Multifunctional Pharmaceutical Effects of the Antibiotic Daptomycin

Daptomycin alleviates collagen-induced arthritis via suppressing inflammatory cytokines and NF-κB pathway

Rheumatoid arthritis (RA) is a chronic autoimmune disease, and its pathogenic factors include bacterial infection and immune inflammation. Daptomycin (DAP) is a cyclic lipopeptide that has been approved to treat skin infections, bacteremia and right-sided endocarditis due to its effective antibacterial effects against most Gram-positive pathogenic bacteria. Herein, we focus on whether DAP exerts anti-inflammatory activity on RA to expand DAP drug indications. Our studies are first time to evaluate anti-inflammatory effect and reveal its molecular pharmacological mechanism of DAP on lipopolysaccharide-activated macrophage and collagen-induced arthritis (CIA) mice. In vitro cytological studies show that 10 µg/mL DAP inhibits secretion of IL-1β, IL-6 and TNF-α to alleviate cell inflammation, and the phosphorylation level of p65 (p-p65) of RAW 264.7 cells is decreased under DAP exposure. Administration with 10 mg/kg/2d DAP via intravenous injection on CIA mice significantly reduces arthritis symptom by inhibiting p-p65 level and decreasing serum level of IL-6, IL-1β and TNF-α. Moreover, our study is the first time to reveal new immunomodulatory effects of DAP on RA, which provides a pharmacological basis for new clinical applications of DAP for other immune-related diseases except to bacterial infections.

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

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

Comparison of daptomycin and glycopeptide efficacy and safety for the treatment of Gram-positive infections: a systematic review and meta-analysis

BACKGROUND

The indications of daptomycin have been extended to off-label indications including prosthesis-related infection, and bone and joint infection (BJI). However, efficacy and safety have not been thoroughly demonstrated compared with the standard of care. This systematic review and meta-analysis aimed to compare the treatment effect of daptomycin and glycopeptides for complicated infections.

MATERIALS AND METHODS

MEDLINE, Embase and Web of Science were searched for randomized controlled trials (RCTs) comparing daptomycin and standard of care for Gram-positive infections, published until 30 June 2021. The primary outcome was defined as all-cause mortality. Secondary outcomes were clinical and microbiological success. The main safety outcome was any severe adverse event (SAE) (grade  ≥3).

RESULTS

Overall, eight RCTs were included in the meta-analysis, totalling 1095 patients. Six (75%) were in complicated skin and soft-structure infections, one (12.5%) in bacteraemia and one (12.5%) in a BJI setting. Six RCTs used vancomycin as a comparator and two used either vancomycin or teicoplanin. All-cause mortality and clinical cure were not different between groups. The microbiological cure rate was superior in patients who received daptomycin [risk ratio (RR) = 1.17 (95% CI: 1.01-1.35)]. The risk of SAEs [RR = 0.57 (95% CI: 0.36-0.90)] was lower in the daptomycin arm.

CONCLUSIONS

While daptomycin is associated with a significantly lower risk of SAEs and a better microbiological eradication, substantial uncertainty remains about the best treatment strategy in the absence of good-quality evidence, especially in bacteraemia and endocarditis where further RCTs should be conducted.

New aspects of lipopeptide-incorporated nanoparticle synthesis and recent advancements in biomedical and environmental sciences: a review

The toxicity of metal nanoparticles has introduced promising research in the current scenario since an enormous number of people have been potentially facing this problem in the world. The extensive attention on green nanoparticle synthesis has been focussed on as a vital step in bio-nanotechnology to improve biocompatibility, biodegradability, eco-friendliness, and huge potential utilization in various environmental and clinical assessments. Inherent influence on the study of green nanoparticles plays a key role to synthesize the controlled and surface-influenced molecule by altering the physical, chemical, and biological assets with the provision of various precursors, templating/co-templating agents, and supporting solvents. However, in this article, the dominant characteristics of several kinds of lipopeptide biosurfactants are discussed to execute a critical study of factors affecting synthesis procedure and applications. The recent approaches of metal, metal oxide, and composite nanomaterial synthesis have been deliberated as well as the elucidation of the reaction mechanism. Furthermore, this approach shows remarkable boosts in the production of nanoparticles with the very less employed harsh and hazardous processes as compared to chemical or physical method-based nanoparticle synthesis. This study also shows that the advances in strain selection for green nanoparticle production could be a worthwhile and strong economical approach in futuristic medical science research.

Data mining for adverse drug reaction signals of daptomycin based on real-world data: a disproportionality analysis of the US Food and Drug Administration adverse event reporting system

BACKGROUND

Previous reports on daptomycin's adverse drug reactions (ADRs) have been insufficient, often because of limited data. Pharmacovigilance risk signal detection is innovative and has been applied to the safety monitoring and reevaluation of drugs post-marketing.

AIM

The study aimed to promote safe daptomycin prescribing by mining and evaluating the daptomycin ADR signals from the US Food and Drug Administration Adverse Event Reporting System (FAERS).

METHOD

A disproportionality analysis (reporting odds ratio ROR and proportional reporting ratio PRR) was utilized for FAERS data mining from the first quarter of 2004 to the second quarter of 2021 (the most recent quarterly data at the time of the study). Preferred Terms of ADR reports were categorized by System Organ Class (SOC) based on the Medical Dictionary for Regulatory Activities.

RESULTS

This study retrieved 12,221 cases within the reporting period. A total of 140 repetitive signals were obtained by ROR and PRR, of which 53 new ADR signals were not recorded in the drug labels/datasheets. The top three ADR reports were "blood creatine phosphokinase elevation" (ROR, 56.66, 95% confidence interval (CI) 51.07-62.87, PRR 51.94), "eosinophilic pneumonia" (ROR 696.71, 95%CI 603.21-804.70, PRR 657.57), and "rhabdomyolysis" (ROR 22.85, 95%CI 19.94-26.18, PRR 21.83). The highest ROR of "antimicrobial susceptibility test resistant" was found at 9808.14. Reports of rare adverse events, such as "necrotizing fasciitis and compartment syndrome," have emerged. The significant SOCs were "Infections and Infestations" and "Investigations."

CONCLUSION

New daptomycin ADR signals were detected. Clinicians should monitor these potential ADRs in patients receiving daptomycin.

Ion Exchange Biomaterials to Capture Daptomycin and Prevent Resistance Evolution in Off-Target Bacterial Populations

Daptomycin (DAP), a cyclic anionic lipopeptide antibiotic, is among the last resorts to treat multidrug-resistant Gram-positive bacterial infections, caused by vancomycin-resistant Enterococcus faecium or methicillin-resistant Staphylococcus aureus. DAP is administered intravenously, and via biliary excretion, ∼5-10% of the intravenous DAP dose arrives in the gastrointestinal (GI) tract where it drives resistance evolution in the off-target populations of E. faecium bacteria. Previously, we have shown in vivo that the oral administration of cholestyramine, an ion exchange biomaterial (IXB) sorbent, prevents DAP treatment from enriching DAP resistance in the populations of E. faecium shed from mice. Here, we investigate the biomaterial-DAP interfacial interactions to uncover the antibiotic removal mechanisms. The IXB-mediated DAP capture from aqueous media was measured in controlled pH/electrolyte solutions and in the simulated intestinal fluid (SIF) to uncover the molecular and colloidal mechanisms of DAP removal from the GI tract. Our findings show that the IXB electrostatically adsorbs the anionic antibiotic via a time-dependent diffusion-controlled process. Unsteady-state diffusion-adsorption mass balance describes the dynamics of adsorption well, and the maximum removal capacity is beyond the electric charge stoichiometric ratio because of DAP self-assembly. This study may open new opportunities for optimizing cholestyramine adjuvant therapy to prevent DAP resistance, as well as designing novel biomaterials to remove off-target antibiotics from the GI tract.

Proteome profiling of evolved methicillin-resistant Staphylococcus aureus strains with distinct daptomycin tolerance and resistance phenotypes

Methicillin-resistant Staphylococcus aureus (MRSA) is a highly dangerous pathogen, and daptomycin has been increasingly used to treat its infections in clinics. Recently, several groups have shown that tolerance and resistance of microbes can evolve rapidly under cyclic antibiotic exposure. We have previously shown that the same tolerance and resistance development occurs in MRSA treated with daptomycin in an adaptive laboratory evolution (ALE) experiment. In the present study, we performed proteomic analysis to compare six daptomycin-tolerant and resistant MRSA strains that were evolved from the same ancestral strain. The strain with a higher tolerance level than the others had the most different proteome and response to antibiotic treatment, resembling those observed in persister cells, which are small subpopulations of bacteria that survive lethal antibiotics treatment. By comparing the proteome changes across strains with similar phenotypes, we identified the key proteins that play important roles in daptomycin tolerance and resistance in MRSA. We selected two candidates to be confirmed by gene overexpression analysis. Overexpression of EcsA1 and FabG, which were up-regulated in all of the tolerant evolved strains, led to increased daptomycin tolerance in wild-type MRSA. The proteomics data also suggested that cell wall modulations were implicated in both resistance and tolerance, but in different ways. While the resistant strains had peptidoglycan changes and a more positive surface charge to directly repel daptomycin, the tolerant strains possessed different cell wall changes that do not involve the peptidoglycan nor alterations of the surface charge. Overall, our study showed the differential proteome profiles among multiple tolerant and resistant strains, pinpointed the key proteins for the two phenotypes and revealed the differences in cell wall modulations between the daptomycin-tolerant/resistant strains.

Mutation in the Two-Component System Regulator YycH Leads to Daptomycin Tolerance in Methicillin-Resistant Staphylococcus aureus upon Evolution with a Population Bottleneck

Adaptive laboratory evolution (ALE) is a useful tool to study the evolution of antibiotic tolerance in bacterial populations under diverse environmental conditions. The role of population bottlenecks in the evolution of tolerance has been investigated in Escherichia coli, but not in a more clinically relevant pathogen, methicillin-resistant Staphylococcus aureus (MRSA). In this study, we used ALE to evolve MRSA under repetitive daptomycin treatment and incorporated population bottlenecks following antibiotic exposure. We observed that the populations finally attained a tolerance mutation in the yycH gene after 2 weeks of evolution with population bottlenecks, and additional mutations in yycI and several other genes further increased the tolerance level. The tolerant populations also became resistant to another glycopeptide antibiotic, vancomycin. Through proteomics, we showed that yycH and yycI mutations led to the loss of function of the proteins and downregulated the WalKR two-component system and the downstream players, including the autolysin Atl and amidase Sle1, which are important for cell wall metabolism. Overall, our study offers new insights into the evolution of daptomycin tolerance under population bottlenecking conditions, which are commonly faced by pathogens during infection; the study also identified new mutations conferring daptomycin tolerance and revealed the proteome alterations in the evolved tolerant populations. IMPORTANCE Although population bottlenecks are known to influence the evolutionary dynamics of microbial populations, how such bottlenecks affect the evolution of tolerance to antibiotics in a clinically relevant methicillin-resistant S. aureus (MRSA) pathogen are still unclear. Here, we performed in vitro evolution of MRSA under cyclic daptomycin treatment and applied population bottlenecks following the treatment. We showed that under these experimental conditions, MRSA populations finally attained mutations in yycH, yycI, and several other genes that led to daptomycin tolerance. The discovered yycH and yycI mutations caused early termination of the genes and loss of function of the proteins, and they subsequently downregulated the expression of proteins controlled by the WalKR two-component system, such as Atl and Sle1. In addition, we compared our proteomics data with multiple studies on distinct daptomycin-tolerant MRSA mutants to identify proteins with a consistent expression pattern that could serve as biological markers for daptomycin tolerance in MRSA.

Daptomycin Population Pharmacokinetics in Patients Affected by Severe Gram-Positive Infections: An Update

Daptomycin pharmacokinetics may not depend on renal function only and it significantly differs between healthy volunteers and severely ill patients. Herein, we propose a population pharmacokinetics model based on 424 plasma daptomycin concentrations collected from 156 patients affected by severe Gram-positive infections during a routine therapeutic drug monitoring protocol. Model building and validation were performed using NONMEM 7.2 (ICON plc), Xpose4 and Perl-speaks-to-NONMEM. The final pop-PK model was a one-compartment first-order elimination model, with a 2.7% IIV for drug clearance (Cl), influence of creatinine clearance on drug clearance and of sex on distribution volume. After model validation, we simulated 10,000 patients with the Monte-Carlo method to predict the efficacy and tolerability of different daptomycin daily dosages. For the most common 6 mg/kg daily dose, the simulated probability of overcoming the toxic minimum concentration (24.3 mg/L) was 14.8% and the efficacy (expressed as a cumulative fraction of response) against methicillin-resistant S. aureus, S. pneumoniae and E. faecium was 95.77%, 99.99% and 68%, respectively. According to the model-informed precision dosing paradigm, pharmacokinetic models such as ours could help clinicians to perform patient-tailored antimicrobial dosing and maximize the odds of therapy success without neglecting toxicity risks.

Pharmacokinetics and pharmacodynamics of peptide antibiotics

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

Polymyxin and lipopeptide antibiotics: membrane-targeting drugs of last resort

The polymyxin and lipopeptide classes of antibiotics are membrane-targeting drugs of last resort used to treat infections caused by multi-drug-resistant pathogens. Despite similar structures, these two antibiotic classes have distinct modes of action and clinical uses. The polymyxins target lipopolysaccharide in the membranes of most Gram-negative species and are often used to treat infections caused by carbapenem-resistant species such as Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa. By contrast, the lipopeptide daptomycin requires membrane phosphatidylglycerol for activity and is only used to treat infections caused by drug-resistant Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. However, despite having distinct targets, both antibiotic classes cause membrane disruption, are potently bactericidal in vitro and share similarities in resistance mechanisms. Furthermore, there are concerns about the efficacy of these antibiotics, and there is increasing interest in using both polymyxins and daptomycin in combination therapies to improve patient outcomes. In this review article, we will explore what is known about these distinct but structurally similar classes of antibiotics, discuss recent advances in the field and highlight remaining gaps in our knowledge.

The role of CDHR3 in susceptibility to otitis media

Otitis media (OM) is common in young children and can cause hearing loss and speech, language, and developmental delays. OM has high heritability; however, little is known about OM-related molecular and genetic processes. CDHR3 was previously identified as a locus for OM susceptibility, but to date, studies have focused on how the CDHR3 p.Cys529Tyr variant increases epithelial binding of rhinovirus-C and risk for lung or sinus pathology. In order to further delineate a role for CDHR3 in OM, we performed the following: exome sequencing using DNA samples from OM-affected individuals from 257 multi-ethnic families; Sanger sequencing, logistic regression and transmission disequilibrium tests for 407 US trios or probands with OM; 16S rRNA sequencing and analysis for middle ear and nasopharyngeal samples; and single-cell RNA sequencing and differential expression analyses for mouse middle ear. From exome sequence data, we identified a novel pathogenic CDHR3 splice variant that co-segregates with OM in US and Finnish families. Additionally, a frameshift and six missense rare or low-frequency variants were identified in Finnish probands. In US probands, the CDHR3 p.Cys529Tyr variant was associated with the absence of middle ear fluid at surgery and also with increased relative abundance of Lysobacter in the nasopharynx and Streptomyces in the middle ear. Consistent with published data on airway epithelial cells and our RNA-sequence data from human middle ear tissues, Cdhr3 expression is restricted to ciliated epithelial cells of the middle ear and is downregulated after acute OM. Overall, these findings suggest a critical role for CDHR3 in OM susceptibility. KEY MESSAGES: • Novel rare or low-frequency CDHR3 variants putatively confer risk for otitis media. • Pathogenic variant CDHR3 c.1653 + 3G > A was found in nine families with otitis media. • CDHR3 p.Cys529Tyr was associated with lack of effusion and bacterial otopathogens. • Cdhr3 expression was limited to ciliated epithelial cells in mouse middle ear. • Cdhr3 was downregulated 3 h after infection of mouse middle ear.

The Global Prevalence of Daptomycin, Tigecycline, and Linezolid-Resistant Enterococcus faecalis and Enterococcus faecium Strains From Human Clinical Samples: A Systematic Review and Meta-Analysis

Background and Aim: The predominant species of the Enterococcus, Enterococcus faecalis (E. faecalis) and Enterococcus faecium (E. faecium) cause great variety of infections. Therefore, the expansion of antimicrobial resistance in the Enterococcus is one of the most important global concerns. This study was conducted to investigate the prevalence of resistance to linezolid, tigecycline, and daptomycin among enterococcal strains isolated from human clinical specimens worldwide.

Methods: Several databases including Web of Science, EMBASE, and Medline (via PubMed), were carefully searched and reviewed for original research articles available in databases and published between 2000 and 2020. A total of 114 studies worldwide that address E. faecalis and E. faecium resistance to linezolid, tigecycline, and daptomycin were analyzed by STATA software.

Results: The overall prevalence of antibiotic-resistant E. faecalis and E. faecium was reported to be 0.9 and 0.6%, respectively. E. faecalis and E. faecium were more resistant to the linezolid (2.2%) and daptomycin (9%), respectively. The prevalence of tigecyline-resistant E. facium (1%) strains was higher than E. faecalis strains (0.3%). Accordingly, the prevalence of linezolid-resistant E. faecalis was higher in Asia (2.8%), while linezolid-resistant E. faecium was higher in the America (3.4%). Regarding tigecycline-resistance, a higher prevalence of E. faecalis (0.4%) and E. faecium (3.9%) was reported in Europe.

Conclusion: In conclusion, this meta-analysis shows that there is an emerging resistance in Enterococcus strains. Despite the rising resistance of enterococci to antibiotics, our results demonstrate that tigecycline, daptomycin, and linezolid can still be used for the treatment of enterococcal infections worldwide.

Advances in pharmacotherapy for diabetic foot osteomyelitis

Introduction: The diagnosis of diabetic foot osteomyelitis (DFO) is usually clinical. Its severity is related to the location and depth of the lesion, and the presence of necrosis or gangrene. The aetiology of diabetic foot osteomyelitis (DFO) is usually polymicrobial, and DFO is often associated with chronic or recurring ulceration.Areas covered: We built on the  International Working Group on the Diabetic Foot (IWGDF) guidelines on the management of diabetic foot infection, providing an outline of the current and new concepts in pharmacotherapy in DFO. We assess future strategies in both medical, surgical and combination management of DFO.Expert opinion: Surgical removal of infected bone is considered as the standard treatment, but a medical approach of certain selected situations has now proven efficacy in selected patients. The combination of new modalities in local antibiotic delivery may provide better long-term solutions and more lasting remission and avoid the disadvantages of prolonged systemic antibiotics.

Exploring the possible targeting strategies of liposomes against methicillin-resistant Staphylococcus aureus (MRSA)

Multi antibiotic-resistant bacterial infections are on the rise due to the overuse of antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the pathogens listed under the category of serious threats where vancomycin remains the mainstay treatment despite the availability of various antibacterial agents. Recently, decreased susceptibility to vancomycin from clinical isolates of MRSA has been reported and has drawn worldwide attention as it is often difficult to overcome and leads to increased medical costs, mortality, and longer hospital stays. Development of antibiotic delivery systems is often necessary to improve bioavailability and biodistribution, in order to reduce antibiotic resistance and increase the lifespan of antibiotics. Liposome entrapment has been used as a method to allow higher drug dosing apart from reducing toxicity associated with drugs. The surface of the liposomes can also be designed and enhanced with drug-release properties, active targeting, and stealth effects to prevent recognition by the mononuclear phagocyte system, thus enhancing its circulation time. The present review aimed to highlight the possible targeting strategies of liposomes against MRSA bacteremia systemically while investigating the magnitude of this effect on the minimum inhibitory concentration level.

Label-free proteomic dissection on dptP-deletion mutant uncovers dptP involvement in strain growth and daptomycin tolerance of Streptomyces roseosporus

Daptomycin (DAP) is a novel microbial lipopeptide antibiotic synthesized by the DAP biosynthetic gene cluster dpt of Streptomyces roseosporus (S. roseosporus). DptP gene locates upstream of dpt and confers DAP resistance to Streptomyces ambofaciens (S. ambofaciens). So far, the biological functions of dptP gene for S. roseosporus growth are still completely uncovered. We performed label‐free quantification proteomic dissections with loss‐ and gain‐of‐function experiments to decipher dptP‐involved functions. Deletion of dptP gene activated energy metabolism and metabolism of secondary metabolites pathways and enhanced the transcription levels and protein abundance of key members of the dpt cluster. Whereas dptP deletion inhibited transport/signal transduction and drug resistance pathways and protein abundance of cell division‐relative proteins, subsequently decreased mycelia cell growth rate. S. roseosporus strain with dptP deletion was more sensitive to DAP treatment compared to the wild type. In contrast, overexpression of dptP gene decreased transcription levels of DAP biosynthetic genes and enhanced growth rate of Streptomcyes strain upon elevated culture temperature and DAP supplementation. Taken together, dptP gene contributes to Streptomcyes primary growth under elevated temperature and DAP treatment, whereas it plays negative roles on metabolism of secondary metabolites and transcription of DAP biosynthetic genes.

Multitarget Approaches against Multiresistant Superbugs

Despite efforts to develop new antibiotics, antibacterial resistance still develops too fast for drug discovery to keep pace. Often, resistance against a new drug develops even before it reaches the market. This continued resistance crisis has demonstrated that resistance to antibiotics with single protein targets develops too rapidly to be sustainable. Most successful long-established antibiotics target more than one molecule or possess targets, which are encoded by multiple genes. This realization has motivated a change in antibiotic development toward drug candidates with multiple targets. Some mechanisms of action presuppose multiple targets or at least multiple effects, such as targeting the cytoplasmic membrane or the carrier molecule bactoprenol phosphate and are therefore particularly promising. Moreover, combination therapy approaches are being developed to break antibiotic resistance or to sensitize bacteria to antibiotic action. In this Review, we provide an overview of antibacterial multitarget approaches and the mechanisms behind them.

An evidence based narrative review on treatment of diabetic foot osteomyelitis

OBJECTIVE

The diagnosis of diabetic food infection is usually clinical, and its severity is related to location and depth of the lesion, and the presence of necrosis or gangrene. Osteomyelitis of the foot and ankle can be extremely debilitating, and, in the preantibiotic era acute staphylococcal osteomyelitis carried a mortality rate of 50%. The microbiology of diabetic foot osteomyelitis (DFO) is usually polymicrobial. Indeed, gram-negative and gram-positive bacilli can be identified using molecular techniques applied to bone biopsies compared to conventional techniques. The aim of the present study is to report a complete overview regarding medical and surgical management of diabetic foot osteomyelitis (DFO) in combination or alone.

MATERIALS AND METHODS

We performed a search in PubMed and Scopus electronic databases (up to January 2019) of articles assessing the epidemiology, diagnostic strategy and pharmacological treatment of diabetic foot infection. In the search strategy, we used various combinations of the following key terms: infection, orthopaedic, diabetic foot, management, DFO.

RESULTS

This article discusses the definition, epidemiology, microbiological assessment, clinical evaluation, pharmacological and surgical management and a comparison between them, of DFO. After the initial literature search and removal of duplicate records, a total of 756 potentially relevant citations were identified. After a further screening and according to the inclusion criteria, a total of 65 articles were included in the present review.

CONCLUSION

The association of antibiotic and surgical therapy seems to be more effective compared to each one alone. The lack of comparison studies and randomized controlled trials makes it difficult to give information about the efficacy of the different management therapies.

Discovery of Kynurenines Containing Oligopeptides as Potent Opioid Receptor Agonists

Kynurenine (kyn) and kynurenic acid (kyna) are well-defined metabolites of tryptophan catabolism collectively known as "kynurenines", which exert regulatory functions in host-microbiome signaling, immune cell response, and neuronal excitability. Kynurenine containing peptides endowed with opioid receptor activity have been isolated from natural organisms; thus, in this work, novel opioid peptide analogs incorporating L-kynurenine (L-kyn) and kynurenic acid (kyna) in place of native amino acids have been designed and synthesized with the aim to investigate the biological effect of these modifications. The kyna-containing peptide (KA1) binds selectively the m-opioid receptor with a Ki = 1.08 ± 0.26 (selectivity ratio m/d/k = 1:514:10000), while the L-kyn-containing peptide (K6) shows a mixed binding affinity for m, d, and k-opioid receptors, with efficacy and potency (E_max = 209.7 + 3.4%; LogEC₅₀ = -5.984 + 0.054) higher than those of the reference compound DAMGO. This novel oligopeptide exhibits a strong antinociceptive effect after i.c.v. and s.c. administrations in in vivo tests, according to good stability in human plasma (t_1/2 = 47 min).

More Than a Pore: A Current Perspective on the In Vivo Mode of Action of the Lipopeptide Antibiotic Daptomycin

Daptomycin is a cyclic lipopeptide antibiotic, which was discovered in 1987 and entered the market in 2003. To date, it serves as last resort antibiotic to treat complicated skin infections, bacteremia, and right-sided endocarditis caused by Gram-positive pathogens, most prominently methicillin-resistant Staphylococcus aureus. Daptomycin was the last representative of a novel antibiotic class that was introduced to the clinic. It is also one of the few membrane-active compounds that can be applied systemically. While membrane-active antibiotics have long been limited to topical applications and were generally excluded from systemic drug development, they promise slower resistance development than many classical drugs that target single proteins. The success of daptomycin together with the emergence of more and more multi-resistant superbugs attracted renewed interest in this compound class. Studying daptomycin as a pioneering systemic membrane-active compound might help to pave the way for future membrane-targeting antibiotics. However, more than 30 years after its discovery, the exact mechanism of action of daptomycin is still debated. In particular, there is a prominent discrepancy between in vivo and in vitro studies. In this review, we discuss the current knowledge on the mechanism of daptomycin against Gram-positive bacteria and try to offer explanations for these conflicting observations.