Assessing Clinician Utilization of Next-Generation Antibiotics Against Resistant Gram-Negative Infections in U.S. Hospitals : A Retrospective Cohort Study

Using a difficult-to-treat resistance index to gauge imbalance between countries' antibiotic resistance prevalence and access to antibiotics: a scoping review and concept proposal

BACKGROUND

Inferring the impact of antimicrobial resistance on patient outcomes is challenging, given the variability in antibiotic access across countries and over time. By denoting resistance to all highly safe and effective antibiotics, the difficult-to-treat resistance (DTR) definition offers a framework for such assessments globally.

OBJECTIVES

This study aims to conduct a scoping review to understand the international adoption, scalability, and prognostic utility of DTR and enable solutions to incorporate antibiotic access into the DTR framework.

METHODS

Data sources: Data sources included Agricola, Embase, Global Index Medicus, PubMed, Scopus, Web of Science: BIOSIS and Core Collection.

STUDY ELIGIBILITY CRITERIA

Study eligibility criteria included original research publications occurring after January 2018 using the term 'difficult-to-treat resistance' to describe antimicrobial-resistant bacterial isolates demonstrating resistance to all first-line antibiotics (i.e. all β-lactam and fluoroquinolone antibiotics).

ASSESSMENT OF RISK OF BIAS

Assessment of risk of bias included Joanna Briggs Institute critical appraisal tool.

METHODS OF DATA SYNTHESIS

We assessed the overall themes of the included studies and classified them into epidemiological, mortality, or antibiotic effectiveness/efficacy studies. Semiquantitative results among studies evaluating the prevalence of resistant bacterial isolates and mortality were reported. We propose a 'DTR index' (DTRi) that extends beyond gram-negative bacteria and complements DTR by estimating national proportions of bacterial isolates resistant to all first-line antibiotics available specifically in that country.

RESULTS

DTR was utilized in 57 studies spanning 94 countries. The DTR definition was predominantly applied unmodified and retained prognostic utility in 70% of studies. The variability in access to first-line antibiotics and emergence of newer agents across countries and over time influence practical treatment options that cannot be captured by 'fixed' DTR definitions underscoring the value of the proposed DTRi.

CONCLUSIONS

The DTRi could appraise the clinical impact of introducing new agents in a country, identify hot zones of resistance-access imbalance, and optimize resource allocation to improve antibiotic resistance outcomes, especially in under-resourced populations.

Sustainable solutions to the continuous threat of antimicrobial resistance

To combat antimicrobial resistance (AMR), advocates have called for passage of the Pioneering Antimicrobial Subscriptions To End Upsurging Resistance (PASTEUR) Act in the United States, which would appropriate $6 billion in new taxpayer-funded subsidies for antibiotic development. However, the number of antibiotics in clinical development, and US Food and Drug Administration approvals of new antibiotics, have already markedly increased in the last 15 years. Thus, instead of focusing on more economic subsidies, we recommend reducing selective pressure driving AMR by (1) establishing pay-for-performance mechanisms that disincentivize overprescribing of antibiotics, (2) focusing existing research and development funding on strategies that decrease reliance on antibiotics, and (3) changing regulation or law to require specialized training in antibiotic stewardship for a clinician to be able to prescribe new antibiotics that target unmet AMR need. To stabilize the antibiotic market, we recommend (1) establishment of an advisory board of clinical practitioners to more accurately target existing antibiotic incentives and (2) endowment of nonprofit companies that sustainably self-fund antibiotic discovery, creating a bench of molecules that can be partnered with industry at later stages of development.

New Kids on the Block: Estimating Use of Next-generation Gram-negative Antibiotics Across Greater Than 700 Hospitals in the United States

Background

In recent years, new broad-spectrum antibiotics targeting Gram-negative organisms have been introduced, including cefiderocol, ceftazidime-avibactam, ceftolozane-tazobactam, eravacycline, imipenem-relebactam, omadacycline, and meropenem-vaborbactam. This study aimed to describe new antibiotic use across a large national cohort.

Methods

We performed a retrospective cohort study of hospital discharges from June 2022 to May 2023 using the Premier Healthcare Database. Antibiotic utilization was ascertained from daily charges. Clinical indication(s) were inferred from International Classification of Diseases, 10th revision, diagnosis codes. Antibiotic therapy was considered definitive if continued >3 days. Piperacillin-tazobactam was used as a comparator.

Results

Across 832 hospitals, 3 890 557 admissions (61.9% of all admissions) included an antibiotic prescription. New antibiotics were prescribed in 9768 admissions (0.25% of antibiotic-prescribing admissions) across 537 hospitals. Ceftolozane-tazobactam was prescribed in 4157 admissions (42.6% of 9768), ceftazidime-avibactam in 3660 (37.5%), eravacycline in 1213 (12.4%), cefiderocol in 1060 (10.9%), meropenem-vaborbactam in 456 (4.7%), omadacycline in 104 (1.1%), and imipenem-relebactam in 99 (1.0%). In contrast, piperacillin-tazobactam was prescribed in 731 719 (18.8%) and colistin in 570 (0.01%) admissions. Forty-six percent (n = 4647/9768) of new antibiotics were started in the first 3 days of hospital admission, and 70% (n = 6799/9768) were used as definitive therapy. Sepsis (76%), pneumonia (46%), and urinary tract infection (39%) were the most common clinical indications. On average, patients treated with new antibiotics had 8 more comorbid conditions than patients receiving piperacillin-tazobactam.

Conclusions

Ceftazidime-avibactam and ceftolozane-tazobactam remain the most frequently prescribed new antibiotics, with uptake of subsequently approved agents trailing. New antibiotics are most commonly used as treatment for sepsis among patients with multiple comorbidities.

Use of adjuvants to improve antibiotic efficacy and reduce the burden of antimicrobial resistance

INTRODUCTION

The increase in antibiotic resistance, together with the absence of novel antibiotics, makes mandatory the introduction of novel strategies to optimize the use of existing antibiotics. Among these strategies, the use of molecules that increase their activity looks promising.

AREAS COVERED

Different categories of adjuvants have been reviewed. Anti-resistance adjuvants increase the activity of antibiotics by inhibiting antibiotic resistance determinants. Anti-virulence approaches focus on the infection process itself; reducing virulence in combination with an antibiotic can improve therapeutic efficacy. Combination of phages with antibiotics can also be useful, since they present different mechanisms of action and targets. Finally, combining antibiotics with adjuvants in the same molecule may serve to improve antibiotics' efficacy and to overcome potential problems of differential pharmacokinetics/pharmacodynamics.

EXPERT OPINION

The successful combination of inhibitors of β-lactamases with β-lactams has shown that adjuvants can improve the efficacy of current antibiotics. In this sense, novel anti-resistance adjuvants able to inhibit efflux pumps are still needed, as well as anti-virulence compounds that improve the efficacy of antibiotics by interfering with the infection process. Although adjuvants may present different pharmacodynamics/pharmacokinetics than antibiotics, conjugates containing both compounds can solve this problem. Finally, already approved drugs can be a promising source of antibiotic adjuvants.

Effectiveness of ceftazidime-avibactam versus ceftolozane-tazobactam for multidrug-resistant Pseudomonas aeruginosa infections in the USA (CACTUS): a multicentre, retrospective, observational study

BACKGROUND

Ceftolozane-tazobactam and ceftazidime-avibactam are preferred treatment options for multidrug-resistant Pseudomonas aeruginosa infections; however, real-world comparative effectiveness studies are scarce. Pharmacokinetic and pharmacodynamic differences between the agents might affect clinical response rates. We aimed to compare the effectiveness of ceftolozane-tazobactam and ceftazidime-avibactam for treatment of invasive multidrug-resistant P aeruginosa infections.

METHODS

This multicentre, retrospective, observational study was conducted at 28 hospitals in the USA between Jan 1, 2016, and Dec 31, 2023. Eligible patients were adults (age ≥18 years old) with microbiologically confirmed multidrug-resistant P aeruginosa pneumonia or bacteraemia treated with ceftolozane-tazobactam or ceftazidime-avibactam for more than 48 h. Patients were matched (1:1) by study site, severity of illness, time to treatment initiation (≤72 h or >72 h), and infection type. The primary outcome was clinical success at day 30, which was defined as survival, resolution of signs and symptoms of infection with the intended treatment course, and the absence of recurrent infection due to P aeruginosa. Secondary outcomes included all-cause mortality and development of resistance to study drug.

FINDINGS

420 eligible patients were included (210 in each treatment group), of whom 350 (83%) had pneumonia and 70 (17%) had bacteraemia. Baseline demographics, comorbidities, and severity of illness indicators were similar between groups. On treatment initiation, 336 (80%) patients were in the intensive care unit, 296 (70%) were receiving mechanical ventilation, and 168 (40%) required vasopressor support. Clinical success was observed in 128 (61%) of 210 patients treated with ceftolozane-tazobactam and 109 (52%) of 210 patients treated with ceftazidime-avibactam. By conditional logistic regression analysis, the adjusted odds ratio (aOR) of success after treatment with ceftolozane-tazobactam compared with ceftazidime-avibactam was 2·07 (95% CI 1·16-3·70). For patients with pneumonia, clinical success was observed in 110 (63%) of 175 patients in the ceftolozane-tazobactam group and 89 (51%) of 175 patients in the ceftazidime-avibactam group (aOR 2·34 [95% CI 1·22-4·47]). Among patients with bacteraemia, rates of clinical success were 51% (18 of 35 patients) for patients treated with ceftolozane-tazobactam and 57% (20 of 35 patients) for those treated with ceftazidime-avibactam (0·76 [0·23-2·57]). There were no significant differences between groups in 30-day or 90-day mortality. Among patients whose baseline isolates were tested for susceptibility, resistance developed in 22% (38 of 173) of patients treated with ceftolozane-tazobactam and 23% (40 of 177) of patients treated with ceftazidime-avibactam.

INTERPRETATION

Treatment with ceftolozane-tazobactam resulted in higher rates of clinical success compared with ceftazidime-avibactam for invasive infections due to multidrug-resistant P aeruginosa. Differences were driven by improved response rates for patients with pneumonia who were treated with ceftolozane-tazobactam. There were no significant differences between study groups with respect to all-cause mortality; treatment-emergent resistance was common with both agents.

FUNDING

Merck Sharp & Dohme.

Advancing global antibiotic research, development and access

The pipeline of new antibiotics is insufficient to keep pace with the growing global burden of drug-resistant infections. Substantial economic challenges discourage private investment in antibiotic research and development (R&D), with a decline in the number of companies and researchers working in the field. Compounding these issues, many countries (from low income to high income) face a growing crisis of antibiotic shortages and inequitable access to existing and emerging treatments. This has led to an increasing role for public and philanthropic funding in supporting antibiotic R&D via the creation of nonprofit public-private partnerships, including Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator (CARB-X) and the Global Antibiotic Research and Development Partnership (GARDP), industry support for the AMR Action Fund, and pilot schemes to evaluate and reimburse antibiotics in innovative ways. Now is the time to raise the urgency, ambition and commitments of the world's leaders to fully support the antibiotic R&D ecosystem, incentivizing all sectors to conduct public health-driven antibiotic R&D and make effective antibiotics accessible to all who need them.

New Agents Are Coming, and So Is the Resistance

Antimicrobial resistance is a global threat that requires urgent attention to slow the spread of resistant pathogens. The United States Centers for Disease Control and Prevention (CDC) has emphasized clinician-driven antimicrobial stewardship approaches including the reporting and proper documentation of antimicrobial usage and resistance. Additional efforts have targeted the development of new antimicrobial agents, but narrow profit margins have hindered manufacturers from investing in novel antimicrobials for clinical use and therefore the production of new antibiotics has decreased. In order to combat this, both antimicrobial drug discovery processes and healthcare reimbursement programs must be improved. Without action, this poses a high probability to culminate in a deadly post-antibiotic era. This review will highlight some of the global health challenges faced both today and in the future. Furthermore, the new Infectious Diseases Society of America (IDSA) guidelines for resistant Gram-negative pathogens will be discussed. This includes new antimicrobial agents which have gained or are likely to gain FDA approval. Emphasis will be placed on which human pathogens each of these agents cover, as well as how these new agents could be utilized in clinical practice.