Assessment of Data Supporting the Efficacy of New Antibiotics for Treating Infections Caused by Multidrug-resistant Bacteria

Bavachin Rejuvenates Sensitivity of Colistin against Colistin-Resistant Gram-Negative Bacteria

The emergence of plasmid-mediated colistin resistance threatens the efficacy of colistin as a last-resort antibiotic used to treat infection caused by Gram-negative bacteria (GNB). Given the shortage of new antibiotics, the discovery of adjuvants to existing antibiotics is a promising strategy to combat infections caused by multidrug-resistant (MDR) GNB. This study was designed to investigate the potential synergistic antibacterial activity of bavachin, a bioactive compound extracted from the Psoralea Fructus, combined with colistin against MDR GNB. Herein, the synergistic efficacy in vitro and the therapeutic efficacy of colistin combined with bavachin in vivo were evaluated. The synergistic mechanism was detected by fluorescent probe and the transcript levels of mcr-1. Bavachin combined with colistin showed an excellent synergistic activity against GNB, as the FICI ≤ 0.5. In contrast to colistin alone, combination therapy dramatically increased the survival rate of Galleria mellonella and mice in vivo. Moreover, the combination of bavachin and colistin significantly reduced the amount of bacterial biofilm formation, improved the membrane disruption of colistin and inhibited mcr-1 transcription. These findings show that bavachin is a potential adjuvant of colistin, which may provide a new strategy to combat colistin-resistant bacteria infection with lower doses of colistin.

Development of Novel Chimeric Endolysin Conjugated with Chitosan-Zn-Metal-Organic Framework Nanocomposites with Antibacterial Activity

Bacterial diseases have been considered the most crucial issue and are threatening human health all around the world. Also, resistance to antimicrobial drugs has become a big hurdle against efficient therapy. As a result, recombinant chimeric endolysin was produced in E. coli host to use as a potential antibacterial agent against bacteria resistance and replacement to conventional antibiotics in this study. Then, chitosan (C)-coated nanoscale metal-organic frameworks (CS-NMOFs) nanocomposite was synthesized as a novel nano delivery system to further improve the antibacterial activity of endolysin. After characterization of nanocomposite with analytical devices such as FT-IR, DLS, and TEM and determining the nanometric size of samples (30 nm to 90 nm), endolysin was covalently (endolysin-CS-NMOFs (C)) and non-covalently (endolysin-CS-NMOFs (NC)) conjugated to nanocomposite. Thereafter, the lytic ability, synergistic interaction, and biofilm reduction manner of endolysin-containing CS-NMOF nanocomposites were evaluated on E. coli, S. aureus, and P. aeruginosa strains. The results depicted an excellent lytic ability of nanocomposites after 24 h and 48 h of treatment, especially endolysin-CS-NMOFs (NC) on E. coli and P. aeruginosa strains. The synergistic interaction between nanocomposite and vancomycin did not attain for P. aeruginosa strain whereas the reverse was true for E. coli and S. aureus strains at 8 ng/mL concentration. Next, nanocomposites demonstrated potential biofilm reduction activities in various strains, especially in S. aureus and P. aeruginosa. Ultimately, our outputs demonstrate an efficient performance of the synthesized nanocomposite as an appropriate substitution for conventional antibiotics against bacteria.

Novel Chimeric Endolysin Conjugated Chitosan Nanocomplex as a Potential Inhibitor Against Gram-Positive and Gram-Negative Bacteria

Resistance to antimicrobial agents has created potential problems in finding efficient treatments against bacteria. Thus, using new therapeutics, such as recombinant chimeric endolysin, would be more beneficial for eliminating resistant bacteria. The treatment ability of these therapeutics can be further improved if they are used with biocompatible nanoparticles like chitosan (CS). In this work, covalently conjugated chimeric endolysin to CS nanoparticles (C) and non-covalently entrapped endolysin in CS nanoparticles (NC) were effectively developed and, consequently, qualified and quantified using analytical devices, including FT-IR, dynamic light scattering, and TEM. Eighty to 150 nm and 100 nm to 200 nm in diameter were measured for CS-endolysin (NC) and CS-endolysin (C) using a TEM, respectively. The lytic activity, synergistic interaction, and biofilm reduction potency of nano-complexes were investigated on Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) strains. The outputs revealed a good lytic activity of nano-complexes after 24 h and 48 h of treatment, especially in P. aeruginosa (approximately 40% cell viability after 48 h of treatment with 8 ng/mL), and potential biofilm reduction performance was attained in E. coli strains (about 70% reduction after treatment with 8 ng/mL). The synergistic interaction between nano-complexes and vancomycin was exhibited in E. coli, P. aeruginosa, and S. aureus strains at 8 ng/mL concentrations, while the synergistic effects of pure endolysin and vancomycin were not remarkable in E. coli strains. These nano-complexes would be more beneficial in suppressing the bacteria with a high level of antibiotic resistance.

Phentolamine Significantly Enhances Macrolide Antibiotic Antibacterial Activity against MDR Gram-Negative Bacteria

OBJECTIVES

Multidrug-resistant (MDR) Gram-negative bacterial infections have limited treatment options due to the impermeability of the outer membrane. New therapeutic strategies or agents are urgently needed, and combination therapies using existing antibiotics are a potentially effective means to treat these infections. In this study, we examined whether phentolamine can enhance the antibacterial activity of macrolide antibiotics against Gram-negative bacteria and investigated its mechanism of action.

METHODS

Synergistic effects between phentolamine and macrolide antibiotics were evaluated by checkerboard and time-kill assays and in vivo using a Galleria mellonella infection model. We utilized a combination of biochemical tests (outer membrane permeability, ATP synthesis, ΔpH gradient measurements, and EtBr accumulation assays) with scanning electron microscopy to clarify the mechanism of phentolamine enhancement of macrolide antibacterial activity against Escherichia coli.

RESULTS

In vitro tests of phentolamine combined with the macrolide antibiotics erythromycin, clarithromycin, and azithromycin indicated a synergistic action against E. coli test strains. The fractional concentration inhibitory indices (FICI) of 0.375 and 0.5 indicated a synergic effect that was consistent with kinetic time-kill assays. This synergy was also seen for Salmonella typhimurium, Klebsiella pneumoniae, and Actinobacter baumannii but not Pseudomonas aeruginosa. Similarly, a phentolamine/erythromycin combination displayed significant synergistic effects in vivo in the G. mellonella model. Phentolamine added singly to bacterial cells also resulted in direct outer membrane damage and was able to dissipate and uncouple membrane proton motive force from ATP synthesis that, resulted in enhanced cytoplasmic antibiotic accumulation via reduced efflux pump activity.

CONCLUSIONS

Phentolamine potentiates macrolide antibiotic activity via reducing efflux pump activity and direct damage to the outer membrane leaflet of Gram-negative bacteria both in vitro and in vivo.

CRISPR-Cas engineering in food science and sustainable agriculture: recent advancements and applications

The developments in the food supply chain to support the growing population of the world is one of today's most pressing issues, and to achieve this goal improvements should be performed in both crops and microbes. For this purpose, novel approaches such as genome editing (GE) methods have upgraded the biological sciences for genome manipulation and, among such methods, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) are the main exciting innovations since the Green Revolution. CRISPR/Cas systems can be a potent tool for the food industry, improvement of agricultural crops and even for protecting food-grade bacteria from foreign genetic invasive elements. This review introduces the history and mechanism of the CRISPR-Cas system as a genome editing tool and its applications in the vaccination of starter cultures, production of antimicrobials and bioactive compounds, and genome editing of microorganisms.

Optimizing patient recruitment into clinical trials of antimicrobial-resistant pathogens

Recruitment of patients with critical priority antimicrobial-resistant (AMR) bacteria into drug approval randomized controlled trials (RCTs) has not been successful to date. Approaching from the viewpoint of clinician-investigators and learning from the experience of AMR-focused investigator-initiated trials, we present suggestions to improve feasibility and efficiency of RCTs evaluating patients with severe infections caused by carbapenem-resistant Gram-negative or other AMR bacteria. Considerations address the trials' eligibility criteria, whether the focus of the trial is pathogen- or syndrome-targeted, trials' case report forms and monitoring, informed consent strategies for the recruitment of extremely ill patients, team dedication and incentives to run the trial and alternative trial designs. Evidence on the effects of new drugs against the AMR that these drugs target is weak and needs to be improved through better industry-academic collaboration, taking advantage of the different strengths of industry-led and investigator-initiated research.

UV C Light from a Light-Emitting Diode at 275 Nanometers Shortens Wound Healing Time in Bacterium- and Fungus-Infected Skin in Mice

Due to the changes in pathogenic species and the absence of research on topical skin antibiotics, the therapy of skin and soft tissue infections (SSTIs) is facing more and more severe challenges. It is particularly urgent to look for alternative therapies without induction of drug resistance. UV C (UVC) light within the range of 200 to 280 nm is one of the most common techniques used to kill and/or inactivate pathogenic microorganisms. However, the traditional most commonly used wavelength of 254 nm irradiated from a low-pressure mercury lamp is hazardous to human health, being both carcinogenic and damaging to eye tissues, which limits its applications in vivo. This research aimed to investigate the antimicrobial properties and influence of 275-nm UVC light from a light-emitting diode (UVC-LED light) on wound healing time. Five bacteria, three fungi, and scalded-mouse models combined with SSTIs were used to evaluate the antimicrobial effect in vitro and in vivo. 275-nm UVC-LED light inactivated both bacteria and fungi with a very short irradiation time in vitro and induced neither DNA damage nor epidermal lesions in the mice's skin. Furthermore, in mouse models of SSTIs induced by either methicillin-resistant Staphylococcus aureus (MRSA) or Candida albicans, the 275-nm UVC-LED light showed significant antimicrobial effects and shortened the wound healing time compared with that in the no-irradiation group. UVC-LED light at 275 nm has the potential to be a new form of physical therapy for SSTIs. IMPORTANCE As a common clinical problem, the therapy of SSTIs is facing growing challenges due to an increase in the number of drug-resistant bacteria and fungi. UV C (UVC) light sterilization has been widely used in all aspects of daily life, but there are very few reports about in vivo therapy using UVC light. It is well known that prolonged exposure to UVC light increases the possibility of skin cancer. In addition, it is also very harmful for eyes. UV irradiation with 254-nm UVC light can cause corneal damage, like thinning of the corneal epithelial layer, superficial punctate keratitis, corneal erosion, etc. In this study, we focused on looking for a more accessible light source and safer UVC wavelength, and 275-nm UVC LED light was chosen. We investigated its applicability for SSTIs therapy with relative skin safety and expected that it could be used as a new physical therapy method for SSTIs.

Trends in the Quality of Evidence Supporting FDA Drug Approvals: Results from a Literature Review

CONTEXT

New drug approvals in the United States must be supported by substantial evidence from "adequate and well-controlled" trials. The Food and Drug Administration (FDA) has flexibility in how it applies this standard.

METHODS

The authors conducted a systematic literature review of studies evaluating the design and outcomes of the key trials supporting new drug approvals in the United States. They extracted data on the trial characteristics, endpoint types, and expedited regulatory pathways.

FINDINGS

Among 48 publications eligible for inclusion, 30 covered trial characteristics, 23 covered surrogate measures, and 30 covered regulatory pathways. Trends point toward less frequent randomization, double-blinding, and active controls, with variation by drug type and indication. Surrogate measures are becoming more common but are not consistently well correlated with clinical outcomes. Drugs approved through expedited regulatory pathways often have less rigorous trial design characteristics.

CONCLUSIONS

The characteristics of trials used to approve new drugs have evolved over the past two decades along with greater use of expedited regulatory pathways and changes in the nature of drugs being evaluated. While flexibility in regulatory standards is important, policy changes can emphasize high-quality data collection before or after FDA approval.

Diagnosis and management of infections caused by multidrug-resistant bacteria: guideline endorsed by the Italian Society of Infection and Tropical Diseases (SIMIT), the Italian Society of Anti-Infective Therapy (SITA), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Association of Clinical Microbiologists (AMCLI) and the Italian Society of Microbiology (SIM)

Management of patients with infections caused by multidrug-resistant organisms is challenging and requires a multidisciplinary approach to achieve successful clinical outcomes. The aim of this paper is to provide recommendations for the diagnosis and optimal management of these infections, with a focus on targeted antibiotic therapy. The document was produced by a panel of experts nominated by the five endorsing Italian societies, namely the Italian Association of Clinical Microbiologists (AMCLI), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Society of Microbiology (SIM), the Italian Society of Infectious and Tropical Diseases (SIMIT) and the Italian Society of Anti-Infective Therapy (SITA). Population, Intervention, Comparison and Outcomes (PICO) questions about microbiological diagnosis, pharmacological strategies and targeted antibiotic therapy were addressed for the following pathogens: carbapenem-resistant Enterobacterales; carbapenem-resistant Pseudomonas aeruginosa; carbapenem-resistant Acinetobacter baumannii; and methicillin-resistant Staphylococcus aureus. A systematic review of the literature published from January 2011 to November 2020 was guided by the PICO strategy. As data from randomised controlled trials (RCTs) were expected to be limited, observational studies were also reviewed. The certainty of evidence was classified using the GRADE approach. Recommendations were classified as strong or conditional. Detailed recommendations were formulated for each pathogen. The majority of available RCTs have serious risk of bias, and many observational studies have several limitations, including small sample size, retrospective design and presence of confounders. Thus, some recommendations are based on low or very-low certainty of evidence. Importantly, these recommendations should be continually updated to reflect emerging evidence from clinical studies and real-world experience.

Evidence at time of regulatory approval and cost of new antibiotics in 2016-19: cohort study of FDA approved drugs

Objective

To review the clinical evidence, regulatory background, and cost of antibiotics approved by the US Food and Drug Administration (FDA), 2016-19.

Design

Cohort study of FDA approved drugs.

Data sources

FDA databases, ClinicalTrials.gov, and drug labelling. Launch prices were extracted from IBM Micromedex Red Book.

Eligibility criteria for selecting studies

Antibiotics approved by the FDA from October 2016 to December 2019 were identified, and key features of their clinical development were extracted from publicly available FDA databases, ClinicalTrials.gov, and drug labelling. Launch prices were extracted from IBM Micromedex Red Book to evaluate the cost of treatment against comparators.

Results

15 new antibiotics received at least one special regulatory designation and were supported by a median of two pivotal trials. More than half of the pivotal trials used an active control non-inferiority design. All drugs were approved based on surrogate outcome measures. 52 postmarketing requirements and commitments were included across the cohort (median 3 for each drug). From January 2021, 27 postmarketing requirements and commitments were listed as pending, seven as ongoing, three as delayed, one as submitted, eight as released, and four as fulfilled. The most expensive new antibiotic was pretomanid at $36 399 (£29 618; €34 582) for a course of treatment, and the least expensive was rifamycin ($176). Cost ratios between study drugs and comparators ranged from 0.48 to 134.

Conclusions

New antibiotics have been approved by the FDA in recent years mostly based on fewer, smaller, and non-inferiority pivotal trials that often used surrogate outcome measures but were commonly more costly. Efforts to incentivise the development of antibiotics should balance growing the antibiotic development pipeline with ensuring that clinical trials provide clinically relevant evidence of effectiveness in showing added benefits for the patient.

All-cause mortality rates in adults with carbapenem-resistant Gram-negative bacterial infections: a comprehensive review of pathogen-focused, prospective, randomized, interventional clinical studies

INTRODUCTION

Pathogen-focused, randomized, controlled trials (PF-RCT) are important in the fight against carbapenem-resistant (CR) Gram-negative infections. Some recently approved antibiotics and older generic antibiotics with activity against CR Gram-negative bacteria were investigated in PF-RCTs in a variety of infections.

AREAS COVERED

We searched Pubmed, Cochrane database and international clinical trial databases for PF-RCTs for the period between 2005 and 2020 and compared the study designs, patient populations, infection types, pathogens, and Day-28 all-cause mortality (ACM).

EXPERT OPINION

PF-RCTs are particularly challenging to quantitatively assess and compare due to the heterogeneity in infection types, pathogens, CR mechanism, inclusion/exclusion criteria, and endpoints. Data interpretation is further complicated by lack of formal statistical analysis plans and/or non-inferiority design, and limited power across most PF-RCTs. The studies with new antibiotics (i.e. plazomicin, meropenem/vaborbactam, cefiderocol) ranked lower regarding feasibility, with relatively small sample sizes (analyzed: 37-118) versus the comparative effectiveness studies of older generic drugs (analyzed: 94-406). ACM ranged between 11.8% and 40% for CR Enterobacterales, 17.7% and 57.4% for CR Acinetobacter spp., and 20.0% and 30.8% for CR Pseudomonas aeruginosa. The information gathered must be considered carefully alongside the study limitations and caution should be exercised when making direct comparisons across trials.

Cost Analysis of New Antibiotics to Treat Multidrug-Resistant Bacterial Infections: Mind the Gap

Introduction

Guidelines for treatment of multidrug-resistant (MDR) bacteria rely on newly approved antibiotics, with limited evidence of their effectiveness for treating these infections. Data regarding cost of such an approach are lacking. We aimed to evaluate estimated cost of using newly approved antibiotic drugs compared to older antibiotics for the treatment of difficult-to-treat pathogens.

Methods

MDR bacteria of interest included those defined by the World Health Organization as critical or of high priority for research. Old and newly approved antibiotics for these bacteria, defined as approved before or after January 2010, respectively, were evaluated for treatment cost and for 14-day treatment course. Estimated annual costs were calculated based on the Centers for Disease Control and Prevention’s' report on MDR bacteria prevalence in US hospitalized patients. Old and new drugs costs were compared.

Results

The cost of a 14-day treatment course for methicillin-resistant Staphylococcus aureus bacteremia with a newly approved drug was found to be 6 to 60 times higher than that of older drugs. Similarly, the cost of a 14-day course for carbapenem-resistant Enterobacterales or MDR Pseudomonas aeruginosa was doubled with new drugs; and for carbapenem-resistant Acinetobacter baumannii, ~ 20 times higher with newer drugs. Annual incremental costs of treating difficult-to-treat Gram-negative bacteria with new drugs ranged from 30 million to over 500 million USD.

Conclusions

Using newly approved antibiotic drugs for MDR infections carries a large incremental cost. Additional data to support survival benefit of these drugs are required to justify the price differences. Subgroups of patients who would benefit most from treatment should be defined.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00412-y.

The Wrong Cure: Financial Incentives for Unimpressive New Antibiotics

Though antimicrobial resistance is a public health concern, the basis of approval for many new antibiotics does not distinguish them from older products. We suggest a more tailored incentive structure for antibiotic development, focused on clinical benefit and patient outcomes.