Oritavancin: A New Lipoglycopeptide Antibiotic in the Treatment of Gram-Positive Infections

Unearthing naturally-occurring cyclic antibacterial peptides and their structural optimization strategies

Natural products with antibacterial activity are highly desired globally to combat against multidrug-resistant (MDR) bacteria. Antibacterial peptide (ABP), especially cyclic ABP (CABP), is one of the abundant classes. Most of them were isolated from microbes, demonstrating excellent bactericidal effects. With the improved proteolytic stability, CABPs are normally considered to have better druggability than linear peptides. However, most clinically-used CABP-based antibiotics, such as colistin, also face the challenges of drug resistance soon after they reached the market, urgently requiring the development of next-generation succedaneums. We present here a detail review on the novel naturally-occurring CABPs discovered in the past decade and some of them are under clinical trials, exhibiting anticipated application potential. According to their chemical structures, they were broadly classified into five groups, including (i) lactam/lactone-based CABPs, (ii) cyclic lipopeptides, (iii) glycopeptides, (iv) cyclic sulfur-rich peptides and (v) multiple-modified CABPs. Their chemical structures, antibacterial spectrums and proposed mechanisms are discussed. Moreover, engineered analogs of these novel CABPs are also summarized to preliminarily analyze their structure-activity relationship. This review aims to provide a global perspective on research and development of novel CABPs to highlight the effectiveness of derivatives design in identifying promising antibacterial agents. Further research efforts in this area are believed to play important roles in fighting against the multidrug-resistance crisis.

Rational construction of a high-quality and high-efficiency biosynthetic system and fermentation optimization for A82846B based on combinatorial strategies in Amycolatopsis orientalis

BACKGROUND

Oritavancin is a new generation of semi-synthetic glycopeptide antibiotics against Gram-positive bacteria, which served as the first and only antibiotic with a single-dose therapeutic regimen to treat ABSSSI. A naturally occurring glycopeptide A82846B is the direct precursor of oritavancin. However, its application has been hampered by low yields and homologous impurities. This study established a multi-step combinatorial strategy to rationally construct a high-quality and high-efficiency biosynthesis system for A82846B and systematically optimize its fermentation process to break through the bottleneck of microbial fermentation production.

RESULTS

Firstly, based on the genome sequencing and analysis, we deleted putative competitive pathways and constructed a better A82846B-producing strain with a cleaner metabolic background, increasing A82846B production from 92 to 174 mg/L. Subsequently, the PhiC31 integrase system was introduced based on the CRISPR-Cas12a system. Then, the fermentation level of A82846B was improved to 226 mg/L by over-expressing the pathway-specific regulator StrR via the constructed PhiC31 system. Furthermore, overexpressing glycosyl-synthesis gene evaE enhanced the production to 332 mg/L due to the great conversion of the intermediate to target product. Finally, the scale-up production of A82846B reached 725 mg/L in a 15 L fermenter under fermentation optimization, which is the highest reported yield of A82846B without the generation of homologous impurities.

CONCLUSION

Under approaches including blocking competitive pathways, inserting site-specific recombination system, overexpressing regulator, overexpressing glycosyl-synthesis gene and optimizing fermentation process, a multi-step combinatorial strategy for the high-level production of A82846B was developed, constructing a high-producing strain AO-6. The combinatorial strategies employed here can be widely applied to improve the fermentation level of other microbial secondary metabolites, providing a reference for constructing an efficient microbial cell factory for high-value natural products.

Navigating Antibacterial Frontiers: A Panoramic Exploration of Antibacterial Landscapes, Resistance Mechanisms, and Emerging Therapeutic Strategies

The development of effective antibacterial solutions has become paramount in maintaining global health in this era of increasing bacterial threats and rampant antibiotic resistance. Traditional antibiotics have played a significant role in combating bacterial infections throughout history. However, the emergence of novel resistant strains necessitates constant innovation in antibacterial research. We have analyzed the data on antibacterials from the CAS Content Collection, the largest human-curated collection of published scientific knowledge, which has proven valuable for quantitative analysis of global scientific knowledge. Our analysis focuses on mining the CAS Content Collection data for recent publications (since 2012). This article aims to explore the intricate landscape of antibacterial research while reviewing the advancement from traditional antibiotics to novel and emerging antibacterial strategies. By delving into the resistance mechanisms, this paper highlights the need to find alternate strategies to address the growing concern.

Efficacy of oritavancin and nisin alone and their combination against vancomycin resistant enterococci strains in hospitalized patients in Turkiye

PURPOSE

Vancomycin-Resistant Enterococci (VREs) have emerged and become a problem that threatens the health of hospitalized patients. VRE can cause different serious infections of the urinary tract, the bloodstream, wound and other body sites. VREs are resistant to multiple antibiotics and treatment options are very limited. We aimed to investigate the efficacy of oritavancin and nisin alone and their combination against VRE strains.

METHODS

VRE isolates from rectal swabs of hospitalized patients were identified by conventional and commercial methods. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of oritavancin and nisin against VRE strains were determined. The synergistic effect of both agent combinations was examined by the Checkerboard test.

RESULTS

All VRE strains were identifined as Enterococcus faecium. The MIC value of oritavancin was found in the range of 0.015-0.24 ​μg/mL; in which 48 strains were susceptible (≤0.12 ​μg/mL) and two strains were resistant (>0.12 ​μg/mL). The MBC of oritavancin was determined in the range of 0.06-3.84 ​μg/mL. The MIC of nisin was found in the range of 12.5-100 ​μg/mL; in which 32 strains were susceptible (≤50 ​μg/mL) and 18 strains were resistant (>50 ​μg/mL). MBC of nisin was determined in the range of 25-800 ​μg/mL. Two oritavancin resistant strains were displayed indifference effect, whereas from 18 nisin resistant strains, 11 showed indifference, and seven displayed synergistic effect. Thirty-eight out of 48 strains which were sensitive to oritavancin showed indifference and 10 revealed synergistic effect, whereas 29 of 32 strains which were sensitive to nisin showed indifference and three had synergistic effect.

CONCLUSIONS

A synergistic combination of oritavansin and nisin was detected in 20 strains (40%), Our study is the first study in Turkiye.

Oritavancin in vitro activity against Gram-positive organisms from European medical centers: a 10-year longitudinal overview from the SENTRY Antimicrobial Surveillance Program (2010-2019)

To assess oritavancin in vitro activity against clinically relevant Gram-positive pathogens in European (EU) hospitals, a total of 51,531 consecutive and unique clinical isolates collected in 2010-2019 were evaluated. All isolates were tested by CLSI broth microdilution methods. The key resistance phenotypes differed considerably between Eastern Europe (E-EU) and Western Europe (W-EU), respectively: methicillin-resistant (MR) Staphylococcus aureus 27.7%/22.9%; multidrug resistant (MDR) S. aureus, 19.7%/15.2%; MR coagulase-negative staphylococci, 77.3%/61.9%; vancomycin-resistant enterococci (E. faecium), 44.2%/20.9%; and MDR E. faecium, 63.8%/55.4%. There were no substantive differences in oritavancin minimum inhibitory concentration (MIC) values for the different species/organism groups over time or by EU region. Oritavancin inhibited 99.9% and 99.1% of all S. aureus and coagulase-negative staphylococci at 0.12 mg/L, respectively, and all isolates of E. faecalis and E. faecium at ≤0.5 mg/L. Oritavancin susceptibility rates against β-hemolytic and Viridans group streptococci isolates were 98.1% and 99.4%, respectively. Oritavancin had potent activity in vitro against this contemporary collection of European Gram-positive isolates from 2010 to 2019.

Design methods for antimicrobial peptides with improved performance

The recalcitrance of pathogens to traditional antibiotics has made treating and eradicating bacterial infections more difficult. In this regard, developing new antimicrobial agents to combat antibiotic-resistant strains has become a top priority. Antimicrobial peptides (AMPs), a ubiquitous class of naturally occurring compounds with broad-spectrum antipathogenic activity, hold significant promise as an effective solution to the current antimicrobial resistance (AMR) crisis. Several AMPs have been identified and evaluated for their therapeutic application, with many already in the drug development pipeline. Their distinct properties, such as high target specificity, potency, and ability to bypass microbial resistance mechanisms, make AMPs a promising alternative to traditional antibiotics. Nonetheless, several challenges, such as high toxicity, lability to proteolytic degradation, low stability, poor pharmacokinetics, and high production costs, continue to hamper their clinical applicability. Therefore, recent research has focused on optimizing the properties of AMPs to improve their performance. By understanding the physicochemical properties of AMPs that correspond to their activity, such as amphipathicity, hydrophobicity, structural conformation, amino acid distribution, and composition, researchers can design AMPs with desired and improved performance. In this review, we highlight some of the key strategies used to optimize the performance of AMPs, including rational design and de novo synthesis. We also discuss the growing role of predictive computational tools, utilizing artificial intelligence and machine learning, in the design and synthesis of highly efficacious lead drug candidates.

Oritavancin vs Standard of Care for Treatment of Nonendovascular Gram-Positive Bloodstream Infections

Background

Data is limited comparing oritavancin (ORT) to the standard-of-care (SOC) for the treatment gram-positive blood stream infections (BSI).

Methods

This was a retrospective study of all patients in the Veteran's Affairs Health Care System treated with at least 1 dose of oritavancin or at least 5 days of vancomycin, daptomycin, ceftaroline, ampicillin, ampicillin-sulbactam, nafcillin, oxacillin, or cefazolin for a documented gram-positive BSI from 1 January 2015 to 30 June 2021. Patients with polymicrobial blood cultures or positive cultures from other sites were included if the organisms were sensitive to the incident antimicrobial; no concomitant antimicrobials could be used once the incident agent was started. Individuals were also excluded if they were diagnosed with endocarditis, had a neutrophil count 96-hours of treatment before the incident antimicrobial was started.The primary composite outcome was clinical failure, defined as all-cause mortality within 30-days from the end of therapy, or blood cultures positive for the incident organisms ≥72 hours after administration of the first dose and ≤30 days after the administration of the final dose of the study antimicrobial, or any drug or line-related readmissions within 30-days of hospital discharge.

Results

Two hundred-forty patients were identified for screening with 96 meeting criteria (27 in ORT and 69 in SOC groups). Baseline characteristics were generally balanced between groups except more patients in the ORT group received >96-hours of treatment before the incident antimicrobial was started (70.3% (19/27) vs 13.04% 9/69); P < .001). The pathogen most prevalent was methicillin susceptible Staphylococcus aureus (MSSA) (ORT 33.3% (9/27) vs SOC 46.4% (32/69)). Clinical failure occurred in 7.4% (2/27) in the ORT group and 17.4% (12/69) in SOC (P = .34). No components of the primary outcome were significantly different between groups, but AKI did occur more commonly in the SOC group (27.5% (19/69) vs 3.7% (1/27); P = .01).

Conclusions

ORT appears to be a safe and effective option when directly compared to the SOC for non-endocarditis BSIs.

New Antimicrobials for Gram-Positive Sustained Infections: A Comprehensive Guide for Clinicians

Antibiotic resistance is a public health problem with increasingly alarming data being reported. Gram-positive bacteria are among the protagonists of severe nosocomial and community infections. The objective of this review is to conduct an extensive examination of emerging treatments for Gram-positive infections including ceftobiprole, ceftaroline, dalbavancin, oritavancin, omadacycline, tedizolid, and delafloxacin. From a methodological standpoint, a comprehensive analysis on clinical trials, molecular structure, mechanism of action, microbiological targeting, clinical use, pharmacokinetic/pharmacodynamic features, and potential for therapeutic drug monitoring will be addressed. Each antibiotic paragraph is divided into specialized microbiological, clinical, and pharmacological sections, including detailed and appropriate tables. A better understanding of the latest promising advances in the field of therapeutic options could lead to the development of a better approach in managing antimicrobial therapy for multidrug-resistant Gram-positive pathogens, which increasingly needs to be better stratified and targeted.

Structural diversity, biosynthesis, and biological functions of lipopeptides from Streptomyces

Covering: up to 2022Streptomyces are ubiquitous in terrestrial and marine environments, where they display a fascinating metabolic diversity. As a result, these bacteria are a prolific source of active natural products. One important class of these natural products is the nonribosomal lipopeptides, which have diverse biological activities and play important roles in the lifestyle of Streptomyces. The importance of this class is highlighted by the use of related antibiotics in the clinic, such as daptomycin (tradename Cubicin). By virtue of recent advances spanning chemistry and biology, significant progress has been made in biosynthetic studies on the lipopeptide antibiotics produced by Streptomyces. This review will serve as a comprehensive guide for researchers working in this multidisciplinary field, providing a summary of recent progress regarding the investigation of lipopeptides from Streptomyces. In particular, we highlight the structures, properties, biosynthetic mechanisms, chemical and chemoenzymatic synthesis, and biological functions of lipopeptides. In addition, the application of genome mining techniques to Streptomyces that have led to the discovery of many novel lipopeptides is discussed, further demonstrating the potential of lipopeptides from Streptomyces for future development in modern medicine.

Single Modification at the N-Terminus of Norvancomycin to Combat Drug-Resistant Gram-Positive Bacteria

In the arsenal of glycopeptide antibiotics, norvancomycin, which differs from vancomycin by a single methyl group, has received much less attention. Facing the risks of serious antibiotic resistance and even the collapse of last-line defenses, we designed and synthesized 40 novel norvancomycin derivatives to combat the threat. 32 compounds are single N-terminally modified derivatives generated through simple and efficient methods. Diversity at the N-terminus was greatly enriched, mainly by lipophilic attachment and strategies for the introduction of lipo-sulfonium moieties for extensive structure-activity relationship analysis. The first incorporation of a sulfonium moiety into the norvancomycin structure gave rise to compounds that exhibited 4- to 2048-fold higher activity against vancomycin-resistant bacteria VISA and VRE. This N-terminal modification for norvancomycin provides an alternatively useful and promising strategy to restore the antibacterial activity of glycopeptide antibiotics against resistant bacteria, highlighting the same importance of the N-terminal site as well as the vancosamine position, which is worth further study and development.

Current and emerging drug treatment strategies to tackle invasive community-associated methicillin-resistant Staphylococcus aureus (MRSA) infection: what are the challenges?

INTRODUCTION

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections represent a leading cause of purulent skin and soft tissue infections in some geographical regions. Traditionally, 'old antibiotics' such as trimethoprim-sulfamethoxazole, tetracyclines, clindamycin, chloramphenicol,vancomycin, and teicoplanin have been used to treat these infections, but these were often associated with low efficacy and excessive side effects and toxicity, especially nephrotoxicity. Along with the development of new compounds, the last decade has seen substantial improvements in the management of CA-MRSA infections.

AREAS COVERED

In this review, the authors discuss the current and emerging drug treatment strategies to tackle invasive CA-MRSA infections. Articles reported in this review were selected from through literature searches using the PubMed database.

EXPERT OPINION

The availability of new drugs showing a potent in vitro activity against CA-MRSA represents a unique opportunity to face the threat of resistance while potentially reducing toxicity. All these compounds represent promising options to enhance our antibiotic armamentarium. However, data regarding the use of these new drugs in real-life studies are limited and their best placement in therapy and in terms of optimization of medical resources and balance of cost-effectiveness requires further investigation.

MRSA compendium of epidemiology, transmission, pathophysiology, treatment, and prevention within one health framework

Staphylococcus aureus is recognized as commensal as well as opportunistic pathogen of humans and animals. Methicillin resistant strain of S. aureus (MRSA) has emerged as a major pathogen in hospitals, community and veterinary settings that compromises the public health and livestock production. MRSA basically emerged from MSSA after acquiring SCCmec element through gene transfer containing mecA gene responsible for encoding PBP-2α. This protein renders the MRSA resistant to most of the β-lactam antibiotics. Due to the continuous increasing prevalence and transmission of MRSA in hospitals, community and veterinary settings posing a major threat to public health. Furthermore, high pathogenicity of MRSA due to a number of virulence factors produced by S. aureus along with antibiotic resistance help to breach the immunity of host and responsible for causing severe infections in humans and animals. The clinical manifestations of MRSA consist of skin and soft tissues infection to bacteremia, septicemia, toxic shock, and scalded skin syndrome. Moreover, due to the increasing resistance of MRSA to number of antibiotics, there is need to approach alternatives ways to overcome economic as well as human losses. This review is going to discuss various aspects of MRSA starting from emergence, transmission, epidemiology, pathophysiology, disease patterns in hosts, novel treatment, and control strategies.

Kimyrsa and Orbactiv - A Tale of Two Formulations

Kimyrsa is a new formulation (NF) of the original formulation of oritavancin ([OF] Orbactiv). Comparatively, the obvious benefit with this product is the shortened infusion time and flexibility with solution compatibility, but otherwise maintains a similar pharmacokinetic and microbiologic profile. At present, the NF lacks significant real-world experience relative to other available lipoglycopeptides and thus its place in therapy remains difficult to predict but would not be expected to be significantly different than its OF.

Recent Advances in the Development of Semisynthetic Glycopeptide Antibiotics: 2014-2022

The accelerated appearance of drug-resistant bacteria poses an ever-growing threat to modern medicine's capacity to fight infectious diseases. Gram-positive species such as methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pneumoniae continue to contribute significantly to the global burden of antimicrobial resistance. For decades, the treatment of serious Gram-positive infections relied upon the glycopeptide family of antibiotics, typified by vancomycin, as a last line of defense. With the emergence of vancomycin resistance, the semisynthetic glycopeptides telavancin, dalbavancin, and oritavancin were developed. The clinical use of these compounds is somewhat limited due to toxicity concerns and their unusual pharmacokinetics, highlighting the importance of developing next-generation semisynthetic glycopeptides with enhanced antibacterial activities and improved safety profiles. This Review provides an updated overview of recent advancements made in the development of novel semisynthetic glycopeptides, spanning the period from 2014 to today. A wide range of approaches are covered, encompassing innovative strategies that have delivered semisynthetic glycopeptides with potent activities against Gram-positive bacteria, including drug-resistant strains. We also address recent efforts aimed at developing targeted therapies and advances made in extending the activity of the glycopeptides toward Gram-negative organisms.

New Perspectives on Antimicrobial Agents: Long-Acting Lipoglycopeptides

The long-acting lipoglycopeptides (LGPs) dalbavancin and oritavancin are semisynthetic antimicrobials with broad and potent activity against Gram-positive bacterial pathogens. While they are approved by the Food and Drug Administration for acute bacterial skin and soft tissue infections, their pharmacological properties suggest a potential role of these agents for the treatment of deep-seated and severe infections, such as bloodstream and bone and joint infections. The use of these antimicrobials is particularly appealing when prolonged therapy, early discharge, and avoidance of long-term intravascular catheter access are desirable or when multidrug-resistant bacteria are suspected. This review describes the current evidence for the use of oritavancin and dalbavancin in the treatment of invasive infections, as well as the hurdles that are preventing their optimal use. Moreover, this review discusses the current knowledge gaps that need to be filled to understand the potential role of LGPs in highly needed clinical scenarios and the ongoing clinical studies that aim to address these voids in the upcoming years.

Bioinformatic prospecting and synthesis of a bifunctional lipopeptide antibiotic that evades resistance

Emerging resistance to currently used antibiotics is a global public health crisis. Because most of the biosynthetic capacity within the bacterial kingdom has remained silent in previous antibiotic discovery efforts, uncharacterized biosynthetic gene clusters found in bacterial genome-sequencing studies remain an appealing source of antibiotics with distinctive modes of action. Here, we report the discovery of a naturally inspired lipopeptide antibiotic called cilagicin, which we chemically synthesized on the basis of a detailed bioinformatic analysis of the cil biosynthetic gene cluster. Cilagicin's ability to sequester two distinct, indispensable undecaprenyl phosphates used in cell wall biosynthesis, together with the absence of detectable resistance in laboratory tests and among multidrug-resistant clinical isolates, makes it an appealing candidate for combating antibiotic-resistant pathogens.

Infectious Complications of Injection Drug Use

The opioid overdose epidemic is one of the leading causes of death in adults. Its devastating effects have included not only a burgeoning overdose crisis but also multiple converging infectious diseases epidemics. The use of both opioids and other substances through intravenous (IV) administration places individuals at increased risks of infectious diseases ranging from invasive bacterial and fungal infections to human immunodeficiency virus (HIV) and viral hepatitis. In 2012, there were 530,000 opioid use disorder (OUD)-related hospitalizations in the United States (US), with $700 million in costs associated with OUD-related infections. The scale of the crisis has continued to increase since that time, with hospitalizations for injection drug use-related infective endocarditis (IDU-IE) increasing by as much as 12-fold from 2010 to 2015. Deaths from IDU-IE alone are estimated to result in over 7,260,000 years of potential life lost over the next 10 years. There have been high-profile injection-related HIV outbreaks, and injection drug use (IDU) is now the most common risk factor for hepatitis C virus (HCV). As this epidemic continues to grow, clinicians in all aspects of medical care are increasingly confronted with infectious complications of IDU. This review will describe the pathogenesis, clinical syndromes, epidemiology, and models of treatment for common infectious complications among persons who inject drugs (PWIDs).

Glycopeptide antibiotic drug stability in aqueous solution

Glycopeptide antimicrobials are a class of naturally occurring or semi-synthetic glycosylated products that have shown antibacterial activity against gram-positive organisms by inhibiting cell-wall synthesis. In most cases, these drugs are prepared in dry powder (lyophilized) form due to chemical and physical instability in aqueous solution; however, from an economic and practical point of view, liquid formulations are preferred. Researchers have recently found ways to formulate some glycopeptide antibiotic therapeutic drugs in aqueous solution at refrigerated or room temperature. Chemical degradation can be significantly slowed by formulating them at a defined pH with specific buffers, avoiding oxygen reactive species, and minimizing solvent exposure. Sugars, amino acids, polyols, and surfactants can reduce physical degradation by restricting glycopeptide mobility and reducing solvent interaction. This review focuses on recent studies on glycopeptide antibiotic drug stability in aqueous solution. It is organized into three sections: (i) glycopeptide antibiotic instability due to chemical and physical degradation, (ii) strategies to improve glycopeptide antibiotic stability in aqueous solution, and (iii) a survey of glycopeptide antibiotic drugs currently available in the market and their stability based on published literature and patents. Antimicrobial resistance deaths are expected to increase by 2050, making heat-stable glycopeptides in aqueous solution an important treatment option for multidrug-resistant and extensively drug-resistant pathogens. In conclusion, it should be possible to formulate heat stable glycopeptide drugs in aqueous solution by understanding the degradation mechanisms of this class of therapeutic drugs in greater detail, making them easily accessible to developing countries with a lack of cold chains.

Efficacy and safety of novel glycopeptides versus vancomycin for the treatment of gram-positive bacterial infections including methicillin resistant Staphylococcus aureus: A systematic review and meta-analysis

OBJECTIVE

To compare between current evidence of novel glycopeptides against vancomycin for the treatment of gram-positive bacterial infections.

METHODOLOGY

A systematic review and meta-analysis was done. Major databases were searched for eligible randomized control trials that assessed clinical success, microbiological success and safety profile of novel glycopeptides versus vancomycin for infections caused by gram-positive bacteria.

RESULTS

This meta-analysis included eleven trials (7289 participants) comparing telavancin, dalbavancin and oritavancin with vancomycin. No differences were detected between novel glycopeptides and vancomycin for the treatment of skin and soft tissue infections (SSTIs) among modified intent-to-treat patients (OR: 1.04, CI: 0.92-1.17) as well as within the clinically evaluable patients (OR: 1.09, CI: 0.91-1.30). Data analysed from SSTIs, HAP and bacteremia studies on telavancin showed insignificant high clinical response in microbiologically evaluable patients infected with methicillin resistant Staphylococcus aureus (MRSA) (OR: 1.57, CI: 0.94-2.62, p: 0.08) and in the eradication of MRSA (OR: 1.39, CI: 0.99-1.96, P:0.06). Dalbavancin was non-inferior to vancomycin for the treatment of osteomyelitis in a phase II trial, while it was superior to vancomycin for the treatment of bacteremia in a phase II trial. Data analysed from all trials showed similar rates of all-cause mortality between compared antibiotics groups (OR: 0.67, CI: 0.11-4.03). Telavancin was significantly related with higher adverse events (OR: 1.24, CI: 1.07-1.44, P: <0.01) while dalbavancin and oritavancin were associated with significant fewer adverse events (OR: 0.73, CI: 0.57-0.94, p: 0.01; OR: 0.72, CI: 0.59-0.89, p: <0.01 respectively).

CONCLUSION

Efficacy and safety profiles of both dalbavancin and oritavancin were the same as vancomycin in the treatment of gram-positive bacterial infections in different clinical settings, while telavancin might be an effective alternative to vancomycin in MRSA infections, but caution is required during its clinical use due to the high risk of adverse events, especially nephrotoxicity.

Multifunctional Antibiotic-Host Defense Peptide Conjugate Kills Bacteria, Eradicates Biofilms, and Modulates the Innate Immune Response

Effective anti-infective therapies are required to offset the rise in antibiotic resistance. A novel vancomycin-innate defense regulator conjugate (V-IDR1018) was constructed with multimodal functionality, including bacterial killing, biofilm eradication, and immune modulation. The conjugate killed bacteria within 30 min, exhibited potent activity against persister cells, and showed no susceptibility to antimicrobial resistance in tissue culture assays. Additionally, it stimulated the release of chemokine MCP-1 and anti-inflammatory cytokine IL-10 and suppressed pro-inflammatory IL-1β from lipopolysaccharide-stimulated white blood cells. The conjugate demonstrated ∼90% eradication efficacy when assessed against the MRSA biofilm formed on an organoid human skin equivalent. Similarly, when evaluated in a murine, high-density skin abscess infection model using MRSA or Staphylococcus epidermidis, the conjugate decreased dermonecrosis and reduced bacterial load. The exceptional in vitro and in vivo efficacy of the conjugate, in addition to its safety profile, makes it a valuable candidate to treat complex infectious diseases.

Strategy for Producing the High-Quality Glycopeptide Antibiotic A82846B in Amycolatopsis orientalis Based on the CRISPR-Cas12a System

Oritavancin is a new-generation semisynthetic lipoglycopeptide antibiotic used to prevent the spread of vancomycin-resistant Gram-positive bacteria. The glycopeptide A82846B is the direct precursor of oritavancin. Considering the structural similarity between A82846B and vancomycin, the vancomycin producer Amycolatopsis orientalis was used as a chassis for the construction of a strain producing high-quality A82846B. To construct the A82846B synthetic pathway, we established a highly efficient CRISPR-Cas12a system by optimizing the conditions of conjugation and by screening the regulatory elements in the A. orientalis, which is difficult to be genetically manipulated. The efficiency of gene knockout was almost 100%. The glycosyltransferases module (gtfDE) and glycosyl synthesis module (vcaAEBD) in the vancomycin gene cluster were replaced with the corresponding glycosyltransferases module (gtfABC) and glycosyl synthesis module (evaAEBD) in the A82846B cluster, respectively. A82846B was successfully produced by the artificially constructed synthetic pathway. Moreover, the titer of A82846B was increased 80% by expressing the pathway-specific regulatory strR. This strategy has excellent potential for remodification of natural products to solve antibiotic resistance.

Role or oritavancin and dalbavancin in acute bacterial skin and skin structure infections and other potential indications

PURPOSE OF REVIEW

To discuss the currently available evidence about the use oritavancin and dalbavancin for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and for other potential indications.

RECENT FINDINGS

In this review, we briefly summarize the available data on efficacy (from randomized controlled trials) and on effectiveness and cure rates (from observational studies) pertaining to the use of oritavancin and dalbavancin either for ABSSSI or for other indications.

SUMMARY

Oritavancin and dalbavancin are valid options for outpatient therapy and early discharge in patients with ABSSSI, especially when adherence to oral therapy cannot be guaranteed or no oral choices are available. Furthermore, it is worth noting that a non-negligible portion (sometimes the majority) of oritavancin and dalbavancin use in available real-life experiences is for indications other than ABSSSI, especially for Gram-positive osteomyelitis and endocarditis. The number of studies on the use of long-acting lipoglycopeptides for these currently off-label indications is rapidly increasing and will help to further optimize the use of these peculiar antibiotics in the forthcoming future.

Potential role of new-generation antibiotics in acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

To summarize the available results of primary analyses from high-quality randomized studies of either recently approved or possible future agents for the treatment of acute bacterial skin and skin structure infections (ABSSSI).

RECENT FINDINGS

In the last 2 decades, several novel agents have been approved for the treatment of ABSSSI, that are also active against methicillin-resistant Staphylococcus aureus (MRSA). In addition to already available agents, further molecules are in clinical development that could become available for treating ABSSSI in the forthcoming future.

SUMMARY

The current and future availability of several new-generation antibiotics will allow to modulate therapeutic choices not only on efficacy but also on other relevant factors such as the combination of the drug safety profile and the comorbidities of any given patient, the expected adherence to outpatient therapy, and the possibilities of early discharge or avoiding hospitalization by means of oral formulations, early switch from intravenous to oral therapy, or single-dose administration of long-acting intravenous agents. With the advent of new-generation antibiotics, all these factors are becoming increasingly essential for tailoring treatment to individual patients in line with the principles of personalized medicine, and for optimizing the use of healthcare resources.

The Increasing Issue of Vancomycin-Resistant Enterococci and the Bacteriocin Solution

Enterococci are commensals of human and other animals’ gastrointestinal tracts. Only making up a small part of the microbiota, they have not played a significant role in research, until the 1980s. Although the exact year is variable according to different geographical areas, this was the decade when vancomycin-resistant enterococci (VRE) were discovered and since then their role as causative agents of human infections has increased. Enterococcus faecium is on the WHO’s list of “bacteria for which new antibiotics are urgently needed,” and with no new antibiotics in development, the situation is desperate. In this review, different aspects of VRE are outlined, including the mortality caused by VRE, antibiotic resistance profiles, animal-modeling efforts, and virulence. In addition, the limitations of current antibiotic treatments for VRE and prospective new treatments, such as bacteriocins, are reviewed.

New-Generation Antibiotics for Treatment of Gram-Positive Infections: A Review with Focus on Endocarditis and Osteomyelitis

Infective endocarditis, osteomyelitis, and osteosynthesis-associated infections are mostly caused by Gram-positive bacteria. They are often difficult to treat and are associated with a poor prognosis. In the past 20 years, nine antibiotic drugs with predominant activity against Gram-positive bacteria have been introduced and approved by the Food and Drug Administration or the European Medicines Agency: ceftaroline, daptomycin, telavancin, dalbavancin, oritavancin, linezolid, tedizolid, delafloxacin, and omadacycline. This narrative review aims to provide an overview on these antibiotics with a special focus on their use in infective endocarditis, osteomyelitis, and osteosynthesis-associated infections. Although some of these approved antibiotics are promising, they should not be used as first- or second-line therapy, awaiting more clinical data.

Future directions of postoperative spinal implant infections

This article outlines some promising future concepts against postoperative spinal implant infections on the basis of today available literature. The ever-adapting bacteria causing this common complication compel a corresponding continuous research about best effective treatment. The aim is to give a perspective on several future attack-points: surgical infection prevention strategies such as technical optimization of implants and surgical technique; faster diagnostic tools to detect infection, especially in the context of late infections with low-virulent germs and with regard to decision-making in the course of the surgical workflow; and combined surgical and medical treatment options against implant infections. The surgical treatment section will also state open issues concerning implant removal, and the medical treatment section will give an outlook to promising medical alternatives in a post-antibiotic era. To keep up in this field will be important to retain spine surgery in the future as the state-of-the-art treatment option for mandatory spinal interventions in the presence of tumor or trauma and even more so as an attractive option for patients with degenerative spinal disorder for improvement of their life quality.

An Update on Antimicrobial Peptides (AMPs) and Their Delivery Strategies for Wound Infections

Bacterial infections occur when wound healing fails to reach the final stage of healing, which is usually hindered by the presence of different pathogens. Different topical antimicrobial agents are used to inhibit bacterial growth due to antibiotic failure in reaching the infected site, which is accompanied very often by increased drug resistance and other side effects. In this review, we focus on antimicrobial peptides (AMPs), especially those with a high potential of efficacy against multidrug-resistant and biofilm-forming bacteria and fungi present in wound infections. Currently, different AMPs undergo preclinical and clinical phase to combat infection-related diseases. AMP dendrimers (AMPDs) have been mentioned as potent microbial agents. Various AMP delivery strategies that are used to combat infection and modulate the healing rate-such as polymers, scaffolds, films and wound dressings, and organic and inorganic nanoparticles-have been discussed as well. New technologies such as Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)-associated protein (CRISPR-Cas) are taken into consideration as potential future tools for AMP delivery in skin therapy.

A Two-Dose Oritavancin Regimen Using Pharmacokinetic Estimation Analysis

Background

Antibiotics for the treatment of complicated, multidrug-resistant Gram-positive infections are limited, especially when prolonged treatment is necessary. Oritavancin is approved for the treatment of serious skin infections as a 1200 mg single-dose regimen, but case reports describe supplemental doses given at weekly intervals ranging from 800 mg to 1200 mg.  

Objective

This study determined population pharmacokinetic estimates for a 1200 mg single dose with and without an 800 mg dose 1 week apart.

Methods

A simulated oritavancin 1200 mg dose was infused over 3 h followed 7 days later by a simulated 800 mg dose infused over 3 h for pharmacokinetic estimation.

Results

The oritavancin dosing displayed predictable linear pharmacokinetics and therapeutic concentrations. The total and free oritavancin concentrations remained above the susceptibility breakpoint (0.12 mg/L) for 8 weeks and 4.6 weeks, respectively, with the two-dose regimen. This was significantly greater than the single-dose regimen. This regimen also results in a greater area under the drug concentration–time curve (AUC) above the susceptibility breakpoint compared to the single-dose regimen (p < 0.001), and it maintains a high AUC:minimum inhibitory concentration (MIC) ratio against organisms with MICs up to 0.25 mg/L.

Conclusion

These results along with the observational clinical reports of success and safety with this dosing scheme of 1200 mg followed by 800 mg 7 days later provide evidence for further evaluation of this approach when prolonged oritavancin treatment may be indicated.

The Real-World Economic and Clinical Management of Adult Patients with Skin and Soft Tissue Infections (SSTIs) with Oritavancin: Data from Two Multicenter Observational Cohort Studies

Background

Oritavancin is a FDA-approved single-dose IV therapy for the treatment of acute bacterial skin and skin structure infections caused (or suspected to be caused) by certain Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). Published data describing the outcomes of patients with skin and soft tissue infections (SSTIs) who received oritavancin beyond its pivotal phase III clinical trials are scant.

Objective

The purpose of this report was to describe the results of two separate multicenter observational cohort studies that described the outcomes associated with two unique real-world usage patterns of oritavancin.

Methods

The first cohort (n = 115) examined patients 18 years or older who were treated with oritavancin at three outpatient sites for SSTIs caused by suspected or confirmed Gram-positive pathogens, including MRSA, to avoid hospital admission. Patients were included if they had not been discharged from the inpatient setting within the previous 24 h and received their single-dose oritavancin treatment at a hospital-based outpatient infusion center. The primary outcomes measured were 30-day healthcare costs and admissions (all cause and infection related). The second cohort (n = 151) was a multicenter, retrospective chart review of adult patients who were discharged early from seven hospitals in 2015 on oritavancin for SSTIs. The primary outcome was readmission of patients within 30 days (all cause and infection related).

Results

In cohort 1, 30-day mean healthcare costs were USD 3698. In the study of patients who started oritavancin in the outpatient setting, 7 patients (6.1%) were admitted to hospital within 30 days of the index treatment, and 3 of those (2.6% overall) were deemed to be due to an infection. In cohort 2, all-cause and infection-related 30-day readmission rates were 6.6% and 2.6%, respectively, among patients who received oritavancin at hospital discharge.

Conclusions

Findings from these studies suggest that oritavancin may be a potentially useful agent to avoid hospitalization or shorten hospital length of stay among appropriate SSTI patients. Future comparator studies are required to properly ascertain the outcomes and potential benefits associated with oritavancin relative to other commonly used antibiotics in patients with SSTIs.

Advantages of Outpatient Treatment with Long-Acting Lipoglycopeptides for Serious Gram-Positive Infections: A Review

Treatment of serious gram-positive infections presents multiple challenges. Treatment often results in prolonged hospitalization for administration of intravenous antimicrobials and presents an inefficient use of hospital resources. Prolonged hospitalization is typically also unfavorable to patient preferences and potentially subjects patients to additional health care-associated complications. Current strategies of transition to outpatient settings-outpatient parenteral antimicrobial therapy and use of oral antibiotics-often do not adequately serve vulnerable populations for whom there is often no alternative to inpatient therapy. Specifically, people who use drugs, those who cannot reliably adhere to unsupervised treatment (poor mental or physical health), people with complicating life circumstances (e.g., homelessness, incarceration, rural location), and those with inadequate health insurance remain hospitalized for weeks longer than persons without such conditions. We suspected that long-acting lipoglycopeptides (laLGP), such as dalbavancin and oritavancin, may be useful in patient transitions to outpatient settings. Thus, we conducted a search of the peer-reviewed literature using the PubMed, Google Scholar, and MEDLINE databases. Based on accumulating literature, it appears that laLGPs offer a reliable alternative therapeutic strategy that addresses many of the personal and systemic barriers to the traditional transitioning approaches. Current evidence also suggests that these agents may be cost-effective from patient, payer, and hospital perspectives. Barriers to broader use of laLGPs include, among others, a relative lack of prospective data regarding efficacy in serious infections, a narrow United States Food and Drug Administration-approved indication restricted to only acute bacterial skin and skin structure infections, and lack of reimbursement infrastructure for inpatient settings.

Enhancing A82846B production by artificial attB-assisted overexpression of orf10-orf11 genes in Kibdelosporangium aridum SIPI-3927

A82846B, producing by Kibdelosporangium aridum, is an important precursor of the semi-synthetic glycopeptide antibiotic Oritavancin. K. aridum produces three components A82846A, B and C, so it is essential to increase A82846B titer and reduce A82846A and C titers by overexpressing halogenase and glycosyltransferase genes. Firstly, we constructed the genetically engineered strain SIPI-3927-attB harboring artificial attB site via homologous recombination. Secondly, two strains SIPI-3927-C1 and C2 were also constructed by integrating halogenase genes vcm8 and orf10 into artificial attB sites of SIPI-3927-attB, respectively. Meantime, three strains SIPI-3927-C3, C4 and C5 containing overexpressing glycosyltransferase A, B and C genes were obtained, respectively. Through fermentation analyses, the results showed that SIPI-3927-C1 and C2 could increase A82846B ratios, in which SIPI-3927-C1 showed a better performance. Moreover, the titer of SIPI-3927-C3 was highest in those of three strains. Finally, the strain SIPI-3927-C6 was constructed by integrating both orf10-encoded halogenase and orf11-encoded glycosyltransferase A, of which the yield and ratio of A82846B in shake-flask fermentation reached 1200 mg/L and 73.6%, respectively. Besides, the yield and ratio of A82846B in SIPI-3927-C6 grew up to 2520 mg/L and 86.5% in the 5-L fermenter culture, respectively. In conclusion, overexpressing orf10 gene can increase A82846B ratio,while overexpressing orf11 gene can increase A82846B titer as well. The artificial attB site is effective for inserting new genes.

Recent Drug-Repurposing-Driven Advances in the Discovery of Novel Antibiotics

Drug repurposing is a safe and successful pathway to speed up the novel drug discovery and development processes compared with de novo drug discovery approaches. Drug repurposing uses FDA-approved drugs and drugs that failed in clinical trials, which have detailed information on potential toxicity, formulation, and pharmacology. Technical advancements in the informatics, genomics, and biological sciences account for the major success of drug repurposing in identifying secondary indications of existing drugs. Drug repurposing is playing a vital role in filling the gap in the discovery of potential antibiotics. Bacterial infections emerged as an ever-increasing global public health threat by dint of multidrug resistance to existing drugs. This raises the urgent need of development of new antibiotics that can effectively fight multidrug-resistant bacterial infections (MDRBIs). The present review describes the key role of drug repurposing in the development of antibiotics during 2016-2017 and of the details of recently FDA-approved antibiotics, pipeline antibiotics, and antibacterial properties of various FDA-approved drugs of anti-cancer, anti-fungal, anti-hyperlipidemia, antiinflammatory, anti-malarial, anti-parasitic, anti-viral, genetic disorder, immune modulator, etc. Further, in view of combination therapies with the existing antibiotics, their potential for new implications for MDRBIs is discussed. The current review may provide essential data for the development of quick, safe, effective, and novel antibiotics for current needs and suggest acuity in its effective implications for inhibiting MDRBIs by repurposing existing drugs.

Biological, chemical, and biochemical strategies for modifying glycopeptide antibiotics

Since the discovery of vancomycin in the 1950s, the glycopeptide antibiotics (GPAs) have been of great interest to the scientific community. These nonribosomally biosynthesized peptides are highly cross-linked, often glycosylated, and inhibit bacterial cell wall assembly by interfering with peptidoglycan synthesis. Interest in glycopeptide antibiotics covers many scientific disciplines, due to their challenging total syntheses, complex biosynthesis pathways, mechanism of action, and high potency. After intense efforts, early enthusiasm has given way to a recognition of the challenges in chemically synthesizing GPAs and of the effort needed to study and modify GPA-producing strains to prepare new GPAs to address the increasing threat of microbial antibiotic resistance. Although the preparation of GPAs, either by modifying the pendant groups such as saccharides or by functionalizing the N- or C-terminal moieties, is readily achievable, the peptide core of these molecules-the GPA aglycone-remains highly challenging to modify. This review aims to present a summary of the results of GPA modification obtained with the three major approaches developed to date: in vivo strain manipulation, total chemical synthesis, and chemoenzymatic synthesis methods.

Long-Acting Lipoglycopeptides: "Lineless Antibiotics" for Serious Infections in Persons Who Use Drugs

Background

Injection drug use is associated with serious infections. Due to challenges with medical management of addiction, relapses and additional infections are common. Persons who use drugs (PWUD) are more likely to leave against medical advice before completing treatment, which could result in treatment failure. Prolonged intravenous (IV) antimicrobial therapy in PWUD may be complicated by concern for IV catheter misuse, sometimes requiring prolonged hospitalization. Ideal alternatives would provide the following: (1) high success rate; (2) reduced rate of medical complications; (3) improved safety profiles; and (4) improved cost-effectiveness. Long-acting lipoglycopeptides present such opportunity for treatment of serious Gram-positive infections.

Methods

We performed a system-wide, retrospective analysis of adults admitted to University of Colorado Health from September 2015 to June 2018 and treated with dalbavancin or oritavancin based on clinical judgment of their treating physicians.

Results

Fifty-six patients met inclusion criteria (17 PWUD vs 39 non-PWUD). The PWUD group were younger, healthier by Charlson comorbidity index, more likely insured by Medicaid, and admitted for conditions requiring longer treatment. Ten patients were lost to follow-up. Of the patients with follow-up, clinical failure was met in 1 PWUD patient (6%) and 6 non-PWUD patients (15%) (P = .413). The median hospital length-of-stay reduction was 20 days (interquartile range [IQR], 10–30 days) in PWUD vs 11 days (IQR, 9–14 days) in non-PWUD; P = .133. Estimated median savings were $40 455.08 (IQR, $20 900.00–$62 700.00) in PWUD vs $19 555.08 (IQR, $15 375.08–$23 735.08) in non-PWUD; P = .065.

Conclusions

Long-acting lipoglycopeptides may be equally effective as standard-of-care, present a safety advantage, and secure earlier discharge and significant cost-savings.

Antimicrobial activity of oritavancin and comparator agents when tested against Gram-positive bacterial isolates causing infections in cancer patients (2014-16)

Objectives

The in vitro activity of oritavancin was assessed against clinically relevant Gram-positive pathogens causing infections in cancer patients in European and US hospitals.

Methods

A total of 1357 Gram-positive cocci (GPC) were included. Isolates were predominantly from bloodstream infections (54.6%). The most frequently isolated GPC were Staphylococcus aureus (43.6%), CoNS (14.4%) and Enterococcus spp. (22.0%).

Results

Oritavancin (99.8% susceptible) showed modal MIC, MIC50 and MIC90 results of 0.015, 0.015-0.03 and 0.06 mg/L, respectively, when tested against S. aureus, regardless of methicillin susceptibility or geographical region. CoNS isolates from the USA demonstrated an MIC90 of oritavancin (MIC90, 0.12 mg/L) that was slightly higher than that for isolates from European countries (MIC90 0.06 mg/L). Oritavancin inhibited all Enterococcus faecalis and Enterococcus faecium, including VRE, at ≤ 0.25 mg/L. Oritavancin exhibited MIC50 results of 0.03 and 0.008-0.015 mg/L when tested against isolates of β-haemolytic streptococci and viridans group streptococci, respectively, regardless of geographical region.

Conclusions

Oritavancin had potent activity in vitro against this contemporary collection of European and US GPC isolates from cancer patients.

Comparative In Vitro Activities of New Antibiotics for the Treatment of Skin Infections

Bacterial skin infections result in significant morbidity and have contributed to enhanced health-care resource utilization. The problem is heightened by emerging antimicrobial resistance. Multiple novel agents active against resistant pathogens that cause skin infections-including dalbavancin, tedizolid phosphate, oritavancin, and delafloxacin-have been approved over the past 5 years. Common features of these agents include gram-positive activity and favorable safety. Of these agents, delafloxacin is unique in being active against both gram-positive and gram-negative pathogens that cause skin infections, including those resistant to other antimicrobial agents. It is, therefore, an effective option for the treatment of skin infections.

Teicoplanin Reprogrammed with the N-Acyl-Glucosamine Pharmacophore at the Penultimate Residue of Aglycone Acquires Broad-Spectrum Antimicrobial Activities Effectively Killing Gram-Positive and -Negative Pathogens

Lipoglycopeptide antibiotics, for example, teicoplanin (Tei) and A40926, are more potent than vancomycin against Gram-positive (Gram-(+)) drug-resistant pathogens, for example, methicillin-resistant Staphylococcus aureus (MRSA). To extend their therapeutic effectiveness on vancomycin-resistant S. aureus (VRSA), the biosynthetic pathway of the N-acyl glucosamine (Glc) pharmacophore at residue 4 (r4) of teicoplanin pseudoaglycone redirection to residue 6 (r6) was attempted. On the basis of crystal structures, two regioselective biocatalysts Orf2*T (a triple-mutation mutant S98A/V121A/F193Y) and Orf11*S (a single-mutation mutant W163A) were engineered, allowing them to act on GlcNAc at r6. New analogs thereby made show marked antimicrobial activity against MRSA and VRSA by 2-3 orders of magnitude better than teicoplanin and vancomycin. The lipid side chain of the Tei-analogs armed with a terminal mono- or diguanidino group extends the antimicrobial specificity from Gram-(+) to Gram-negative (Gram-(-)), comparable to that of kanamycin. In addition to low cytotoxicity and high safety, the Tei analogs exhibit new modes of action as a result of resensitization of VRSA and Acinetobacter baumannii. The redirection of the biosynthetic pathway for the N-acyl-Glc pharmacophore from r4 to r6 bodes well for large-scale production of selected r6,Tei congeners in an environmentally friendly synthetic biology approach.

Membrane-targeting antibiotics: recent developments outside the peptide space

The rise of antibiotic resistant bacteria requires unconventional strategies toward efficient chemotherapeutic agents, preferably with alternative mechanisms of action. The bacterial cell membrane has become an appealing target since its essential and highly conservative structure are key challenges to resistance mechanisms. Inspired by natural antimicrobial peptides, research on membrane-targeting antimicrobials has been growing out of the peptide space. The pursuit of more druggable molecules led to the discovery that the pharmacophore of antimicrobial peptides is smaller than anticipated. Several promising classes of membrane-targeting antimicrobials have been discovered, such as ceragenins, reutericyclines, carbohydrate amphiphiles - among others. This review will discuss the most recent findings on membrane-targeting antibiotics, focusing on small molecules outside the antimicrobial peptide molecular space.

Methicillin-Resistant Staphylococcus aureus Prosthetic Valve Endocarditis: Pathophysiology, Epidemiology, Clinical Presentation, Diagnosis, and Management

Staphylococcus aureus prosthetic valve endocarditis (PVE) remains among the most morbid bacterial infections, with mortality estimates ranging from 40% to 80%. The proportion of PVE cases due to methicillin-resistant Staphylococcus aureus (MRSA) has grown in recent decades, to account for more than 15% of cases of S. aureus PVE and 6% of all cases of PVE. Because no large studies or clinical trials for PVE have been published, most guidelines on the diagnosis and management of MRSA PVE rely upon expert opinion and data from animal models or related conditions (e.g., coagulase-negative Staphylococcus infection). We performed a review of the literature on MRSA PVE to summarize data on pathogenic mechanisms and updates in epidemiology and therapeutic management and to inform diagnostic strategies and priority areas where additional clinical and laboratory data will be particularly useful to guide therapy. Major updates discussed in this review include novel diagnostics, indications for surgical management, the utility of aminoglycosides in medical therapy, and a review of newer antistaphylococcal agents used for the management of MRSA PVE.

A Dual-Function Antibiotic-Transporter Conjugate Exhibits Superior Activity in Sterilizing MRSA Biofilms and Killing Persister Cells

New strategies are urgently needed to target MRSA, a major global health problem and the leading cause of mortality from antibiotic-resistant infections in many countries. Here, we report a general approach to this problem exemplified by the design and synthesis of a vancomycin-d-octaarginine conjugate (V-r8) and investigation of its efficacy in addressing antibiotic-insensitive bacterial populations. V-r8 eradicated MRSA biofilm and persister cells in vitro, outperforming vancomycin by orders of magnitude. It also eliminated 97% of biofilm-associated MRSA in a murine wound infection model and displayed no acute dermal toxicity. This new dual-function conjugate displays enhanced cellular accumulation and membrane perturbation as compared to vancomycin. Based on its rapid and potent activity against biofilm and persister cells, V-r8 is a promising agent against clinical MRSA infections.

New Innovations in the Treatment of PJI and Biofilms-Clinical and Preclinical Topics

PURPOSE OF REVIEW

Periprosthetic joint infection (PJI) is a devastating complication after total joint replacement. A main source for antibiotic tolerance and treatment failure is bacterial production of biofilm-a resilient barrier against antibiotics, immune system, and mechanical debridement. The purpose of this review is to explore some novel approaches to treat PJI and biofilm-related infections.

RECENT FINDINGS

Innovative treatment strategies of bacterial and biofilm infections revolve around (a) augmenting current therapies, such as improving the delivery and efficiency of conventional antibiotics and enhancing the efficacy of antiseptics and (b) administrating completely new therapeutic modalities, such as using immunotherapy, nanoparticles, lytic bacteriophages, photodynamic therapy, novel antibiotics, and antimicrobial peptides. Several promising treatment strategies for PJI are available to be tested further. The next requirement for most of the novel treatments is reproducing their effects in clinically representative animal models of PJI against clinical isolates of relevant bacteria.

Design and Synthesis of Pyrophosphate-Targeting Vancomycin Derivatives for Combating Vancomycin-Resistant Enterococci

As the last resort for intractable Gram-positive bacterial infections, vancomycin is losing efficacy with the emergence of vancomycin-resistant bacteria, especially vancomycin-resistant Enterococci (VRE). To combat this threat, we rationally designed and synthesized 39 novel vancomycin derivatives by respective or combined modifications using metal-chelating, lipophilic, and galactose-attachment strategies for extensive structure-activity relationship (SAR) analysis. In a proposed mechanism, the conjugation of dipicolylamine on the seventh amino acid resorcinol position or C-terminus endowed the vancomycin backbone with binding capacity for the pyrophosphate moiety in lipid II while maintaining the intrinsic binding affinity for the dipeptide terminus of the bacterial cell wall peptidoglycan precursor. The in vitro antibacterial activities were evaluated, and the optimal compounds indicated 16- to 1024-fold higher activity against VRE than that of vancomycin. Compound 11 b (3',5'-bis(dipicolylaminomethyl)tyrosine [1,2,3]triazolylmethoxylethyoxyl ethylaminomethyl-N-decylvancomycin) was found to have particularly potent activity against VRE through synergistic effects brought about by combining two peripheral modifications.

Developments in Glycopeptide Antibiotics

Glycopeptide antibiotics (GPAs) are a key weapon in the fight against drug resistant bacteria, with vancomycin still a mainstream therapy against serious Gram-positive infections more than 50 years after it was first introduced. New, more potent semisynthetic derivatives that have entered the clinic, such as dalbavancin and oritavancin, have superior pharmacokinetic and target engagement profiles that enable successful treatment of vancomycin-resistant infections. In the face of resistance development, with multidrug resistant (MDR) S. pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) together causing 20-fold more infections than all MDR Gram-negative infections combined, further improvements are desirable to ensure the Gram-positive armamentarium is adequately maintained for future generations. A range of modified glycopeptides has been generated in the past decade via total syntheses, semisynthetic modifications of natural products, or biological engineering. Several of these have undergone extensive characterization with demonstrated in vivo efficacy, good PK/PD profiles, and no reported preclinical toxicity; some may be suitable for formal preclinical development. The natural product monobactam, cephalosporin, and β-lactam antibiotics all spawned multiple generations of commercially and clinically successful semisynthetic derivatives. Similarly, next-generation glycopeptides are now technically well positioned to advance to the clinic, if sufficient funding and market support returns to antibiotic development.

Mechanisms of antimicrobial resistance among hospital-associated pathogens

INTRODUCTION

The introduction of antibiotics revolutionized medicine in the 20th-century permitting the treatment of once incurable infections. Widespread use of antibiotics, however, has led to the development of resistant organisms, particularly in the healthcare setting. Today, the clinician is often faced with pathogens carrying a cadre of resistance determinants that severely limit therapeutic options. The genetic plasticity of microbes allows them to adapt to stressors via genetic mutations, acquisition or sharing of genetic material and modulation of genetic expression leading to resistance to virtually any antimicrobial used in clinical practice. Areas covered: This is a comprehensive review that outlines major mechanisms of resistance in the most common hospital-associated pathogens including bacteria and fungi. Expert commentary: Understanding the genetic and biochemical mechanisms of such antimicrobial adaptation is crucial to tackling the rapid spread of resistance, can expose unconventional therapeutic targets to combat multidrug resistant pathogens and lead to more accurate prediction of antimicrobial susceptibility using rapid molecular diagnostics. Clinicians making treatment decisions based on the molecular basis of resistance may design therapeutic strategies that include de-escalation of broad spectrum antimicrobial usage, more focused therapies or combination therapies. These strategies are likely to improve patient outcomes and decrease the risk of resistance in hospital settings.