Safety of Newer Parenteral Antibiotics

Safety evaluation of current therapies for high-risk severely ill patients with carbapenem-resistant infections

INTRODUCTION

Infections due to carbapenem-resistant Gram-negative bacteria (CR-GNB) are increasingly frequent events, which are associated with a high mortality rate. Traditionally, combination regimens including high doses of "old antibiotics" such as polymyxins, tigecycline, and aminoglycosides have been used to treat these infections, but they were often associated with low efficacy and high excess of side effects and toxicity, especially nephrotoxicity. Along with the development of new compounds, the last decade has seen substantial improvements in the management of CR infections.

AREAS COVERED

In this review, we aimed to discuss the safety characteristics and tolerability of different new options for treatment of CR infections.

EXPERT OPINION

The availability of new drugs showing a potent in vitro activity against CR-GNB represents a unique opportunity to face the threat of resistance, while potentially reducing toxicity. A thorough understanding of the safety profile from clinical trials may guide the use of these new drugs in critically ill patients at high risk for the development of adverse events. Future data coming from real-life studies for drugs targeting CR infections are crucial to confirm the safety profile observed in pivotal trials.

Potential RNA-dependent RNA polymerase inhibitors as prospective therapeutics against SARS-CoV-2

Introduction. The emergence of SARS-CoV-2 has taken humanity off guard. Following an outbreak of SARS-CoV in 2002, and MERS-CoV about 10 years later, SARS-CoV-2 is the third coronavirus in less than 20 years to cross the species barrier and start spreading by human-to-human transmission. It is the most infectious of the three, currently causing the COVID-19 pandemic. No treatment has been approved for COVID-19. We previously proposed targets that can serve as binding sites for antiviral drugs for multiple coronaviruses, and here we set out to find current drugs that can be repurposed as COVID-19 therapeutics.Aim. To identify drugs against COVID-19, we performed an in silico virtual screen with the US Food and Drug Administration (FDA)-approved drugs targeting the RNA-dependent RNA polymerase (RdRP), a critical enzyme for coronavirus replication.Methodology. Initially, no RdRP structure of SARS-CoV-2 was available. We performed basic sequence and structural analysis to determine if RdRP from SARS-CoV was a suitable replacement. We performed molecular dynamics simulations to generate multiple starting conformations that were used for the in silico virtual screen. During this work, a structure of RdRP from SARS-CoV-2 became available and was also included in the in silico virtual screen.Results. The virtual screen identified several drugs predicted to bind in the conserved RNA tunnel of RdRP, where many of the proposed targets were located. Among these candidates, quinupristin is particularly interesting because it is expected to bind across the RNA tunnel, blocking access from both sides and suggesting that it has the potential to arrest viral replication by preventing viral RNA synthesis. Quinupristin is an antibiotic that has been in clinical use for two decades and is known to cause relatively minor side effects.Conclusion. Quinupristin represents a potential anti-SARS-CoV-2 therapeutic. At present, we have no evidence that this drug is effective against SARS-CoV-2 but expect that the biomedical community will expeditiously follow up on our in silico findings.

Neurological and Psychiatric Adverse Effects of Antimicrobials

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

Antimicrobial resistance and treatment: an unmet clinical safety need

INTRODUCTION

Infections due to multidrug-resistant (MDR) bacteria are burdened by high mortality rates. The development of new compounds to face the global threat of resistance is urgently needed. Combination regimens including "old" high-dose antimicrobials are currently limited by the risk of toxicity, resistance selection, and reduced efficacy. Following the Infectious Diseases Society of America call to develop 10 new antibacterials by 2020, new molecules are currently under development or have become available for use in clinical practice.

AREAS COVERED

We have reviewed safety characteristics and tolerability of old antimicrobials that are currently employed in combination regimens as well as new antimicrobials, including beta-lactams/beta-lactamase inhibitors, new cephalosporins, quinolones, and aminoglycosides.

EXPERT OPINION

The availability of new compounds that show in vitro efficacy against MDR represents a unique opportunity to face the threat of resistance and to optimize the current use of antimicrobials, potentially reducing toxicity. Agents that are potentially active against MDR Gram-negatives are ceftozolane/tazobactam, new carbapenems and cephalosporins, the combination of avibactam with ceftazidime, and plazomicin. Further data from clinical trials and post-marketing studies for drugs targeting MDR pathogens are crucial to confirm their efficacy and safety.

Frontline antibiotic therapy

The need to use front-line antibiotics wisely has never been greater. Antibiotic resistance and multi-drug resistant infection, driven by antibiotic use, remain major public health and professional concerns. To overcome these infection problems, use of older antibiotics active against multi drug-resistant pathogens is increasing - for example, colistin, fosfomycin, pivmecillinam, pristinamycin, temocillin and oral tetracyclines. The number of new antibacterials reaching clinical practice has reduced significantly in the last 20 years, most being focused on therapy of Gram-positive infection - eg linezolid, daptomycin, telavancin and ceftaroline. Recent guidance on antibiotic stewardship in NHS trusts in England is likely to provide a backdrop to antibiotic use in hospitals in the next 5 years.

IL-4 mediates dicloxacillin-induced liver injury in mice

Drug-induced liver injury (DILI) is a major problem in drug development and clinical drug therapy. In most cases, the mechanisms are still unknown. It is difficult to predict DILI in humans due to the lack of experimental animal models. Dicloxacillin, penicillinase-sensitive penicillin, rarely causes cholestatic or mixed liver injury, and there is some evidence for immunoallergic idiosyncratic reaction in human. In this study, we investigated the mechanisms of dicloxacillin-induced liver injury. Plasma ALT and total-bilirubin (T-Bil) levels were significantly increased in dicloxacillin-administered (600 mg/kg, i.p.) mice. Dicloxacillin administration induced Th2 (helper T cells)-mediated factors and increased the plasma interleukin (IL)-4 level. Neutralization of IL-4 suppressed the hepatotoxicity of dicloxacillin, and recombinant mouse IL-4 administration (0.5 or 2.0 μg/mouse, i.p.) exacerbated it. Chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTh2) is a cognate receptor for prostaglandin (PG) D(2), and is suggested to be involved in Th2-dependent allergic inflammation. We investigated the effect of 13,14-Dihydro-15-keto-PGD(2) (DK-PGD(2); 10 μg/mouse, i.p.) administration on dicloxacillin-induced liver injury. DK-PGD(2)/dicloxacillin coadministration resulted in a significant increase of alanine aminotransferases and a remarkable increase of macrophage inflammatory protein 2 expression. In conclusion, to the best of our knowledge, this is the first report to demonstrate that dicloxacillin-induced liver injury is mediated by a Th2-type immune reaction and exacerbated by DK-PGD(2).

Tigecycline for the treatment of patients with community-acquired pneumonia requiring hospitalization

Pneumonia, along with influenza, is the leading cause of mortality associated with infectious diseases in the USA. Tigecycline is a novel antimicrobial agent that is active against a broad spectrum of pathogens. Our objective is to review the literature about the efficacy of tigecycline in community-acquired pneumonia (CAP). Data from various sources, including Pubmed, the European Medicines Agency (EMEA) and the US FDA were appraised. Tigecycline was found to be noninferior compared with levofloxacin for the treatment of patients with bacterial CAP requiring hospitalization. Recently, the drug was approved for the treatment of these patients by the FDA, but owing to some concerns, its application in the EMEA has been withdrawn. In addition, in a recent study concerns were expressed about the efficacy of tigecycline in the lungs using the current dosage. More data are needed about the pharmacokinetics of tigecycline in the lungs and its efficacy in severe CAP.

New treatments for methicillin-resistant Staphylococcus aureus

PURPOSE OF REVIEW

Methicillin-resistant Staphylococcus aureus (MRSA) is a dynamic pathogen. Rates of MRSA are increasing worldwide. In some centers, MRSA is becoming less susceptible to vancomycin, and these strains have been associated with worse clinical outcomes. Intermediate or fully resistant vancomycin strains of MRSA have emerged clinically, whereas MRSA acquired in the community has become epidemic. The purpose of this manuscript is to provide clinicians with an evidence-based review on new treatments for MRSA.

RECENT FINDINGS

Linezolid, daptomycin and tigecycline have been approved during the last decade to treat infections due to MRSA. Although these agents are extremely valuable in the fight against MRSA, each one has limitations. New lypoglycopeptides (telavancin, dalbavancin and oritavancin) are in advanced phase of clinical development. Similarly, new broad-spectrum cephalosporins active against MRSA (e.g. ceftobiprole and ceftaroline) and a new dihydrofolate reductase inhibitor (iclaprim) are in or have completed phase 3 studies.

SUMMARY

Here, we review the most relevant information on new drugs to treat MRSA. New studies with available agents and upcoming studies with investigational drugs will help to better understand the role of each compound in the treatment of patients infected with MRSA and assist the clinician in keeping pace with this challenging pathogen.

Infection of intravascular prostheses: how to treat other than surgery

Long-term antimicrobial therapy may be effective in some patients with intravascular prosthesis infection. However, this approach does not represent an alternative to surgery when this is feasible, but is merely the best opportunity for patients too ill to tolerate a re-intervention. Prosthetic valve endocarditis may be treated with antibiotic therapy alone in selected patients who are haemodynamically stable with non-staphylococcal infections and no para-valvular complications. In contrast, infections of pacemaker leads or other implantable cardiac devices require complete hardware removal, as infection recurrence always occurs, even after a seemingly effective initial treatment. Attempts to treat conservatively infections of abdominal aortic grafts can be successful in a few cases, provided the patient is stable, the pathogen has been identified, and antibiotic susceptibility has been demonstrated. Treatment requires at least 4-6 weeks and may be followed by a sequential oral regimen once the acute phase of the infection has subsided. The correct duration of this treatment is often unknown and relapses are common after treatment withdrawal. The availability of novel antibacterial and antifungal agents - showing fast microbicidal activity that includes biofilm micro-organisms - such as daptomycin and caspofungin, or having a wide antimicrobial spectrum, such as tigecycline, may increase the probability of long-standing suppression or even eradication of the infection in these particular subsets of inoperable patients. However, so far, very little experience is available on the efficacy and tolerability of these drugs in intravascular prosthesis infections. Controlled studies are lacking and difficult to plan. Well-designed prospective studies may help to establish guidelines and reach a multidisciplinary consensus on the optimal therapeutic approach, and are therefore awaited.

Crotylation versus Propargylation: Two Routes for the Synthesis of the C13−C18 Fragment of the Antibiotic Branimycin

The C13-C18 fragment 3 of the novel antibiotic branimycin was prepared along two highly stereocontrolled routes. The first one uses a standard Roush crotylation protocol, whereas the second one proceeds via an allenyl silane propargylation with unexpected stereochemical consequences, which are discussed in detail.

In vitro activities of daptomycin, vancomycin, and penicillin against Clostridium difficile, C. perfringens, Finegoldia magna, and Propionibacterium acnes

Daptomycin has in vitro activity against gram-positive anaerobic bacteria, although limited numbers of species have been tested. We studied the in vitro activities of daptomycin, vancomycin, and penicillin against more than 100 strains each of Clostridium difficile, C. perfringens, Finegoldia magna, and Propionibacterium acnes. Daptomycin Etest MICs and results from time-kill studies were determined for selected strains. For 392 of 421 strains (93%), daptomycin was inhibitory at < or =1 microg/ml, including 15 of 16 strains of C. difficile with elevated linezolid MICs of 8 and 16 microg/ml, all 32 strains with moxifloxacin MICs of > or =4 microg/ml, and all 16 strains resistant to clindamycin. Daptomycin MICs were also < or =1 microg/ml for all 16 F. magna strains resistant to clindamycin and all 32 strains resistant to tetracycline. Only one strain, a C. perfringens strain, had a MIC of >2 microg/ml to daptomycin. Eighty-five and 92.5% of the Etest MICs were within 1 dilution of the agar dilution method for all drugs at 24 and 48 h, respectively. In time-kill studies, a C. difficile strain was inhibited by both daptomycin and vancomycin at 1, 2, 4, 8, and 24 h; colony counts were decreased by 2.3 to 2.9 log at 24 h. Vancomycin was not bactericidal for C. perfringens; however, daptomycin showed bactericidal activity as early as 1 h at four and eight times the MIC and at 2 and 4 h at two and four times the MIC.

Tigecycline: A Critical Analysis

Tigecycline (GAR-936) is the first glycylcycline antibiotic to be approved by the US Food and Drug Administration (FDA). The drug overcomes the 2 major resistance mechansisms of tetracycline: drug-specific efflux pump acquisition and ribosomal protection. Tigecycline is active against many gram-positive and -negative organisms, including methicillin-resistant Staphylococcus aureus, vancomycin-intermediate and -resistant enterococci, and extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae. It is also active against many anaerobic bacteria, as well as atypical pathogens, including rapidly growing, nontuberculous mycobacteria. Tigecycline is concentrated in cells and is eliminated primarily via biliary excretion. Diminished renal function does not significantly alter its systemic clearance. Furthermore, tigecycline does not interfere with common cytochrome P450 enzymes, making pharmacokinetic drug interactions uncommon. It provides parenteral therapy for complicated skin/skin-structure and intra-abdominal infections. The only prominent adverse effects are associated with tolerability, most notably nausea and vomiting. Tigecycline will be most useful as empirical therapy for polymicrobial infections, especially in cases in which deep tissue penetration is needed or in which multidrug-resistant pathogens are suspected.