International Consensus Guidelines for the Optimal Use of the Polymyxins: Endorsed by the American College of Clinical Pharmacy (ACCP), European Society of Clinical Microbiology and Infectious Diseases (ESCMID), Infectious Diseases Society of America (IDSA), International Society for Anti-infective Pharmacology (ISAP), Society of Critical Care Medicine (SCCM), and Society of Infectious Diseases Pharmacists (SIDP)

Extended structure-activity relationship studies of the [1,2,5]oxadiazolo[3,4-b]pyrazine-containing colistin adjuvants

Antimicrobial resistance (AMR) is a formidable global health challenge. Multidrug-resistant (MDR) Gram-negative bacterial infections are of primary concern due to diminishing treatment options and high morbidity and mortality. Colistin, a polymyxin family antibiotic, is a last-resort treatment for MDR Gram-negative infections, but its wider use has resulted in escalating resistance. In 2022, using a screening approach, we discovered that a [1,2,5]oxadiazolo[3,4-b]pyrazine (ODP)-containing compound selectively re-sensitized various MDR Gram-negative bacteria to colistin. Initial structure-activity relationship (SAR) studies confirmed that bisanilino ODP compounds are colistin adjuvants with low mammalian toxicity. Herein, we report our extended SAR studies on a wide range of ODP analogs bearing alkyl- or arylalkylamines. Specifically, we discovered two new compounds, 5q and 8g, with potent colistin-potentiating activity and low mammalian toxicity in a wide range of clinically relevant pathogens.

Aerosolized plus intravenous polymyxin B in comparison to intravenous polymyxin B alone for the management of HAP caused by carbapenem-resistant gram-negative bacteria: a prospective multicenter cohort study

OBJECTIVES

This study aimed to evaluate the clinical effectiveness of combined aerosolized (AER) and intravenous (IV) polymyxin B in managing patients with hospital-acquired pneumonia (HAP) caused by carbapenem-resistant gram-negative organism (CRO) .

METHODS

This multicenter prospective cohort study was conducted across six intensive care units in municipal and above-municipal hospitals in Shaanxi, China, from January 1, 2021 to December 31, 2022. Patients with CRO pneumonia were categorized into the intravenous group (IV polymyxin B alone) and the combination group (AER plus IV polymyxin B). Primary outcomes included ICU mortality, 28-day mortality and bacterial clearance, while secondary outcomes included the duration of mechanical ventilation and length of ICU stay.

RESULTS

A total of 64 patients were included in the study, with 29 receiving AER plus IV polymyxin B and 35 receiving IV polymyxin B alone. On the seventh day of treatment, the combination group showed a significant reduction in the APACHE II score (17.86±5.03 vs. 19.17±11.02, P = 0.041) and procalcitonin levels (1.27±0.20 vs. 3.18±0.69, P < 0.001) compared to the intravenous group. Additionally, the combination group exhibited a higher bacterial eradication rate (62.1% vs. 42.9%), lower ICU mortality (27.6% vs. 37.1%), shorter duration of mechanical ventilation (371.39±68.97h vs. 563.94±100.25h), and reduced ICU stay (34.41±17.87 d vs. 35.03±21.66 d), although the differences were not statistically significant.

CONCLUSIONS

In patients with CRO pneumonia, combination therapy resulted in significant reductions in APACHE II scores and procalcitonin, but did not lead to statistically significant improvements in clinical outcomes, compared to IV polymyxin B alone.

Analysis of anti-infective therapy in a challenging case of brainstem hemorrhage complicated with pneumonia

We present a highly challenging case of brainstem hemorrhage complicated with pneumonia in a 41-year-old male patient. The patient had intermittent and recurrent fever for nearly two months from June 24, 2022 to August 22, 2022, along with extremely unstable vital signs. Multiple consultations were conducted among clinicians and pharmacists. In view of the patient's actual situation, they initially carried out empirical treatment and then comprehensively considered factors such as the characteristics of anti-infective drugs, interactions, susceptibility testing, and blood drug concentration to analyze and adjust the types and dosages of drugs and implement individualized therapy. Eventually, the patient's body temperature returned to normal, vital signs stabilized, and the patient was discharged smoothly. The author presents this case with the intention of providing a valuable reference for the treatment of patients with cerebral hemorrhage and pneumonia.

The in vitro Activity of Omadacycline Alone and in Combination Against Carbapenem-Resistant Klebsiella pneumoniae

Objective

This study aimed to evaluate the in vitro activity of omadacycline (OMC) and OMC-based combination therapy against carbapenem-resistant Klebsiella pneumoniae (CRKP).

Methods

The broth microdilution assay assessed the in vitro susceptibility of CRKP to OMC. The checkerboard assay was performed to evaluate the activity of OMC combined with polymyxin B (PB), amikacin (AN), or meropenem (MEM) against KPC-producing (class A) CRKP strains, and OMC combined with PB, aztreonam (ATM), MEM, or AN against class B and class A plus class B CRKP strains. Synergistic effects of OMC and PB were further evaluated by time-kill assays in the KPC-producing CRKP strains.

Results

Broth microdilution assays revealed a notable variation in susceptibility between KPC-producing and class B CRKP strains, with MIC50/90 of 32/32 mg/L and 0.5/8 mg/L, respectively. Although KPC-producing CRKP strains were resistant to OMC, a synergistic effect was observed in 37.5% of KPC-producing CRKP strains when OMC was combined with PB. In the nine KPC-producing CRKP strains, time-kill assays found that cell densities of six strains (66.7%) decreased by 3.61 ± 0.23 log10 CFU/mL compared to the initial inoculum after 2 hours of PB exposure. The cell densities further decreased by an average of 2.38 ± 0.23 log10 CFU/mL when the six strains were exposed to OMC plus PB, confirming their potent synergism.

Conclusion

OMC monotherapy is ineffective against KPC-producing CRKP strains, but OMC plus PB has a potent synergistic effect on them, suggesting that OMC plus PB is the preferred combination therapy against KPC-producing CRKP in vitro.

Carbapenem-resistant Acinetobacter baumannii raises global alarm for new antibiotic regimens

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a top-priority pathogen causing a nosocomial infection that increases morbidity and mortality. Treatment options for CRAB are relatively limited by pharmacokinetic restrictions, such as substantial toxicity. Therefore, we must better understand this pathogen to develop new treatments and control strategies. The review aims to provide an overview of the current understanding of acquired, adaptive, and intrinsic Carbapenem-resistant pathways in A. baumannii, as well as its consequences on healthcare systems, particularly critical care units. The review also provides insights into how CRAB infections are currently managed worldwide and why novel therapeutic regimens are needed. The peculiarity of A. baumannii and its often reported virulence factors have been discussed further. In conclusion, the purpose of this review is to emphasize the current knowledge on CRAB, as it causes major worry in the field of nosocomial infections as well as overall public health.

The challenges of difficult-to-treat Acinetobacter infections

SUMMARYInfections due to Acinetobacter spp. are among the most difficult to treat. Most are resistant to standard antibiotics, and there is difficulty in distinguishing colonizers from pathogens. This mini-review examines the available antibiotics that exhibit activity against these organisms and provides guidance as to which cultures are relevant and how to treat active infections. Antibiograms describing resistance mechanisms and the minimum inhibitory concentration (MIC) are essential to determine which agent or combination of agents should be used after confirmation of infection, utilizing clinical parameters and biomarkers such as procalcitonin. Directed therapy should be prompt as despite its reputation as a colonizer, the attributable mortality is high. However, although combination therapy is advised, no specific combination has definite evidence of superiority.

Advances in the clinical treatment of multidrug-resistant pathogens using polymyxins

OBJECTIVES

Polymyxins are a vital class of antibiotics used to combat multidrug-resistant Gram-negative bacteria. However, their use is limited due to potential nephrotoxicity and the availability of alternative antibiotics. This review aims to examine the properties of polymyxins and the clinical advances in their use for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB).

METHODS

This review analyses literature on polymyxin properties and various clinical approaches, including intravenous drip infusion, nebulized or dry powder inhalation, and ointment application. Treatment efficacy in terms of bacterial eradication, cure rate and mortality rate are reviewed and evaluated.

RESULTS

Polymyxins have been reintroduced to treat critical infections due to the increasing prevalence of CR-GNB. Clinical trials and studies have confirmed that polymyxins can effectively treat CR-GNB infections when the formulation and administration are appropriate, with acceptable levels of nephrotoxicity.

CONCLUSIONS

In the future, the development of polymyxin formulations will aim to improve their clinical effectiveness while reducing toxicity and side effects and preventing the emergence of polymyxin-resistant strains. Enhanced efficacy and minimized potential side effects can be achieved by developing new polymyxin-delivery systems that provide a smart and controlled release or customized patient administration.

Pharmacodynamic target attainment at infection site during treatment of post-neurosurgical ventriculitis caused by carbapenem-resistant klebsiella pneumoniae with ceftazidime-avibactam-based regimens: a case report

A patient developed a post-neurosurgical ventriculitis with carbapenem-resistant Klebsiella pneumoniae and mold, initially treated with ceftazidime/avibactam and voriconazole. A Klebsiella pneumoniae carbapenemase mutation led to therapy adjustment to ceftazidime/avibactam and polymyxin B, achieving cure. Pharmacokinetic/pharmacodynamic analysis highlights effective ceftazidime/avibactam brain penetration and bacterial clearance efficacy.

A systematic evaluation of population pharmacokinetic models for polymyxin B in patients with liver and/or kidney dysfunction

Polymyxin B (PMB) is considered a last-line treatment for multidrug-resistant (MDR) gram-negative bacterial infections. Model-informed precision dosing with population pharmacokinetics (PopPK) models could help to individualize PMB dosing regimens and improve therapy. However, the external prediction ability of the established PopPK models has not been fully elaborated. This study aimed to systemically evaluate eleven PMB PopPK models from ten published literature based on a new independent population, which was divided into four different populations, patients with liver dysfunction, kidney dysfunction, liver and kidney dysfunction, and normal liver and kidney function. The whole data set consisted of 146 patients with 391 PMB concentrations. The prediction- and simulation-based diagnostics and Bayesian forecasting were conducted to evaluate model predictability. In the overall evaluation process, none of the models exhibited satisfactory predictive ability in both prediction- and simulation-based diagnostic simultaneously. However, the evaluation of the models in the subgroup of patients with normal liver and kidney function revealed improved predictive performance compared to those with liver and/or kidney dysfunction. Bayesian forecasting demonstrated enhanced predictability with the incorporation of two to three prior observations. The external evaluation highlighted a lack of consistency between the prediction results of published models and the external validation dataset. Nonetheless, Bayesian forecasting holds promise in improving the predictive performance of the models, and feedback from therapeutic drug monitoring is crucial in optimizing individual dosing regimens.

Pharmacokinetic study of polymyxin B in healthy subjects and subjects with renal insufficiency

Polymyxin B is a viable option for treating antibiotic-resistant infections; however, current data on its pharmacokinetics, particularly in patients with renal insufficiency, remain inconclusive and necessitates further investigation. To address this gap, we conducted an open-label, single-center, single-dose, parallel-group pharmacokinetic study. Participants received an intravenous dose of 0.75 mg/kg of polymyxin B and were categorized based on their renal function: those with normal function (creatinine clearance [CLcr] ≥ 90 mL/min), mild renal insufficiency (CLcr 60-89 mL/min), and end-stage kidney disease patients on intermittent hemodialysis (IHD) (CLcr < 10 mL/min). The pharmacokinetic parameters assessed included the area under the curve (AUC), maximum concentration (Cmax), clearance rate (CL), volume of distribution (Vz), and half-life (t1/2). Results indicated that subjects with mild renal insufficiency exhibited pharmacokinetic profiles similar to healthy individuals. Nevertheless, in patients undergoing long-term IHD, we observed significant differences: the AUC was 58% higher, Cmax was 29% lower, CL was 42% lower, Vz was 60% larger, and t1/2 was extended by 10 h compared to healthy controls. Secondary outcomes revealed good tolerability of polymyxin B across all groups, with no serious adverse effects related to renal function. In summary, while kidney function may have a slight impact on the pharmacokinetic of polymyxin B, it does not compromise the drug's therapeutic effectiveness.

Effective strategies for managing trimethoprim-sulfamethoxazole and levofloxacin-resistant Stenotrophomonas maltophilia infections: bridging the gap between scientific evidence and clinical practice

PURPOSE OF REVIEW

To discuss the therapeutic options available for the management of difficult-to-treat strains of Stenotrophomonas maltophilia ( Sma ), namely those resistant to trimethoprim-sulfamethoxazole and fluoroquinolones.

RECENT FINDINGS

Recent pharmacological studies have highlighted the fact that current breakpoints for first-line antibiotics against Sma are too high. In light of these data, it is likely that the prevalence of difficult-to-treat (DTR) Sma is underestimated worldwide. Two promising alternatives for treating DTR strains are cefiderocol and the combination of aztreonam and an L2 inhibitor. However, clinical trials are currently very limited for these antibiotics and no comparative studies have been carried out to date. It is important to note that the clinical efficacy of cefiderocol appears to be inferior to that initially anticipated from in-vitro and animal studies. Consequently, minocycline and ceftazidime may remain viable options if they are used against strains with a low minimum inhibitory concentration. We advise against the use of intravenous polymyxins and tigecycline. Finally, recent literature does not support the systematic use of combination therapy or long-course treatments. In the coming years, phage therapy may become a promising approach against DTR Sma infections.

SUMMARY

Overall, clinical comparative studies focused on DTR strains are required in order to provide more accurate and actionable information for therapeutic decisions.

A simple, robust and high-throughput LC-MS/MS method for the therapeutic drug monitoring of polymyxin B1, polymyxin B2, polymyxin B3, isoleucine-polymyxin B1, polymyxin E1 and polymyxin E2 in human plasma

To facilitate clinical therapeutic drug monitoring (TDM) of polymyxin B (PB) and polymyxin E (PE), we developed and validated a simple LC-MS/MS method for simultaneous determination of PB (including polymyxin B1 (PB1), polymyxin B2 (PB2), polymyxin B3 (PB3) and isoleucine-polymyxin B1 (ile-PB1)) and PE (including polymyxin E1 (PE1) and polymyxin E2 (PE2)) in human plasma. PB or PE was extracted from 20.0 μL plasma using a 5% (v/v) formic acid acetonitrile solution and separated on a BEH-C18 column (2.1 × 100 mm, 1.7 μm) with a mobile phase consisting of 0.8% formic acid aqueous solution and 0.2% formic acid acetonitrile solution. Gradient elution was performed over 5.5 min at a flow rate of 0.250 mL/min. Quantitative analysis was conducted in positive ion scanning mode by electrospray ionization and multiple reaction monitoring. The method validation was conducted based on bioanalytical method validation guidance, including specificity, calibration curve, precision, accuracy, recovery, matrix effect, stability and dilution integrity and all of the results satisfied the requirements. The method was simple, robust and high-throughput and is currently being used to provide a TDM service to enhancing therapeutic efficacy and safety use of the PB and PE.

Effectiveness of combination therapy with intrathecal or intraventricular administration of polymyxin B for hospital-acquired central nervous system infections caused by carbapenem-resistant Acinetobacter baumannii: A retrospective study

OBJECTIVES

To evaluate the therapeutic regimen, efficacy and safety of intrathecal or intraventricular (ITH/IVT) administration of polymyxin B for hospital-acquired central nervous system (CNS) infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB).

METHODS

A retrospective study was undertaken of patients with CNS infections caused by CRAB treated with ITH/IVT combination therapy. The primary outcome was the clinical efficacy of treatment. The secondary outcomes were the bacterial clearance rate and the safety of therapy.

RESULTS

In total, 35 patients who received ITH [n=13 (37.1%)] or IVT [n=22 (62.9%)] polymyxin B as combination therapy were included in this study. The median duration of ITH/IVT polymyxin B therapy was 9 (interquartile range 7-11) days. The overall clinical cure rate and bacterial clearance rate were 77.1% and 85.7%, respectively. No adverse effects considered to be related to ITH/IVT polymyxin B were recorded. Clinical failure was independently associated with an Acute Physiology and Chronic Health Evaluation II score ≥15 [odds ratio (OR) 1.24, 95% confidence interval (CI) 1.05-1.42; P=0.038] and a Glasgow Coma Scale score ≤8 (OR 0.69, 95% CI 0.49-0.88; P=0.029). Early administration (≤4 days of infection onset) of ITH/IVT polymyxin B therapy resulted in a significantly higher clinical cure rate (OR 0.65, 95% CI 0.49-1.12; P<0.001), and may reduce the length of treatment and adverse effects.

CONCLUSIONS

ITH/IVT administration of polymyxin B is a valid alternative for the treatment of CNS infections caused by CRAB. Early use of ITH/IVT polymyxin B can result in greater clinical success.

The Challenge of Treating Infections Caused by Metallo-β-Lactamase-Producing Gram-Negative Bacteria: A Narrative Review

Gram-negative multidrug-resistant (MDR) bacteria, including Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa, pose a significant challenge in clinical practice. Infections caused by metallo-β-lactamase (MBL)-producing Gram-negative organisms, in particular, require careful consideration due to their complexity and varied prevalence, given that the microbiological diagnosis of these pathogens is intricate and compounded by challenges in assessing the efficacy of anti-MBL antimicrobials. We discuss both established and new approaches in the treatment of MBL-producing Gram-negative infections, focusing on 3 strategies: colistin; the recently approved combination of aztreonam with avibactam (or with ceftazidime/avibactam); and cefiderocol. Despite its significant activity against various Gram-negative pathogens, the efficacy of colistin is limited by resistance mechanisms, while nephrotoxicity and acute renal injury call for careful dosing and monitoring in clinical practice. Aztreonam combined with avibactam (or with avibactam/ceftazidime if aztreonam plus avibactam is not available) exhibits potent activity against MBL-producing Gram-negative pathogens. Cefiderocol in monotherapy is effective against a wide range of multidrug-resistant organisms, including MBL producers, and favorable clinical outcomes have been observed in various clinical trials and case series. After examining scientific evidence in the management of infections caused by MBL-producing Gram-negative bacteria, we have developed a comprehensive clinical algorithm to guide therapeutic decision making. We recommend reserving colistin as a last-resort option for MDR Gram-negative infections. Cefiderocol and aztreonam/avibactam represent favorable options against MBL-producing pathogens. In the case of P. aeruginosa with MBL-producing enzymes and with difficult-to-treat resistance, cefiderocol is the preferred option. Further research is needed to optimize treatment strategies and minimize resistance.

Discovery, development and optimisation of a novel frog antimicrobial peptide with combined mode of action against drug-resistant bacteria

Antimicrobial peptides (AMP) have emerged as promising candidates for addressing the clinical challenges posed by the rapid evolution of antibiotic-resistant microorganisms. Brevinins, a representative frog-derived AMP family, exhibited broad-spectrum antimicrobial activities, attacking great attentions in previous studies. However, their strong haemolytic activity and cytotoxicity, greatly limit their further development. In this work, we identified and characterised a novel brevinin-1 peptide, brevinin-1pl, from the skin secretions of the northern leopard frog, Rana pipiens. Like many brevinins, brevinin-1pl also displayed strong haemolytic activity, resulting in a lower therapeutic index. We employed several bioinformatics tools to analyse the structure and potential membrane interactions of brevinin-1pl, leading to a series of modifications. Among these analogues, des-Ala16-[Lys4]brevinin-1pl exhibited great enhanced therapeutic efficacy in both in vitro and in vivo tests, particularly against some antibiotics-resistant Escherichia coli strains. Mechanistic studies suggest that des-Ala16-[Lys4]brevinin-1pl may exert bactericidal effects through multiple mechanisms, including membrane disruption and DNA binding. Consequently, des-Ala16-[Lys4]brevinin-1pl holds promise as a candidate for the treatment of drug-resistant Escherichia coli infections.

Seasonal dynamics of the phage-bacterium linkage and associated antibiotic resistome in airborne PM2.5 of urban areas

Inhalable microorganisms in airborne fine particulate matter (PM2.5), including bacteria and phages, are major carriers of antibiotic resistance genes (ARGs) with strong ecological linkages and potential health implications for urban populations. A full-spectrum study on ARG carriers and phage-bacterium linkages will shed light on the environmental processes of antibiotic resistance from airborne dissemination to the human lung microbiome. Our metagenomic study reveals the seasonal dynamics of phage communities in PM2.5, their impacts on clinically important ARGs, and potential implications for the human respiratory microbiome in selected cities of China. Gene-sharing network comparisons show that air harbours a distinct phage community connected to human- and water-associated viromes, with 57 % of the predicted hosts being potential bacterial pathogens. The ARGs of common antibiotics, e.g., peptide and tetracycline, dominate both the antibiotic resistome associated with bacteria and phages in PM2.5. Over 60 % of the predicted hosts of vARG-carrying phages are potential bacterial pathogens, and about 67 % of these hosts have not been discovered as direct carriers of the same ARGs. The profiles of ARG-carrying phages are distinct among urban sites, but show a significant enrichment in abundance, diversity, temperate lifestyle, and matches of CRISPR (short for 'clustered regularly interspaced short palindromic repeats') to identified bacterial genomes in winter and spring. Moreover, phages putatively carry 52 % of the total mobile genetic element (MGE)-ARG pairs with a unique 'flu season' pattern in urban areas. This study highlights the role that phages play in the airborne dissemination of ARGs and their delivery of ARGs to specific opportunistic pathogens in human lungs, independent of other pathways of horizontal gene transfer. Natural and anthropogenic stressors, particularly wind speed, UV index, and level of ozone, potentially explained over 80 % of the seasonal dynamics of phage-bacterial pathogen linkages on antibiotic resistance. Therefore, understanding the phage-host linkages in airborne PM2.5, the full-spectrum of antibiotic resistomes, and the potential human pathogens involved, will be of benefit to protect human health in urban areas.

Intravenous combined with aerosolised polymyxins vs intravenous polymyxins monotherapy for ventilator-associated pneumonia: A systematic review and meta-analysis

Polymyxins were applied via different administration routes to treat ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Gram-negative bacteria (CR-GNB). The potential benefits of aerosolised polymyxins as adjunctive treatment for patients are contradictory. This review assessed the safety and efficacy of intravenous (IV) combined with aerosolised polymyxins vs IV polymyxins monotherapy in patients with VAP caused by CR-GNB. Two reviewers independently evaluated and extracted data from PubMed, Embase, Cochrane library and Web of Science. The primary outcome was all-cause mortality and secondary outcomes included clinical cure rate, clinical improvement rate, microbiological eradication rate and nephrotoxicity. Differences for dichotomous outcomes were expressed as odds ratios (ORs) with 95% confidence intervals (CIs). Eleven eligible studies were included. The results showed that compared with IV polymyxins monotherapy, IV plus aerosolised polymyxins therapy significantly reduced all-cause mortality rate (OR = 0.75, 95% CI 0.57-0.99, P = 0.045) and improved clinical improvement rate (OR = 1.62, 95% CI 1.02-2.60, P = 0.043) and microbial eradication rate (OR = 2.07, 95% CI 1.40-3.05, P = 0.000). However, there were no significant differences in terms of clinical cure rate (OR = 1.59, 95% CI 0.96-2.63, P = 0.072) and nephrotoxicity (OR = 1.14, 95% CI 0.80-1.63, P = 0.467) for IV plus aerosolised polymyxins therapy. Subgroup analysis revealed that the clinical improvement rate was significantly improved in case-control studies. Aerosolised polymyxins may be a useful adjunct to IV polymyxins for patients with CR-GNB VAP.

New antibiotics in clinical pipeline for treating infections caused by metallo-β-lactamases producing Gram-negative bacteria

PURPOSE OF REVIEW

To discuss novel antibiotics under clinical development, focusing on agents showing in-vitro activity against metallo-β-lactamases (MBL)-producing carbapenem-resistant Gram-negative bacteria (CR-GNB).

RECENT FINDINGS

Currently, only a few approved agents show activity, alone or in synergistic combinations, against MBL-producing CR-GNB. If approved by regulatory agencies in case of favorable results from ongoing (and, for some agents, already completed) phase-3 studies, some novel β-lactam/β-lactamase inhibitor (BL/BLI) combinations could become available in the next few years as additional important options for treating MBL-producing CR-GNB infections. Additional interesting agents that belong both to BL/BLI combinations and to antibiotic classes other than BL and BL/BLI combinations have also shown activity against MBL-producing CR-GNB, with most of them being in early phases of clinical development.

SUMMARY

Improving the use of these novel agents through virtuous antimicrobial stewardship frameworks able to guarantee both the efficacious treatment of infections requiring their use and the avoidance of their use whenever not necessary remains a challenge of utmost importance that should not be overlooked.

Clinical outcomes and safety of polymyxin B versus tigecycline combination therapy for pneumonia of carbapenem-resistant Klebsiella pneumoniae: a retrospective cohort study

PURPOSE

Infection by carbapenem-resistant Klebsiella pneumoniae (CRKP) has high mortality. There is no clear optimal therapeutic choice for pneumonia caused by CRKP. The aim of this study was to compare the clinical outcomes and safety of the standard doses of polymyxin B-based regimens vs tigecycline-based regimens and to identify risk factors for mortality.

METHODS

This retrospective cohort study included patients with pneumonia caused by CRKP between January 1, 2020 and December 31, 2022. The primary outcomes were 7-day bacterial eradication rate and 14- and 28-day all-cause mortality. The secondary outcome was incidence of acute kidney injury.

RESULTS

Seventy-three patients were included in this study, 29 in the polymyxin B-based combination therapy group and 44 in tigecycline-based combination therapy group. There were no significant differences between the two groups in terms of the 7-day bacterial eradication rate (31.03% vs 20.45%, p = 0.409), the 14-day all-cause mortality (37.93% vs 22.73%, p = 0.160), and the incidence of acute kidney injury (14.29% vs 6.82%, p = 0.526). The 28-day all-cause mortality in the polymyxin B-based therapy group was higher than in the tigecycline-based group (75.86% vs 45.45%, p = 0.010). Binary logistic regression analysis revealed that male and previous use of carbapenems were independent factors associated with 28-day all-cause mortality for patients treated with polymyxin B (p < 0.05).

CONCLUSIONS

Polymyxin B-based combination therapy at the standard dose should be used with caution for patients with CRKP-induced pneumonia, especially for men who used carbapenems prior to CRKP detection.

Transcriptomic investigations of polymyxins and colistin/sulbactam combination against carbapenem-resistant Acinetobacter baumannii

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a Priority 1 (Critical) pathogen urgently requiring new antibiotics. Polymyxins are a last-line option against CRAB-associated infections. This transcriptomic study utilized a CRAB strain to investigate mechanisms of bacterial killing with polymyxin B, colistin, colistin B, and colistin/sulbactam combination therapy. After 4 h of 2 mg/L polymyxin monotherapy, all polymyxins exhibited common transcriptomic responses which primarily involved disruption to amino acid and fatty acid metabolism. Of the three monotherapies, polymyxin B induced the greatest number of differentially expressed genes (DEGs), including for genes involved with fatty acid metabolism. Gene disturbances with colistin and colistin B were highly similar (89 % common genes for colistin B), though effects on gene expression were generally lower (0-1.5-fold in most cases) with colistin B. Colistin alone (2 mg/L) or combined with sulbactam (64 mg/L) resulted in rapid membrane disruption as early as 1 h. Transcriptomic analysis of this combination revealed that the effects were driven by colistin, which included disturbances in fatty acid synthesis and catabolism, and inhibition of nutrient uptake. Combination therapy produced substantially higher fold changes in 72 % of DEGs shared with monotherapy, leading to substantially greater reductions in fatty acid biosynthesis and increases in biofilm, cell wall, and phospholipid synthesis. This indicates synergistic bacterial killing with the colistin/sulbactam combination results from a systematic increase in perturbation of many genes associated with bacterial metabolism. These mechanistic insights enhance our understanding of bacterial responses to polymyxin mono- and combination therapy and will assist to optimize polymyxin use in patients.

Treatment Approaches for Carbapenem-Resistant Acinetobacter baumannii Infections

Carbapenem-resistant Acinetobacter baumannii has been associated with over three hundred thousand annual deaths globally. It is resistant to most available antibiotics and associated with high morbidity and mortality. No global consensus currently exists for treatment strategies that balance safety and efficacy because of heterogeneity of treatment regimens in current clinical practice and scarcity of large-scale controlled studies arising from difficulties in establishing robust clinical outcomes. This review outlines the epidemiology and resistance mechanisms of carbapenem-resistant A. baumannii, then summarizes available clinical data on each approved agent with activity against this pathogen. Emerging treatment options such as cefiderocol and sulbactam-durlobactam show promise, but their success hinges on comprehensive clinical validation and access in regions most impacted by this pathogen. New therapeutic modalities that are in various stages of clinical development are also discussed.

Progress in the study of mefloquine as an antibiotic adjuvant for combination bacterial inhibition treatment

Antimicrobial resistance is among the greatest threats to public health globally, and drug repurposing strategies may be advantageous to addressing this problem. Mefloquine, a drug traditionally used to treat malaria, has emerged as a promising antibiotic adjuvant, due to its ability to enhance the effectiveness of conventional antibiotics against resistant bacterial strains. In this paper, we first outline the enhancement properties of mefloquine and its mechanisms of action as an adjuvant antibiotic against multidrug-resistant bacteria. Mefloquine exhibits synergistic bacteriostatic effects when combined with colistin, β-lactams, antituberculosis drugs, quinolones, and linezolid. Potential mechanisms underlying its synergistic effects include inhibition of antibiotic efflux, disruption of bacterial cell membrane integrity, and disturbance of biofilm formation. In addition, we explore the bacteriostatic effects of several mefloquine derivatives against Mycobacterium tuberculosis and some fungi. Further, we summarize the findings of recent studies on other aspects of mefloquine activity, including its antiviral and antitumor effects. Finally, the advantages and challenges of mefloquine use as an antibiotic adjuvant in combination with antibiotics for bacterial inhibition are discussed. Overall, mefloquine shows excellent potential as an antibiotic adjuvant therapy against multidrug-resistant bacteria and is a promising candidate for combination therapy; however, further studies are needed to fully elucidate its mechanism of action and address the challenges associated with its clinical application.

Toxicokinetic Profiling of VRP-034: Evaluating its Potential in Mitigating Polymyxin B-Associated Nephrotoxicity

This study assessed the nephrotoxicity and toxicokinetic profile of VRP-034 (novel formulation of polymyxin B [PMB]) compared to marketed PMB over a seven-day repeat-dose regimen. Three objectives were pursued: evaluating PMB pharmacokinetics in both groups, alongside assessing VRP-034's impact on mitigating PMB-associated kidney injury; analyzing kidney injury reversibility; and validating novel kidney injury biomarkers against traditional markers using histopathology scoring. 68 Sprague-Dawley rats were divided into three groups: 30 each for marketed PMB and VRP-034 groups, and 8 for control. Animals received drugs at 6 mg/kg subcutaneously every 8 hours (HED ∼3 mg/kg/day). Toxicokinetic evaluations were conducted on selected animals on days 1, 2, 4 and 7 (after 3rd, 6th, 12th and 21st dose), while remaining animals were observed for an additional 7-days of treatment-free period. Samples were collected up to 12h post-administration, followed by necropsy and histopathological examinations. Plasma PMB concentrations were quantified; and kidney injury biomarkers, oxidative stress and anti-inflammatory markers were evaluated. Receiver operator characteristic curve analysis was performed to validate kidney injury biomarkers against histopathological grading. Results showed similar plasma PMB concentrations and pharmacokinetics parameters between both treatment groups. However, VRP-034 group exhibited significantly lower nephrotoxicity, with reduced kidney injury biomarkers levels, and diminished oxidative stress, and inflammation levels compared to marketed PMB group. Histopathological examination confirmed reduced renal damage in the VRP-034 group. Novel kidney injury biomarkers demonstrated superior sensitivity, specificity, and early detection capability over traditional markers. In conclusion, VRP-034 demonstrated reduced nephrotoxicity compared to marketed PMB, suggesting its potential as a safer alternative.

Efficacy of ceftazidime-avibactam with or without polymyxin for carbapenem-resistant Klebsiella pneumoniae infections after initial treatment with polymyxin

Although polymyxins are a suboptimal option for difficult-to-treat resistant infections, they are still preferred as the first-line treatment, especially in low- and middle-income countries. This study assesses the efficacy of ceftazidime-avibactam (CAZ-AVI) following polymyxin B failure in patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) infections. We retrospectively reviewed cases of infections caused by CRKP in adults who received CAZ-AVI as salvage therapy. Clinical features and outcomes were described, and a logistic regression model was used to assess the risk factors associated with in-hospital crude mortality. One hundred and six patients were included in this study. The median age was 56 years. The most common infectious sites were lung. The patients received CAZ-AVI as salvage therapy for a median duration of 9 days following initial treatment with polymyxin B (median, 12.5 days). Also, 91 (85.8%) patients received CAZ-AVI combination therapy, and 34 (32.1%) patients received CAZ-AVI in combination with polymyxin B. The rate of in-hospital crude mortality was 25.5% (27/106), with the highest rate observed in patients treated with regimens containing polymyxin B (41.2%; 14/34). Therapeutic response was observed in 81 (76.4%) patients, with microbiological eradication achieved in 77.1% (74/96) of cases. Multivariable analysis identified that the length of intensive care unit stays, the sequential organ failure assessment (SOFA) score at CAZ-AVI withdrawal, and regimens containing polymyxin B were independently associated with in-hospital mortality, whereas the duration of CAZ-AVI treatment was independently associated with survival. CAZ-AVI salvage therapy demonstrated improved survival outcomes in patients who experienced failure with polymyxin B therapy.IMPORTANCEFor patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) infections, published experience with salvage therapy is limited after the failure of polymyxin-based initial therapy. Here, we found that ceftazidime-avibactam salvage therapy for patients with CRKP infections offers benefit in mortality.

Antibacterial Therapy Options for Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

The review presents current treatment regimens for infections associated with carbapenem-resistant Acinetobacter baumannii, which are leading nosocomial pathogens exhibiting multidrug resistance to available antibacterial drugs. To date, widely used beta-lactam antibiotics, including carbapenems, have lost their effectiveness in combating acinetobacter infections, while new antibiotics remain poorly available to patients. Therefore, the only measure to combat the antibiotic resistance of carbapenem-resistant A. baumannii is to evaluate the efficiency of combination therapy in vitro and in vivo, which is of particular interest to Russian and foreign researchers.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the determination of polymixin B1, B2, ile-B1, E1, and E2 in human plasma and its clinical pharmacokinetic application

Polymyxin B (PB) and Polymyxin E (PE, also called colistin) are used as the last treatment resort for multidrug-resistant Gram-negative bacterial infections. The nephrotoxicity and neurotoxicity of polymyxins limit their clinical use, and guidelines recommend therapeutic drug monitoring (TDM) to optimize efficacy and reduce toxicity. However, there are limited analytical methods available for the determination of PB and PE. This study aimed to develop a simple and robust liquid chromatography with tandem mass spectrometry (LC-MS/MS) analytical method for determining the main compounds of PB and PE, namely PB1, PB2, ile-PB1, PE1, and PE2, in human plasma and to investigate of their pharmacokinetics in critically ill patients with the use of PB and PE, respectively. Plasma PB1, PB2, ile-PB1, PE1, and PE2 were chromatographically separated on a Welch LP-C18 column and detected using electrospray ionization mode coupled with multiple reaction monitoring. The calibration curve showed acceptable linearity over 20-10,000 ng/mL for PB1, PE1, and PE2 and 10-5000 ng/mL for PB2 and ile-PB1 in the plasma, respectively. After validation following approved guidelines, this method was successfully applied for PB and PE pharmacokinetic analysis and TDM in critically ill patients. Additionally, the composition of PB1, PB2, ile-PB1, PE1, and PE2 remains unchanged from 0 to 12 h after entering the patient's body.

Impact of porin deficiency on the synergistic potential of colistin in combination with β-lactam/β-lactamase inhibitors against ESBL- and carbapenemase-producing Klebsiella pneumoniae

Combinations of colistin and β-lactam/β-lactamase inhibitors (BLBLIs) have shown in vitro synergy against β-lactamase-producing strains. However, data are limited and conflicting, potentially attributed to variations among the examined strains. This study investigated whether loss of porins OmpK35 and OmpK36 impacts the synergistic potential of colistin in combination with ceftazidime-avibactam or meropenem-avibactam against β-lactamase-producing Klebsiella pneumoniae. Genetically modified strains were constructed by introducing blaCTX-M-15, blaKPC-2, and blaOXA-48 chromosomally into K. pneumoniae ATCC 35657, in which the major porin-encoding genes (ompK35, ompK36) were either intact or knocked out. The in vitro activity of colistin in combination with ceftazidime-avibactam or meropenem-avibactam was evaluated by time-lapse microscopy screening and in static time-kill experiments. The deletion of porins in the β-lactamase-producing strains resulted in 2- to 128-fold increases in MICs for the β-lactams and BLBLIs. The activity of avibactam was concentration-dependent, and 4- to 16-fold higher concentrations were required to achieve similar inhibition of the β-lactamases in strains with porin loss. In the screening, synergy was observed for colistin and ceftazidime-avibactam against the CTX-M-15-producing strains and colistin and meropenem-avibactam against the KPC-2- and OXA-48-producing strains. The combination effects were less pronounced in the time-kill experiments, where synergy was rarely detected. No apparent associations were found between the loss of OmpK35 and OmpK36 and combination effects with colistin and BLBLIs, indicating that additional factors determine the synergistic potential of such combinations.

Navigating the Current Treatment Landscape of Metallo-β-Lactamase-Producing Gram-Negative Infections: What are the Limitations?

The spread of carbapenemase-producing gram-negative pathogens, especially those producing metallo-β-lactamases (MBLs), has become a major health concern. MBLs are molecularly the most diverse carbapenemases, produced by a wide spectrum of gram-negative organisms, including the Enterobacterales, Pseudomonas spp., Acinetobacter baumannii, and Stenotrophomonas maltophilia, and can hydrolyze most β-lactams using metal ion cofactors in their active sites. Over the years, the prevalence of MBL-carrying isolates has increased globally, particularly in Asia. MBL infections are associated with adverse clinical outcomes including longer length of hospital stay, ICU admission, and increased mortality across the globe. The optimal treatment for MBL infections not only depends on the pathogen but also on the underlying resistance mechanisms. Currently, there are only few drugs or drug combinations that can efficiently offset MBL-mediated resistance, which makes the treatment of MBL infections challenging. The rising concern of MBLs along with the limited treatment options has led to the need and development of drugs that are specifically targeted towards MBLs. This review discusses the prevalence of MBLs, their clinical impact, and the current treatment options for MBL infections and their limitations. Furthermore, this review will discuss agents currently in the pipeline for treatment of MBL infections.

Population pharmacokinetic analysis and dosing optimization of colistin sulphate in lung transplant recipients with pneumonia: A prospective study

OBJECTIVE

Currently, there is a lack of information on the clinical pharmacokinetics (PK), effectiveness, and safety of colistin sulphate (CS) in lung transplant recipients. This study aims to improve CS dosing regimens and evaluate its population PK in lung transplant recipients.

METHODS

This study evaluated the clinical efficacy, microbiological efficacy, and adverse events of CS in lung transplant recipients. The NONMEM program was employed to construct the population PK model, and Monte Carlo simulations were executed to establish dosing regimens according to the probability of target attainment (PTA).

RESULTS

The study included 146 CS concentrations, spanning from 0.05 to 4.18 mg/L from 39 lung transplant recipients with multidrug-resistant Gram-negative bacteria. 26 (66.67%) patients successfully eradicated bacteria, and 30 (76.92%) patients had clinical cure or improvement. Additionally, only 2 (5.13%) patients developed CS-related nephrotoxicity. The PK profile was effectively represented by a one-compartmental model with linear elimination. Creatinine clearance and concomitant furosemide use were recognized as covariates influencing the clearance of CS. Based on the PTA results, a daily dosage of 1.5 million IU, divided into 2-3 administrations, could attain a PTA exceeding 90% for MIC ≤ 1 µg/mL at creatinine clearance of about 110 mL/min. However, this regimen would lead to insufficient exposure for MIC ≥ 2 µg/mL.

CONCLUSIONS

The clearance of CS is significantly influenced by concomitant furosemide use and renal function. The currently recommended dosing regimens by label sheet may result in subtherapeutic exposure for MIC exceeding 1 mg/L in lung transplant recipients.

Outcomes of adult patients with multidrug-resistant Acinetobacter baumannii ventilator-associated pneumonia treated with monotherapy versus combination therapy in a tertiary hospital

We compared clinical outcomes of patients who received monotherapy and combination therapy for treatment of MDR A. baumannii VAP. 170 patients were included. Vasopressor use and mortality rate were higher for combination therapy (69.3% versus 28.6%, p=0.024; 67.5% versus 14.3%, p=0.007; respectively). Majority received polymyxin B-based combination therapy, with higher mortality than those without polymyxin B (80.2% versus 19.8%, p=0.043). After adjusting for vasopressor use, monotherapy, dual combination, and triple combination therapy were not associated with mortality (aHR 0.24, 95% CI 0.03 to 1.79, p=0.169; aHR 1.26, 95% CI 0.79 to 2.00, p=0.367; aHR 0.93, 95% CI 0.57 to 1.49, p=0.744; respectively). There was no difference in adverse effects and length of stay between the two groups. Mortality from MDR A. baumannii VAP was high and not associated with monotherapy or combination therapy after adjustment for vasopressor use. Antibiotic regimens other than those containing polymyxin are urgently needed for the treatment of these infections.

Unraveling Neurotoxicity Discrepancies: Comparative In vitro and In vivo Analysis of Colistin and Polymyxin B and the Underlying Mechanisms

Polymyxins, including colistin and polymyxin B, are the final resort against Gram-negative bacterial infections. However, its clinical application is restricted due to concerns related to neurotoxicity. Despite the similar antibacterial spectrum and mode of action shared between colistin and polymyxin B, there is still a lack of definitive evidence to support the idea that their neurotoxicity profiles are identical. To comprehensively compare the neurotoxicity between colistin and polymyxin B both in vivo and in vitro and establish a theoretical foundation to guide the rational use of polymyxins within clinical settings. in vitro experiments simulated nerve damage by exposing N2a and RSC96 cells to colistin and polymyxin B. The evaluation of nerve injury included assessments of cell viability and apoptosis. To discern the variance in the mechanisms of nerve injury between colistin and polymyxin B, oxidative stress levels were examined, such as SOD, CAT, GSH, and malondialdehyde (MDA). In in vivo experiments, a rat nerve injury model was created by intraventricular injections of colistin and polymyxin B, respectively. The impact of these drugs on brain injury in rats, particularly within the hippocampus and medulla oblongata, was measured using HE and Nissl staining. The potential influence of polymyxins on the ferroptosis pathway was evaluated by assessing LPO and Fe2+ levels and the degree of mitochondrial impairment. At equivalent doses, colistin demonstrated a reduced level of neurotoxicity compared to polymyxin B, both in vitro and in vivo. in vitro experiments revealed greater cell viability and a lower apoptosis rate after colistin treatment than after polymyxin B treatment. This variance in outcomes could be attributed to the comparatively lower levels of oxidative stress associated with colistin administration. In a rat model, nerve injury resulted in observable damage to both the hippocampus and the medulla oblongata. A comprehensive assessment of the extent of damage in the CA1 to CA4 regions of the hippocampus, and the solitary tract nucleus of the medulla oblongata underscored that the neurotoxic effects of colistin remained milder compared to those elicited by polymyxin B. Even when evaluated at equivalent multiples of clinically recommended doses, colistin exhibited lower neurotoxicity in vivo than polymyxin B. For the first time, this study demonstrated the role of ferroptosis in polymyxin B-induced nerve damage. The activation levels observed within the ferroptosis pathway due to polymyxin B exceeded those triggered by colistin. Colistin exhibited a marked reduction in neurotoxicity compared to polymyxin B, evident in both the equivalent and clinically recommended doses. These findings suggest that, from the perspective of neurotoxicity, colistin presents a more favorable option for clinical use.

Ceftazidime-Avibactam Versus Polymyxin-Based Combination Therapies: A Study on 30-Day Mortality in Carbapenem-Resistant Enterobacterales Bloodstream Infections in an OXA-48-Endemic Region

Background: Ceftazidime-avibactam (CAZ-AVI) is recommended as first-line treatment for Oxacillinase-48 (OXA-48) β-Lactamase-producing carbapenem-resistant Enterobacterales (CRE) infections, while polymyxin-based combination therapies (PBCTs) are used as a last resort when CAZ-AVI is unavailable. Research comparing the effectiveness of CAZ-AVI and PBCT in CRE blood stream infections (CRE-BSIs) is limited, mostly focusing on Klebsiella pneumoniae carbapenemase (KPC)-producing isolates. In Turkey, OXA-48 is endemic and OXA-48-Like is common. Therefore, our study aimed to compare the impact of these treatments on 30-day mortality in patients with CRE-BSIs in endemic regions. Methods: Retrospective data from January 2019 to May 2023 were collected from four tertiary healthcare centers in Istanbul. Demographic, clinical, and outcome data of ICU patients treated with CAZ-AVI monotherapy or PBCT for CRE-BSIs were analyzed. The effect on 30-day survival was evaluated using Cox regression analysis post propensity score matching (PSM). Results: Out of 151 patients, 44.4% (n: 67) received CAZ-AVI and 55.6% (n: 84) received PBCT. All-cause mortality rates were 20% (n: 13) with CAZ-AVI and 36.9% (n: 31) with PBCT. Cox regression analysis post PSM indicated CAZ-AVI monotherapy significantly reduced the mortality risk compared to PBCT (HR: 0.16, 95%CI: 0.07-0.37, p < 0.001), while age increased the risk (HR: 1.02 per year, 95% CI 1.0-1.04, p: 0.01). Conclusions: In OXA-48-predominant areas, CAZ-AVI demonstrated significantly lower mortality in patients with CRE-BSIs compared to PBCT. The results were attributed to the pharmacokinetic and pharmacodynamic disadvantages of polymyxins compared to CAZ-AVI, and the impact of age-related physical conditions. Therefore, CAZ-AVI should be the preferred treatment for CRE-BSIs in OXA-48-endemic regions.

Schistosomiasis-Microbiota Interactions: A Systematic Review and Meta-Analysis

INTRODUCTION

Schistosomiasis, a tropical disease affecting humans and animals, affected 251.4 million people in 2021. Schistosoma mansoni, S. haematobium, S. intercalatum, and S. japonicum are primary human schistosomes, causing tissue damage, granulomas, ulceration, hemorrhage, and opportunistic pathogen entry. The gut and urinary tract microbiota significantly impact a host's susceptibility to schistosomiasis, disrupting microbial balance; however, this relationship is not well understood. This systematic review and meta-analysis explores the intricate relationship between schistosomiasis and the host's microbiota, providing crucial insights into disease pathogenesis and management.

METHODS

This systematic review used PRISMA guidelines to identify peer-reviewed articles on schistosomiasis and its interactions with the host microbiome, using multiple databases and Google Scholar, providing a robust dataset for analysis. The study utilized Meta-Mar v3.5.1; descriptive tests, random-effects models, and subgroups were analyzed for the interaction between Schistosomiasis and the microbiome. Forest plots, Cochran's Q test, and Higgins' inconsistency statistic (I2) were used to assess heterogeneity.

RESULTS

The human Schistosoma species were observed to be associated with various bacterial species isolated from blood, stool, urine, sputum, skin, and vaginal or cervical samples. A meta-analysis of the interaction between schistosomiasis and the host microbiome, based on 31 studies, showed 29,784 observations and 5871 events. The pooled estimates indicated a significant association between schistosomiasis and changes in the microbiome of infected individuals. There was considerable heterogeneity with variance effect sizes (p < 0.0001). Subgroup analysis of Schistosoma species demonstrated that S. haematobium was the most significant contributor to the overall heterogeneity, accounting for 62.1% (p < 0.01). S. mansoni contributed 13.0% (p = 0.02), and the coinfection of S. haematobium and S. mansoni accounted for 16.8% of the heterogeneity (p < 0.01), contributing to the variability seen in the pooled analysis. Similarly, praziquantel treatment (RR = 1.68, 95% CI: 1.07-2.64) showed high heterogeneity (Chi2 = 71.42, df = 11, p < 0.01) and also indicated that Schistosoma infections in males (RR = 1.46, 95% CI: 0.00 to 551.30) and females (RR = 2.09, 95% CI: 0.24 to 18.31) have a higher risk of altering the host microbiome.

CONCLUSIONS

Schistosomiasis significantly disrupts the host microbiota across various bodily sites, leading to increased susceptibility to different bacterial taxa such as E. coli, Klebsiella, Proteus, Pseudomonas, Salmonella, Staphylococcus, Streptococcus, and Mycobacterium species (M. tuberculosis and M. leprae). This disruption enables these bacteria to produce toxic metabolites, which in turn cause inflammation and facilitate the progression of disease. The impact of schistosomiasis on the vaginal microbiome underscores the necessity for gender-specific approaches to treatment and prevention. Effective management of female genital schistosomiasis (FGS) requires addressing both the parasitic infection and the resulting microbiome imbalances. Additionally, praziquantel-treated individuals have different microbiome compositions compared to individuals with no praziquantel treatment. This suggests that combining praziquantel treatment with probiotics could potentially decrease the disease severity caused by an altered microbiome.

Activity of polymyxin B combined with cefepime-avibactam against the biofilms of polymyxin B-resistant Pseudomonas aeruginosa and Klebsiella pneumoniae in in vitro and in vivo models

Bacterial biofilms, often forming on medical devices, can lead to treatment failure due to their increased antimicrobial resistance. Cefepime-avibactam (CFP-AVI) exhibits potent activities against Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) when used with polymyxin B (PMB). However, its efficacy in biofilm-related infections is unknown. The present study aimed to evaluate the activity of PMB combined with CFP-AVI against the biofilms of PMB-resistant Gram-negative bacteria. Five K. pneumoniae strains and three P. aeruginosa strains known to be PMB-resistant and prone to biofilm formation were selected and evaluated. Antimicrobial susceptibility assays demonstrated that the minimal biofilm inhibitory and eradication concentrations of PMB and CFP-AVI for biofilms formed by the eight strains were significantly higher than the minimal inhibitory concentrations of the antibiotics for planktonic cells. The biofilm formation inhibition and eradication assays showed that PMB combined with CFP-AVI cannot only suppress the formation of biofilm but also effectively eradicate the preformed mature biofilms. In a modified in vitro pharmacokinetic/pharmacodynamic biofilm model, CFP-AVI monotherapy exhibited a bacteriostatic or effective activity against the biofilms of seven strains, whereas PMB monotherapy did not have any activity at 72 h. However, PMB combined with CFP-AVI demonstrated bactericidal activity against the biofilms of all strains at 72 h. In an in vivo Galleria mellonella infection model, the 7-day survival rates of larvae infected with biofilm implants of K. pneumoniae or P. aeruginosa were 0-6.7%, 40.0-63.3%, and 46.7-90.0%, respectively, for PMB alone, CFP-AVI alone, and PMB combined with CFP-AVI; the combination therapy increased the rate by 6.7-33.3% (P < 0.05, n = 6), compared to CFP-AVI monotherapy. It is concluded that PMB combined with CFP-AVI exhibits effective anti-biofilm activities against PMB-resistant K. pneumoniae and P. aeruginosa both in vitro and in vivo, and thus may be a promising therapeutic strategy to treat biofilm-related infections.

Comprehensive analysis and novel insights into the efficacy of polymyxin B sulfate in the treatment of sepsis caused by carbapenem-resistant gram-negative bacteria

OBJECTIVE

To investigate and analyze the clinical efficacy and safety of polymyxin B sulfate in the treatment of carbapenem-resistant gram-negative bacteria (CR-GNB) in sepsis; in order to provide reference for the clinical diagnosis, treatment and prognosis evaluation of sepsis.

METHODS

The clinical data of 76 patients with CR-GNB sepsis treated with polymyxin B sulfate combined with an anti-infection regimen in the First Affiliated Hospital of Gannan Medical University from January 2020 to February 2024 were retrospectively studied. To analyze and discuss the clinical characteristics, results of the bacterial culture and drug sensitivity, clinical efficacy and prognosis of CR-GNB patients, efficacy comparison of different doses of polymyxin B sulfate treatment regimens, efficacy comparison of different combination regimens based on polymyxin B sulfate, changes in clinical indexes before and after treatment of polymyxin B sulfate, adverse drug reactions and adverse events of polymyxin B sulfate were investigated.

RESULTS

A total of 76 patients with CR-GNB sepsis were included in this study, with 55 males and 21 females, with an average age of 59.86 years old, 44 of which were (57.89%) were > 60 years old. All patients included in this study were treated with polymyxin B based combination therapy, 49 cases (64.47%) received the two-drug combination regimen, 27 cases (35.53%) received the three-drug or more combination regimen, and all the patients had the above treatment followed by systematic symptomatic supportive treatment. Patients in this study received polymyxin B for an average of (8.6±4.3) days, there were 60 (78.95%) patients with effective clinical treatment, and 49 patients (64.47%) achieved pathogen (bacterial) clearance of infection. Twenty-two cases (28.95%) died within 28 days, 31 cases (40.79%) died within 90 days, and the remaining 23 cases (30.26%) survived. There were statistically significant differences in the therapeutic effective rates and bacterial clearance rates among different courses of treatment or different initial doses of polymyxin B (all P < 0.05). Moreover, there were significant differences in APACHE II score, WBC, NE, HGB, platelet count, albumin, NT-proBNP and CRP before and after polymyxin B treatment (all P < 0.001). In this study, 7 cases (9.21%) developed drug-related kidney injury, which recovered or decreased below the pre-medication level after discontinuation or dose adjustment and infection control. Skin darkening (melanin deposition) occurred in 5 cases (6.58%), and the above patients basically returned to normal several months after withdrawal of the drug, but there was still a certain degree of skin pigmentation. Meanwhile, 3 cases (3.95%) had neurotoxic reactions, mainly manifested as numbness at the extremities, and the neurotoxic symptoms were improved after reducing the dosage. Accordingly, there was no statistically significant difference in the prognosis of CR-GNB sepsis patients between different age and gender groups (all P > 0.05), while the treatment course and dosage of polymyxin B had statistically significant effects on the prognosis of CR-GNB sepsis patients (all P < 0.05).

CONCLUSION

A Polymyxin B sulfate based combination regimen is an effective choice for CR-GNB sepsis, which can maximize the survival and prognosis benefits of sepsis patients.

Rapid quantification of polymyxin B in human pulmonary epithelial lining fluid by LC-MS/MS and its clinical application

Pulmonary epithelial lining fluid (ELF) was commonly used for the pharmacokinetic study in lower respiratory tract infections. To characterize the intrapulmonary pharmacokinetic properties of polymyxin B following aerosol delivery, we developed and fully validated a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for quantifying polymyxin B in human bronchoalveolar lavage fluid (BALF). The ELF concentrations were calculated by the BALF values of polymyxin B using urea as a volume normalizer. Chromatographic separation was achieved on a Phonomenex Kinetex XB-C18 column(100 mm × 2.1 mm I.D., 2.6 μm)in acetonitrile and water both containing 0.2 % formic acid. The flow rate was set as 0.4 mL/min for a 3.5 min running time. Protein precipitation was used in preparing BALF samples with polymyxin E1 as an internal standard. Polymyxin B was detected under multiple reaction monitoring conditions using the electrospray ionization interface running in the positive ionization mode. The assay showed a good linear relationship over the tested concentration ranges of 0.0300/0.00306---10.0/1.02 mg/L for polymyxin B1/B2 in bronchoalveolar lavage fluid (R2 > 0.99). The inter- and inter-day precisions (RSD, %) were < 12.2 %(15.2 % for LLOQ samples)and the accuracies (%) were within the range of 94.3 ∼ 110.4 %. This reliable LC-MS/MS method for detection of polymyxin B was successfully applied to conduct a pulmonary penetration study in patients following aerosol administration.

Cost-effectiveness analysis of polymyxin B versus colistin for treating patients with carbapenem-resistant gram-negative bacterial infections

The prevalence of carbapenem-resistant gram-negative bacterial (CRGNB) infection is continuously increasing, and polymyxin B and colistin are considered last-resort drugs. This study compared the cost-effectiveness of polymyxin B with that of colistin for the treatment of intensive care unit patients with CRGNB infection from the Chinese healthcare perspective. A decision-analytic Markov model was constructed to assess the cost-effectiveness of polymyxin B compared with colistin over a period of 5 years using evidence from phase trials and other publicly available studies. The model was developed in Treeage Pro 2022 and comprises a decision tree depicting initial hospitalization and a Markov model with four states projecting long-term health and economic impacts following discharge. Uncertainty was tested with one-way sensitivity analyses and probabilistic sensitivity analyses. The quality-adjusted life years (QALYs), direct medical costs, and incremental cost-effectiveness ratio (ICER) were estimated at willingness-to-pay (WTP) thresholds of $12,674 to $38,024 per QALY. According to the base analyses, the cost incurred by patients receiving colistin treatment was $12,244.77, leading to a gain of 1.35 QALYs. In contrast, patients treated with polymyxin B had a lower cost of $7,306.71 but yielded 1.07 QALYs. The ICRE of colistin was $18032.25/QALY. At a $12,674/QALY threshold, the results were sensitive to several variables, including the probability of cure with polymyxin B, the cost of drugs, the utility of discharge to home, the utility of discharge to long-term care, and the cost of nephrotoxicity with renal replacement therapy. After all model inputs varied across a wide range of reasonable values, only the probability of being cured with polymyxin B resulted in an ICER above the $38,024/QALY threshold. According to the probabilistic sensitivity analyses, colistin was the optimal strategy in 38.2% and 62.8% of the simulations, at $12,674/QALY and $38,024/QALY, respectively. Our study findings suggest that, when considering the Chinese healthcare perspective, colistin is likely to be more cost-effective than polymyxin B for patients with CRGNB infection, especially when the WTP threshold is set at one-time the per capita GDP. However, as the WTP threshold increases from one to three times the per capita GDP, the cost-effectiveness acceptability of colistin improves, increasing from 38.2 to 62.8%.

Maximally precise combinations to overcome metallo-β-lactamase-producing Klebsiella pneumoniae

Gram-negatives harboring metallo-β-lactamases (MBLs) and extended-spectrum β-lactamases (ESBLs) pose a substantial risk to the public health landscape. In ongoing efforts to combat these "superbugs," we explored the clinical combination of aztreonam and ceftazidime/avibactam together with varying dosages of polymyxin B and imipenem against Klebsiella pneumoniae (Kp CDC Nevada) in a 9-day hollow fiber infection model (HFIM). As previously reported by our group, although the base of aztreonam and ceftazidime/avibactam alone leads to 3.34 log10 fold reductions within 72 hours, addition of polymyxin B or imipenem to the base regimen caused maximal killing of 7.55 log10 and 7.4 log10 fold reduction, respectively, by the 72-hour time point. Although low-dose polymyxin B and imipenem enhanced the bactericidal activity as an adjuvant to aztreonam +ceftazidime/avibactam, regrowth to ~9 log10CFU/mL by 216 hours rendered these combinations ineffective. When aztreonam +ceftazidime/avibactam was supplemented with high-dose polymyxin B and or low-dose polymyxin B + imipenem, it resulted in effective long-term clearance of the bacterial population. Time lapse microscopy profiled the emergence of long filamentous cells in response to PBP3 binding due to aztreonam and ceftazidime. The emergence of spheroplasts via imipenem and damage to the outer membrane via polymyxin B was visualized as a mechanism of persister killing. Despite intrinsic mgrB and blaNDM-1 resistance, polymyxin B and β-lactam combinations represent a promising strategy. Future studies using an integrated molecularly precise pharmacodynamic approach are warranted to unravel the mechanistic details to propose optimal antibiotic combinations to combat untreatable, pan-drug-resistant Gram-negatives.

Prediction of tissue exposures of polymyxin-B, amikacin and sulbactam using physiologically-based pharmacokinetic modeling

Background

The combination antimicrobial therapy consisting of amikacin, polymyxin-B, and sulbactam demonstrated in vitro synergy against multi-drug resistant Acinetobacter baumannii.

Objectives

The objectives were to predict drug disposition and extrapolate their efficacy in the blood, lung, heart, muscle and skin tissues using a physiologically-based pharmacokinetic (PBPK) modeling approach and to evaluate achievement of target pharmacodynamic (PD) indices against A. baumannii.

Methods

A PBPK model was initially developed for amikacin, polymyxin-B, and sulbactam in adult subjects, and then scaled to pediatrics, accounting for both renal and non-renal clearances. The simulated plasma and tissue drug exposures were compared to the observed data from humans and rats. Efficacy was inferred using joint probability of target attainment of target PD indices.

Results

The simulated plasma drug exposures in adults and pediatrics were within the 0.5 to 2 boundary of the mean fold error for the ratio between simulated and observed means. Simulated drug exposures in blood, skin, lung, and heart were consistent with reported penetration ratio between tissue and plasma drug exposure. In a virtual pediatric population from 2 to <18 years of age using pediatric dosing regimens, the interpretive breakpoints were achieved in 85-90% of the population.

Conclusion

The utility of PBPK to predict and simulate the amount of antibacterial drug exposure in tissue is a practical approach to overcome the difficulty of obtaining tissue drug concentrations in pediatric population. As combination therapy, amikacin/polymyxin-B/sulbactam drug concentrations in the tissues exhibited sufficient penetration to combat extremely drug resistant A. baumannii clinical isolates.

Clinical Characteristics and Molecular Insights of Carbapenem-Resistant Klebsiella pneumoniae Isolates from Patients in Intensive Care Units

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP), a significant worldwide public health threat, is common in patients in intensive care units. Methods: A retrospective study was conducted over a period of 22 months to assess the risk factors associated with infection caused by CRKP isolates. Strain identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and antimicrobial sensitivity was assessed using the micro broth dilution method and Kirby-Bauer test. The genes blaKPC, blaOXA-48, blaNDM, blaVIM, and blaGES were amplified using polymerase chain reaction (PCR), followed by sequencing of the PCR products. The polymerase hypermucoviscosity phenotype was determined using the string test. Capsular serotypes (K1, K2) and presence of the virulence gene (rmpA) in positive isolates were investigated using phenotypic tests followed by PCR. Results: Length of hospitalization and use of carbapenems were associated with CRKP infection. CRKP isolates exhibited extensive drug resistance, but retained sensitivity to colistin and ceftazidime-avibactam (CZA). The main gene detected in 35 CRKP isolates was blaKPC-2. In addition, 11 strains were positive in the string test, and two of these strains carried rmpA. Conclusions: Prolonged hospitalization and carbapenem exposure increased the risk of CRKP infection in intensive care unit (ICU) patients. The prevalence of CRKP carrying the blaKPC-2 gene was high, and suspected hypervirulent carbapenem-resistant K. pneumoniae isolates were scattered.

Recent Trends in Therapeutic Drug Monitoring of Peptide Antibiotics

Antimicrobial peptides take a specific position in the field of antibiotics (ATBs), however, from a large number of available molecules only a few of them were approved and are used in clinics. These therapeutic modalities play a crucial role in the management of diseases caused by multidrug-resistant bacterial pathogens and represent the last-line therapy for bacterial infections. Therefore, there is a demand for a rationale use of such ATBs based on optimization of the dosing strategy to minimize the risk of resistance and ensure the sustainable efficacy of the drug in real clinical practice. Therapeutic drug monitoring, as a measurement of drug concentration in the body fluids or tissues, results in the optimization of the patient´s medication and therapy outcome. This strategy is beneficial and could result in tailored therapy for different types of infection and the prolongation of the use and efficacy of ATBs in hospitals. This review paper provides an actual overview of approved antimicrobial peptides used in clinical practice and covers current trends in their analysis by convenient and advanced methodologies used for their identification and/or quantitation in biological matrices for therapeutic drug monitoring purposes. Special emphasis is given to the methods with perspective clinical outcomes.

Combination therapy with IV fosfomycin for adult patients with serious Gram-negative infections: a review of the literature

Treatment of patients with serious infections due to resistant Gram-negative bacteria remains highly problematic and has prompted clinicians to use existing antimicrobial agents in innovative ways. One approach gaining increased therapeutic use is combination therapy with IV fosfomycin. This article reviews the preclinical pharmacokinetic/pharmacodynamic (PK/PD) infection model and clinical data surrounding the use of combination therapy with IV fosfomycin for the treatment of serious infections caused by resistant Gram-negative bacteria. Data from dynamic in vitro and animal infection model studies of highly resistant Enterobacterales and non-lactose fermenters are positive and suggest IV fosfomycin in combination with a β-lactam, polymyxin or aminoglycoside produces a synergistic effect that rivals or surpasses that of other aminoglycoside- or polymyxin-containing regimens. Clinical studies performed to date primarily have involved patients with pneumonia and/or bacteraemia due to Klebsiella pneumoniae, Pseudomonas aeruginosa or Acinetobacter baumannii. Overall, the observed success rates with fosfomycin combination regimens were consistent with those reported for other combination regimens commonly used to treat these patients. In studies in which direct treatment comparisons can be derived, the results suggest that patients who received fosfomycin combination therapy had similar or improved outcomes compared with other therapies and combinations, especially when it was used in combination with a β-lactam that (1) targets PBP-3 and (2) has exceptional stability in the presence of β-lactamases. Collectively, the data indicate that combination therapy with IV fosfomycin should be considered as a potential alternative to aminoglycoside or polymyxin combinations for patients with antibiotic-resistant Gram-negative infections when benefits outweigh risks.

Outcome of intravenous and inhaled polymyxin B treatment in patients with multidrug-resistant gram-negative bacterial pneumonia

PURPOSE

The incidence of pneumonia caused by multidrug-resistant gram-negative bacteria (MDR GNB) is increasing, which imposes significant burden on public health. Inhalation combined with intravenous polymyxins has emerged as a viable treatment option. However, pharmacokinetic studies focusing on intravenous and inhaled polymyxin B (PMB) are limited.

METHODS

This study included seven patients with MDR GNB-induced pneumonia who were treated with intravenous plus inhaled PMB from March 1 to November 30, 2022, in the intensive care unit of the First Affiliated Hospital of Zhejiang University School of Medicine. Clinical outcomes and therapeutic drug monitoring data of PMB in both plasma and epithelial lining fluid (ELF) were retrospectively reviewed.

RESULTS

Median PMB concentrations in the ELF were 7.83 (0.72-66.5), 116.72 (17.37-571.26), 41.1 (3.69-133.78) and 33.82 (0.83-126.68) mg/L at 0, 2, 6 and 12 h, respectively, and were much higher than those detected in the serum. ELF concentrations of PMB at 0, 2, 6 and 12 h were higher than the minimum inhibitory concentrations of pathogens isolated from the patients. Steady-state concentrations of PMB in the plasma were >2 mg/L in most patients. Of the patients, 57.14% were cured and 71.43% showed a favourable microbiological response. The incidence of side effects with PMB was low.

CONCLUSIONS

Inhaled plus intravenous PMB can achieve high ELF concentrations and favourable clinical outcomes without an increased adverse effect profile. This treatment approach appears promising for the treatment of patients with pneumonia caused by MDR-GNB.

New Predictive Equation for the Estimation of Plasma Concentrations of Formed Colistin in Patients Treated With Colistimethate Sodium for Multidrug-Resistant Gram-Negative Bacterial Infections

BACKGROUND

The clinical use of colistin methanesulphonate (CMS) is limited by potential nephrotoxicity. The selection of an efficient and safe CMS dose for individual patients is complicated by the narrow therapeutic window and high interpatient pharmacokinetic variability. In this study, a simple predictive equation for estimating the plasma concentration of formed colistin in patients with multidrug and extremely drug-resistant gram-negative bacterial infections was developed.

METHODS

The equation was derived from the largest clinical cohort of patients undergoing therapeutic drug monitoring (TDM) of colistin for over 8 years in a tertiary Spanish hospital. All variables associated with C ss,avg were selected in a multiple linear regression model that was validated in a second cohort of 40 patients. Measured C ss,avg values were compared with those predicted by our model and a previous published algorithm for critically ill patients.

RESULTS

In total, 276 patients were enrolled [the mean age was 67.2 (13.7) years, 203 (73.6%)] were male, and the mean (SD) C ss,avg was 1.12 (0.98) mg/L. Age, gender, estimated glomerular filtration rate, CMS dose and frequency, and concomitant drugs were included in the model. In the external validation, the previous algorithm appeared to yield more optimized colistin plasma concentrations when all types of C ss,avg values (high and low) were considered, while our equation yielded a more optimized prediction in the subgroup of patients with low colistin plasma concentrations (C ss,avg <1.5 mg/L).

CONCLUSIONS

The proposed equation may help clinicians to better use CMS among a wide variety of patients, to maximize efficacy and prevent nephrotoxicity. A further prospective PK study is warranted to externally validate this algorithm.

Agar dilution test and its Merits and Drawbacks in evolving dynamics of colistin susceptibility

Objectives

Automated results for determining colistin susceptibility tests are unreliable, micro broth dilution requires expertise, and CBDE has limited dilutions. International Consensus Document of 2022 suggested that agar dilution was unacceptable due to varying results in the literature.

Methods

The study was designed to evaluate the agar dilution method for colistin susceptibility in CRE isolates compared to CBDE. In the study, 108 carbapenem-resistant isolates were tested for Colistin susceptibility by Microbroth Dilution, agar dilution, and colistin broth disc elution. The comparisons were made using various statistical parameters.

Results

The results of the agar dilution method revealed an essential agreement of 75 % and a categorical agreement of 92.5 %. The method showed a sensitivity of 75 % and a specificity of 97.7 %. The positive and negative predictive values were 88.2 % and 94.5 %, respectively. Youden's index was 0.727, indicating a moderate level of accuracy. Meanwhile, CBDE diagnostic accuracy tests were better, with Youden's index at 0.939.

Conclusions

While CBDE demonstrated better accuracy parameters, it did not offer a broader MIC range. In contrast, agar dilution showed reasonable specificity and reliability for isolates with high MIC. Therefore, we propose using CBDE for screening and agar dilution as a supplementary test in the approach to colistin susceptibility.

High-dose colistin pharmacokinetics in critically ill patients receiving continuous renal replacement therapy

BACKGROUND

Colistin, administered as intravenous colistimethate (CMS), is still used in the critical care setting and current guidelines recommend high dosage CMS in patients undergoing continuous renal replacement therapy (CRRT). Due to the paucity of real-life data, we aimed to describe colistin pharmacokinetic/pharmacodynamic (PK/PD) profile in a cohort of critically ill patients with infections due to carbapenem-resistant (CR) bacteria undergoing CRRT.

RESULTS

All consecutive patients admitted to three Intensive Care Units (ICUs) of a large metropolitan University Hospital, treated with colistin for at least 48 h at the dosage of 6.75 MUI q12, after 9 MIU loading dose, and undergoing CRRT were included. After the seventh dose, patients underwent blood serial sampling during a time frame of 24 h. We included 20 patients, who had CR-Acinetobacter baumannii ventilator-associated pneumonia and were characterized by a median SAPS II and SOFA score of 41 [34.5-59.3] and 9 [6.7-11], respectively. Fifteen patients died during ICU stay and six recovered renal function. Median peak and trough colistin concentrations were 16.6 mcg/mL [14.8-20.6] and 3.9 mcg/mL [3.3-4.4], respectively. Median area under the time-concentration curve (AUC0 - 24) and average steady-state concentration (Css, avg) were 193.9 mcg h/mL [170.6-208.6] and 8.07 mcg/mL [7.1-8.7]. Probability of target attainment of colistin pharmacodynamics according to the fAUC0 - 24/MIC target ≥ 12 was 100% for MIC ≤ 2 mcg/mL and 85% for MIC = 4 mcg/ML, although exceeding the toxicity limit of Css, avg 3-4 mcg/mL.

CONCLUSIONS

In critically ill patients with CR infections undergoing CRRT, recommended CMS dosage resulted in colistin plasmatic levels above bacterial MIC90, but exceeding the safety Css, avg. limit.

TRIAL REGISTRATION

This trial was registered in ClinicalTrials.gov on 23/07/2021 with the ID NCT04995133 (https//clinicaltrials.gov/study/NCT04995133).

Combination of aloe emodin, emodin, and rhein from Aloe with EDTA sensitizes the resistant Acinetobacter baumannii to polymyxins

Background

The continuous emergence and spread of polymyxin-resistant Acinetobacter baumannii pose a significant global health challenge, necessitating the development of novel therapeutic strategies. Aloe, with its long-standing history of medicinal use, has recently been the subject of substantial research for its efficacy against pathogenic infections.

Methods

This study investigates the potential application of anthraquinone components in aloe against polymyxin-resistant A. baumannii by liquid chromatography-mass spectrometry, in vitro activity assessment, and construction of animal infection models.

Results

The findings demonstrate that aloe emodin, emodin, rhein, and their mixtures in equal mass ratios (EAR) exhibit strain-specific antibacterial activities against polymyxin-resistant A. baumannii. Co-administration of EAR with EDTA synergistically and universally enhanced the antibacterial activity and bactericidal efficacy of polymyxins against polymyxin-resistant A. baumannii, while also reducing the frequency of polymyxin-resistant mutations in polymyxinssensitive A. baumannii. Following toxicity assessment on human hepatic and renal cell lines, the combination therapy was applied to skin wounds in mice infected with polymyxin-resistant A. baumannii. Compared to monotherapy, the combination therapy significantly accelerated wound healing and reduced bacterial burden.

Conclusions

The combination of EAR and EDTA with polymyxins offers a novel therapeutic approach for managing skin infections caused by polymyxinresistant A. baumannii.

Clinical Effectiveness and Safety of Colistin Sulphate in Treating Infections Caused by Carbapenem-Resistant Organisms and Analysis of Influencing Factors

Objective

To assess the efficacy and safety of colistin sulfate in treating infections caused by carbapenem-resistant organisms (CRO) and to analyze potential factors impacting its effectiveness.

Methods

In this retrospective study, medical records of CRO-infected patients from June 2020 to June 2023 were analyzed, divided into effective and ineffective treatment groups, and compared for clinical outcomes and adverse reactions. Multifactorial logistic regression and ROC curve analysis were used to identify influencing factors.

Results

The study included 226 patients, with 124 in the effective treatment group and 102 in the ineffective group. A total of 293 CRO strains were cultured. The clinical efficacy rate of colistin sulfate was 54.87%, the microbiological efficacy rate 46.46%, and the hospital mortality rate 20.80%, with nephrotoxicity observed in 11.50% of patients. Multifactorial analysis identified APACHE II scores and vasoactive drug use as independent predictors of ineffective treatment, while treatment duration and albumin levels predicted effective treatment. ROC analysis indicated that albumin levels >34 g/L, APACHE II scores <13, and treatment duration >10 days correlated with better clinical efficacy.

Conclusion

Colistin sulfate is both safe and effective in clinical settings. Factors such as treatment duration, albumin levels, APACHE II scores, and vasoactive drug use independently affect its clinical efficacy, providing valuable guidance for its informed clinical application.

Clinical outcome assessment of colistin sulphate in children with carbapenem-resistant organism infections: First data from China

OBJECTIVES

Colistin sulphate for injection (CSI) became clinically available in China in July 2019. To date, there is no published data regarding its usage in children. Our research group has been following data on the efficacy and safety of CSI in Chinese paediatric patients with carbapenem-resistant organism infections. The purpose of this short communication is to provide a brief overview of the findings to date.

METHODS

We reviewed the electronic medical records of paediatric patients (aged 9-17 y) who were administered CSI during their hospital stay at Tongji Hospital in Wuhan, China, between June 2021 and November 2023. Drug efficacy was evaluated based on clinical and microbiological outcomes, while drug safety was assessed using surveillance markers that reflect adverse reactions.

RESULTS

A total of 20 patients met the inclusion criteria. The predominant pathogens were Klebsiella pneumoniae (8 strains), followed by Acinetobacter baumannii (5 strains) and Pseudomonas aeruginosa (2 strains). The clinical response rate of CSI was 85%, with a bacterial clearance rate of 79%. None of the patients experienced colistin-related nephrotoxicity or neurotoxicity during the treatment.

CONCLUSIONS

In this real-world setting, CSI demonstrated a high level of clinical response and was well tolerated for the treatment of carbapenem-resistant organism infections in Chinese children.

Three methods to optimise polymyxin B dosing using estimated AUC after first dose: validation with the data generated by Monte Carlo simulation

To achieve the AUC-guided dosing, we proposed three methods to estimate polymyxin B AUC across 24 h at steady state (AUCSS,24h) using limited concentrations after its first dose.Monte Carlo simulation based on a well-established population PK model was performed to generate the PK profiles of 1000 patients with normal or abnormal renal function. Polymyxin B AUCSS,24h was estimated for each subject using three methods (two-point PK approach, three-point PK approach, and four-point PK approach) based on limited concentration data in its first dose and compared with the actual AUC at steady state calculated using the linear-trapezoidal formula.In patients with normal renal function, the mean bias of two-point PK approach, three-point PK approach, and four-point PK approach was -8.73%, 1.37%, and -0.48%, respectively. The corresponding value was -11.15%, 1.99%, and -0.28% in patients with renal impairment, respectively. The largest mean bias of two-point PK approach, three-point PK approach, and four-point PK approach was -12.63%, -6.47%, and -0.54% when the sampling time shifted.The Excel calculators designed based on the three methods can be potentially used to optimise the dosing regimen of polymyxin B in the clinic.