Daptomycin: another novel agent for treating infections due to drug-resistant gram-positive pathogens

Treatment of Enterococcus faecalis Infective Endocarditis: A Continuing Challenge

Today, Enterococcus faecalis is one of the main causes of infective endocarditis in the world, generally affecting an elderly and fragile population, with a high mortality rate. Enterococci are partially resistant to many commonly used antimicrobial agents such as penicillin and ampicillin, as well as high-level resistance to most cephalosporins and sometimes carbapenems, because of low-affinity penicillin-binding proteins, that lead to an unacceptable number of therapeutic failures with monotherapy. For many years, the synergistic combination of penicillins and aminoglycosides has been the cornerstone of treatment, but the emergence of strains with high resistance to aminoglycosides led to the search for new alternatives, like dual beta-lactam therapy. The development of multi-drug resistant strains of Enterococcus faecium is a matter of considerable concern due to its probable spread to E. faecalis and have necessitated the search of new guidelines with the combination of daptomycin, fosfomycin or tigecycline. Some of them have scarce clinical experience and others are still under investigation and will be analyzed in this review. In addition, the need for prolonged treatment (6–8 weeks) to avoid relapses has forced to the consideration of other viable options as outpatient parenteral strategies, long-acting administrations with the new lipoglycopeptides (dalbavancin or oritavancin), and sequential oral treatments, which will also be discussed.

Flourishing Antibacterial Strategies for Osteomyelitis Therapy

Osteomyelitis is a destructive disease of bone tissue caused by infection with pathogenic microorganisms. Because of the complex and long-term abnormal conditions, osteomyelitis is one of the refractory diseases in orthopedics. Currently, anti-infective therapy is the primary modality for osteomyelitis therapy in addition to thorough surgical debridement. However, bacterial resistance has gradually reduced the benefits of traditional antibiotics, and the development of advanced antibacterial agents has received growing attention. This review introduces the main targets of antibacterial agents for treating osteomyelitis, including bacterial cell wall, cell membrane, intracellular macromolecules, and bacterial energy metabolism, focuses on their mechanisms, and predicts prospects for clinical applications.

Structure-activity relationships of antibacterial peptides

Antimicrobial peptides play a crucial role in innate immunity, whose components are mainly peptide-based molecules with antibacterial properties. Indeed, the exploration of the immune system over the past 40 years has revealed a number of natural peptides playing a pivotal role in the defence mechanisms of vertebrates and invertebrates, including amphibians, insects, and mammalians. This review provides a discussion regarding the antibacterial mechanisms of peptide-based agents and their structure-activity relationships (SARs) with the aim of describing a topic that is not yet fully explored. Some growing evidence suggests that innate immunity should be strongly considered for the development of novel antibiotic peptide-based libraries. Also, due to the constantly rising concern of antibiotic resistance, the development of new antibiotic drugs is becoming a priority of global importance. Hence, the study and the understanding of defence phenomena occurring in the immune system may inspire the development of novel antibiotic compound libraries and set the stage to overcome drug-resistant pathogens. Here, we provide an overview of the importance of peptide-based antibacterial sources, focusing on accurately selected molecular structures, their SARs including recently introduced modifications, their latest biotechnology applications, and their potential against multi-drug resistant pathogens. Last, we provide cues to describe how antibacterial peptides show a better scope of action selectivity than several anti-infective agents, which are characterized by non-selective activities and non-targeted actions toward pathogens.

A Comprehensive Overview of the Antibiotics Approved in the Last Two Decades: Retrospects and Prospects

Due to the overuse of antibiotics, bacterial resistance has markedly increased to become a global problem and a major threat to human health. Fortunately, in recent years, various new antibiotics have been developed through both improvements to traditional antibiotics and the discovery of antibiotics with novel mechanisms with the aim of addressing the decrease in the efficacy of traditional antibiotics. This manuscript reviews the antibiotics that have been approved for marketing in the last 20 years with an emphasis on the antibacterial properties, mechanisms, structure-activity relationships (SARs), and clinical safety of these antibiotics. Furthermore, the current deficiencies, opportunities for improvement, and prospects of antibiotics are thoroughly discussed to provide new insights for the design and development of safer and more potent antibiotics.

Native and Prosthetic Simultaneously Double Valve Infective Endocarditis with Enterococcus faecalis-Case-Based Review

Infective endocarditis is a severe infective heart disease, commonly involving native or prosthetic valves. It frequently presents with univalvular involvement and simultaneous double valve or multivalvular involvement is rarely described. The third leading cause of infective endocarditis worldwide is Enterococcus faecalis, which is associated with high mortality rates despite important advances in antimicrobial therapy. It develops secondary to enterococcal bacteremia, with its origin from the gastrointestinal or genitourinary tract and predominantly affecting the elderly population with multiple comorbidities. Clinical presentation is usually less typical, and the treatment is challenging. It can be marked by antibiotic resistance, side effects, and subsequent complications. Surgical treatment can be considered if deemed appropriate. To the best of our knowledge, we present the first case-based narrative review of Enterococcus faecalis double valve endocarditis involving both the aortic native and prosthetic mitral valve, highlighting the clinical characteristics, treatment, and complications of this condition.

Silver-dendrimer nanocomposite as emerging therapeutics in anti-bacteria and beyond

To develop next-generation nanomedicine, theranostic nanotherapeutic strategies are increasingly being emphasized. In recent years, it is observed that the effective lifetime of anti-bacterial and anti-cancer agent is diminishing, which undermines the economic incentives necessary for clinical development and therapeutic applications. Thus, novel formulations ought to not only kill drug resistant strains and cancerous cells but also inhibit their formation. Recently, metallic nanoparticles [for example- silver (Ag) nanoparticles] have been widely investigated for their biomedical applications. The so-called applications necessitate the inclusion of these nanoparticles inside polymeric matrices (for example- dendrimer) leading to chemical functionalization of the metallic nanoparticles. Silver and silver nanoparticles' antibacterial activity has already been well established over years. Dendrimers due to their homogeneous highly branched structure and uniform composition are perfectly suitable for the inclusion of silver nanoparticles [Ag NPs]. Recently, the increasing trend in the development of Ag-dendrimer nanocomposites is attributed to the excellent antibacterial activity of Ag as well as dendrimer's unique properties like variable functional terminal ends and potential antibacterial effect necessarily. This review provides an informative overview regarding the numerous aspects of bactericidal and other biomedical applications of Ag-dendrimer nanocomposites, particularly emphasizing analysis of existing research and prospective worth to the pharmaceutical sector in future.

Eradication of Staphylococcus aureus Biofilm Infection by Persister Drug Combination

Staphylococcus aureus can cause a variety of infections, including persistent biofilm infections, which are difficult to eradicate with current antibiotic treatments. Here, we demonstrate that combining drugs that have robust anti-persister activity, such as clinafloxacin or oritavancin, in combination with drugs that have high activity against growing bacteria, such as vancomycin or meropenem, could completely eradicate S. aureus biofilm bacteria in vitro. In contrast, single or two drugs, including the current treatment doxycycline plus rifampin for persistent S. aureus infection, failed to kill all biofilm bacteria in vitro. In a chronic persistent skin infection mouse model, we showed that the drug combination clinafloxacin + meropenem + daptomycin which killed all biofilm bacteria in vitro completely eradicated S. aureus biofilm infection in mice while the current treatments failed to do so. The complete eradication of biofilm bacteria is attributed to the unique high anti-persister activity of clinafloxacin, which could not be replaced by other fluoroquinolones including moxifloxacin, levofloxacin, or ciprofloxacin. We also compared our persister drug combination with the current approaches for treating persistent infections, including gentamicin + fructose and ADEP4 + rifampin in the S. aureus biofilm infection mouse model, and found neither treatment could eradicate the biofilm infection. Our study demonstrates an important treatment principle, the Yin–Yang model, for persistent infections by targeting both growing and non-growing heterogeneous bacterial populations, utilizing persister drugs for the more effective eradication of persistent and biofilm infections. Our findings have implications for the improved treatment of other persistent and biofilm infections in general.

Daptomycin-Associated Diarrhea: A Case Report and Review of the Literature

Antibiotic-associated diarrhea (AAD) describes any unexplained diarrhea associated with the use of antibiotics. AAD develops through diverse mechanisms, ranging from pharmacologic effects on gut motility to disturbance of the function and carbohydrate metabolism of the indigenous intestinal flora and overgrowth by pathogenic micro-organisms. Clostridioides difficile-associated diarrhea (CDAD) is a subset of AAD; however, it accounts only for a small percentage of diarrhea caused by antibiotics. Diarrhea has been reported as a side effect of daptomycin use, nevertheless, it's thought to be mild and carries significantly less risk of diarrhea than other alternative treatments of S. aureus bacteremia, i.e., vancomycin or cefazolin. The authors present an interesting case of daptomycin-associated diarrhea presenting with a protracted and severe course. Patient symptoms didn’t improve with empiric Clostridioides difficile therapy and CDAD testing was negative. Diarrhea promptly resolved after discontinuation of daptomycin. Furthermore, a thorough literature review was conducted and discussed in this article to raise awareness of this under-recognized complication. Clinicians should be mindful of daptomycin-associated diarrhea along with its presentation and treatment. Further studies are needed to identify the pathophysiology of daptomycin-associated diarrhea and other forms of AAD. Understanding their mechanism could help prevent, treat, and reduce the significant medical costs associated with antibiotic adverse events.

Recent Developments in Methicillin-Resistant Staphylococcus aureus (MRSA) Treatment: A Review

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium that may cause life-threatening diseases and some minor infections in living organisms. However, it shows notorious effects when it becomes resistant to antibiotics. Strain variants of bacteria, viruses, fungi, and parasites that have become resistant to existing multiple antimicrobials are termed as superbugs. Methicillin is a semisynthetic antibiotic drug that was used to inhibit staphylococci pathogens. The S. aureus resistant to methicillin is known as methicillin-resistant Staphylococcus aureus (MRSA), which became a superbug due to its defiant activity against the antibiotics and medications most commonly used to treat major and minor infections. Successful MRSA infection management involves rapid identification of the infected site, culture and susceptibility tests, evidence-based treatment, and appropriate preventive protocols. This review describes the clinical management of MRSA pathogenesis, recent developments in rapid diagnosis, and antimicrobial treatment choices for MRSA.

Phosphate Ions Alter the Binding of Daptomycin to Living Bacterial Cell Surfaces

Advancements in antibiotic drug design are often hindered by missing information on how these small molecules interact with living cells. The antibiotic, daptomycin, has found clinical success and an emerging resistance, but a comprehensive picture of its mechanism of action has remained elusive. Using a surface-specific spectroscopy technique, second harmonic generation, we are able to quantitatively assess the binding of daptomycin to living cell membranes without the addition of exogenous labels. Our results reveal similar binding affinities for both Gram-positive and Gram-negative bacteria studied, including Escherichia coli. More importantly, we show that the presence of phosphate ions influences the binding of daptomycin to the Gram-positive bacterium Enterococcus faecalis. The role of environmental phosphate has not previously been considered in any proposed mechanism, and its implications are expected to be important in vivo.

Antimicrobial peptides (AMPs): A promising class of antimicrobial compounds

Antimicrobial peptides (AMPs) are compounds, which have inhibitory activity against microorganisms. In the last decades, AMPs have become powerful alternative agents that have met the need for novel anti-infectives to overcome increasing antibiotic resistance problems. Moreover, recent epidemics and pandemics are increasing the popularity of AMPs, due to the urgent necessity for effective antimicrobial agents in combating the new emergence of microbial diseases. AMPs inhibit a wide range of microorganisms through diverse and special mechanisms by targeting mainly cell membranes or specific intracellular components. In addition to extraction from natural sources, AMPs are produced in various hosts using recombinant methods. More recently, the synthetic analogues of AMPs, designed with some modifications, are predicted to overcome the limitations of stability, toxicity and activity associated with natural AMPs. AMPs have potential applications as antimicrobial agents in food, agriculture, environment, animal husbandry and pharmaceutical industries. In this review, we have provided an overview of the structure, classification and mechanism of action of AMPs, as well as discussed opportunities for their current and potential applications.

The multifaceted nature of antimicrobial peptides: current synthetic chemistry approaches and future directions

Bacterial infections caused by 'superbugs' are increasing globally, and conventional antibiotics are becoming less effective against these bacteria, such that we risk entering a post-antibiotic era. In recent years, antimicrobial peptides (AMPs) have gained significant attention for their clinical potential as a new class of antibiotics to combat antimicrobial resistance. In this review, we discuss several facets of AMPs including their diversity, physicochemical properties, mechanisms of action, and effects of environmental factors on these features. This review outlines various chemical synthetic strategies that have been applied to develop novel AMPs, including chemical modifications of existing peptides, semi-synthesis, and computer-aided design. We will also highlight novel AMP structures, including hybrids, antimicrobial dendrimers and polypeptides, peptidomimetics, and AMP-drug conjugates and consider recent developments in their chemical synthesis.

Novel Broad-Spectrum Antimicrobial Peptide Derived from Anoplin and Its Activity on Bacterial Pneumonia in Mice

The emergence of multidrug-resistant bacteria has major issues for treating bacterial pneumonia. Currently, anoplin (GLLKRIKTLL-NH₂) is a natural antimicrobial candidate derived from wasp venom. In this study, a series of new antimicrobial peptide (AMP) anoplin analogues were designed and synthesized. The relationship between their biological activities and their positive charge, hydrophobicity, amphipathicity, and secondary structure are described. The characteristic shared by these peptides is that positively charged amino acids and hydrophobic amino acids are severally arranged on the hydrophilic and hydrophobic surface of the α-helix to form a completely amphiphilic structure. To achieve ideal AMPs, below the range of the threshold of the cytotoxicity and hemolytic activity, their charges and hydrophobicity were increased as much. Among the new analogues, A-21 (KWWKKWKKWW-NH₂) exhibited the greatest antimicrobial activity (geometric mean of minimum inhibitory concentrations = 4.76 μM) against all the tested bacterial strains, high bacterial cell selectivity in vitro, high effectiveness against bacterial pneumonia in mice infected with Klebsiella pneumoniae, and low toxicity in mice (LD₅₀ = 82.01 mg/kg). A-21 exhibited a potent bacterial membrane-damaging mechanism and lipopolysaccharide-binding ability. These data provide evidence that A-21 is a promising antimicrobial candidate for the treatment of bacterial pneumonia.

Daptomycin-Induced Lipid Phases on Model Lipid Bilayers: Effect of Lipid Type and of Lipid Leaflet Order on Membrane Permeability

Daptomycin's bacterial membrane activity is partly due to the defects of lipid-packing at the boundaries of daptomycin-induced, separated lipid phases, which are rich in phosphatidylglycerol (PG). On model membranes, the permeability of phase boundaries is strongly dependent on the extent of saturation of the lipid acyl tails, which affect the lipids' ability to pack within these boundaries, and on the cross-leaflet registration of these boundaries. Using vesicles with asymmetric lipid leaflet compositions, we evaluated the role of headgroup type and/or extent of acyl-tail saturation on daptomycin-induced membrane permeability. We demonstrate that the release rates of vesicle-encapsulated contents scales with the total length of daptomycin-induced, PG-rich phase boundaries. On the outer leaflet, lipids with PG-headgroups (in contact with daptomycin) were a necessary condition, but they still were not adequate for release. Increased membrane permeability was observed only when inner leaflet lipids had saturated acyl tails; we postulate that the latter may have enabled the recruitment, by the outer leaflet daptomycin-induced phases, of inner leaflet lipids in cross-registered phases with boundaries of defective packing that spanned the bilayer. These findings provide insights on the potential role of lipids as a whole (headgroup and acyl tails) and of lipid leaflet order on the boundaries of daptomycin-induced separated lipid phases in model membranes.

Machine Learning Establishes Single-Cell Calcium Dynamics as an Early Indicator of Antibiotic Response

Changes in bacterial physiology necessarily precede cell death in response to antibiotics. Herein we investigate the early disruption of Ca²⁺ homeostasis as a marker for antibiotic response. Using a machine learning framework, we quantify the temporal information encoded in single-cell Ca²⁺ dynamics. We find Ca²⁺ dynamics distinguish kanamycin sensitive and resistant cells before changes in gross cell phenotypes such as cell growth or protein stability. The onset time (pharmacokinetics) and probability (pharmacodynamics) of these aberrant Ca²⁺ dynamics are dose and time-dependent, even at the resolution of single-cells. Of the compounds profiled, we find Ca²⁺ dynamics are also an indicator of Polymyxin B activity. In Polymyxin B treated cells, we find aberrant Ca²⁺ dynamics precedes the entry of propidium iodide marking membrane permeabilization. Additionally, we find modifying membrane voltage and external Ca²⁺ concentration alters the time between these aberrant dynamics and membrane breakdown suggesting a previously unappreciated role of Ca²⁺ in the membrane destabilization during Polymyxin B treatment. In conclusion, leveraging live, single-cell, Ca²⁺ imaging coupled with machine learning, we have demonstrated the discriminative capacity of Ca²⁺ dynamics in identifying antibiotic-resistant bacteria.

Rediscovery of antimicrobial peptides as therapeutic agents

In recent years, the occurrence of antibiotic-resistant pathogens is increasing rapidly. There is growing concern as the development of antibiotics is slower than the increase in the resistance of pathogenic bacteria. Antimicrobial peptides (AMPs) are promising alternatives to antibiotics. Despite their name, which implies their antimicrobial activity, AMPs have recently been rediscovered as compounds having antifungal, antiviral, anticancer, antioxidant, and insecticidal effects. Moreover, many AMPs are relatively safe from toxic side effects and the generation of resistant microorganisms due to their target specificity and complexity of the mechanisms underlying their action. In this review, we summarize the history, classification, and mechanisms of action of AMPs, and provide descriptions of AMPs undergoing clinical trials. We also discuss the obstacles associated with the development of AMPs as therapeutic agents and recent strategies formulated to circumvent these obstacles.

Patient Case Report Daptomycin Holiday-A Daptomycin Dosing Strategy for Asymptomatic Increases in Creatine Phosphokinase Levels

Daptomycin possesses excellent activity against many multidrug-resistant gram positive organisms. However, a side effect of concern with daptomycin is skeletal muscle injury, which is manifested in the form of elevated creatine phosphokinase (CPK). Management of such CPK elevations has traditionally been discontinuation of the offending agent, with many studies showing a resolution of a normal CPK level within 1 week of discontinuation and no long term adverse effects. Nevertheless, the question remains if daptomycin can be successfully restarted in such patients. Here, we present a case of a "daptomycin holiday" in which daptomycin was withheld upon CPK elevation and successfully reintroduced to the patient's regimen again after several days without further elevation of the CPK. The patient had a peak CPK of 2,557 U/L, and had no associated symptoms. A hypothesis for this holiday could be the adaptability of the skeletal muscle myocytes, in which the extra period between doses may allow for additional recovery of the membrane structure to further daptomycin exposure. Giving an asymptomatic patient with elevated CPK level, a short daptomycin holiday to allow for the CPK level to trend downward before resuming daptomycin therapy could be a potential strategy in patients for whom continuing daptomycin is still preferred.

Impact of β-Lactam and Daptomycin Combination Therapy on Clinical Outcomes in Methicillin-susceptible Staphylococcus aureus Bacteremia: A Propensity Score-matched Analysis

BACKGROUND

Mortality rates from Staphylococcus aureus bacteremia are high and have only modestly improved in recent decades. We compared the efficacies of a β-lactam in combination with daptomycin (BL/D-C) and β-lactam monotherapy (BL-M) in improving clinical outcomes in methicillin-susceptible S. aureus (MSSA) bacteremia.

METHODS

A retrospective cohort study of MSSA bacteremia was performed in a tertiary hospital from January 2011 to December 2017. Patients receiving BL/D-C and BL-M were compared to assess 7-, 30-, and 90-day mortality rates. A 1:2 propensity score matching analysis was performed. Differences were assessed using Cox regression models.

RESULTS

Of the 514 patients with MSSA bacteremia, 164 were excluded as they had received combination therapies other than BL/D-C, had pneumonia, or died within 48 hours of admission. Of the remaining 350 patients, 136 and 214 received BL/D-C and BL-M, respectively. BL/D-C patients had higher Pitt scores and persistent bacteremia more often than BL-M patients. In the raw analysis, there were no differences in mortality rates between groups. After propensity score matching, there were no significant differences between the BL/D-C (110 patients) and BL-M (168 patients) groups for all-cause mortality rates at 7 days (8.18% vs 7.74%; P = 1.000), 30 days (17.3% vs 16.1%; P = .922), and 90 days (22.7% vs 23.2%; P = 1.000), even in a subanalysis of patients with high-risk source of infection and in a subgroup excluding catheter-related bacteremia.

CONCLUSIONS

BL/D-C failed to reduce mortality rates in patients with MSSA bacteremia. Treatment strategies to improve survival in MSSA bacteremia are urgently needed.

Effect of N-methylated and fatty acid conjugation on analogs of antimicrobial peptide Anoplin

With the increment of drug-resistant bacteria and the slow development of novel antibiotics, antimicrobial peptides have gained increasing attention as a potential antibiotic alternative. They not only displayed a broad-spectrum antimicrobial activity but also were difficult to induce resistance development because of their unique membrane-lytic activity. Herein, to improve the limitations of Anoplin, the N-methyl amino acids were first used to replace the amino acids of Anoplin at sensitive enzymatic cleave sites (Leu, Ile, Lys and Arg). Afterward, the N-methylated analogs M3.6/M4.7/M5.7 with high stability were screened out and further modified by N-terminal fatty acid conjugation to develop new antimicrobial peptide analogs with both potent antimicrobial activity and high proteolytic stability, and 12 new Anoplin analogs Cn-M3.6/M4.7/M5.7 (n = 8,10,12,14) were designed and synthesized. Our results showed that compared with native Anoplin, the stability of these N-methylated lipopeptides against trypsin and chymotrypsin degradation were increased by 10⁴-10⁶ times. Besides, they still possessed potent antimicrobial activity under physiological salts and serum environment. Among them, the new designed analogs C12-M3.6/M4.7/M5.7 showed the optimal antimicrobial activity, synergy and additive effects were also observed when they were combined with traditional antibiotics polymyxin B, rifampin, and kanamycin. Moreover, they could effectively inhibit the formation of biofilms by P. aeruginosa and S. aureus. The antimicrobial mechanism studied revealed that these N-methylated lipopeptides could display a rapid bactericidal effect by destroying the bacterial cell membrane. Notably, no detectable resistance of these new designed peptides was developed after continuous cultured with E. coli for 20 passages. In summary, we have designed a new class of antimicrobial peptide analogs with potent antimicrobial activity and high proteolytic stability through N-methyl amino acids substitution and N-terminal fatty acid conjugation. This study also provides new ideas and methods for the modification of antimicrobial peptides in the future.

Antimicrobial-Resistant Gram-Positive Bacteria in PD Peritonitis and the Newer Antibiotics Used to Treat Them

The incidence of resistant gram-positive bacteria in nosocomial and, more recently, community-acquired infections is increasing. Staphylococci, because of their natural habitat on the skin, have always been the leading cause of peritonitis in patients receiving peritoneal dialysis (PD). These organisms have demonstrated a remarkable ability to develop resistance to antibiotics, first with penicillin, then antistaphylococcal penicillins (methicillin-resistant Staphylococcus aureus), and more recently, strains expressing resistance to vancomycin (vancomycin-intermediate and vancomycin-resistant S. aureus) have emerged. Enterococci are normal inhabitants of the gastrointestinal tract and occasionally cause PD peritonitis. In the past 15 years, vancomycin-resistant enterococci have emerged as significant pathogens in many areas. In the past 5 years, novel antibiotics that have activity on gram-positive bacteria, including vancomycin-resistant strains, have become available. The problem of resistant gram-positive bacteria in PD peritonitis, their therapy, and the role of these newer agents, quinupristin/dalfopristin, linezolid, and daptomycin, are reviewed.

Development and Challenges of Antimicrobial Peptides for Therapeutic Applications

More than 3000 antimicrobial peptides (AMPs) have been discovered, seven of which have been approved by the U.S. Food and Drug Administration (FDA). Now commercialized, these seven peptides have mostly been utilized for topical medications, though some have been injected into the body to treat severe bacterial infections. To understand the translational potential for AMPs, we analyzed FDA-approved drugs in the FDA drug database. We examined their physicochemical properties, secondary structures, and mechanisms of action, and compared them with the peptides in the AMP database. All FDA-approved AMPs were discovered in Gram-positive soil bacteria, and 98% of known AMPs also come from natural sources (skin secretions of frogs and toxins from different species). However, AMPs can have undesirable properties as drugs, including instability and toxicity. Thus, the design and construction of effective AMPs require an understanding of the mechanisms of known peptides and their effects on the human body. This review provides an overview to guide the development of AMPs that can potentially be used as antimicrobial drugs.

Daptomycin use in adult inpatients in a Canadian tertiary care setting

BACKGROUND

Daptomycin is approved by Health Canada for the treatment of Staphylococcus aureus bacteremia and complicated skin and soft tissue infections caused by gram-positive organisms, but is often used for other indications. We aimed to understand the indications, dosing, and safety profile of daptomycin use in a Canadian inpatient setting.

METHODS

We included consecutive adult patients who received intravenous daptomycin as inpatients from January 1, 2016, to December 31, 2016, at two tertiary care teaching hospitals in Hamilton, Ontario.

RESULTS

We identified 86 courses in 77 unique patients. S. aureus was the most common pathogen (n = 38, 44%) of which 87% (n = 33) were methicillin-resistant. The most common indications were bloodstream infections (n = 31, 36%). The average treatment duration was 10 days, at an average dose of 7.4 mg/kg. The infectious diseases service was consulted in all but two courses. Less than half of treatment courses were given for an indication approved by Health Canada (n = 41, 48%). Almost half of the unapproved indications (n = 21, 47%) followed Infectious Diseases Society of America (IDSA) recommendations. Creatine kinase elevation of 3 × the upper limit of normal or higher occurred in a small number of courses (n = 7, 8%), with only one instance requiring discontinuation of the drug.

CONCLUSIONS

Daptomycin is being used to treat inpatients for a variety of unapproved indications. Importantly, a sizable portion of these are within IDSA guideline recommendations. Most patients are treated with doses higher than the approved 6 mg/kg without major safety concerns.

Neurological and Psychiatric Adverse Effects of Antimicrobials

Antimicrobials are a widely used class of medications, but several of them are associated with neurological and psychiatric side effects. The exact incidence of neurotoxicity with anti-infectives is unknown, although it is estimated to be < 1%. Neurotoxicity occurs with all classes of antimicrobials, such as antibiotics, antimycobacterials, antivirals, antifungals and antiretrovirals, with side effects ranging from headaches, anxiety and depression to confusion, delirium, psychosis, mania and seizures, among others. It is important to consider these possible side effects to prevent misdiagnosis or delayed treatment as drug withdrawal can be associated with reversibility in most cases. This article highlights the different neurotoxic effects of a range of antimicrobials, discusses proposed mechanisms of onset and offers general management recommendations. The effects of antibiotics on the gut microbiome and how they may ultimately affect cognition is also briefly examined.

Cecropin-like antimicrobial peptide protects mice from lethal E.coli infection

Resistance of pathogenic bacteria to standard antibiotics is an issue of great concern, and new treatments for bacterial infections are needed. Antimicrobial peptides (AMPs) are small, cationic, and amphipathic molecules expressed by metazoans that kill pathogens. They are a key part of the innate immune system in both vertebrates and invertebrates. Due to their low toxicity and broad antimicrobial activities, there has been increasing attention to their therapeutic usage. Our previous research demonstrated that four peptides-DAN1, DAN2, HOLO1 and LOUDEF1-derived from recently sequenced arthropod genomes exhibited potent antimicrobial effects in-vitro. In this study, we show that DAN2 protected 100% of mice when it was administered at a concentration of 20 mg/kg thirty minutes after the inoculation of a lethal dose of E. coli intraperitoneally. Lower concentrations of DAN2-10mg/kg and 5mg/kg protected more than 2/3s of the mice. All three dose levels reduced bacterial loads in blood and peritoneal fluid by 10-fold or more when counted six hours after bacterial challenge. We determined that DAN2 acts by compromising the integrity of the E. coli membrane. This study supports the potential of DAN2 peptide as a therapeutic agent for treating antibiotic resistant Gram-negative bacterial infections.

Simple LC-MS/MS Methods Using Core-Shell Octadecylsilyl Microparticulate for the Quantitation of Total and Free Daptomycin in Human Plasma

BACKGROUND

Daptomycin, a cyclic lipopeptide antibiotic, displays high plasma protein binding. This study developed the simple method of liquid chromatographic separation using a core-shell octadecylsilyl microparticulate coupled to tandem mass spectrometry for the quantitation of total and free daptomycin in human plasma.

METHODS

Free daptomycin in plasma was obtained by centrifugal ultrafiltration. Deproteinized plasma specimens were directly separated using a core-shell octadecylsilyl microparticulate with isocratic elution. The mass spectrometer was run in positive-ion electrospray ionization mode. This method was applied to the quantitation of plasma samples in patients treated with intravenous daptomycin.

RESULTS

Daptomycin and diazepam as an internal standard were eluted with a total run time of 10 minutes. The calibration curves of total and free daptomycin in human plasma were linear over the concentration ranges of 1-100 and 0.1-10 mcg/mL, respectively. The lower limits of quantitation of the total and free daptomycin in human plasma were 1.0 and 0.1 mcg/mL, respectively. Their extraction recovery rates in nonfiltrated and ultrafiltrated plasma samples were 106.1% and 98.2%, respectively. Total and free daptomycin did not exhibit any matrix effects in human plasma. The intraday and interday accuracies and imprecisions of total daptomycin were 88.7%-106.0% and 98.7%-105.9%, and within 4.1% and 10.4%, whereas those of free daptomycin were 86.8%-101.6% and 103.0%-107.8%, and within 14.6% and 14.6%, respectively. The plasma concentration ranges of total and free daptomycin in 15 infected patients were 3.01-34.1 and 0.39-3.64 mcg/mL, respectively. The plasma protein binding rate of daptomycin ranged from 80.8% to 94.9%.

CONCLUSIONS

The present simple method with an acceptable analytical performance can be helpful for monitoring the pharmacokinetics of daptomycin in infected patients observed in clinical settings.

Evolution and mutations predisposing to daptomycin resistance in vancomycin-resistant Enterococcus faecium ST736 strains

We recently identified a novel vancomycin-resistant Enterococcus faecium (VREfm) clone ST736 with reduced daptomycin susceptibility. The objectives of this study were to assess the population dynamics of local VREfm strains and genetic alterations predisposing to daptomycin resistance in VREfm ST736 strains. Multilocus sequence typing and single nucleotide variant data were derived from whole-genome sequencing of 250 E. faecium isolates from 1994–1995 (n = 43), 2009–2012 (n = 115) and 2013 (n = 92). A remarkable change was noticed in the clonality and antimicrobial resistance profiles of E. faecium strains between 1994–1995 and 2013. VREfm sequence type 17 (ST17), the prototype strain of clade A1, was the dominant clone (76.7%) recognized in 1994–1995. By contrast, clone ST736 accounted for 46.7% of VREfm isolates, followed by ST18 (26.1%) and ST412 (20.7%) in 2013. Bayesian evolutionary analysis suggested that clone ST736 emerged between 1996 and 2009. Co-mutations (liaR.W73C and liaS.T120A) of the liaFSR system were identified in all ST736 isolates (n = 111, 100%) examined. Thirty-eight (34.2%) ST736 isolates exhibited daptomycin-resistant phenotype, of which 13 isolates had mutations in both the liaFSR and cardiolipin synthase (cls) genes and showed high level of resistance with a daptomycin MIC₅₀ of 32 μg/mL. The emergence of ST736 strains with mutations predisposing to daptomycin resistance and subsequent clonal spread among inpatients contributed to the observed high occurrence of daptomycin resistance in VREfm at our institution. The expanding geographic distribution of ST736 strains in other states and countries raises concerns about its global dissemination.

A case report and literature review of daptomycin-induced liver injury

Daptomycin is a lipopeptide antimicrobial used to treat gram positive organisms including multi-drug resistant infections. It has been shown to occasionally cause abnormalities in liver function but more commonly is associated with elevations in serum creatinine phosphokinase (CK) (Hair and Keam, 2007) [1]. We describe a case where a patient being treated for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia with daptomycin developed asymptomatic elevated transaminases without evidence of multiorgan failure, hyperbilirubinemia or elevation of CK levels. Other etiologies for liver injury were considered and ruled out, and after daptomycin was discontinued, the transaminases returned to normal levels. We also provide a review of other cases to date documenting possible cases of daptomycin-induced liver injury.

Guideline for Antibiotic Use in Adults with Community-acquired Pneumonia

Community-acquired pneumonia is common and important infectious disease in adults. This work represents an update to 2009 treatment guideline for community-acquired pneumonia in Korea. The present clinical practice guideline provides revised recommendations on the appropriate diagnosis, treatment, and prevention of community-acquired pneumonia in adults aged 19 years or older, taking into account the current situation regarding community-acquired pneumonia in Korea. This guideline may help reduce the difference in the level of treatment between medical institutions and medical staff, and enable efficient treatment. It may also reduce antibiotic resistance by preventing antibiotic misuse against acute lower respiratory tract infection in Korea.

A randomized phase 2B trial of vancomycin versus daptomycin for the treatment of methicillin-resistant Staphylococcus aureus bacteremia due to isolates with high vancomycin minimum inhibitory concentrations - results of a prematurely terminated study

Background

Studies have suggested the reduced effectiveness of vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections with high vancomycin minimum inhibitory concentrations. Alternative agents such as daptomycin may be considered. We conducted a randomized controlled study comparing daptomycin against vancomycin in the treatment of MRSA bloodstream infections with high vancomycin minimum inhibitory concentrations.

Methods

Patients were randomized to receive vancomycin or daptomycin for a minimum of 14 days. The primary end point was the rate of all-cause mortality at day 60.

Results

A total of 14 patients were randomized in this study, with 7 patients in each treatment arm. The study was terminated early due to slow patient accrual. At day 60, there was one death in the vancomycin arm and none in the daptomycin arm. The median time to microbiological clearance was 4 days in both arms (IQR 3–5 days in the vancomycin arm and 3–7 days in daptomycin arm). Only one patient in the vancomycin arm had recurrence of bacteremia. Rates of adverse events were similar in both arms. There was one case of musculoskeletal toxicity and one case of drug-related nephrotoxicity - both events occurred in the daptomycin arm. None of the patients in either treatment arm required cessation of study treatment or addition of a second anti-MRSA agent because of worsening infection.

Conclusion

Based on the limited number of patients evaluated in this study, it remains unclear if alternative, more expensive agents such as daptomycin are superior to vancomycin in the treatment of high vancomycin minimum inhibitory concentration MRSA bloodstream infections. More studies are urgently needed but investigators may wish to consider employing novel, alternative trial methodologies to ensure a greater chance of success.

Trial registration

ClinicalTrials.gov, NCT01975662. Registered on 5 November 2013.

Do physico-chemical properties of silver nanoparticles decide their interaction with biological media and bactericidal action? A review

The unprecedented increase in antibiotic resistance in this era has resuscitated the attention of scientific community to exploit silver and its various species as antimicrobial agents. Plenty of studies have been done to measure the antimicrobial potential of silver species (cationic silver, metallic Ag⁰ or silver nanoparticles, silver oxide particulates etc.) and indicated that membrane damage, oxidative stress, protein dysfunction and DNA damage to be the possible cause of injury to the microbial cell. However, the precise molecular mechanism of their mode of action has remained unclear, which makes an obstacle towards the generation of potential antibacterial agent against various pathogenic and multidrug resistant (MDR) bacteria. In order to endeavor this issue, one should first have the complete understanding about the resistance mechanisms present in bacteria that can be a therapeutic target for the silver-based drug formulations. Apart from this, in-depth understanding of the interactions of various silver species (with the biological media) is a probable deciding factor for the synthesis of silver-based drug formulations because the particular form and physico-chemical properties of silver can ultimately decide their antimicrobial action. In context to above mentioned serious concerns, the present article aims to discuss the mechanisms behind the confrontation of bacteria against various drugs and the effect of physico-chemical properties of silver species on their bactericidal action as well as critically evaluates the available reports on bacterial transcriptomic and proteomic profiles upon the exposure of various silver species. Further, this review state the mechanism of action that needs to be followed for the complete understanding of toxic potential of silver nanoparticles, which will open a possibility to synthesize new silver nanoparticle based antimicrobial systems with desired properties to ensure their safe use, exposure over extended period and fate in human body and environment.

Mode of Action and Heterologous Expression of the Natural Product Antibiotic Vancoresmycin

Antibiotics that interfere with the bacterial cytoplasmic membrane have long-term potential for the treatment of infectious diseases as this mode of action is anticipated to result in low resistance frequency. Vancoresmycin is an understudied natural product antibiotic consisting of a terminal tetramic acid moiety fused to a linear, highly oxygenated, stereochemically complex polyketide chain. Vancoresmycin shows minimum inhibitory concentrations (MICs) from 0.125 to 2 μg/mL against a range of clinically relevant, antibiotic-resistant Gram-positive bacteria. Through a comprehensive mode-of-action study, utilizing Bacillus subtilis reporter strains, DiSC₃(5) depolarization assays, and fluorescence microscopy, we have shown that vancoresmycin selectively targets the cytoplasmic membrane of Gram-positive bacteria via a non-pore-forming, concentration-dependent depolarization mechanism. Whole genome sequencing of the producing strain allowed identification of the 141 kbp gene cluster encoding for vancoresmycin biosynthesis and a preliminary model for its biosynthesis. The size and complex structure of vancoresmycin could confound attempts to generate synthetic analogues. To overcome this problem and facilitate future studies, we identified, cloned, and expressed the 141 kbp biosynthetic gene cluster in Streptomyces coelicolor M1152. Elucidation of the mode-of-action of vancoresmycin, together with the heterologous expression system, will greatly facilitate further studies of this and related molecules.

Role of Antibiotic Lock Therapy for the Treatment of Catheter-Related Bloodstream Infections

Catheter-related bloodstream infections are often difficult to treat because they are caused by organisms that embed themselves in a bio film layer on the catheter surface, resulting in an increased resistance to antimicrobial agents. Systemic antibiotics are usually administered but, although generally effective in eliminating circulating bacteria, they frequently fail to sterilize the line, leaving the patient at a continuing risk of complications or recurrence. A successful approach to managing these infections requires making an appropriate decision regarding whether the catheter should be removed or retained using antibiotic lock therapy; and choosing the type and duration of antimicrobial therapy based on the type of organism and its resistance pattern. Studies that have evaluated antibiotic lock therapy have varied in the types of antibiotics and concentrations used, the addition of heparin to the solutions, and dwell times in the catheter lumen. Guidelines from the Infectious Diseases Society of America include use of antibiotic lock therapy as a therapeutic option for intraluminal infections when the device is not removed and, although not routine, as prophylaxis for catheter-related infection in select patient populations. However, there are no published guidelines on the concentration of heparin or antibiotics that should be used, and minimal published data on the stability of heparin combinations with antibiotics. It is to be hoped that antibiotic locks will be subject to randomized controlled trials of sufficient power to confirm or refute their use.

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

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

Burden and Management of Multidrug-Resistant Organisms in Palliative Care

Palliative care includes comprehensive strategies to optimize quality of life for patients and families confronting terminal illness. Infections are a common complication in terminal illness, and infections due to multidrug-resistant organisms (MDROs) are particularly challenging to manage in palliative care. Limited data suggest that palliative care patients often harbor MDRO. When MDROs are present, distinguishing colonization from infection is challenging due to cognitive impairment or metastatic disease limiting symptom assessment and the lack of common signs of infection. Multidrug-resistant organisms also add psychological burden through infection prevention measures including patient isolation and contact precautions which conflict with the goals of palliation. Moreover, if antimicrobial therapy is indicated per goals of care discussions, available treatment options are often limited, invasive, expensive, or associated with adverse effects that burden patients and families. These issues raise important ethical considerations for managing and containing MDROs in the palliative care setting.

Intracavitary and Systemic Daptomycin for Successful Treatment of a Postpneumonectomy Intrathoracic Infection

Treatment of an infected postpneumonectomy cavity is very difficult. We present a patient with an infection of a postpneumonectomy cavity by Staphylococcus epidermidis treated with local daptomycin for different dwell times, maintaining high antibiotic levels above the MIC. Clinical and microbiological cure were achieved successfully.

Emergence of Daptomycin-Nonsusceptible Methicillin-Resistant Staphylococcus aureus Clinical Isolates Among Daptomycin-Naive Patients in Korea

This study was conducted to assess emergence of daptomycin-nonsusceptible (DAP-NS) phenotype in DAP-naive patients with invasive Staphylococcus aureus (ISA) infections in Korea. A total of 208 S. aureus clinical isolates were selected from a previous prospective study on ISA infections and evaluated for DAP-NS. Although DAP has never been introduced in Korea, five DAP-NS S. aureus strains (2.4%) were identified among 208 S. aureus strains collected from ISA infections. The DAP-NS phenotype was observed only in methicillin-resistant S. aureus (MRSA) strains, but not in methicillin-susceptible S. aureus strains. One DAP-NS MRSA strain belonged to sequence type 72 (ST72) and four were ST5 MRSA strains, three of which were heteroresistant vancomycin (VAN)-intermediate S. aureus. All these five DAP-NS MRSA strains were from healthcare-associated infections without prior exposure to VAN within 30 days. While the ST72 MRSA strain exhibited DAP-NS phenotype via charge repulsion mechanism, four ST5 DAP-NS S. aureus strains had charge-independent DAP-NS mechanism. None of the five DAP-NS strains displayed significant increase in cell wall thickness, indicating that altered cell wall thickness was not associated with the observed DAP-NS phenotype.

Once-Daily Treatments for Methicillin-Susceptible Staphylococcus aureus Bacteremia: Are They Good Enough?

PURPOSE OF THE REVIEW

Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a common cause of morbidity and mortality. First-line treatment requires frequent daily doses of an anti-staphylococcal beta-lactam. However, some physicians prescribe simpler once-daily regimens to improve compliance and improve healthcare utilization. We reviewed the literature regarding advantages, pitfalls, and efficacy of once-daily treatment options for MSSA bacteremia.

RECENT FINDINGS

Several once-daily antibiotics are effective in vitro against MSSA (ceftriaxone, daptomycin, telavancin, dalbavancin, oritavancin, tedizolid, ertapenem, fluoroquinolones, and others), but there is insufficient evidence to support these agents for MSSA bacteremia. Ceftriaxone may be considered for therapy completion with MSSA bacteremia from osteomyelitis, and daptomycin may be considered in patients who cannot tolerate first-line therapy. However, they have not been compared to traditional second-line agents, and their role remains uncertain. Current evidence does not support the use of once-daily treatment options for MSSA bacteremia.

Syntheses, Characterization, Resolution, and Biological Studies of Coordination Compounds of Aspartic Acid and Glycine

Enantiomerically enriched coordination compounds of aspartic acid and racemic mixtures of coordination compounds of glycine metal-ligand ratio 1 : 3 were synthesized and characterized using infrared and UV-Vis spectrophotometric techniques and magnetic susceptibility measurements. Five of the complexes were resolved using (+)-cis-dichlorobis(ethylenediamine)cobalt(III) chloride, (+)-bis(glycinato)(1,10-phenanthroline)cobalt(III) chloride, and (+)-tris(1,10-phenanthroline)nickel(II) chloride as resolving agents. The antimicrobial and cytotoxic activities of these complexes were then determined. The results obtained indicated that aspartic acid and glycine coordinated in a bidentate fashion. The enantiomeric purity of the compounds was in the range of 22.10–32.10%, with (+)-cis-dichlorobis(ethylenediamine)cobalt(III) complex as the more efficient resolving agent. The resolved complexes exhibited better activity in some cases compared to the parent complexes for both biological activities. It was therefore inferred that although the increase in the lipophilicity of the complexes may assist in the permeability of the complexes through the cell membrane of the pathogens, the enantiomeric purity of the complexes is also of importance in their activity as antimicrobial and cytotoxic agents.

Daptomycin-Induced Acute Eosinophilic Pneumonia: Late Onset and Quick Recovery

Background

Daptomycin is a cyclic lipopeptide antibiotic that provides great coverage for gram positive cocci. From the early years of daptomycin use, concerns were raised regarding the pulmonary side effects of daptomycin and potential development of acute eosinophilic pneumonia (AEP) secondary to daptomycin therapy.

Discussion

AEP could be idiopathic or induced by drugs or toxins. It is a distinct entity from atopic diseases and autoimmune, parasitic, or fungal infections that can also cause pulmonary eosinophilia. Multiple medications are associated with acute eosinophilic pneumonia. Multiple cases of daptomycin-induced AEP have been reported in the literature. Diagnosis of AEP is based on clinical history, laboratory tests, and radiographic studies. Obtaining bronchoalveolar lavage or lung biopsy is needed to confirm the diagnosis. Timing of the drug use and clinical presentation is crucial in the diagnosis of drug-induced AEP. Discontinuation of the offending drug and systemic corticosteroids are the mainstay treatment with great outcomes and recovery.

Conclusion

We present a case of AEP caused by daptomycin, with complete recovery after discontinuation of daptomycin and administration of steroids. The patient had AEP after almost 6 weeks of daptomycin therapy which has never been reported in literature and our patient achieved complete recovery with appropriate management.

Antibacterial mechanism of daptomycin antibiotic against Staphylococcus aureus based on a quantitative bacterial proteome analysis

Daptomycin (DAP) is a novel lipopeptide antibiotic which exhibits excellent antibacterial activity against most clinically relevant Gram-positive bacteria, but the DAP-targeting protein molecules against host bacterial infection are far from clear. In order to discover bacterial protein response to DAP treatment, an iTRAQ-based quantitative proteomic analysis was applied to identify differential bacterial proteome profiling of Staphylococcus aureus (S. aureus) ATCC 25923 to 0.125μg/ml DAP exposure. Totally 51 bacterial proteins were significantly changed with DAP treatment, among which 34 proteins were obviously up-regulated and 17 proteins were down-regulated. Meanwhile, 139 bacterial cell membrane (CM) proteins were identified, and 7 CM proteins were significantly altered to decrease CM potential to disrupt bacterial cell membrane. Especially the up-regulation of NDK and down-regulation of NT5 in several S. aureus strains are validated to be a universal variation tendency response to DAP treatment. Under DAP exposure, bacterial membrane potential is decreased and cell membrane is disrupted, and bacterial chromosome is aggregated, which contributes to bacterial DNA rapid release and induces bacteria death within 2-5h. In general, multiple bacterial protein expressions are changed in response to DAP antibiotic exposure, which disrupts host bacterial physiology by multiple cellular levels. To our knowledge, this is the first time to exactly identify infectious bacterial proteins in response to DAP antibiotic action. Our findings help better understand DAP antibacterial mechanism and develop novel DAP derivatives against the upcoming antibiotic-resistant bacterial infection.

BIOLOGICAL SIGNIFICANCE

DAP is a novel lipopeptide antibiotic that it exhibits excellent in vitro activity against most clinically relevant Gram-positive bacteria, and the investigations on its pharmaceutical action mode of DAP have dramatically increased in the past decade due to its unique antimicrobial mechanism. However, the target molecules of DAP acting on the infectious bacteria, are far from clear. The state-of-the-art quantitative proteomic technologies provide new avenues to uncover underlying mechanism of antibiotics. Our research main aims to identify bacterial proteome profiling of host strain S. aureus response to DAP treatment through an iTRAQ-based quantitative proteomic analysis, which contributes to understand DAP efficient antibacterial activity and the microbial-antibiotic interactions.

Diminished Susceptibility to Daptomycin Accompanied by Clinical Failure in a Patient With Methicillin-Resistant Staphylococcus aureus Bacteremia

We cared for a patient with methicillin-resistant Staphylococcus aureus bacteremia who experienced clinical failure with daptomycin. The failure was accompanied by progressive elevation of the daptomycin minimum inhibitory concentration during treatment. DNA fingerprinting confirmed that the minimum inhibitory concentration elevation occurred within the same strain of methicillin-resistant Staphylococcus aureus. This observation provides important new information to clinicians who adopt this promising drug for treatment of serious infections caused by methicillin-resistant Staphylococcus aureus.

Daptomycin in Combination with Ceftolozane-Tazobactam or Cefazolin against Daptomycin-Susceptible and -Nonsusceptible Staphylococcus aureus in an In Vitro, Hollow-Fiber Model

Ceftolozane-tazobactam (TOL-TAZ) is a novel cephalosporin/beta-lactamase inhibitor with activity against several Gram-negative pathogens. Daptomycin (DAP) has demonstrated synergistic activity with beta-lactams against methicillin-resistant Staphylococcus aureus (MRSA) isolates with reduced lipopeptide and glycopeptide susceptibilities. Our objective was to determine if DAP and TOL-TAZ possess synergy in hollow-fiber pharmacokinetic/pharmacodynamic (PK/PD) models. One isogenic pair of daptomycin-susceptible and daptomycin-nonsusceptible MRSA strains was evaluated. DAP, TOL-TAZ, and cefazolin (CFZ) MIC determinations were performed. DAP MIC determinations were also performed in the presence of subinhibitory concentrations of TOL-TAZ and CFZ. Ninety-six-hour in vitro models were run, simulating DAP at 10 mg/kg of body weight/day; TOL-TAZ at 1,500 mg every 8 h; TOL at 1,000 mg every 8 h; and DAP combined with TOL-TAZ (DAP+TOL-TAZ), DAP+TOL, DAP+TAZ, and DAP+CFZ at 2,000 mg every 8 h. DAP MICs were 0.5 and 4 μg/ml for strains R8845 and R8846, respectively. In the presence of CFZ, R8845 and R8846 DAP MICs were reduced 8-fold and 16-fold, respectively. TOL and TAZ had no effect on DAP MICs. PK/PD models demonstrated bactericidal activity with DAP+CFZ against both strains. The combination of DAP+TOL-TAZ was bactericidal against R8845 but was not bactericidal against daptomycin-nonsusceptible strain R8846. DAP+TOL and DAP+TAZ were not bactericidal. No other regimens were bactericidal. DAP+TOL-TAZ did not demonstrate synergistic activity against daptomycin-nonsusceptible S. aureus but prevented daptomycin-nonsusceptible MRSA emergence. Because DAP+TOL or TAZ alone did not prevent daptomycin-nonsusceptible MRSA emergence, the combination TOL-TAZ may be necessary for synergy with DAP. DAP+CFZ demonstrated enhancement against both strains. The combination of DAP+CFZ warrants further clinical study.

Genotyping of Methicillin Resistant Staphylococcus aureus from Tertiary Care Hospitals in Coimbatore, South India

Background:

Globally, methicillin resistant Staphylococcus aureus (MRSA) is one of the most common pathogens that causes hospital- and community-acquired infections. The use of molecular typing methods is essential for determining the origin of the isolates, their clonal relations, and also epidemiological investigations.

Objective:

The purpose of this study was to determine the prevalence of antibiotic-resistant MRSA investigate the accessory gene regulator (agr) and staphylococcal cassette chromosome mec (SCCmec) types and perform multilocus sequence typing (MLST). Furthermore, the minimum inhibitory concentration of MRSA isolates was determined for vancomycin and daptomycin.

Materials and Methods:

Two hundred and fifty-nine MRSA isolates were collected from Tertiary Care Hospitals in Coimbatore. Disk diffusion method was employed to assess the sensitivity of MRSA isolates to selected antibiotics and genetic analysis was performed using SCCmec, agr, and MLST typing by multiplex-polymerase chain reaction strategy. Minimal inhibitory concentration (MIC) was determined using Ezy MIC (vancomycin) and Biomerieux (daptomycin) E-test strip.

Results:

Of 259 MRSA isolates, 209 (80.7%) were confirmed as methicillin resistant. Antibiotic susceptibility pattern revealed that all the MRSA isolates were 100% sensitive to linezolid, rifampicin, teicoplanin, and vancomycin. MIC results showed that of 209 MRSA isolates, 10 were found to be vancomycin intermediate S. aureus and 100% of the MRSA isolates were daptomycin-susceptible. The agr group I and SCCmec Type III were the major type among MRSA isolates. In addition to these MLST typing revealed the prevalence of sequence type (ST) 239 (SLV of ST8) among the MRSA isolates.

Conclusion:

This study confirms that ST239 (Brazilian clone) of MRSA is predominant in this region which is responsible for the hospital-acquired MRSA infections. Thus, the study also suggests that vancomycin and daptomycin can still be used as an alternative drug for treating severe MRSA infections.

Treatment of Methicillin-Resistant Staphylococcus aureus Bacteremia

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of health care-associated infections. Vancomycin remains an acceptable treatment option. There has been a welcome increase in the number of agents available for the treatment of MRSA infection. These drugs have certain differentiating attributes and may offer some advantages over vancomycin, but they also have significant limitations. These agents provide some alternative when no other options are available.

Current and emerging therapies in the management of diabetic foot ulcers

BACKGROUND

Diabetic foot ulcers are one of the major causes of mortality in diabetic patients. Very few drugs and therapies have regulatory approval for this indication and several agents from diverse pharmacological classes are currently in various phases of clinical trials for the management of diabetic foot ulcers.

SCOPE

The purpose of this review is to provide concise information of the drugs and therapies which are approved and present in clinical trials.

REVIEW METHODS

This review was carried out by systematic searches of relevant guidelines, patents, published articles, reviews and abstracts in PubMed/Medline, Web of Science, clinicaltrials.gov, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews and Google Scholar of all English language articles up to 1 March 2015. The following search terms were used: diabetes, diabetic foot, diabetic foot ulcer, diabetic wound, diabetic foot infections, wound management, randomized controlled trials, approved treatments, new treatments and clinical trials.

CONCLUSIONS

The various drugs and therapies for the management of diabetic foot ulcers comprise antibiotics, neuropathic drugs, wound dressings, skin substitutes, growth factors and inflammatory modulators. The majority of these therapies target the treatment of diabetic foot ulcers to address the altered biochemical composition of the diabetic wound. However, no single treatment can be definitively recommended for the treatment of diabetic foot ulcers.