Evaluation of Plazomicin, Tigecycline, and Meropenem Pharmacodynamic Exposure against Carbapenem-Resistant Enterobacteriaceae in Patients with Bloodstream Infection or Hospital-Acquired/Ventilator-Associated Pneumonia from the CARE Study (ACHN-490-007)

Development of a Weighted-Incidence Syndromic Combination Antibiogram (WISCA) to guide empiric antibiotic treatment for ventilator-associated pneumonia in a Mexican tertiary care university hospital

BACKGROUND

Ventilator-associated pneumonia (VAP) is a significant nosocomial infection in critically ill patients, leading to high morbidity, mortality, and increased healthcare costs. The diversity of local microbiology and resistance patterns complicates the empirical treatment selection. The Weighted-Incidence Syndromic Combination Antibiogram (WISCA) offers an innovative tool to optimize empirical antibiotic therapy by integrating local microbiological data and resistance profiles.

OBJECTIVE

To develop a WISCA tailored for VAP in a Mexican tertiary care university hospital, aiming to enhance empirical antibiotic coverage by addressing the unique pathogen distribution and resistance patterns within the institution.

METHODS

This retrospective study included 197 VAP episodes from 129 patients admitted to a critical care unit between June 2021 and June 2024. Clinical and microbiological data, including pathogen susceptibility profiles, were analyzed using a Bayesian hierarchical model to evaluate the coverage of multiple antibiotic regimens. We also assessed the current impact of inappropriate empiric or directed treatment on in-hospital mortality using Cox regression models to support the development of a WISCA model.

RESULTS

The median age of the patients was 44 years (IQR 35-56), with Acinetobacter baumannii (n = 71), Enterobacterales (n = 53) and Pseudomonas aeruginosa (n = 36) identified as the most frequently isolated pathogens. The developed WISCA models showed variable coverage based on antibiotic regimens and the duration of invasive mechanical ventilation (IMV). Inappropriate directed therapy during the VAP episode was associated with increased mortality, as were the diagnosis of Acute Respiratory Distress Syndrome (ARDS) and a high Sequential Organ Failure Assessment (SOFA) score (p < 0.01).

CONCLUSIONS

The tailored WISCA with Bayesian hierarchical modeling provided more adaptive, subgroup-specific estimates and managed uncertainty better compared to fixed models. The implementation of this WISCA model demonstrated potential to optimize antibiotic strategies and improve clinical outcomes in critically ill patients in our hospital.

TOPIC

Optimizing Empirical Antibiotic Therapy for Ventilator-Associated Pneumonia Using a Weighted-Incidence Syndromic Combination Antibiogram in a Mexican Tertiary Care Hospital.

Emergence of tet(X4)-positive Enterobacterales in retail eggs and the widespread of IncFIA(HI1)-HI1A-HI1B(R27) plasmids carrying tet(X4)

The proliferation of antimicrobial-resistant microbes and resistance genes in various foods poses a serious hazard to public health. The plasmid-mediated tigecycline resistance gene tet(X4) has been detected in Enterobacterales from various niches but has not yet been reported in eggs. This study aimed to investigate the occurrence and characteristics of tigecycline-resistant strains from retail eggs. A total of 144 eggs were purchased from farmers' markets in Guangdong province, China, and eggshell (n = 144) and egg content (n = 96) samples were used to screen for tigecycline-resistant strains. Eight Escherichia coli strains (two ST195, one ST48, ST8165, ST752, ST93, ST189, and ST224) and one Klebsiella pneumoniae strain (ST252) recovered from eight (5.56 %, 8/144) egg samples (eggshells, n = 6; egg content, n = 2) were positive for tet(X4). Notably, the two E. coli ST195 strains were closely (15-54 SNPs) related to all the tet(X4)-positive E. coli ST195 from various origins (food animals, foods, migratory birds, human, and environment) deposited in GenBank. The E. coli ST224 showed a close phylogenetic relationship (9-12 SNPs) with two tet(X4)-positive E. coli strains from chicken feces and retail chicken in Guangdong province. The hybrid plasmid IncFIA(HI1)-HI1A-HI1B(R27) constitutes the predominant tet(X4) vector both herein (7/9, 77.78 %) and in the GenBank database (32/160, 20 %). The tet(X4)-positive IncFIA(HI1)-HI1A-HI1B(R27) plasmids, sharing highly similar structures, have been widely disseminated across China. However, the IncFIA(HI1)-HI1A-HI1B(R27) plasmids exhibit poor stability and low conjugation frequency. The contamination of tet(X4)-positive bacteria internally and externally in retail eggs poses a prospective food safety threat. More attention should be paid to the spread of the tet(X4) gene via epidemic clone E. coli ST195 and the plasmid IncFIA(HI1)-HI1A-HI1B(R27).

First detection of tet(X4)-positive Enterobacterales in retail vegetables and clonal spread of Escherichia coli ST195 producing Tet(X4) in animals, foods, and humans across China and Thailand

The mobile tigecycline-resistant gene tet(X4), which confers resistance to all tetracyclines, has been identified in bacterial isolates from various sources. However, there are no reports on the occurrence of tet(X4) in bacterial isolates of ready-to-eat fresh vegetables. In this study, 113 vegetable samples from farmers' markets were screened for tigecycline-resistant strains. Ten Escherichia coli (two ST195, two ST48, and one ST10, ST58, ST88, ST394, ST641, and ST101) and one Klebsiella pneumoniae (ST327) recovered from nine vegetable samples (7.96 %) were identified as carrying tet(X4). The core genome sequences of the two E. coli ST195 isolates showed a close relationship (14-41 single-nucleotide polymorphisms) with 31 tet(X4)-bearing E. coli ST195 isolates from humans, pigs, pork, and bird in China and Thailand, and the 33 E. coli ST195 isolates producing Tet(X4) shared similar resistance genes and plasmid replicons. Nanopore sequencing and conjugation experiments confirmed that the tet(X4) genes were located on the hybrid plasmids IncFIA-HI1A-HI1B (n = 6), IncX1 (n = 3), and IncFII2 (n = 1) in E. coli, and IncFII plasmid in K. pneumoniae. IncFIA-HI1A-HI1B and IncX1 plasmids shared highly similar structures with plasmids from various sources in the GenBank database. This is the first study to report the observation of tet(X4)-positive bacteria in retail vegetables. The epidemic clones and plasmids contribute to tet(X4) dissemination in vegetables. The clonal spread of Tet(X4)-producing E. coli ST195 across multiple niches and countries could pose a potential threat to public health.

Population pharmacokinetics of tigecycline in critically ill patients

Objective: In critically ill patients, the change of pathophysiological status may affect the pharmacokinetic (PK) process of drugs. The purpose of this study was to develop a PK model for tigecycline in critically ill patients, identify the factors influencing the PK and optimiz dosing regimens.

Method: The concentration of tigecycline was measured LC-MS/MS. We established population PK model with the non-linear mixed effect model and optimized the dosing regimens by Monte Carlo simulation.

Result: A total of 143 blood samples from 54 patients were adequately described by a one-compartment linear model with first-order elimination. In the covariate screening analysis, the APACHEII score and age as significant covariates. The population-typical values of CL and Vd in the final model were 11.30 ± 3.54 L/h and 105.00 ± 4.47 L, respectively. The PTA value of the standard dose regimen (100 mg loading dose followed by a 50 mg maintenance dose at q12 h) was 40.96% with an MIC of 2 mg/L in patients with HAP, the ideal effect can be achieved by increasing the dosage. No dose adjustment was needed for Klebsiella pneumoniae for AUC0–24/MIC targets of 4.5 and 6.96, and the three dose regimens almost all reached 90%. A target AUC0–24/MIC of ≥17.9 reached 100% in patients with cSSSI in the three tigecycline dose regimens, considering MIC ≤ 0.25 mg/L.

Conclusion: The final model indicated that APACHEII score and age could affect the Cl and Vd of tigecycline, respectively. The standard dose regimen of tigecycline was often not able to obtain satisfactory therapeutic effects for critically ill patients. For patients with HAP and cIAI caused by one of three pathogens, the efficacy rate can be improved by increasing the dose, but for cSSSI infections caused by Acinetobacter baumannii and K. pneumoniae, it is recommended to change the drug or use a combination of drugs.

Alternatives Therapeutic Approaches to Conventional Antibiotics: Advantages, Limitations and Potential Application in Medicine

Resistance to antimicrobials and particularly multidrug resistance is one of the greatest challenges in the health system nowadays. The continual increase in the rates of antimicrobial resistance worldwide boosted by the ongoing COVID-19 pandemic poses a major public health threat. Different approaches have been employed to minimize the effect of resistance and control this threat, but the question still lingers as to their safety and efficiency. In this context, new anti-infectious approaches against multidrug resistance are being examined. Use of new antibiotics and their combination with new β-lactamase inhibitors, phage therapy, antimicrobial peptides, nanoparticles, and antisense antimicrobial therapeutics are considered as one such promising approach for overcoming bacterial resistance. In this review, we provide insights into these emerging alternative therapies that are currently being evaluated and which may be developed in the future to break the progression of antimicrobial resistance. We focus on their advantages and limitations and potential application in medicine. We further highlight the importance of the combination therapy approach, wherein two or more therapies are used in combination in order to more effectively combat infectious disease and increasing access to quality healthcare. These advances could give an alternate solution to overcome antimicrobial drug resistance. We eventually hope to provide useful information for clinicians who are seeking solutions to the problems caused by antimicrobial resistance.

Use of pharmacokinetic/pharmacodynamic approaches for dose optimization: a case study of plazomicin

With limited treatment options available for multidrug-resistant bacteria, dose optimization is critical for achieving effective drug concentrations at the site of infection. Yet, selecting an appropriate dose and appropriate time to administer the dose with dosing frequency requires extensive understanding of the interplay between drug pharmacokinetics/pharmacodynamics (PK/PD), the host immune system, and bacterial-resistant mechanisms. Model-informed dose optimization (MIDO) uses PK/PD models (e.g. population PK, mechanism-based models, etc.) that incorporate preclinical and clinical data to simulate/predict performance of treatment regimens in appropriate patient populations and/or infection types that may not be well-represented in clinical trials. Here, we highlight the stages of a MIDO approach for designing optimized regimens by reviewing current clinical, preclinical, and PK/PD modeling data available for plazomicin. Plazomicin is an aminoglycoside approved in 2018 for the treatment of complicated urinary tract infections in adults. Applying knowledge gained by PK/PD modeling can guide therapeutic drug monitoring to ensure that drug exposure is appropriate for clinical efficacy while limiting drug-related toxicity.

Dosing Colistimethate Every 8 h Results in Higher Plasma Concentrations of Active Colistin Than Every 12-Hourly Dosing without Increase in Nephrotoxicity: A Phase 1 Pharmacokinetics Trial in Healthy Adult Volunteers

Despite its use for decades, pharmacokinetic (PK) and safety studies on colistin are limited. We conducted a phase l, open-label trial to evaluate the safety and PK of multiple doses of intravenous (IV) and aerosolized colistimethate sodium (CMS) administered separately and in combination. In total, 31 healthy adults were enrolled into three cohorts of 9, 10, and 12 participants, respectively. Each cohort received increasing doses of CMS over three dosing periods as follows: Period 1 (IV only), 2.5 mg/kg every 12 h (q12h) to 3.3 mg/kg every 8 h (q8h); Period 2 (aerosolized only), 75 mg 2–4 doses, and Period 3 (combined IV aerosolized), in which was Periods 1 and 2 combined. Safety assessments, serum and lung concentrations of colistin analytes (colistin A, colistin B, CMS A, and CMS B), and kidney biomarkers were measured at specified time points. Increasing the CMS dose from 2.5 mg/kg q12h to q8h resulted in a 33% increase in serum colistin A concentrations from 3.9 μg/mL to 5.3 μg/mL—well above the accepted target of 2 μg/mL for 6 h after dosing, without evidence of nephrotoxicity. However, there was an increase in neurotoxicity, primarily perioral and lingual paresthesias, and self-limited ataxia. IV administration did not increase the lung concentrations of colistin.

New evidence for managing Gram-negative bloodstream infections

PURPOSE OF REVIEW

Gram-negative bloodstream infections (GNBSI) are common and carry considerable mortality. Treatment is complicated by increasing antimicrobial resistance, posing a challenge for timely appropriate antibiotics and limiting the choices of effective definitive therapy. The present review aims to summarize recent studies addressing the management of GNBSI.

RECENT FINDINGS

New rapid diagnostic tests (RDT) for pathogen identification and antibiotic susceptibility are associated with improved antimicrobial stewardship and reduced length of stay. No mortality benefit or patient-related outcomes are reported. Data regarding the use of new beta-lactam beta-lactamase inhibitors (BLBLIs) for treating multidrug resistance Gram-negative bacteria is supportive, though questions regarding combinations, optimal dosing, mode of administration, and resistance emergence remain to be clarified. Current data regarding cefiderocol necessitates further studies in order to support its use in GNBSI. Shortened (≤7 days) duration of therapy and early oral step down for GNBSI are supported by the literature. The role of repeated blood cultures should be further defined.

SUMMARY

RDTs should be implemented to improve antibiotic stewardship. Clinical implications on patient-related outcomes should be evaluated. New BLBLIs show promise in the treatment of GNBSI. Additional data are needed regarding the use of cefiderocol. Antibiotic therapy should be shortened and early oral step down should be considered.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Plazomicin: a new aminoglycoside in the fight against antimicrobial resistance

Objective

To review the mechanism of action, mechanisms of resistance, in vitro activity, pharmacokinetics, pharmacodynamics, and clinical data for a novel aminoglycoside.

Data sources

A PubMed search was performed from January 2006 to August 2019 using the following search terms: plazomicin and ACHN-490. Another search was conducted on clinicaltrials.gov for published clinical data. References from selected studies were also used to find additional literature.

Study selection and data extraction

All English-language studies presenting original research (in vitro, in vivo, pharmacokinetic, and clinical) were evaluated.

Data synthesis

Plazomicin has in vitro activity against several multi-drug-resistant organisms, including carbapenem-resistant Enterobacteriaceae. It was Food and Drug Administration (FDA) approved to treat complicated urinary tract infections (cUTIs), including acute pyelonephritis, following phase II and III trials compared with levofloxacin and meropenem, respectively. Despite the FDA Black Box Warning for aminoglycoside class effects (nephrotoxicity, ototoxicity, neuromuscular blockade, and pregnancy risk), it exhibited a favorable safety profile with the most common adverse effects being decreased renal function (3.7%), diarrhea (2.3%), hypertension (2.3%), headache (1.3%), nausea (1.3%), vomiting (1.3%), and hypotension (1.0%) in the largest in-human trial.

Relevance to patient care and clinical practice

Plazomicin will likely be used in the treatment of multi-drug-resistant cUTIs or in combination to treat serious carbapenem-resistant Enterobacteriaceae infections.

Conclusions

Plazomicin appears poised to help fill the need for new agents to treat infections caused by multi-drug-resistant Enterobacteriaceae.

Pharmacologic optimization of antibiotics for Gram-negative infections

PURPOSE OF REVIEW

Antimicrobial resistance among Gram-negative organisms is a rapidly escalating global challenge. Pharmacologic dose optimization based on pharmacokinetic/pharmacodynamic principles is essential for managing Gram-negative infections. High-risk patient populations may receive nonoptimized antimicrobial dosing because pf physiologic changes in acute illness and/or medical interventions. The purpose of this review is to discuss opportunities for pharmacologic optimization of new agents and highlight patient populations that are often associated with poor drug exposure profiles.

RECENT FINDINGS

Dose optimization of the novel β-lactam-β-lactamase inhibitor combinations has been evaluated through optimizing exposure at the site of infection, evaluating target attainment of both the β-lactam and the β-lactamase-inhibitor in critically ill patients, and evaluating drug exposure to prevent the development of resistance. Plazomicin, a novel aminoglycoside, has pharmacodynamic optimization potential via therapeutic drug monitoring and nomogram-based dosing. Recent studies have evaluated the adequacy of dosing in varying degrees of renal function specifically acute kidney injury, continuous renal replacement therapy (CRRT), and augmented renal clearance (ARC).

SUMMARY

The application of fundamental pharmacokinetic/pharmacodynamic principles is required to optimize new antimicrobials in the treatment of serious Gram-negative infections. Exposure at the site of infection, pharmacokinetics in critically ill patients, and exposures to prevent resistance are all considerations to improve microbiologic and clinical outcomes. Therapeutic drug monitoring may be needed for high-risk patients.

Comparison of Treatment Outcomes between Analysis Populations in the RESTORE-IMI 1 Phase 3 Trial of Imipenem-Cilastatin-Relebactam versus Colistin plus Imipenem-Cilastatin in Patients with Imipenem-Nonsusceptible Bacterial Infections

The RESTORE-IMI 1 phase 3 trial demonstrated the efficacy and safety of imipenem-cilastatin (IMI) combined with relebactam (REL) for treating imipenem-nonsusceptible infections. The objective of this analysis was to compare the outcomes among patients meeting eligibility requirements based on central laboratory susceptibility versus local laboratory susceptibility. Patients with serious infections caused by imipenem-nonsusceptible, colistin-susceptible, and imipenem-REL-susceptible pathogens were randomized 2:1 to IMI-REL plus placebo or colistin plus IMI for 5 to 21 days. The primary endpoint was a favorable overall response. Key endpoints included the clinical response and all-cause mortality. We compared outcomes between the primary microbiological modified intent-to-treat (mMITT) population, where eligibility was based on central laboratory susceptibility testing, and the supplemental mMITT (SmMITT) population, where eligibility was based on local, site-level testing. The SmMITT (n = 41) and MITT (n = 31) populations had similar baseline characteristics, including sex, age, illness severity, and renal function. In both analysis populations, favorable overall response rates in the IMI-REL treatment group were >70%. Favorable clinical response rates at day 28 were 71.4% for IMI-REL and 40.0% for colistin plus IMI in the mMITT population, whereas they were 75.0% for IMI-REL and 53.8% for colistin plus IMI in the SmMITT population. Day 28 all-cause mortality rates were 9.5% for IMI-REL and 30.0% for colistin plus IMI in the mMITT population, whereas they were 10.7% for IMI-REL and 23.1% for colistin plus IMI in the SmMITT population. The outcomes in the SmMITT population were generally consistent with those in the mMITT population, suggesting that outcomes may be applicable to the real-world use of IMI-REL for treating infections caused by imipenem-nonsusceptible Gram-negative pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT02452047.).

Effectiveness and Safety of High Dose Tigecycline for the Treatment of Severe Infections: A Systematic Review and Meta-Analysis

BACKGROUND

Studies assessing the effect of high dose tigecycline on severe infections are limited and remain controversial.

OBJECTIVES

To assess systematically the effectiveness and safety of high dose tigecycline in the treatment of severe infections.

METHODS

Pubmed, Web of Science, Embase, MEDLINE, Cochrane Library and ClinicalTrials were searched up to February 20, 2019 for studies that compared the effectiveness and safety of high dose tigecycline with standard dose tigecycline or other non-tigecycline-containing regimens in the treatment of severe infections. Rates for all-cause mortality, clinical cure, microbiological eradication and adverse events were analysed.

RESULTS

Ten studies with 593 patients were included. The results indicated that using high dose tigecycline resulted in better outcomes compared with controls with lower all-cause mortality (OR 0.44, 95% CI 0.30-0.66, p < 0.0001), higher clinical cure (OR 3.43, 95% CI 2.09-5.63, p < 0.00001), higher microbiological eradication (OR 2.25, 95% CI 1.44-3.50, p = 0.0003), and without increasing adverse events rates. Subgroup analysis showed that high dose tigecycline reduced all-cause mortality in nosocomial acquired pneumonia (OR 0.39, 95% CI 0.22-0.70, p = 0.002), bloodstream infections (OR 0.19, 95% CI 0.06-0.58, p = 0.004) and mixed infections (OR 0.20, 95% CI 0.07-0.59, p = 0.003), with no statistical differences in complicated intra-abdominal infections (OR 2.04, 95% CI 0.80-5.23, p = 0.14). In carbapenem-resistant pathogens, the microbiological eradication rate in those given high dose tigecycline did not differ from controls (OR 1.07, 95% CI 0.44-2.60, p = 0.87), although mortality was reduced (OR 0.20, 95% CI 0.09-0.45, p = 0.0001). The main limitation of the review is that most of the included studies are observational studies with small sample sizes and high risks of bias.

CONCLUSIONS

High dose tigecycline treatment is effective and safe for severe infections owing to its lower all-cause mortality, higher clinical cure, microbiological eradication and comparable adverse events. However, as a result of the high risks of bias of the included studies, well-designed randomised clinical trials are warranted to establish the effectiveness and safety of high dose tigecycline compared with standard dose tigecycline and other commonly used antibiotics.

Carbapenem-Resistant Enterobacterales: Considerations for Treatment in the Era of New Antimicrobials and Evolving Enzymology

Purpose of Review

Gram-negative resistance is a growing concern globally. Enterobacterales, formerly Enterobacteriaceae, have developed resistance mechanisms to carbapenems that leave very few antimicrobial options in the clinician’s armamentarium.

Recent Findings

New antimicrobials like ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, cefiderocol, and plazomicin have the potential to overcome resistance mechanisms in Enterobacterales including different classes of carbapenemases.

Summary

Novel β-lactam/β-lactamase inhibitors, plazomicin, and cefiderocol give the clinician options that were once not available. Utilizing these options is of the utmost importance when treating carbapenem-resistant Enterobacterales.

Is Meropenem as a Monotherapy Truly Incompetent for Meropenem-Nonsusceptible Bacterial Strains? A Pharmacokinetic/Pharmacodynamic Modeling With Monte Carlo Simulation

Infections due to meropenem-nonsusceptible bacterial strains (MNBSs) with meropenem minimum inhibitory concentrations (MICs) ≥ 16 mg/L have become an urgent problem. Currently, the optimal treatment strategy for these cases remains uncertain due to some limitations of currently available mono- and combination therapy regimens. Meropenem monotherapy using a high dose of 2 g every 8 h (q 8 h) and a 3-h traditional simple prolonged-infusion (TSPI) has proven to be helpful for the treatment of infections due to MNBSs with MICs of 4–8 mg/L but is limited for cases with higher MICs of ≥16 mg/L. This study demonstrated that optimized two-step-administration therapy (OTAT, i.e., a new administration model of i.v. bolus plus prolonged infusion) for meropenem, even in monotherapy, can resolve this problem and was thus an important approach of suppressing such highly resistant bacterial isolates. Herein, a pharmacokinetic (PK)/pharmacodynamic (PD) modeling with Monte Carlo simulation was performed to calculate the probabilities of target attainment (PTAs) and the cumulative fractions of response (CFRs) provided by dosage regimens and 39 OTAT regimens in five dosing models targeting eight highly resistant bacterial species with meropenem MICs ≥ 16 mg/L, including Acinetobacter baumannii, Acinetobacter spp., Enterococcus faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Stenotrophomonas maltophilia, were designed and evaluated. The data indicated that meropenem monotherapy administered at a high dose of 2 g q 8 h and as an OTAT achieved a PTA of ≥90% for isolates with an MIC of up to 128 mg/L and a CFR of ≥90% for all of the targeted pathogen populations when 50% f T > MIC (50% of the dosing interval during which free drug concentrations remain above the MIC) is chosen as the PD target, with Enterococcus faecalis being the sole exception. Even though 50% f T > 5 × MIC is chosen as the PD target, the aforementioned dosage regimen still reached a PTA of ≥90% for isolates with an MIC of up to 32 mg/L and a CFR of ≥90% for Acinetobacter spp., Pseudomonas aeruginosa, and Klebsiella pneumoniae populations. In conclusion, meropenem monotherapy displays potential competency for infections due to such highly resistant bacterial isolates provided that it is administered as a reasonable OTAT but not as the currently widely recommended TSPI.