ceftaroline and telavancin received regulatory approval for the treatment of infections caused by resistant Gram-positive pathogens. Although these drugs may offer some advantages over vancomycin, they also have significant limitations. These includes vancomycin's slow bactericidal activity, poor lung penetration and nephrotxicity;linezolid therapy induced myelosuppression and high cost of daptomycin greatly limits their clinical use. Moreover, daptomycin also gets inactivated by lung naturally occurring surfactants. Thus, currently available therapeutic options are unable to provide safe and efficacious treatment for those patients suffering from hospital-acquired pneumonia, bloodstream infections (BSIs), bone and joint infections and diabetic foot infections (DFI). An unmet need also exists for a safe and efficacious oral option for switch-over convenience and community treatment. Herein, the review is intended to describe the supporting role of anti-staphylococcal antibiotics used in the management of S. aureus infections with a special reference to levonadifloxacin. Levonadifloxacin and its prodrug alalevonadifloxacin are novel benzoquinolizine subclass of quinolone with broad-spectrum of anti-MRSA activity. It has been recently approved for the treatment of complicated skin and soft-tissue infection as well as concurrent bacteraemia and DFI in India.

Daptomycin-containing regimens for treatment of Gram-positive endocarditis

PURPOSE

Infective endocarditis (IE) is a severe infection, and a leading cause of mortality and morbidity. Due to its favourable microbiological and pharmacological characteristics, daptomycin is routinely used in clinical practice for treating IE.

METHODS

A prospective study was conducted at a large tertiary-care hospital in Italy over an 8-year period (January 2010-January 2018) on all patients with native-valve endocarditis (NVE) or prosthetic-valve endocarditis (PVE) caused by Gram-positive bacteria. Patients with NVE and PVE treated with regimens that included daptomycin at different dosages (daptomycin-containing regimens, DCR) were compared with those treated with non-DCR. Primary endpoints of the study were 30-day mortality and clinical treatment failure.

RESULTS

During the study period, 327 patients with Gram-positive NVE (n = 224, 68.8%) or PVE (n = 103, 31.2%) were analysed. Eighty-four (37.5%) NVE patients were treated with daptomycin, alone (59.9%) or with other antimicrobials. Most PVE patients (n = 61, 58%) were treated with a DCR, which always consisted of daptomycin plus other drugs. Among PVE patients, treatment with a DCR was associated with lower 30-day mortality than treatment with a non-DCR (6.5% vs. 38%, P < 0.001). Among NVE patients treated with DCRs, risk factors for 30-day mortality were streptococcal infections, persistent bacteraemia, and standard-dose (4-6 mg/kg) rather than high-dose daptomycin therapy. Overall, surgical treatment of IE and DCR were associated with clinical success and 30-day survival.

CONCLUSIONS

Compared with non-DCRs, using single-drug or multiple-drug DCRs is associated with lower 30-day mortality in PVE, but with higher 30-day mortality in NVE at approved doses and in a subgroup of streptococcal IE.

[Design, Synthesis and Structure-activity Relationship Study of a Series of Bis(bibenzyl)-type Natural Products, Riccardin C Derivatives, as Candidate Anti-MRSA Agents]

We previously showed that a naturally occurring macrocyclic bis(bibenzyl) derivative, riccardin C (RC), exhibits antibacterial activity towards methicillin-resistant Staphylococcus aureus (MRSA), with a potency comparable to that of the clinically used drug vancomycin. Here, we synthesized a series of RC derivatives to explore the structure-activity relationships (SAR). The SAR results clearly indicated that the number and positions of the phenolic hydroxyl groups are primary determinants of the anti-MRSA activity. Pharmacological characterization of the macrocyclic bis(bibenzyl) derivatives, together with fragment compounds and their dimers, indicated that the macrocycles and the fragment compounds elicit anti-MRSA activity with different mechanism(s) of action. The macrocyclic bis(bibenzyl)s are bactericidal, while the fragment compounds are bacteriostatic, showing only weak bactericidal activity. Treatment with a macrocyclic bis(bibenzyl) derivative significantly changed the intracellular Na⁺ and K⁺ concentrations of Staphylococcus aureus, and transmission electron microscopy revealed that treated cells developed intracellular lamellar mesosomal-like structures. These results indicated that the macrocyclic compound directly damages the gram-positive bacterial membrane, resulting in increased permeability.

Evaluation of pharmacokinetics and the stability of daptomycin in serum at various temperatures

BACKGROUND

Daptomycin exhibits concentration-dependent antibacterial activity. By monitoring daptomycin serum concentrations, clinicians may be able to predict the effectiveness of treatments for infections more accurately. However, it has been reported that daptomycin concentrations in plasma samples stored at -20°C decrease approximately 25% after 4 weeks. The aim of this study was to evaluate the stability of daptomycin in serum at various temperatures.

METHODS

Daptomycin serum samples were prepared and stored at different temperatures. The stability of daptomycin under various conditions was evaluated by sequential measurements of concentration.

RESULTS

Although the loss of concentration of daptomycin in serum samples stored in freezers (-80°C and -20°C) was less than 10% after 168days (6 months), the concentrations in samples stored in a refrigerator (4°C) decreased by more than 70% over the same period. Furthermore, daptomycin concentrations in serum samples stored at close to body temperature (35°C, 37°C, and 39°C) decreased by more than 50% after only 24h.

CONCLUSIONS

The results of the present study demonstrate that the measurement of serum concentrations of daptomycin needs to be performed rapidly. Furthermore, the degradation of daptomycin in serum may be involved in its elimination from the living body.

Tackling Threats and Future Problems of Multidrug-Resistant Bacteria

With the advent of the antibiotic era, the overuse and inappropriate consumption and application of antibiotics have driven the rapid emergence of multidrug-resistant pathogens. Antimicrobial resistance increases the morbidity, mortality, length of hospitalization and healthcare costs. Among Gram-positive bacteria, Staphylococcus aureus (MRSA) and multidrug-resistant (MDR) Mycobacterium tuberculosis, and among the Gram-negative bacteria, extended-spectrum beta-lactamase (ESBLs)-producing bacteria have become a major global healthcare problem in the 21st century. The pressure to use antibiotics guarantees that the spread and prevalence of these as well as of future emerging multidrug-resistant pathogens will be a persistent phenomenon. The unfeasibility of reversing antimicrobial resistance back towards susceptibility and the critical need to treat bacterial infection in modern medicine have burdened researchers and pharmaceutical companies to develop new antimicrobials effective against these difficult-to-treat multidrug-resistant pathogens. However, it can be anticipated that antibiotic resistance will continue to develop more rapidly than new agents to treat these infections become available and a better understanding of the molecular, evolutionary and ecological mechanisms governing the spread of antibiotic resistance is needed. The only way to curb the current crisis of antimicrobial resistance will be to develop entirely novel strategies to fight these pathogens such as combining antimicrobial drugs with other agents that counteract and obstruct the antibiotic resistant mechanisms expressed by the pathogen. Furthermore, as many antibiotics are often inappropriately prescribed, a more personalized approach based on precise diagnosis tools will ensure that proper treatments can be promptly applied leading to more targeted and effective therapies. However, in more general terms, also the overall use and release of antibiotics in the environment needs to be better controlled.

Towards a definition of daptomycin optimal dose: Lessons learned from experimental and clinical data

Daptomycin exhibits excellent antibacterial activity against a wide range of Gram-positive bacteria. The on-label standard daily doses for daptomycin are 4 mg/kg for skin infections and 6 mg/kg for bacteraemia or right-sided endocarditis. Daptomycin bactericidal activity is predominantly concentration-dependent and by considering the values of pharmacokinetic targets established by several authors as well as the peak and trough concentrations of daptomycin obtained at various daily dosages, it appears that these targets can easily be reached with a dose of 6 mg/kg but only for a minimum inhibitory concentration (MIC) at 0.1 mg/L, and that for increasing MICs (e.g. 0.5 mg/L or 1 mg/L) these targets may only be attained with higher dosages (i.e. ≥10 mg/kg). High-dose (HD) daptomycin therapy has also been proven to be effective for reducing the risk of selection of daptomycin-resistant strains. Given the concentration-dependent bactericidal activity of daptomycin, the absence of a dose-toxicity relationship and the need to prevent the selection of resistant strains, we propose to consider for staphylococcal (i) skin and soft-tissue infections, daily doses of daptomycin of 6 mg/kg (new standard dose) and (ii) endocarditis or bacteraemia including those associated with intravascular catheter and implant-related infections, ≥10 mg/kg (HD) when the MIC is unknown or >0.25 mg/L, and 6-10 mg/kg (intermediate doses) when the MIC is ≤0.25 mg/L. For severe and deep-seated enterococcal infections, we propose high (≥10 mg/kg) daily doses of daptomycin in combination with another active agent, especially a β-lactam.

Optimizing therapy for vancomycin-resistant enterococcal bacteremia in children

PURPOSE OF REVIEW

Uncertainties exist regarding the optimal treatment for vancomycin-resistant enterococcal (VRE) bloodstream infections, particularly in settings in which ampicillin cannot be used.

RECENT FINDINGS

Quinupristin-dalfopristin, linezolid, and daptomycin, all approved between 1999 and 2003, represent the mainstays of therapy for VRE bacteremia, although only linezolid has been specifically approved by the United States Food and Drug Administration for this indication. The main objective of this review is to compare the relative efficacies, dosing strategies, and side-effect profiles of quinupristin-dalfopristin, linezolid, and daptomycin for VRE bacteremia in the pediatric population. A brief description of recently approved broad-spectrum Gram-positive agents that may have a role in the management of VRE bacteremia in upcoming years is also provided.

SUMMARY

Linezolid, despite its bacteriostatic activity against VRE, may be the most versatile of the available drugs. It has activity against both Enterococcus faecalis and E. faecium, can be administered orally, and resistance appears to be less of a concern with linezolid compared with the other agents. Additionally, the results of two recent meta-analyses demonstrate more favorable outcomes with linezolid compared with daptomycin for the treatment of VRE bacteremia. The clinical pharmacokinetics of linezolid have been well described in children. The most notable concern with linezolid, however, is toxicities associated with prolonged use. Until more prospective data are available, we favor linezolid as first-line therapy for the treatment of VRE bacteremia in children.

Monte Carlo simulation analysis of ceftobiprole, dalbavancin, daptomycin, tigecycline, linezolid and vancomycin pharmacodynamics against intensive care unit-isolated methicillin-resistant Staphylococcus aureus

The aim of the present study was to compare the potential of ceftobiprole, dalbavancin, daptomycin, tigecycline, linezolid and vancomycin to achieve their requisite pharmacokinetic/pharmacodynamic (PK/PD) targets against methicillin-resistant Staphylococcus aureus isolates collected from intensive care unit (ICU) settings. Monte Carlo simulations were carried out to simulate the PK/PD indices of the investigated antimicrobials. The probability of target attainment (PTA) was estimated at minimum inhibitory concentration values ranging from 0.03 to 32 μg/mL to define the PK/PD susceptibility breakpoints. The cumulative fraction of response (CFR) was computed using minimum inhibitory concentration data from the Canadian National Intensive Care Unit study. Analysis of the simulation results suggested the breakpoints of 4 μg/mL for ceftobiprole (500 mg/2 h t.i.d.), 0.25 μg/mL for dalbavancin (1000 mg), 0.12 μg/mL for daptomycin (4 mg/kg q.d. and 6 mg/kg q.d.) and tigecycline (50 mg b.i.d.), and 2 μg/mL for linezolid (600 mg b.i.d.) and vancomycin (1 g b.i.d. and 1.5 g b.i.d.). The estimated CFR were 100, 100, 70.6, 88.8, 96.5, 82.4, 89.4, and 98.3% for ceftobiprole, dalbavancin, daptomycin (4 mg/kg/day), daptomycin (6 mg/kg/day), linezolid, tigecycline, vancomycin (1 g b.i.d.) and vancomycin (1.5 g b.i.d.), respectively. In conclusion, ceftobiprole and dalbavancin have the highest probability of achieving their requisite PK/PD targets against methicillin-resistant Staphylococcus aureus isolated from ICU settings. The susceptibility predictions suggested a reduction of the vancomycin breakpoint to 1 μg/mL.

Daptomycin in combination with other antibiotics for the treatment of complicated methicillin-resistant Staphylococcus aureus bacteremia

PURPOSE

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the most important nosocomial pathogens. Resistance to antibiotic therapy has been known to emerge especially in clinically complex scenarios, resulting in challenges in determining optimal treatment of serious MRSA. Daptomycin, in combination with other antibiotics, has been successfully used in the treatment of these infections, with the aims of resulting in reducing the prevention of antimicrobial resistance and increased killing compared with daptomycin monotherapy.

METHODS

This article reviews all the published studies that used daptomycin combination therapy for the treatment of bacteremia and associated complicated infections caused by gram-positive organisms, including MRSA. We discuss the rationale of combination antibiotics and the mechanisms that enhance the activity of daptomycin, with special focus on the role of β-lactam antibiotics.

FINDINGS

There are limited clinical data on the use of daptomycin in combination with other antibiotics. Most of this use was as successful salvage therapy in the setting of failing primary, secondary, or tertiary therapy and/or relapsing infection. Synergy between β-lactams and daptomycin is associated with several characteristics, including increased daptomycin binding and β-lactam-mediated potentiation of innate immunity, but the precise molecular mechanism is unknown.

IMPLICATIONS

Use of daptomycin in combination with other antibiotics, especially β-lactams, offers a promising treatment option for complicated MRSA bacteremia in which emergence of resistance during treatment may be anticipated. Because it is currently not possible to differentiate complicated from uncomplicated bacteremia at the time of presentation, combination therapy may be considered as first-line therapy, with de-escalation to monotherapy in uncomplicated cases and cases with stable pharmacologic and surgical source control.

Anti-infective drug development for MRSA

Staphylococcus aureus is an important pathogen linked to serious infections both in the hospital and the community settings. The challenge to treat infections caused by S. aureus has increased because of the emergence of multidrug-resistant strains such as methicillin-resistant S. aureus (MRSA). A limited spectrum of antibiotics is available to treat MRSA infections. This chapter reviews antimicrobial agents currently in use for the treatment of MRSA infections as well as agents that are in various stages of development. This chapter also reviews the alternate approaches that are being explored for the treatment of staphylococcal infections.

Nafcillin enhances innate immune-mediated killing of methicillin-resistant Staphylococcus aureus

Based on in vitro synergy studies, the addition of nafcillin to daptomycin was used to treat refractory methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. Daptomycin is a de facto cationic antimicrobial peptide in vivo, with antistaphylococcal mechanisms reminiscent of innate host defense peptides (HDPs). In this study, the effects of nafcillin on HDP activity against MRSA were examined in vitro and in vivo. Exposures to β-lactam antimicrobials in general, and nafcillin in particular, significantly increased killing of S. aureus by selected HDPs from keratinocytes, neutrophils, and platelets. This finding correlated with enhanced killing of MRSA by whole blood, neutrophils, and keratinocytes after growth in nafcillin. Finally, nafcillin pretreatment ex vivo reduced MRSA virulence in a murine subcutaneous infection model. Despite the lack of direct activity against MRSA, these studies show potent, consistent, and generalized nafcillin-mediated "sensitization" to increased killing of MRSA by various components of the innate host response. The use of nafcillin as adjunctive therapy in MRSA bacteremia merits further study and should be considered in cases refractory to standard therapy.

KEY MESSAGES

Nafcillin has been used as adjunctive therapy to clear persistent MRSA bacteremia. Nafcillin enhances killing of MRSA by a cadre of innate host defense peptides. Nafcillin increases binding of human cathelicidin LL-37 to the MRSA membrane. Nafcillin enhances killing of MRSA by neutrophils. Nafcillin reduces virulence of MRSA in a murine subcutaneous infection model.

Evaluation of Daptomycin Non-Susceptible Staphylococcus aureus for Stability, Population Profiles, mprF Mutations, and Daptomycin Activity

Introduction

Despite studies examining daptomycin non-susceptible (DNS) Staphylococcus aureus, examination of the stability and population profiles is limited. The objective was to evaluate the stability, population profiles, and daptomycin activity against DNS isolates.

Methods

The stability of 12 consecutive clinical DNS strains was evaluated by minimum inhibitory concentration (MICs) and population analysis profiles before and after 5 days of serial passage. Two pairs of DNS S. aureus having the same daptomycin MIC but different daptomycin population profiles were evaluated via an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model of simulated endocardial vegetations for 96 h against daptomycin 6 and 10 mg/kg/day. The sequence of mprF was determined for these isolates before and after 96 h of daptomycin exposure in the in vitro PK/PD model.

Results

Daptomycin MIC values were 2–4 mg/L (via Microscan) for the 12 clinical isolates; 9 were confirmed DNS and 3 were within 1 tube dilution of Microscan (daptomycin MIC 1 mg/L). All were stable to serial passage. There was variation in the isolates susceptibility to daptomycin on population analysis (daptomycin population AUC 14.01–26.85). The killing patterns of daptomycin 6 and 10 mg/kg/day differed between isolates with a left-shift and right-shift population profile to daptomycin. Two strains developed additional mprF mutations during daptomycin exposure in the in vitro PK/PD model resulting in P314L, L826F, S337L and a novel Q326Stop mutation.

Conclusions

The collection of DNS isolates was stable and displayed variation in susceptibility to daptomycin on population profile. Further research examining this clinical relevance is warranted.

Electronic supplementary material

The online version of this article (doi:10.1007/s40121-013-0021-7) contains supplementary material, which is available to authorized users.

High-dose, short-interval daptomycin regimen was safe and well tolerated in three patients with chronic renal failure

BACKGROUND

The recommended daptomycin dosage is 4 or 6 mg/kg/day for the treatment of complicated skin and soft tissue infections or for Staphylococcus aureus bacteremia, endocarditis, and osteomyelitis. Every other day administration is usually recommended for patients with mild to moderate renal impairment. Higher doses (>6 mg/kg/day) have been explored as a possible alternative. Daptomycin is considered a safe anti-methicillin-resistant S. aureus (MRSA) drug, although renal dysfunction may be worsened. In this paper we report on three patients with chronic renal failure who received a higher dose of daptomycin daily for successful treatment for MRSA bacteremia, MRSA osteomyelitis, and methicillin-resistant S. epidermidis (MRSE) endocarditis.

RESULTS

Previous administration of other drugs, including vancomycin, teicoplanin, and linezolid, had failed. In spite of daily treatment with daptomycin instead of the recommended alternate day regimen, adverse effects, such as elevation of creatinine and creatine phosphokinase, did not occur.

CONCLUSION

These experiences suggest that administration of high-dose/short-interval daptomycin can be efficient and safe even in the setting of renal dysfunction, and should be considered for the treatment of severe MRSA/MRSE infections in these patients.

Current use of daptomycin in cardiac surgery and postoperative intensive care

Infections due to multidrug-resistant pathogens have an increasing impact on patients undergoing cardiac surgery. Preoperative infections, such as endocarditis, and postoperative infections, including wound and device infection, influence patient outcomes. Special interest needs to be taken in patients admitted to cardiac surgical intensive care units, as these patients are at high risk for infections, particularly nosocomial pneumonia, catheter-related and wound infections. The increasing numbers of infections due to Gram-positive multidrug-resistant pathogens underline the necessity for newer antibiotics with bactericidal effects and a more favorable profile of side effects. Daptomycin, a lipopeptide antimicrobial agent with bactericide activity against Gram-positive organisms, has been successfully used in the treatment of complicated infections due to Gram-positive multidrug-resistant pathogens, especially regarding endocarditis, wound infections, device and catheter-related infections in intensive care units. In this review, the authors will summarize therapeutic potential of daptomycin in cardiac surgery and postoperative intensive care.

A multicentre evaluation of the effectiveness and safety of high-dose daptomycin for the treatment of infective endocarditis

OBJECTIVES

Despite significant medical advances, infective endocarditis (IE) remains an infection associated with high morbidity and mortality. The objective was to assess the safety and efficacy of high-dose daptomycin, defined as ≥ 8 mg/kg/day, in patients with confirmed or suspected staphylococcal and/or enterococcal IE.

METHODS

This was a multicentre, retrospective observational study (2005-11). Adult patients, not undergoing haemodialysis, with blood cultures positive for staphylococci or enterococci and a definitive or possible diagnosis of IE, who received daptomycin ≥ 8 mg/kg/day (based on total body weight) for ≥ 72 h were included.

RESULTS

Seventy patients met the inclusion criteria and comprised 33 (47.1%) with right-sided IE (RIE), 35 (50%) with left-sided IE (LIE) and 2 with both RIE and LIE. Several patients had concomitant sites of infection, with bone/joint infection being most prevalent (12.9%). Sixty-five patients received daptomycin as salvage therapy. Pathogens were isolated from 64 patients, with methicillin-resistant Staphylococcus aureus as the most common organism (84.4%), followed by vancomycin-resistant Enterococcus faecium (7.8%). The median (IQR) daptomycin dose was 9.8 mg/kg/day (8.2-10.0 mg/kg/day), and was similar in RIE and LIE patients (9.8 and 9.3 mg/kg/day, respectively). A total of 24 (34.3%) received combination therapy. For those patients with pathogens isolated (n = 64), the organism was eradicated in 57 (89.1%) patients. Among 64 clinically evaluable patients, 55 (85.9%) achieved clinical success. No patients required discontinuation of high-dose daptomycin due to creatine phosphokinase elevations.

CONCLUSIONS

Patients with both RIE and LIE had successful outcomes with high-dose daptomycin therapy. Additional clinical trials evaluating high daptomycin dosages in patients with IE are warranted.

The Pharmacokinetics of Daptomycin in Moderately Obese, Morbidly Obese, and Matched Nonobese Subjects

Daptomycin pharmacokinetics were studied in adult volunteers who were moderately obese (body mass index [BMI] = 25-39.9 kg/m2) or morbidly obese (BMI > or =40 kg/m2) and a matched (gender, age, renal function) nonobese (BMI between 18.5 and 24.9 kg/m2) control group. All subjects received a dose of 4 mg/kg total body weight (TBW) by intravenous infusion (30 minutes). Daptomycin plasma half-life, the fraction of the dose excreted unchanged in urine, and daptomycin absolute renal clearance (mL/h) were unchanged as a function of obesity. The absolute volume of distribution (Vz and Vss) and plasma clearance (CL) for daptomycin were higher in obese subjects as compared to nonobese matched controls. The rate of change of Vz and CL with increasing BMI was greater when these pharmacokinetic parameters were expressed in absolute terms compared to when they were normalized for TBW or ideal body weight. This suggests that increases in body mass associated with obesity are proportionality higher than the corresponding increases in Vd and CL. Exposure to daptomycin in obese subjects (Cmax, AUC) was increased 25% and 30%, respectively, compared to nonobese matched controls, well within the range that was previously determined to be safe and well tolerated. Daptomycin may be dosed based on total body weight, and no adjustment in daptomycin dose or dose regimen should be required based solely on obesity.

High-dose daptomycin for treatment of complicated gram-positive infections: a large, multicenter, retrospective study

STUDY OBJECTIVE

To evaluate the clinical response and safety of high-dose daptomycin for treatment of complicated gram-positive infections.

DESIGN

Multicenter, retrospective, observational, case series analysis.

SETTING

Five academic medical centers in four major United States cities.

PATIENTS

Two hundred fifty adults, not undergoing dialysis, who received high-dose daptomycin (≥ 8 mg/kg/day) for at least 72 hours for complicated gram-positive infections between January 1, 2005, and March 1, 2010.

MEASUREMENTS AND MAIN RESULTS

Clinical and microbiologic outcomes were assessed at the end of high-dose daptomycin therapy. Safety evaluations were recorded for all patients, and when available, baseline, end-of-therapy, and highest observed serum creatine phosphokinase (CPK) levels were recorded. Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE) were the primary organisms isolated. The median dose of daptomycin was 8.9 mg/kg/day (interquartile range [IQR] 8.0-10.0 mg/kg/day). The median duration of daptomycin during hospitalization for MRSA and VRE infection was 10 days (IQR 5-16 days) and 13 days (IQR 6-18 days), respectively. Among the 250 patients, high-dose daptomycin was primarily used as salvage therapy after vancomycin treatment (184 patients [73.6%]). Primary infections included complicated bacteremia (119 patients [47.6%]), endocarditis (59 [23.6%]), skin or wound (70 [28.0%]), and bone or joint (67 [26.8%]). Overall, clinical response and microbiologic success were assessed in 83.6% (209/250 patients) and 80.3% (175/218 patients), respectively. Isolates from 13 patients (5.2%) developed nonsusceptibility to daptomycin, with most of these patients having extended vancomycin exposure. Three patients (1.2%) developed an adverse event attributable to high-dose daptomycin therapy, with the event considered either mild or moderate in severity. The median end-of-therapy CPK level was 39 U/L (IQR 26-67 U/L). No significant correlation was found between daptomycin dose and highest observed CPK level.

CONCLUSION

Daptomycin dosages of 8 mg/kg/day or greater may be safe and effective in patients with complicated gram-positive infections. Further clinical studies are warranted.

Impact of dose de-escalation and escalation on daptomycin's pharmacodynamics against clinical methicillin-resistant Staphylococcus aureus isolates in an in vitro model

De-escalation and escalation therapeutic strategies are commonly employed by clinicians on the basis of susceptibility results and patient response. Since no in vitro or in vivo data are currently available to support one strategy over the other for daptomycin, we attempted to evaluate the effects of dose escalation and de-escalation on daptomycin activity against methicillin-resistant Staphylococcus aureus (MRSA) isolates using an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model with simulated endocardial vegetations. Three clinical MRSA isolates, including one heterogeneous vancomycin-intermediate S. aureus (hVISA) isolate and one vancomycin-intermediate S. aureus (VISA) isolate, were exposed to daptomycin at 10 or 6 mg/kg of body weight/day for 8 days using a starting inoculum of ∼10(9) CFU/g of vegetations, with dose escalation and de-escalation initiated on the fourth day. Daptomycin MIC values ranged from 0.5 to 1 μg/ml. In the PK/PD model, high-dose daptomycin (10 mg/kg/day) and de-escalation simulation (10 to 6 mg/kg/day) appeared to be the most efficient regimens against the three tested isolates, exhibiting the fastest bactericidal activity (4 to 8 h) compared to that of the standard regimen of 6 mg/kg/day and the escalation therapy of 6 to 10 mg/kg/day. The differences in the numbers of CFU/g observed between dose escalation and de-escalation were significant for the hVISA strain, with the de-escalation simulation exhibiting a better killing effect than the escalation simulation (P<0.024). Although our results need to be carefully considered, the use of high-dose daptomycin up front demonstrated the most efficient activity against the tested isolates. Different therapeutic scenarios including isolates with higher MICs and prolonged drug exposures are warranted to better understand the outcomes of escalation and de-escalation strategies.

Pharmacotherapy in the critically ill obese patient

Despite the growing epidemic of obesity in the United States, dosing medications in such patients remains poorly studied and understood. Most recommendations are based on small independent studies, case reports, and expert opinion. Applying manufacturer kinetics and dosing recommendations in the obese patient may result in toxicity or treatment failure, leading to increased morbidity, mortality, and hospital length of stay.

Daptomycin: a novel lipopeptide antibiotic against Gram-positive pathogens

The aim of this review is to summarize the historical background of drug resistance of Gram-positive pathogens as well as to describe in detail the novel lipopeptide antibiotic daptomycin. Pharmacological and pharmacokinetic aspects are reviewed and the current clinical use of daptomycin is presented. Daptomycin seems to be a reliable drug in the treatment of complicated skin and skin structure infections, infective right-sided endocarditis, and bacteremia caused by Gram-positive agents. Its unique mechanism of action and its low resistance profile, together with its rapid bactericidal action make it a favorable alternative to vancomycin in multi-drug resistant cocci. The role of daptomycin in the treatment of prosthetic material infections, osteomyelitis, and urogenital infections needs to be evaluated in randomized clinical trials.

Daptomycin in bone and joint infections: a review of the literature

INTRODUCTION

To review the pharmacology, pharmacokinetics, efficacy, and safety of daptomycin, a novel antibiotic for the treatment of bone and joint infections, a literature search of relevant articles was conducted.

MATERIALS AND METHODS

A PubMed/MEDLINE search (1990-April 2008) to identify relevant English-language literature was conducted. Search terms included bone and joint infection, osteomyelitis, daptomycin, and methicillin-resistant Staphylococcus aureus (MRSA). Additional articles were identified by reviewing the bibliographies of articles cited. Programs and abstracts from infectious disease meetings were searched, and prescribing information of antibiotics indicated for bone and joint infections consulted. All articles identified from data sources published in English were evaluated.

RESULTS

Caused primarily by Gram-positive pathogens such as S. aureus and, to a lesser extent, Enterococcus faecalis, bone and joint infections are difficult to treat successfully. Surgical intervention and prolonged courses of antibiotics are frequently required, and failure of first-line antibiotic therapy is common. The emergence of S. aureus strains with reduced susceptibility to vancomycin, the longstanding gold standard for bone and joint infections, has complicated the clinical scenario. Few randomized trials comparing the efficacy of different antibiotics for bone and joint infections exist. Daptomycin, a novel intravenous lipopeptide antibiotic, has shown potent in vitro activity against a broad spectrum of Gram-positive bacteria, including many resistant pathogens commonly associated with bone and joint infections such as MRSA and vancomycin-resistant E. faecalis. Early clinical investigation of daptomycin in bone and joint infections unresponsive to antibiotics, such as vancomycin, has found a cure rate of approximately 80%, with a low incidence of adverse events and drug resistance.

CONCLUSION

Further studies are warranted to determine if limited clinical evidence, described in individual case reports and a daptomycin-specific retrospective registry, suggests daptomycin is a promising option for patients with bone and joint infections such as MRSA osteomyelitis.

The biochemistry of disease: desperately seeking syzygy

The elucidation of the precise molecular structure and dynamics of biological processes is the great work of biochemistry. From this, insights into the changes leading to process dysfunction or disease are derived, as well as the possible approaches to restore healthy function. Translating this information into effective and safe treatments for disease requires a coordinated interdisciplinary effort, a fusion of creativity and practicality, and a healthy dose of luck. Using several reviews in this volume as springboards, I discuss the broader issues of drug development, highlighting some recent successes and future directions. Such occurrences inspire awe but remain too rare for comfort.

Antimicrobial agents for surgical infections

Antimicrobial drugs are useful for the empiric and definitive treatment of infections in surgical patients. They are also important agents for perioperative antimicrobial prophylaxis. The proper selection and use of these drugs is a critical skill for surgeons. Although these agents have many beneficial effects, they also possess occasional adverse effects and should not be used indiscriminately.

The use of daptomycin for Staphylococcus aureus infections in critical care medicine

The proliferation of methicillin-resistant Staphylococcus aureus (MRSA) and the severity of nosocomial critical care infections necessitate the development of viable alternative therapies. An increase in the tolerance of MRSA to the activity of vancomycin and to the associated suboptimal therapeutic measures is of particular concern. Daptomycin, the first of a new class of antimicrobials known as the lipopeptides, is indicated for the treatment of S aureus, including MRSA, in bacteremia, right-sided endocarditis, and complicated skin and skin structure infections. Daptomycin has a novel mechanism of action, rapid bactericidal activity, and a lack of cross resistance with other antibiotic classes. Daptomycin has also demonstrated efficacy in case studies involving the treatment of osteomyelitis and involving complicated persistent infections associated with indwelling medical devices. Because of its efficacy and safety in a variety of infectious conditions and because of its rapid bactericidal activity, daptomycin is well suited as a viable alternative for patients in the critical care setting.

Daptomycin and tigecycline: a review of clinical efficacy in the antimicrobial era

There is a clinical need for new treatment options as a result of continued increase in the expression of resistance among bacterial pathogens. A number of compounds currently in development show promise. However, in some cases, there is concern that resistance may develop quickly to new compounds that are based on existing antimicrobial agents. Therefore, daptomycin, a novel lipopeptide with a unique mode of action, is of particular interest. It has rapid bactericidal activity against growing and stationary-phase bacteria, once-daily dosing regimen, and has a low potential for the development of resistance. It has been approved for the treatment of complicated skin and soft tissue infections caused by Gram-positive bacteria, and registration for treatment of infective endocarditis and bacteraemia is anticipated. Daptomycin is a welcome addition to the antimicrobial armamentarium for the treatment of bacterial infections. Tigecycline is a new glycyclcycline antimicrobial recently approved for use in the USA, Europe and elsewhere. While related to the tetracyclines, tigecycline overcomes many of the mechanisms responsible for resistance to this class. It is a novel broad spectrum glycylcycline with good activity against Gram-positive, many Gram-negative, anaerobic, and some atypical pathogens that has been developed to address this need. It is efficacious in complicated skin and soft tissue infections and in intra-abdominal infections. This review aims to summarise the key clinical data of daptomycin and tigecycline which hold promise for widespread clinical use in the next decade.