Incidence and predictors of acute kidney injury associated with intravenous polymyxin B therapy

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.

An early and stable mouse model of polymyxin-induced acute kidney injury

BACKGROUND

Polymyxins have been revived as a last-line therapeutic option for multi-drug resistant bacteria and continue to account for a significant proportion of global antibiotic usage. However, kidney injury is often a treatment limiting event with kidney failure rates ranging from 5 to 13%. The mechanisms underlying polymyxin-induced nephrotoxicity are currently unclear. Researches of polymyxin-associated acute kidney injury (AKI) models need to be more standardized, which is crucial for obtaining consistent and robust mechanistic results.

METHODS

In this study, male C57BL/6 mice received different doses of polymyxin B (PB) and polymyxin E (PE, also known as colistin) by different routes once daily (QD), twice daily (BID), and thrice daily (TID) for 3 days. We continuously monitored the glomerular filtration rate (GFR) and the AKI biomarkers, including serum creatinine (Scr), blood urea nitrogen (BUN), neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule-1 (KIM-1). We also performed histopathological examinations to assess the extent of kidney injury.

RESULTS

Mice receiving PB (35 mg/kg/day subcutaneously) once daily exhibited a significant decrease in GFR and a notable increase in KIM-1 two hours after the first dose. Changes in GFR and KIM-1 at 24, 48 and 72 h were consistent and demonstrated the occurrence of kidney injury. Histopathological assessments showed a positive correlation between the severity of kidney injury and the changes in GFR and KIM-1 (Spearman's rho = 0.3167, P = 0.0264). The other groups of mice injected with PB and PE did not show significant changes in GFR and AKI biomarkers compared to the control group.

CONCLUSION

The group receiving PB (35 mg/kg/day subcutaneously) once daily consistently developed AKI at 2 h after the first dose. Establishing an early and stable AKI model facilitates researches into the mechanisms of early-stage kidney injury. In addition, our results indicated that PE had less toxicity than PB and mice receiving the same dose of PB in the QD group exhibited more severe kidney injury than the BID and TID groups.

Evaluating nephrotoxicity reduction in a novel polymyxin B formulation: insights from a 3D kidney-on-a-chip model

This study aimed to assess the nephrotoxicity associated with VRP-034 (novel formulation of polymyxin B [PMB]) compared to marketed PMB in a three-dimensional (3D) kidney-on-a-chip model. To model the human kidney proximal tubule for analysis, tubular structures were established using 23 triple-channel chips seeded with RPTEC/hTERT1 cells. These cells were exposed to VRP-034 or PMB at seven concentrations (1-200 µM) over 12, 24, and 48 h. A suite of novel kidney injury biomarkers, cell health, and inflammatory markers were quantitatively assessed in the effluent. Additionally, caspase and cytochrome C levels were measured, and cell viability was evaluated using calcein AM and ethidium homodimer-1 (EthD-1). Exposure to marketed PMB resulted in significantly elevated levels (P < 0.05) of four key biomarkers (KIM-1, cystatin C, clusterin, and OPN) compared to VRP-034, particularly at clinically relevant concentrations of ≥10 µM. At 25 µM, all biomarkers demonstrated a significant increase (P < 0.05) with marketed PMB exposure compared to VRP-034. Inflammatory markers (interleukin-6 and interleukin-8) increased significantly (P < 0.05) with marketed PMB at concentrations of ≥5 µM, relative to VRP-034. VRP-034 displayed superior cell health outcomes, exhibiting lower lactate dehydrogenase release, while ATP levels remained comparable. Morphological analysis revealed that marketed PMB induced more severe damage, disrupting tubular integrity. Both treatments activated cytochrome C, caspase-3, caspase-8, caspase-9, and caspase-12 in a concentration-dependent manner; however, caspase activation was significantly reduced (P < 0.05) with VRP-034. This study demonstrates that VRP-034 significantly reduces nephrotoxicity compared to marketed PMB within a 3D microphysiological system, suggesting its potential to enable the use of full therapeutic doses of PMB with an improved safety profile, addressing the need for less nephrotoxic polymyxin antibiotics.

Comparison of the Impact of VRP-034 and Polymyxin B upon Markers of Kidney Injury in Human Proximal Tubule Monolayers In Vitro

In this study, we assessed the impact of commercially available polymyxin B against VRP-034 (novel formulation of polymyxin B) using a validated in vitro human renal model, aProximateTM. Freshly isolated primary proximal tubule cells (PTCs) were cultured in Transwell plates and treated with various concentrations of the formulations for up to 48 h. The functional expression of megalin-cubilin receptors in PTC monolayers was validated using FITC-conjugated albumin uptake assays. Polymyxin B and VRP-034 were evaluated at six concentrations (0.3, 1, 3, 10, 30, and 60 µM), and nephrotoxicity was assessed through measurements of transepithelial electrical resistance (TEER), intracellular adenosine triphosphate (ATP) levels, lactate dehydrogenase (LDH) release, and novel injury biomarkers [kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and clusterin]. Additionally, histological analysis using annexin V apoptosis staining was performed. Our results indicated a significant decrease in TEER with polymyxin B at concentrations ≥10 μM compared to VRP-034. Toxic effects were observed from ATP and LDH release only at concentrations ≥30 μM for both formulations. Furthermore, injury biomarker release was higher with polymyxin B compared to VRP-034, particularly at concentrations ≥10 µM. Histologically, polymyxin B-treated PTCs showed increased apoptosis compared to VRP-034-treated cells. Overall, VRP-034 demonstrated improved tolerance in the aProximateTM model compared to polymyxin B, suggesting its potential as a safer alternative for renal protection.

A pharmacovigilance study of adverse events associated with polymyxins based on the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) database

BACKGROUND

Polymyxins have been regarded as last-line treatment for multidrug-resistant gram-negative bacterial infections. Nonetheless, concerns regarding toxicity persist. This study aimed to explore and compare potential adverse events (AEs) between colistin and polymyxin B (PMB).

METHODS

Polymyxins-related AEs were retrieved from the U.S. Food and Drug Administration Adverse Event Reporting System between 2004 and 2022. Potential signals were estimated by the reporting odds ratio (ROR), and subgroup analyses were preformed to adjust for potential factors in AEs with significant disproportionality.

RESULTS

Analysis of 3,915 records involving 718 patients revealed a higher disproportionality of renal and urinary disorders (ROR 1.62, 95% CI 1.01-2.59) and acute kidney injury (ROR 1.75, 95% CI 1.07-2.87) with colistin treatment. Conversely, colistin exhibited a lower risk for neurotoxicity (ROR 0.47, 95% CI 0.30-0.73). Seven cases of skin hyperpigmentation were reported with PMB, whereas none were reported with colistin. Over 80% of cases involving polymyxin-related AEs occurred during the first two weeks of therapies, with a median onset time of 4.5 days.

CONCLUSIONS

Patients received colistin displayed a higher potential risk of nephrotoxicity but a lower risk of neurotoxicity. Clinicians should be vigilant in monitoring the AEs of hyperpigmentation disorders induced by PMB.

Pharmacokinetics and safety of EVER206, a novel polymyxin antimicrobial, in healthy Chinese subjects

EVER206 (also known as SPR206) is a novel polymyxin analog that has shown in vitro potency and in vivo efficacy against multidrug-resistant (MDR) Gram-negative pathogens. This randomized, double-blinded, placebo-controlled, Phase I study evaluated the safety, tolerability, and pharmacokinetics of EVER206 in healthy Chinese subjects. After single administration of 50-300 mg EVER206, the Cmax ranged from 3.94 to 25.82 mg/L, and the AUC0-inf ranged from 12.42 to 101.67 h·mg/L. The plasma exposure displayed a linear relationship with the dose administered. After administration of 75 and 100 mg of EVER206 every 8 hours (q8 hour), a steady state was achieved on Day 2. The accumulation ratios of Cmax and AUC from Day 1 to Day 7 were in the range of 1.12 to 1.3. The elimination half-lives ranged from 2.86 to 4.32 hours in the single-ascending-dose (SAD) study and 4.71 to 6.18 hours in the multiple-ascending-dose (MAD) study. The urinary excretion of unchanged EVER206 increased with the dose, with the mean cumulative fraction ranging from 23.70% to 47.10%. EVER206 was safe and well-tolerated in Chinese healthy subjects. No severe treatment emerging adverse events (TEAEs), serious adverse events, or TEAEs leading to discontinuation were reported. The results of the present study demonstrated a similar safety profile of EVER206 with data reported in an earlier study on SPR206-101. The exposure of EVER206 in Chinese healthy subjects was higher than that in Australian healthy subjects. These results could enable further clinical development of EVER206 in Chinese patients with severe MDR Gram-negative pathogen infections.CLINICAL TRIALSThis study was registered at the Chinese Clinical Trial Registry under identifier ChiCTR2200056692.

Mid-dosing interval concentration is important for polymyxin B exposure and acute kidney injury in critically ill patients

This study aimed to evaluate the association between polymyxin B (PMB) exposure and acute kidney injury (AKI) and analyze the risk factors for PMB-induced AKI in critically ill patients. Plasma concentrations of PMB were determined using an ultraperformance liquid chromatography-tandem mass spectrometer in intensive care unit patients who were administered PMB. Univariate and multivariate analyses were conducted to identify risk factors. A receiver operating characteristic curve was constructed to assess the discriminant power of the factors and to identify the cutoff value for AKI. The white blood cell count and estimated area under the concentration-time curve (AUC) of patients administered PMB were independent risk factors for PMB-induced AKI, where AUC were calculated using a first-order pharmacokinetic equation based on the mid-dosing interval concentration (C1/2t ) and peak concentration. The area under the receiver operating characteristic curve of the final model was 0.805 (95% confidence interval, 0.690-0.921). The cutoff value for the combined predictor was 0.57. Alternatively, when using C1/2t , which was strongly correlated with AUC, as the only independent risk factor, the analysis showed that the 3.47 μg/ml threshold provides favorable differentiation between the AKI and non-AKI groups. These results provide insightful information for therapeutic drug monitoring-guiding PMB dosing in clinical practice.

Use of polymyxin B with different administration methods in the critically ill patients with ventilation associated pneumonia: a single-center experience

Background: Whether nebulized polymyxin B should be used as an adjunctive therapy or substitution strategy to intravenous polymyxin B for the treatment of ventilator-associated pneumonia (VAP) remains controversial. This study's aim is to evaluate the efficacy and safety of different administration ways of polymyxin B in the treatment of ventilator-associated pneumonia caused by extensively drug-resistant Gram-negative bacteria(XDR-GNB). Methods: This retrospective cohort study enrolled ventilator-associated pneumonia patients caused by XDR-GNB treated with polymyxin B in the intensive care unit. Patients were categorized by the administration methods as intravenous (IV) group, inhaled (IH) group, and the intravenous combined with inhaled (IV + IH) group. Microbiological outcome and clinical outcome were compared in each group. The side effects were also explored. Results: A total of 111 patients were enrolled and there was no difference in demographic and clinical characteristics among the three groups. In terms of efficacy, clinical cure or improvement was achieved in 21 patients (55.3%) in the intravenous group, 19 patients (50%) in the IH group, and 20 patients (57.1%) in IV + IH group (p = 0.815). All three groups showed high success rates in microbiological eradication, as 29 patients with negative cultures after medication in inhaled group. Among all the patients who had negative bacterial cultures after polymyxin B, the inhaled group had significantly shorter clearance time than the intravenous group (p = 0.002), but with no significant difference in 28-day mortality. Compared with intravenous group, a trend towards a lower risk of acute kidney injury was observed in inhaled group (p = 0.025). Conclusion: From the perspective of minimal systemic renal toxicity, nebulized polymyxin B as a substitution strategy to intravenous polymyxin B for the treatment of ventilator-associated pneumonia caused by XDR-GNB is feasible.

Sinonasal mucormycosis during 2 years of COVID-19 pandemic in central Iran: incidence rate and clinical features

INTRODUCTION

As a novel infectious disease, COVID-19 is caused by SARS-COV-2, spreading rapidly worldwide. ENT specialists have faced this challenging disease in various ways since the emergence of the COVID-19 pandemic. We are currently facing an increase in cases referred due to sinonasal mucormycosis which is a rare but invasive, rapidly progressive, and life-threatening infection. We provide an overview of this disease's incidence rate and clinical features.

METHODS

This descriptive cross-sectional study was conducted on 46 sinonasal mucormycosis patients who were histopathologically confirmed after sinonasal endoscopic surgery in our educational therapeutic hospital during 2 years of the COVID-19 pandemic from March 20, 2020, to March 20, 2022.

RESULTS

There was an increase in the incidence of mucormycosis more than twice as much as before. All patients had a history of COVID-19 and 69.6% were diabetic. The median time to symptom onset from COVID-19 detection was 3.3 weeks. A total of 60.9% received steroids while 85.7% were prescribed during COVID-19 treatment. The most common manifestation was orbital involvement (80.4%). Of the 46 study cases, unfortunately, 17 (37%) died. An exciting point in our study was the incidence of peripheral facial palsy which is associated involvement of multiple other cranial nerves (II, III, IV, V, VI) considered to be the likely occurrence of a rare phenomenon called Garcin's syndrome.

CONCLUSION

Based on the results of this study, during 2 years of the COVID -19 pandemic, there was an increase in the incidence of sinonasal mucormycosis more than twice as much as before.

Risks of Polymyxin B Nephrotoxicity and Its Precursors in the Intensive Care Unit: A Retrospective Cohort Study

BACKGROUND AND AIM

Polymyxin group antibiotics constitute a part of our limited arsenal in the treatment of multidrug-resistant gram-negative bacteria. However, their use is limited especially due to nephrotoxicity and other side effects. In this study, we primarily aimed to determine the effect of polymyxin B on the rate of nephrotoxicity in critically ill patients, and secondly to identify the factors that facilitate nephrotoxicity caused by polymyxin B.

MATERIALS AND METHODS

The study was designed as a retrospective cohort study and conducted by scanning patients aged 18 years or older who had been admitted to our intensive care unit (ICU) in 2022 and treated with polymyxin B for at least 72 hours. Patients without chronic renal failure and acute kidney injury (AKI) before starting polymyxin B therapy were included and AKI was examined after the use of polymyxin B. The patients were then divided into two groups, those with AKI and those without AKI. We tried to find factors that may facilitate AKI by comparing the two groups.

RESULTS

Of the patients, 26 were female and 34 were male. In 21 of the patients (35%), renal damage of varying degrees developed; these patients belonged to the nephrotoxicity (NT) group, while the rest belonged to the non-nephrotoxicity (non-NT) group. We found that advanced age (p=0.008), low baseline GFR (p=0.01), baseline creatinine (p=0.006), BMI (p=0.011), concomitant diseases (p<0.001), and days of use of polymyxin B (p=0.006) were statistically different between the two groups. In multivariate analysis of univariate analysis, we found that duration of polymyxin B use, BMI, and advanced age were independent risk factors for AKI development.

CONCLUSION

We found that 21 (35%) of 60 intensive care unit patients who had no previous history of kidney injury developed kidney injury after being treated with polymyxin B. We identified advanced age, high BMI, and duration of polymyxin B use as independent risk factors. Therefore, we recommend close monitoring of renal function and prompt intervention, particularly in patients with risk factors, during polymyxin B use.

Design, synthesis and antibacterial activity of novel colistin derivatives with thioether bond-mediated cyclic scaffold

The escalating crisis of multidrug resistance is raising the fear of untreatable Gram-negative infections and killing a substantial number of patients. The underpopulated antibiotic drug development pipelines drive polymyxins (polymyxin B and colistin) as crucial therapeutic options. However, the cumbersome synthesis process and inefficient cyclization method limit the efficient preparation of polymyxin core scaffolds in the development of polymyxin derivatives. Here, we innovatively applied a substitution reaction between bromobenzene and sulfhydryl to cyclize colistin core scaffolds. The reaction was mild and efficient, improving the total yield of the compound from less than 10% to 55.90%. Nearly 30 novel derivatives with thioether bond-mediated cyclic scaffolds were designed and synthesized. Evaluation of antibacterial activities and biological properties revealed that many new compounds that are stable in mouse plasma possess high antimicrobial potency against Gram-negative bacteria and display no hemolytic toxicity. Our optimal peptide PE-2C-C8-DH eradicated Acinetobacter baumannii within 24 h in vitro, and had lower acute toxicity and significant therapeutic effects on mice infected with Pseudomonas aeruginosa, which deserves further development.

Treatment of Acinetobacter baumannii severe infections

Acinetobacter baumannii is a Gram-negative, multidrug-resistant (MDR) pathogen that causes nosocomial infections, especially in intensive care units (ICUs) and immunocompromised patients. A. baumannii has developed a broad spectrum of antimicrobial resistance, associated with a higher mortality rate among infected patients compared with other non-baumannii species. In terms of clinical impact, resistant strains are associated with increases in both in-hospital length of stay and mortality. A. baumannii can cause a variety of infections, especially ventilator-associated pneumonia, bacteremia, and skin wound infections, among others. The most common risk factors for the acquisition of MDR A. baumannii are previous antibiotic use, mechanical ventilation, length of ICU and hospital stay, severity of illness, and use of medical devices. Current efforts are focused on addressing all the antimicrobial resistance mechanisms described in A. baumannii, with the objective of identifying the most promising therapeutic scheme.

Correlation between the drug concentration of polymyxin B and polymyxin B-associated acute kidney injury in critically ill patients: A prospective study

In recent years, polymyxin B-associated acute kidney injury (PB-AKI) in critically ill patients has been reported frequently, but polymyxin B (PB) is mainly cleared through non-renal pathways, and the reasons of PB-AKI remain unclear. The aim of this study was to investigate the relationship between the serum concentration of PB and PB-AKI. We conducted a prospective cohort study in an intensive care unit between May 2019 and July 2021. Over the study period, 52 patients were included and divided into an AKI group (n = 26) and a non-AKI group (n = 26). The loading dose of PB in the AKI group was significantly higher than that in the non-AKI group. The C_1/2 , C_min , and estimated area under the concentration-time curve (AUC)_0-24 of PB in the AKI group were dramatically increased compared with those in the non-AKI group, but the C_max between the two groups showed no differences. Upon obtaining the ROC curve, the areas for the C_1/2 , C_min , and estimated AUC_0-24 were 0.742, 0.710, and 0.710, respectively. The sensitivity was ascertained to be 61.54%, and the specificity was 76.92% when the cutoff value for the estimated AUC_0-24 of 97.72 mg·h/L was used preferentially. The incidence of PB-AKI is high and related to the loading dose of PB. PB-AKI could be predicted when the estimated AUC_0-24 of PB was greater than 97.72 mg·h/L.

Does Monitoring Total and Free Polymyxin B1 Plasma Concentrations Predict Polymyxin B-Induced Nephrotoxicity? A Retrospective Study in Critically Ill Patients

INTRODUCTION

The correlation between total and free polymyxin B (PMB including PMB1 and PMB2) exposure in vivo and acute kidney injury (AKI) remains obscure. This study explores the relationships between plasma exposure of PMB1 and PMB2 and nephrotoxicity, and investigates the risk factors for PMB-induced acute kidney injury (AKI) in critically ill patients.

METHODS

Critically ill patients who used PMB and met the criteria were enrolled. The total plasma concentration and plasma binding of PMB1 and PMB2 were analysed by liquid chromatography-tandem mass spectrometry and equilibrium dialysis.

RESULTS

A total of 89 patients were finally included, and AKI developed in 28.1% of them. The peak concentration of PMB1 (C_max (B1)) (adjusted odds ratio (AOR) = 1.68, 95% CI 1.08-2.62, p = 0.023), baseline BUN level (AOR = 1.08, 95% CI 1.01-1.16, p = 0.039) and hypertension (AOR = 3.73, 95% CI 1.21-11.54, p = 0.022) were independent risk factors for PMB-induced AKI. The area under the ROC curve of the model was 0.799. When C_max (B1) was 5.23 μg/ml or more, the probability of AKI was higher than 50%. The ratio of PMB1/PMB2 decreased after PMB preparation entered into the body. The protein binding rate in critically ill patients indicated significant individual differences. Free C_max (B) and free C_max (B1) levels in the AKI group were significantly (p < 0.05) higher than those in the non-AKI group. Total and free concentrations of PMB in patients showed a positive correlation.

CONCLUSIONS

Both the ROC curve and logistic regression model showed that C_max (B1) was a good predictor for the probability of PMB-induced AKI. Early therapeutic drug monitoring (TDM) of PMB should be considered in critically ill patients. Compared with C_min (B), C_max (B) and C_max (B1) may be helpful for the early prediction of PMB-induced AKI in critically ill patients.

Colonization of White-Tailed Deer (Odocoileus virginianus) from Urban and Suburban Environments with Cephalosporinase- and Carbapenemase-Producing Enterobacterales

Wildlife play a role in the acquisition, maintenance, and dissemination of antimicrobial resistance (AMR). This is especially true at the human-domestic animal-wildlife interface, like urbanized areas, where interactions occur that can promote the cross-over of AMR bacteria and genes. We conducted a 2-year fecal surveillance (n = 783) of a white-tailed deer (WTD) herd from an urban park system in Ohio to identify and characterize cephalosporin-resistant and carbapenemase-producing bacteria using selective enrichment. Using generalized linear mixed models we found that older (OR = 2.3, P < 0.001), male (OR = 1.8, P = 0.001) deer from urbanized habitats (OR = 1.4, P = 0.001) were more likely to harbor extended-spectrum cephalosporin-resistant Enterobacterales. In addition, we isolated two carbapenemase-producing Enterobacterales (CPE), a Klebsiella quasipneumoniae harboring bla_KPC-2 and an Escherichia coli harboring bla_NDM-5, from two deer from urban habitats. The genetic landscape of the plasmid carrying bla_KPC-2 was unique, not clustering with other reported plasmids encoding KPC-2, and only sharing 78% of its sequence with its nearest match. While the plasmid carrying bla_NDM-5 shared sequence similarity with other reported plasmids encoding NDM-5, the intact IS26 mobile genetic elements surrounding multiple drug resistant regions, including the bla_NDM-5, has been reported infrequently. Both carbapenemase genes were successfully conjugated to a J53 recipient conferring a carbapenem-resistant phenotype. Our findings highlight that urban environments play a significant role on the transmission of AMR bacteria and genes to wildlife and suggest WTD may play a role in the dissemination of clinically and epidemiologically relevant antimicrobial resistant bacteria. IMPORTANCE The role of wildlife in the spread of antimicrobial resistance is not fully characterized. Some wildlife, including white-tailed deer (WTD), can thrive in suburban and urban environments. This may result in the exchange of antimicrobial resistant bacteria and resistance genes between humans and wildlife, and lead to their spread in the environment. We found that WTD living in an urban park system carried antimicrobial resistant bacteria that were important to human health and resistant to antibiotics used to treat serious bacterial infections. This included two deer that carried bacteria resistant to carbapenem antibiotics which are critically important for treatment of life-threatening infections. These two bacteria had the ability to transfer their AMR resistance genes to other bacteria, making them a threat to public health. Our results suggest that WTD may contribute to the spread of antimicrobial resistant bacteria in the environment.

Adverse effects of polymyxin B administration to healthy horses

BACKGROUND

Polymyxin B (PolyB) is used to treat endotoxemia in horses; neurologic and nephrogenic adverse effects occur in humans.

OBJECTIVES

To describe PolyB adverse effects in horses.

ANIMALS

Five healthy horses (ataxia 0/5), 1 horse with cervical osteoarthritis (ataxia 1/5).

METHODS

Prospective blinded randomized cross-over trial; 3-weeks wash out. Horses received PolyB (PolyB 6000 IU/kg IV, 7 doses q12h, n = 6) and PolyB/gentamicin (PolyB 6000 IU/kg IV, q12h 7 doses; gentamicin 10 mg/kg IV q24h 4 doses n = 4, or q12-24 h 5 doses because of an additional erroneous dose, n = 2). Daily neurological examinations were video recorded, and ataxia graded by 3 observers. Urine status, urinary GGT/creatinine ratio, plasma creatinine, and urea were assessed every other day, EMG daily. Mixed model analysis was used to evaluate factors associated with ataxia grade and [PolyB].

RESULTS

Median ataxia score increased from 0/5 (range 0-2/5) to 2/5 (range 1-3/5) during administration and declined to 0.5/5 (range 0-2/5) after cessation. Gentamicin co-administration (P < .01, effect size: .8), number of PolyB doses (P < .001, effect size: .6), and time since last PolyB dose (P < .001, effect size: .5) had a significant effect on ataxia grades, while horse, day, [Genta], [PolyB], and [PolyB]CSF did not. Gentamicin co-administration and [Genta] Cpeak had no effect on median [PolyB] Cpeak (4.67 and 4.89 μg/ml for PolyB and PolyB/gentamicin, respectively). Urinary GGT/creatinine ratio was elevated in 3/6 horses receiving PolyB/gentamicin. The EMG remained unchanged.

CONCLUSIONS AND CLINICAL IMPORTANCE

PolyB caused transient ataxia, worsening with cumulative PolyB doses and gentamicin co-administration. Nephrotoxicity of PolyB was only evident when gentamicin was co-administered.

Mapping Adverse Outcome Pathways for Kidney Injury as a Basis for the Development of Mechanism-Based Animal-Sparing Approaches to Assessment of Nephrotoxicity

In line with recent OECD activities on the use of AOPs in developing Integrated Approaches to Testing and Assessment (IATAs), it is expected that systematic mapping of AOPs leading to systemic toxicity may provide a mechanistic framework for the development and implementation of mechanism-based in vitro endpoints. These may form part of an integrated testing strategy to reduce the need for repeated dose toxicity studies. Focusing on kidney and in particular the proximal tubule epithelium as a key target site of chemical-induced injury, the overall aim of this work is to contribute to building a network of AOPs leading to nephrotoxicity. Current mechanistic understanding of kidney injury initiated by 1) inhibition of mitochondrial DNA polymerase γ (mtDNA Polγ), 2) receptor mediated endocytosis and lysosomal overload, and 3) covalent protein binding, which all present fairly well established, common mechanisms by which certain chemicals or drugs may cause nephrotoxicity, is presented and systematically captured in a formal description of AOPs in line with the OECD AOP development programme and in accordance with the harmonized terminology provided by the Collaborative Adverse Outcome Pathway Wiki. The relative level of confidence in the established AOPs is assessed based on evolved Bradford-Hill weight of evidence considerations of biological plausibility, essentiality and empirical support (temporal and dose-response concordance).

Higher Incidence of Neurotoxicity and Skin Hyperpigmentation in Renal Transplant Patients Treated With Polymyxin B

BACKGROUND

Toxicity is a major concern related to the clinical use of polymyxin B, and available safety data for renal transplant patients are limited.

AIMS

We investigated the safety of polymyxin B and toxicity risk factors in renal transplant patients.

METHODS

A prospective study was performed on a group of renal transplant patients who received intravenous polymyxin B between January 2018 and August 2021. Polymyxin B treatment was monitored to evaluate toxicity and risk factors.

RESULTS

A total of 235 courses of polymyxin B were administered to 213 patients. Of these, 121 (51.5%) developed SH, 149 (63.4%) developed neurotoxicity, and 10 (5.5%) developed acute kidney injury of which 80% was reversible. Risk factors for developing SH included a high total dose by weight (OR=1.31, 95%CI: 1.08-1.60, p=0.008) and the presence of neurotoxicity (OR=2.86, 95%CI: 1.56-5.26, p=0.001). Neurotoxicity manifested during the first two days of treatment. Neurotoxicity occurred most commonly in women (OR=3.84, 95%CI: 1.82-8.10, p<0.0001), and the presence of SH (OR=1.98, 95%CI: 1.13-3.46, p=0.016) was also an independent risk factor.

CONCLUSIONS

Neurotoxicity and SH are the two major adverse effects of polymyxin B in renal transplant patients, which may limit its clinical use.

Recent Advances in Multifunctional Hydrogels for the Treatment of Osteomyelitis

Osteomyelitis (OM), a devastating disease caused by microbial infection of bones, remains a major challenge for orthopedic surgeons. Conventional approaches for prevention and treatment of OM are unsatisfactory. Various alternative strategies have been proposed, among which, hydrogel-based strategies have demonstrated potential due to their unique properties, including loadable, implantable, injectable, printable, degradable, and responsive to stimuli. Several protocols, including different hydrogel designs, selection of antimicrobial agent, co-administration of bone morphogenetic protein 2 (BMP 2), and nanoparticles, have been shown to improve the biological properties, including antimicrobial effects, osteo-induction, and controlled drug delivery. In this review, we describe the current and future directions for designing hydrogels and their applications to improve the biological response to OM in vivo.

A synthetic lipopeptide targeting top-priority multidrug-resistant Gram-negative pathogens

The emergence of multidrug-resistant (MDR) Gram-negative pathogens is an urgent global medical challenge. The old polymyxin lipopeptide antibiotics (polymyxin B and colistin) are often the only therapeutic option due to resistance to all other classes of antibiotics and the lean antibiotic drug development pipeline. However, polymyxin B and colistin suffer from major issues in safety (dose-limiting nephrotoxicity, acute toxicity), pharmacokinetics (poor exposure in the lungs) and efficacy (negligible activity against pulmonary infections) that have severely limited their clinical utility. Here we employ chemical biology to systematically optimize multiple non-conserved positions in the polymyxin scaffold, and successfully disconnect the therapeutic efficacy from the toxicity to develop a new synthetic lipopeptide, structurally and pharmacologically distinct from polymyxin B and colistin. This resulted in the clinical candidate F365 (QPX9003) with superior safety and efficacy against lung infections caused by top-priority MDR pathogens Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae.

Polymyxins are often the last therapeutic option for multidrug-resistant (MDR) bacteria, but have suboptimal safety and efficacy. Here the authors report the discovery and development of a synthetic lipopeptide with an improved safety and efficacy against top-priority MDR Gram-negative pathogens.

Polymyxin Induces Significant Transcriptomic Perturbations of Cellular Signalling Networks in Human Lung Epithelial Cells

Inhaled polymyxins are increasingly used to treat pulmonary infections caused by multidrug-resistant Gram-negative pathogens. We have previously shown that apoptotic pathways, autophagy and oxidative stress are involved in polymyxin-induced toxicity in human lung epithelial cells. In the present study, we employed human lung epithelial cells A549 treated with polymyxin B as a model to elucidate the complex interplay of multiple signalling networks underpinning cellular responses to polymyxin toxicity. Polymyxin B induced toxicity (1.0 mM, 24 h) in A549 cells was assessed by flow cytometry and transcriptomics was performed using microarray. Polymyxin B induced cell death was 19.0 ± 4.2% at 24 h. Differentially expressed genes (DEGs) between the control and polymyxin B treated cells were identified with Student’s t-test. Pathway analysis was conducted with KEGG and Reactome and key hub genes related to polymyxin B induced toxicity were examined using the STRING database. In total we identified 899 DEGs (FDR < 0.01), KEGG and Reactome pathway analyses revealed significantly up-regulated genes related to cell cycle, DNA repair and DNA replication. NF-κB and nucleotide-binding oligomerization domain-like receptor (NOD) signalling pathways were identified as markedly down-regulated genes. Network analysis revealed the top 5 hub genes (i.e., degree) affected by polymyxin B treatment were PLK1(48), CDK20 (46), CCNA2 (42), BUB1 (40) and BUB1B (37). Overall, perturbations of cell cycle, DNA damage and pro-inflammatory NF-κB and NOD-like receptor signalling pathways play key roles in polymyxin-induced toxicity in human lung epithelial cells. Noting that NOD-like receptor signalling represents a group of key sensors for microorganisms and damage in the lung, understanding the mechanism of polymyxin-induced pulmonary toxicity will facilitate the optimisation of polymyxin inhalation therapy in patients.

Assessing the predictive performance of population pharmacokinetic models for intravenous polymyxin B in critically ill patients

Polymyxin B (PMB) has reemerged as a last‐line therapy for infections caused by multidrug‐resistant gram‐negative pathogens, but dosing is challenging because of its narrow therapeutic window and pharmacokinetic (PK) variability. Population PK (POPPK) models based on suitably powered clinical studies with appropriate sampling strategies that take variability into consideration can inform PMB dosing to maximize efficacy and minimize toxicity and resistance. Here we reviewed published PMB POPPK models and evaluated them using an external validation data set (EVD) of patients who are critically ill and enrolled in an ongoing clinical study to assess their utility. Seven published POPPK models were employed using the reported model equations, parameter values, covariate relationships, interpatient variability, parameter covariance, and unexplained residual variability in NONMEM (Version 7.4.3). The predictive ability of the models was assessed using prediction‐based and simulation‐based diagnostics. Patient characteristics and treatment information were comparable across studies and with the EVD (n = 40), but the sampling strategy was a main source of PK variability across studies. All models visually and statistically underpredicted EVD plasma concentrations, but the two‐compartment models more accurately described the external data set. As current POPPK models were inadequately predictive of the EVD, creation of a new POPPK model based on an appropriately powered clinical study with an informed PK sampling strategy would be expected to improve characterization of PMB PK and identify covariates to explain interpatient variability. Such a model would support model‐informed precision dosing frameworks, which are urgently needed to improve PMB treatment efficacy, limit resistance, and reduce toxicity in patients who are critically ill.

Trough polymyxin B plasma concentration is an independent risk factor for its nephrotoxicity

AIMS

Data regarding clinical pharmacokinetic/toxicodynamic (PK/TD) of polymyxin B is short of direct quantitative data. This study aims to investigate the risk factors of polymyxin B associated acute kidney injury (AKI) and to assess the relationship between polymyxin B plasma levels and its nephrotoxicity.

METHODS

A retrospective study was performed in adult patients treated with polymyxin B. Risk factors associated with AKI and plasma trough concentrations of polymyxin B were identified via medical record review. A multivariate logistic regression model was established and the risk of polymyxin B-associated AKI were predicted by a receiver operating characteristic curve, with maximal Youden index used to identify safety thresholds among the study population.

RESULTS

Fifty-four adult patients were included in the study. AKI was detected in 14 patients during polymyxin B treatment (25.9%, 14 out of 54). C_min (odds ratio [OR] 2.071; 95% confidence interval [CI] 1.235-3.472) and baseline serum creatinine (OR 1.024; 95% CI 1.005-1.043) were significant independent risk factors for developing AKI. The area under the ROC curve of the combined predictor was larger based on the above factors. When the Youden index was at maximum, the optimal cut-off point was 6.678 of the ROC curve. When C_min  ≥ 3.13 mg/L, the probability of AKI was more than 50%.

CONCLUSION

In this study, when the calculated combined predictor value was >6.678, there was an increased risk of AKI. Maintaining a polymyxin B C_min level below 3.13 mg/L may be helpful in reducing the incidence of polymyxin B associated nephrotoxicity.

Assessment of potential risk factors for coronavirus disease-19 (COVID-19) among health care workers

Background

Understanding COVID-19 infection among health workers and the risk factors for adverse outcomes is important not only for characterizing virus transmission patterns and risk factors for infection, but also for preventing the future infection of health workers and other patients and reducing secondary COVID-19 transmission within health care settings. Our aim was to identify risk factors for infection among health care workers to limit adverse events in health care facilities.

Subjects and Methods

A total of 336 HCWs from COVID-19 treatment hospitals took part in the study with varying COVID-19 exposure risk depending on job function and working site. All participants were asked about risk factors for COVID-19 infection.

Results

Among our participants, 42.6% were medical doctors, 28.6% nurses and 7.4% assistant nurses and 21.4% were others. Forty four percent of participants had work experience 5–10 years. More than half of participants received training in Infection Prevention and Control (IPC) (56.8%) about COVID 19; 91% have hand hygiene facilities and 69% admitted availability of PPE. More than half of participants admitted that they always follow IPC measures. Two thirds of participants (66.7%) had close contact with a patient since admission; 42.3% were present in aerosolizing procedures for patients. Forty two percent of participants had respiratory symptom; the most common was sore throat representing (32.4%). The highest frequency of respiratory symptoms was among of nurses and assistant nurses 51%. Frequency of respiratory symptoms was higher among those who contacted the patient directly or for prolonged period compared to those who do not admitted these contacts.

Conclusions

Risk factors for COVID-19 represented by those who were smokers, nurses and assistant nurses were more liable to catch COVID-19 than doctors as they contacted the patient directly for prolonged period or his/her body fluids, materials or surfaces around him.

Optimal Empiric Polymyxin B Treatment of Patients Infected with Gram-Negative Organisms Detected Using a Blood Antimicrobial Surveillance Network in China

Background

Few pharmacodynamics studies to date have evaluated the efficacy and safety of polymyxin B (PMB) in treating patients with bloodstream infections (BSIs) in China.

Methods

Patients with BSIs were identified using an antimicrobial surveillance network, and their pathogens were isolated. Patients were treated with a loading dose of PMB followed by either a weight-based or weight-independent maintenance dose. Monte Carlo simulation was utilized to calculate the probability of target attainment (PTA) and cumulative fraction of response (CFR) against Gram-negative organisms in patients with normal or decreased renal function.

Results

A total of 10,066 Gram-negative organisms, including 5500 Escherichia coli (Eco), 2519 Klebsiella pneumoniae (Kpn), 501 Acinetobacter baumannii (Aba), were isolated from patients with BSIs. Although these strains were highly resistant to carbapenem, they remained susceptible to PMB. Among patients with renal impairment (mean CrCL, 42 mL/min), a PMB 2.5 mg/kg loading dose followed by a maintenance dose of 60 mg q12h reached ≥90% PTA against isolates with an MIC of 2 mg/L, with a low risk of toxicity. Among patients with normal renal function (mean CrCL, 123 mL/min), all simulated regimens showed PTAs of 25–80%. A weight-based loading dose followed by either a weight-based or weight-independent maintenance dose showed a promising CFR, especially in patients with renal impairment, with CFRs ≥90% against carbapenem-resistant Eco, Kpn, and Aba. Simulated regimens showed a disappointing CFR (<80%) against carbapenem-resistant Pae in patients with normal renal function. Based on the optimal balance of efficacy and toxicity, a fixed maintenance dose of 60 mg q12h among patients with renal impairment yielded a CFR similar to regimens based on total body weight and was associated with a probability of toxicity (12.5%) significantly lower than that of simulations based on total body weight. Among patients with normal renal function, a weight-based maintenance dose of 1.25 mg/kg q12h achieved a higher CFR than a fixed maintenance dose, without significantly increasing toxicity.

Conclusion

A 2.5 mg/kg loading dose of PMB is optimal, regardless of renal function. A fixed maintenance dose of 60 mg q12h is recommended for empirical treatment of patients with renal impairment infected with Eco, Kpn, and Aba, whereas a weight-based maintenance dose of 1.25 mg/kg is recommended for patients with normal renal function.

Evaluation of prognosis and nephrotoxicity in patients treated with colistin in intensive care unit

Introduction

Nephrotoxicity is the most important adverse effect of colistin therapy. We investigated the frequency of nephrotoxicity, risk factors related to nephrotoxicity, and its relationship with mortality in patients who received intravenous colistin in intensive care units (ICUs).

Materials and methods

We retrospectively reviewed the data of patients who received intravenous colistin in ICUs between 2011 and 2017. Acute kidney injury (AKI) diagnosis and staging were made based on the Kidney Disease Improving Global Outcome criteria.

Results

There were 149 patients included in the study with 61% being male. The mean age was 58.7 ± 20.3 years. AKI was detected in 96 (64.4%) patients. There were 25 patients with AKI stage 1 (16.8%) and 71 patients with AKI stage 2 or 3 (47.7%). Advanced age (65.0 vs. 47.4 years; p < .001), diabetes mellitus (p < .001), heart failure (p = .01), high APACHE II score (31.7 vs. 28.08, p = .019), and inotrope usage (p = .01) were found as risk factors for AKI. The 14-day mortality rate was higher in the AKI group (p = .027).

Discussion

Higher AKI and mortality rates are observed in patients with diabetes, heart failure, advanced age and the hemodynamically impaired. However, it is a fact that there are no alternative therapies other than colistin in the treatment of multidrug-resistant Gram-negative bacterial infections. Therefore, the development of AKI in this patient group should not be considered a sufficient reason for discontinuing colistin treatment. Understanding the risk factors in this potential nephrotoxic treatment can provide a more careful patient follow-up.

Nephrotoxic antisense oligonucleotide SPC5001 induces kidney injury biomarkers in a proximal tubule-on-a-chip

Antisense oligonucleotides (ASOs) are a promising therapeutic modality. However, failure to predict acute kidney injury induced by SPC5001 ASO observed in a clinical trial suggests the need for additional preclinical models to complement the preceding animal toxicity studies. To explore the utility of in vitro systems in this space, we evaluated the induction of nephrotoxicity and kidney injury biomarkers by SPC5001 in human renal proximal tubule epithelial cells (HRPTEC), cultured in 2D, and in a recently developed kidney proximal tubule-on-a-chip. 2D HRPTEC cultures were exposed to the nephrotoxic ASO SPC5001 or the safe control ASO 556089 (0.16-40 µM) for up to 72 h, targeting PCSK9 and MALAT1, respectively. Both ASOs induced a concentration-dependent downregulation of their respective mRNA targets but cytotoxicity (determined by LDH activity) was not observed at any concentration. Next, chip-cultured HRPTEC were exposed to SPC5001 (0.5 and 5 µM) and 556089 (1 and 10 µM) for 48 h to confirm downregulation of their respective target transcripts, with 74.1 ± 5.2% for SPC5001 (5 µM) and 79.4 ± 0.8% for 556089 (10 µM). During extended exposure for up to 20 consecutive days, only SPC5001 induced cytotoxicity (at the higher concentration; 5 µM), as evaluated by LDH in the perfusate medium. Moreover, perfusate levels of biomarkers KIM-1, NGAL, clusterin, osteopontin and VEGF increased 2.5 ± 0.2-fold, 3.9 ± 0.9-fold, 2.3 ± 0.6-fold, 3.9 ± 1.7-fold and 1.9 ± 0.4-fold respectively, in response to SPC5001, generating distinct time-dependent profiles. In conclusion, target downregulation, cytotoxicity and kidney injury biomarkers were induced by the clinically nephrotoxic ASO SPC5001, demonstrating the translational potential of this kidney on-a-chip.

Total and Semisyntheses of Polymyxin Analogues with 2-Thr or 10-Thr Modifications to Decipher the Structure-Activity Relationship and Improve the Antibacterial Activity

Herein, we report the total and semisyntheses of a series of polymyxin analogues with 2-Thr and 10-Thr modifications to reveal the structure-activity relationship (SAR), which has not been fully elucidated previously. We employed two total-synthetic strategies to facilitate the diversified replacements on 2-Thr or 10-Thr, respectively. Moreover, semisynthetic approaches were utilized to achieve selective esterification of 2-Thr or dual esterification of both 2- and 10-Thr. Based on the results of in vitro antibacterial assays, SAR analysis implicated that the replacement of 2-/10-Thr with amino acids carrying hydrophobic side chains can maintain the activity against Pseudomonas aeruginosa but had varied effects on other tested Gram-negative bacteria. The aminoacetyl esterification on 2-/10-Thr achieved excellent antibacterial activity, and the compound 76 exhibited 2-8-fold higher activity against different strains and lower toxicity toward the HK-2 cell line. This work explored the SAR of polymyxin 2-/10-Thr and provided a promising strategy for the development of novel polymyxin derivatives.

Synchrotron-based X-ray fluorescence microscopy reveals accumulation of polymyxins in single human alveolar epithelial cells

Intravenous administration of the last-line polymyxins results in poor drug exposure in the lungs and potential nephrotoxicity; while inhalation therapy offers better pharmacokinetics/pharmacodynamics for pulmonary infections by delivering the antibiotic to the infection site directly. However, polymyxin inhalation therapy has not been optimized and adverse effects can occur. This study aimed to quantitatively determine the intracellular accumulation and distribution of polymyxins in single human alveolar epithelial A549 cells. Cells were treated with an iodine-labeled polymyxin probe FADDI-096 (5.0 and 10.0 μM) for 1, 4, and 24 h. Concentrations of FADDI-096 in single A549 cells were determined by synchrotron-based X-ray fluorescence microscopy. Concentration- and time-dependent accumulation of FADDI-096 within A549 cells was observed. The intracellular concentrations (mean ± SEM, n ≥ 189) of FADDI-096 were 1.58 ± 0.11, 2.25 ± 0.10, and 2.46 ± 0.07 mM following 1, 4 and 24 h of treatment at 10 μM, respectively. The corresponding intracellular concentrations following the treatment at 5 μM were 0.05 ± 0.01, 0.24 ± 0.04, and 0.25 ± 0.02 mM (n ≥ 189). FADDI-096 was mainly localized throughout the cytoplasm and nuclear region over 24 h. The intracellular zinc concentration increased in a concentration- and time-dependent manner. This is the first study to quantitatively map the accumulation of polymyxins in human alveolar epithelial cells and provides crucial insights for deciphering the mechanisms of their pulmonary toxicity. Importantly, our results may shed light on the optimization of inhaled polymyxins in patients and the development of new-generation safer polymyxins.

Rescuing the Last-Line Polymyxins: Achievements and Challenges

Antibiotic resistance is a major global health challenge and, worryingly, several key Gram negative pathogens can become resistant to most currently available antibiotics. Polymyxins have been revived as a last-line therapeutic option for the treatment of infections caused by multidrug-resistant Gram negative bacteria, in particular Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacterales. Polymyxins were first discovered in the late 1940s but were abandoned soon after their approval in the late 1950s as a result of toxicities (e.g., nephrotoxicity) and the availability of "safer" antibiotics approved at that time. Therefore, knowledge on polymyxins had been scarce until recently, when enormous efforts have been made by several research teams around the world to elucidate the chemical, microbiological, pharmacokinetic/pharmacodynamic, and toxicological properties of polymyxins. One of the major achievements is the development of the first scientifically based dosage regimens for colistin that are crucial to ensure its safe and effective use in patients. Although the guideline has not been developed for polymyxin B, a large clinical trial is currently being conducted to optimize its clinical use. Importantly, several novel, safer polymyxin-like lipopeptides are developed to overcome the nephrotoxicity, poor efficacy against pulmonary infections, and narrow therapeutic windows of the currently used polymyxin B and colistin. This review discusses the latest achievements on polymyxins and highlights the major challenges ahead in optimizing their clinical use and discovering new-generation polymyxins. To save lives from the deadly infections caused by Gram negative "superbugs," every effort must be made to improve the clinical utility of the last-line polymyxins. SIGNIFICANCE STATEMENT: Antimicrobial resistance poses a significant threat to global health. The increasing prevalence of multidrug-resistant (MDR) bacterial infections has been highlighted by leading global health organizations and authorities. Polymyxins are a last-line defense against difficult-to-treat MDR Gram negative pathogens. Unfortunately, the pharmacological information on polymyxins was very limited until recently. This review provides a comprehensive overview on the major achievements and challenges in polymyxin pharmacology and clinical use and how the recent findings have been employed to improve clinical practice worldwide.

Conventional and Nanotechnology-Based Sensing Methods for SARS Coronavirus (2019-nCoV)

Ongoing pandemic coronavirus (COVID-19) has affected over 218 countries and infected 88,512,243 and 1,906,853 deaths reported by Jan. 8, 2021. At present, vaccines are being developed in Europe, Russia, USA, and China, although some of these are in phase III of trials, which are waiting to be available for the general public. The only option available now is by vigorous testing, isolation of the infected cases, and maintaining physical and social distances. Numerous methods are now available or being developed for testing the suspected cases, which may act as carriers of the virus. In this review, efforts have been made to discuss the conventional as well as fast, rapid, and efficient testing methods developed for the diagnosis of 2019-nCoV.Testing methods can be based on the sensing of targets, which include RNA, spike proteins and antibodies such as IgG and IgM. Apart from the development of RNA targeted PCR, antibody and VSV pseudovirus neutralization assay along with several other diagnostic techniques have been developed. Additionally, nanotechnology-based sensors are being developed for the diagnosis of the virus, and these are also discussed.

Therapeutic Options for Metallo-β-Lactamase-Producing Enterobacterales

The spread of metallo-β-lactamase (MBL)-producing Enterobacterales worldwide without the simultaneous increase in active antibiotics makes these organisms an urgent public health threat. This review summarizes recent advancements in diagnostic and treatment strategies for infections caused by MBL-producing Enterobacterales. Adequate treatment of patients infected with MBL-producing Enterobacterales relies on detection of the β-lactamase in the clinic. There are several molecular platforms that are currently available to identify clinically relevant MBLs as well as other important serine-β-lactamases. Once detected, there are several antibiotics that have historically been used for the treatment of MBL-producing Enterobacterales. Antimicrobials such as aminoglycosides, tetracyclines, fosfomycin, and polymyxins often show promising in vitro activity though clinical data are currently lacking to support their widespread use. Ceftazidime-avibactam combined with aztreonam is promising for treatment of infections caused by MBL-producing Enterobacterales and currently has the most clinical data of any available antibiotic to support its use. While cefiderocol has displayed promising activity against MBL-producing Enterobacterales in vitro and in preliminary clinical studies, further clinical studies will better shed light on its place in treatment. Lastly, there are several promising MBL inhibitors in the pipeline, which may further improve the treatment of MBL-producing Enterobacterales.

Enhanced bacterial killing with colistin/sulbactam combination against carbapenem-resistant Acinetobacter baumannii

AIMS

Polymyxin-based combination therapy is often used to treat carbapenem-resistant Acinetobacter baumannii (A. baumannii) infections. Although sulbactam is intrinsically active against A. baumannii, few studies have investigated colistin/sulbactam combinations against carbapenem-resistant A. baumannii.

METHODS

Whole genome sequencing was undertaken on eight carbapenem-resistant (colistin-susceptible) isolates of A. baumannii from Chinese patients. Bacterial killing of colistin and sulbactam, alone and in combination, was examined with checkerboard (all isolates) and static and dynamic time-kill studies (three isolates). In the dynamic studies, antibiotics were administered in various clinically-relevant dosing regimens that mimicked patient pharmacokinetics.

RESULTS

The eight isolates consisted of ST195, ST191 and ST208 belonging to clonal complex 208, which is the most epidemic clonal type of A. baumannii globally. All isolates possessed Acinetobacter-derived cephalosporinase (ADC-61 or ADC-78) and seven of eight isolates contained the carbapenem-resistance gene bla_OXA-23. The colistin/sulbactam combination was synergistic against two of eight isolates in checkerboard studies. In time-kill studies, rapid bacterial killing of ca. 3-6 log₁₀ CFU/mL was observed with colistin monotherapy, followed by steady regrowth. Sulbactam monotherapy was generally ineffective. Substantially enhanced bacterial killing was observed with colistin/sulbactam combinations in both static and dynamic models, especially with the higher sulbactam concentration (2 g) and/or longer sulbactam infusion time (2 hours) in the dynamic model.

CONCLUSIONS

This study was the first to use a pharmacokinetics/pharmacodynamics model to investigate synergistic activity of colistin/sulbactam combinations against A. baumannii. It showed that clinically-relevant dosing regimens of colistin combined with sulbactam may substantially improve bacterial killing of multidrug-resistant and carbapenem-resistant A. baumannii.

ColistinDose, a Mobile App for Determining Intravenous Dosage Regimens of Colistimethate in Critically Ill Adult Patients: Clinician-Centered Design and Development Study

Background

Determining a suitable dose of intravenous colistimethate is challenging because of complicated pharmacokinetics, confusing terminology, and the potential for renal toxicity. Only recently have reliable pharmacokinetic/pharmacodynamic data and dosing recommendations for intravenous colistimethate become available.

Objective

The aim of this work was to develop a clinician-friendly, easy-to-use mobile app incorporating up-to-date dosing recommendations for intravenous colistimethate in critically ill adult patients.

Methods

Swift programming language and common libraries were used for the development of an app, ColistinDose, on the iPhone operating system (iOS; Apple Inc). The compatibility among different iOS versions and mobile devices was validated. Dosing calculations were based on equations developed in our recent population pharmacokinetic study. Recommended doses generated by the app were validated by comparison against doses calculated manually using the appropriate equations.

Results

ColistinDose provides 3 major functionalities, namely (1) calculation of a loading dose, (2) calculation of a daily dose based on the renal function of the patient (including differing types of renal replacement therapies), and (3) retrieval of historical calculation results. It is freely available at the Apple App Store for iOS (version 9 and above). Calculated doses accurately reflected doses recommended in patients with varying degrees of renal function based on the published equations. ColistinDose performs calculations on a local mobile device (iPhone or iPad) without the need for an internet connection.

Conclusions

With its user-friendly interface, ColistinDose provides an accurate and easy-to-use tool for clinicians to calculate dosage regimens of intravenous colistimethate in critically ill patients with varying degrees of renal function. It has significant potential to avoid the prescribing errors and patient safety issues that currently confound the clinical use of colistimethate, thereby optimizing patient treatment.

Polymyxin-induced nephrotoxicity and its predictors: a systematic review and meta-analysis of studies conducted using RIFLE criteria of acute kidney injury

Polymyxins are last-resort antibiotics re-emerged to treat infections caused by multidrug resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacterial infections. However, polymyxin-associated nephrotoxicity has become the main safety concern. Therefore, we conducted this systematic review and meta-analysis on polymyxin-induced nephrotoxicity and its predictors using studies conducted based on the validated RIFLE (Risk, Injury, Failure, Loss of Function and End-stage renal disease) criteria of acute kidney damage. Literature search was carried out through visiting legitimate databases and indexing services including PubMed, MEDLINE (Ovid®), EMBASE (Ovid®), and Scopus to retrieve relevant studies. Following screening and eligibility evaluation, relevant data were extracted from included studies and analyzed using STATA 15.0 and Rev-Man 5.3. Inverse variance method with random effects pooling model was used for the analysis of outcome measures at 95% confidence interval. Besides, meta-regression, meta-influence, and publication bias analyses were conducted. A total of 48 studies involving 6,199 adult patients aged ≥ 18 years were included for systematic review and meta-analysis. The pooled incidence of polymyxin-induced nephrotoxicity was found to be 45% (95% CI: 41- 49%; I² = 92.52%). Stratifying with RIFLE severity scales, pooled estimates of polymyxin-treated patients identified as 'risk', 'injury' and 'failure' were 17% (95% CI: 14-20%), 13% (95% CI: 11-15%), and 10% (95% CI: 9-11%), respectively. Besides, the pooled incidence of colistin-induced nephrotoxicity was about 48% (95% CI: 42-54%), whereas that of polymyxin B was 38% (95% CI: 32-44%). Likewise, colistin had 37% increased risk of developing nephrotoxicity compared to the polymyxin B treated cohorts (RR = 1.37, 95% CI: 1.13-1.67; I² = 57%). Older age (AOR = 1.03, 95% CI: 1.01-1.05), daily dose (AOR = 1.46, 95% CI: 1.09-1.96), underlying diabetes mellitus (AOR = 1.81, 95% CI: 1.25-2.63), and concomitant nephrotoxic drugs (AOR = 2.31, 95% CI: 1.79-3.00) were independent risk factors for polymyxin-induced nephrotoxicity. Patients with high serum albumin level were less likely (AOR = 0.69, 95% CI: 0.56-0.85] to experience nephrotoxicity compared to those with low albumin level. Despite the resurgence of these antibiotics for the chemotherapy of MDR/XDR-Gram-negative superbugs, the high incidence of nephrotoxicity has become a contemporary clinical concern. Being elderly, high daily dose, having underlying diseases such as diabetes, and use of concomitant nephrotoxic drugs were independent predictors of nephrotoxicity. Therefore, therapeutic drug monitoring should be done to these patients to outweigh the potential benefits of polymyxin therapy from its risk.

Polymyxin-Induced Cell Death of Human Macrophage-Like THP-1 and Neutrophil-Like HL-60 Cells Associated with the Activation of Apoptotic Pathways

Innate immunity is crucial for the host to defend against infections, and understanding the effect of polymyxins on innate immunity is important for optimizing their clinical use. In this study, we investigated the potential toxicity of polymyxins on human macrophage-like THP-1 and neutrophil-like HL-60 cells. Differentiated THP-1 human macrophages (THP-1-dMs) and HL-60 human neutrophils (HL-60-dNs) were employed. Flow cytometry was used to measure the concentration-dependent effects (100 to 2,500 μM for THP-1-dMs and 5 to 2,500 μM for HL-60-dNs) and time-dependent effects (1,000 μM for THP-1-dMs and 300 μM for HL-60-dNs) of polymyxin B over 24 h. Effects of polymyxin B on mitochondrial activity, activation of caspase-3, caspase-8, and caspase-9, and Fas ligand (FasL) expression in both cell lines were examined using fluorescence imaging, colorimetric, and fluorometric assays. In both cell lines, polymyxin B induced concentration- and time-dependent loss of viability at 24 h with 50% effective concentration (EC₅₀) values of 751.8 μM (95% confidence interval [CI], 692.1 to 816.6 μM; Hill slope, 3.09 to 5.64) for THP-1-dM cells and 175.4 μM (95% CI, 154.8 to 198.7 μM; Hill slope, 1.42 to 2.21) for HL-60-dN cells. A concentration-dependent loss of mitochondrial membrane potential and generation of mitochondrial superoxide was also observed. Polymyxin B-induced apoptosis was associated with concentration-dependent activation of all three tested caspases. The death receptor apoptotic pathway activation was demonstrated by a concentration-dependent increase of FasL expression. For the first time, our results reveal that polymyxin B induced concentration- and time-dependent cell death in human macrophage-like THP-1 and neutrophil-like HL-60 cells associated with mitochondrial and death receptor apoptotic pathways.

Structure-Interaction Relationship of Polymyxins with the Membrane of Human Kidney Proximal Tubular Cells

Multidrug-resistant Gram-negative bacteria are a serious global threat to human health. Polymyxins are increasingly used in patients as a last-line therapy to treat infections caused by these life-threatening 'superbugs'. Unfortunately, polymyxin-induced nephrotoxicity is the major dose-limiting factor and understanding its mechanism is crucial for the development of novel, safer polymyxins. Here, we undertook the first all-atom molecular dynamics simulations of the interaction between four naturally occurring polymyxins A1, B1, M1 and colistin A (representative structural variations of the polymyxin core structure) and the membrane of human kidney proximal tubular cells. All polymyxins inserted spontaneously into the hydrophobic region of the membrane where they were retained, although their insertion abilities varied. Polymyxin A1 completely penetrated into the hydrophobic region of the membrane with a unique folded conformation, whereas the other three polymyxins only inserted their fatty acyl tails into this region. Furthermore, local membrane defects and increased water penetration were induced by each polymyxin, which may represent the initial stage of cellular membrane damage. Finally, the structure-interaction relationship of polymyxins was investigated based on atomic interactions at the cell membrane level. The hydrophobicity at positions 6/7 and stereochemistry at position 3 regulated the interactions of polymyxins with the cell membrane. Collectively, our results provide new mechanistic insights into polymyxin-induced nephrotoxicity at the atomic level and will facilitate the development of new-generation polymyxins.

7-Hydroxycoumarin Attenuates Colistin-Induced Kidney Injury in Mice Through the Decreased Level of Histone Deacetylase 1 and the Activation of Nrf2 Signaling Pathway

Colistin has been considered as the last line of defense against Gram-negative bacterial infections, however, the potential nephrotoxicity limited its clinical use. 7-Hydroxycoumarin (7-HC) possesses many beneficial pharmacological activities. This study aimed to investigate the nephroprotective effects of 7-HC against colistin-induced kidney injury. In vivo experiments showed that 7-HC alleviated kidney injury induced by colistin, as indicated by lower levels of serum neutrophil gelatinase-associated lipocalin, blood urea nitrogen and creatinine levels. Both in vivo and in vitro results demonstrated that 7-HC alleviated oxidative stress and apoptosis induced by colistin, as shown by decreased malondialdehyde levels, decreased caspase-3 and caspase-9 activities, and increased superoxide dismutase and catalase activities. We also found that colistin significantly induced histone deacetylase (HDAC) 1 expression that deacetylated histone 3 at Lys27 acetylation (H3K27AC) of Nrf2 promoter region and hence inhibiting Nrf2 signaling. 7-HC treatment restored histone acetylation at the Nrf2 promoter region and hence promoted Nrf2 expression. These results suggested that 7-HC alleviates colistin-induced renal injury and this effect was achieved by enhancement of renal antioxidant capacity with the decreased level of HDAC1 and the activation of Nrf2 signaling pathway.

Near-infrared-excited upconversion photodynamic therapy of extensively drug-resistant Acinetobacter baumannii based on lanthanide nanoparticles

Extensively drug-resistant Acinetobacter baumannii (XDR-AB) has raised considerable concerns due to its mortal damage to humans and its high transmission rate of infections in hospitals. However, current antibiotics not only show poor anti-infection effects in vivo but also frequently cause high nephrotoxicity and neurotoxicity. Herein, we report a near-infrared (NIR) light-initiated antimicrobial photodynamic therapy (aPDT) to effectively treat in vivo XDR-AB infections based on photosensitizer (PS) loaded upconversion nanoparticles (UCNPs, LiYF₄:Yb/Er). Such nanoagents feature robust NIR triggered UC luminescence and high-efficiency energy transfer from UCNPs to the loaded PS, thereby allowing NIR-triggered generation of reactive oxygen species (ROS) for destroying the bacterial cell membrane. This strategy permits a high antibacterial activity against XDR-AB, resulting in a decline of 4.72 log₁₀ in viability at a dose of 50 μg mL^-1 UCNPs-PVP-RB with 980 nm laser irradiation (1 W cm^-2). More significantly, we can achieve excellent therapeutic efficacy against deep-tissue (about 5 mm) XDR-AB infections without causing any side effects in the murine model. In brief, such NIR-activated aPDT may open up new avenues for treating various deep-tissue intractable infections.

Design, Synthesis, and Bioactivity of Cyclic Lipopeptide Antibiotics with Varied Polarity, Hydrophobicity, and Positive Charge Distribution

Twenty-three polymyxin analogs with variations at nine amino acid positions were synthesized and assessed for antimicrobial activity and renal cytotoxicity. Compounds M₂, 14, S₂, and 16 (MIC = 0.125-4 μg/mL) had similar or stronger activities against susceptible and drug-resistant strains of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii compared to polymyxin B (MIC = 1-2 μg/mL). Most synthesized compounds (50% cytotoxic concentration, CC₅₀ ≥ 200 μg/mL) exhibited lower cytotoxicity than polymyxin B (CC₅₀ = 99 ± 6 μg/mL). Polymyxin S₂ showed high plasma stability in vitro and strong efficacy in a mouse systemic infection model (ED₅₀ = 0.9 mg/kg) against NDM-1-producing Klebsiella pneumoniae, suggesting that it is a potential candidate for drug development. The activity and cytotoxicity results indicated that the amino acids at positions 2, 3, 6, and 7 might be replaced. Effects on activity and cytotoxicity linked to changes in the number of positively charged amino acids varied among different cyclopeptide skeletons, but the underlying mechanisms are unknown.

Impact of total body weight on rate of acute kidney injury in patients treated with piperacillin-tazobactam and vancomycin

PURPOSE

Results of a study to determine whether obesity is associated with acute kidney injury (AKI) among patients receiving combination therapy with piperacillin-tazobactam and vancomycin are reported.

METHODS

A retrospective, single-center cohort study of patients who received combination therapy for at least 48 hours was conducted using data from the University of Kentucky Center for Clinical and Translational Science's Enterprise Data Trust. Patients with chronic kidney disease, baseline creatinine clearance of less than 30 mL/min, cystic fibrosis, or missing height or weight information were excluded.

RESULTS

A total of 8,125 patients were included in the cohort. Among the variables evaluated, total body weight of 91 kg or more was the variable most predictive of AKI. Patients with a weight of 91 kg or higher were more likely than lower-weight patients to have diabetes (39% versus 21%, p < 0.00001), hypertension (64% versus 47%, p < 0.00001), and heart failure (15% versus 13%, p = 0.007). The median daily vancomcyin dose was lower in patients with a weight of less than 91 kg (2,000 mg versus 3,000 mg, p < 0.00001); however, weight-based doses were lower in patients weighing 91 kg or more (25.5 mg/kg/day versus 27.9 mg/kg/day, p < 0.00001). AKI was more common in patients weighing 91 kg or more (24% versus 18%, p < 0.00001; adjusted odds ratio, 1.46 [95% confidence interval, 1.28-1.66]).

CONCLUSION

Increased total body weight increased the rate of AKI among patients concurrently treated with piperacillin-tazobactam and vancomycin independent of clinically important confounders, with an important breakpoint occurring at 91 kg.

In vitro interaction of various antibiotic combinations recommended by Chinese consensus statement against carbapenems-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is related to nosocomial infections, and it tends to become resistant during or after antimicrobial treatment. The ability to develop carbapenems resistance makes it difficult to treat. P. aeruginosa infections are often associated with high mortality, morbidity and treatment costs. A group of Chinese experts drafted a consensus for treatment of extensively drug-resistant Gram-negative bacilli (XDR-GNB) including extensively drug-resistant P. aeruginosa (XDR-PA). In this study, we studied the antibacterial activities of different antibiotic combinations against six carbapenems-resistant P. aeruginosa (CRPA) strains in vitro, and the results indicated that the combination of ceftazidime with cefoperazone-sulbatam was the best combination with excellent synergistic rate (100%). Besides, some combinations exhibited better effects than using antibiotics alone, reducing the MICs of both drugs significantly, such as ceftazidime/piperacillin-tazobactam and ceftazidime/aztreonam etc. However, there are also some combinations that showed no additional or synergistic effects, suggesting that not all combinations recommended by the guideline have the same effect against resistant P. aeruginosa. Our study screened out some effective combinations against six CRPA strains which might help to prevent the spread of antibiotic resistance through improving antibiotic effectiveness. SIGNIFICANCE AND IMPACT OF THE STUDY: This study measured the synergistic interactions between various antibiotics in vitro recommended by Chinese consensus statement against carbapenems-resistant Pseudomonas aeruginosa. The results of this study provide valuable evidence that some combinations may be a promising option for clinical treatment.

Pro-caspase-3 protects cells from polymyxin B-induced cytotoxicity by preventing ROS accumulation

Polymyxin B (PMB), a last-line antibiotic used against antibiotic-resistant superbugs, causes undesirable cytotoxic side effects. However, its mechanisms remain unknown. In this study, we unexpectedly found that caspase-3, a main executor of apoptosis, plays a protective role in PMB-induced cytotoxicity. Caspase-3 knockout (KO) cells exhibited higher susceptibility to PMB-induced cytotoxicity compared with wild-type (WT) cells, accompanied by increased levels of reactive oxygen species (ROS). Interestingly, co-treatment with the antioxidant N-acetylcysteine (NAC) rescued cell viability to a similar extent as WT cells. Furthermore, PMB failed to facilitate the processing of inactive caspase-3 (pro-caspase-3) into active forms, suggesting that pro-caspase-3 nonenzymatically suppresses PMB-driven ROS accumulation and its cytotoxicity. Thus, our findings that demonstrate the potential ability of PMB to stimulate ROS generation, but which is normally masked by pro-caspase-3-dependent mechanisms, may provide novel insights into the mechanisms of PMB-induced side effects.