Polymyxins for the treatment of lower respiratory tract infections: lessons learned from the integration of clinical pharmacokinetic studies and clinical outcomes

Polymyxin B-Enriched Exogenous Lung Surfactant: Thermodynamics and Structure

The use of an exogenous pulmonary surfactant (EPS) to deliver other relevant drugs to the lungs is a promising strategy for combined therapy. We evaluated the interaction of polymyxin B (PxB) with a clinically used EPS, the poractant alfa Curosurf (PSUR). The effect of PxB on the protein-free model system (MS) composed of four phospholipids (diC16:0PC/16:0-18:1PC/16:0-18:2PC/16:0-18:1PG) was examined in parallel to distinguish the specificity of the composition of PSUR. We used several experimental techniques (differential scanning calorimetry, small- and wide-angle X-ray scattering, small-angle neutron scattering, fluorescence spectroscopy, and electrophoretic light scattering) to characterize the binding of PxB to both EPS. Electrostatic interactions PxB-EPS are dominant. The results obtained support the concept of cationic PxB molecules lying on the surface of the PSUR bilayer, strengthening the multilamellar structure of PSUR as derived from SAXS and SANS. A protein-free MS mimics a natural EPS well but was found to be less resistant to penetration of PxB into the lipid bilayer. PxB does not affect the gel-to-fluid phase transition temperature, Tm, of PSUR, while Tm increased by ∼+ 2 °C in MS. The decrease of the thickness of the lipid bilayer (dL) of PSUR upon PxB binding is negligible. The hydrophobic tail of the PxB molecule does not penetrate the bilayer as derived from SANS data analysis and changes in lateral pressure monitored by excimer fluorescence at two depths of the hydrophobic region of the bilayer. Changes in dL of protein-free MS show a biphasic dependence on the adsorbed amount of PxB with a minimum close to the point of electroneutrality of the mixture. Our results do not discourage the concept of a combined treatment with PxB-enriched Curosurf. However, the amount of PxB must be carefully assessed (less than 5 wt % relative to the mass of the surfactant) to avoid inversion of the surface charge of the membrane.

Tobramycin Reduces Pulmonary Toxicity of Polymyxin B via Inhibiting the Megalin-Mediated Drug Uptake in the Human Lung Epithelial Cells

Accumulation of polymyxins in the lung epithelial cells can lead to increased mitochondrial oxidative stress and pulmonary toxicity. Aminoglycosides and polymyxins are used, via intravenous and pulmonary delivery, against multidrug-resistant Gram-negative pathogens. Our recent in vitro and animal studies demonstrated that the co-administration of polymyxins with aminoglycosides decreases polymyxin-induced pulmonary toxicity. The aim of this study was to investigate the in vitro transport and uptake of polymyxin B and tobramycin in human lung epithelial Calu-3 cells and the mechanism of reduced pulmonary toxicity resulting from this combination. Transport, intracellular localization, and accumulation of polymyxin B and tobramycin were investigated using doses of 30 mg/L polymyxin B, 70 mg/L tobramycin, and the combination of both. Adding tobramycin significantly (p < 0.05) decreased the polymyxin B-induced cytotoxicity in Calu-3 cells. The combination treatment significantly reduced the transport and uptake of polymyxin B and tobramycin in Calu-3 cells, compared to each drug alone, which supported the reduced pulmonary toxicity. We hypothesized that cellular uptake of polymyxin B and tobramycin shared a common transporter, megalin. We further investigated the megalin expression of Calu-3 cells using confocal microscopy and evaluated megalin activity using a megalin substrate, FITC-BSA, and a megalin inhibitor, sodium maleate. Both polymyxin B and tobramycin significantly inhibited FITC-BSA uptake by Calu-3 cells in a concentration-dependent manner. Sodium maleate substantially inhibited polymyxin B and tobramycin transport and cellular accumulation in the Calu-3 cell monolayer. Our study demonstrated that the significantly reduced uptake of polymyxin B and tobramycin in Calu-3 cells is attributed to the mechanism of action that determines that polymyxin B and tobramycin share a common transporter, megalin.

In vitro antimicrobial susceptibility data of global meropenem-resistant Acinetobacter baumannii isolates causing pneumonia: Data from the Antimicrobial Testing Leadership and Surveillance Program, 2014-2021, and re-estimations of susceptibility breakpoints and appropriate dosages of important antibiotics for pneumonia treatment

OBJECTIVES

To evaluate the susceptibility of globally pneumonia-causing meropenem-resistant (MEM-R) Acinetobacter baumannii isolates against important antibiotics and estimate appropriate dosages of indicated antibiotics.

METHODS

We extracted the 2014-2021 Antimicrobial Testing of Leadership Surveillance database regarding the susceptibility of MEM-R A. baumannii isolates causing pneumonia against important antibiotics. The susceptibility and carbapenemase-encoding gene (CPEG) data of pneumonia-causing MEM-R A. baumannii isolates from patients hospitalized in intensive care units of five major regions were analyzed. The susceptibility breakpoints (SBP) recommended by the Clinical and Laboratory Standards Institute (CLSI) in 2022, other necessary criteria [SBP of MIC for colistin, 2 mg/L, in the CLSI 2018; and cefoperazone-sulbactam (CFP-SUL), 16 mg/L], and the pharmacokinetic and pharmacodynamic data of indicated antibiotics were employed.

RESULTS

Applying the aforementioned criteria, we observed the susceptible rates of colistin, minocycline, and CFP-SUL against the pneumonia-causing MEM-R A. baumannii isolates globally (n = 2905) were 93.2%, 69.1%, and 26.3%, respectively. Minocycline was significantly more active in vitro (MIC ≤4 mg/L) against the pneumonia-causing MEM-R A. baumannii isolates collected from North and South America compared to those from other regions (>90% vs. 58-72%). Additionally, blaOXA-23 and blaOXA-72 were the predominant CPEG in pneumonia-causing MEM-R A. baumannii isolates.

CONCLUSIONS

After deliberative estimations, dosages of 200 mg minocycline intravenously every 12 h (SBP, 8 mg/L), 100 mg tigecycline intravenously every 12 h (SBP, 1 mg/L), and 160 mg nebulized colistin methanesulphonate every 8 h (SBP, 2 mg/L) are needed for the effective treatment of pneumonia-causing MEM-R A. baumannii isolates.

Ceftazidime-avibactam versus polymyxins in treating patients with carbapenem-resistant Enterobacteriaceae infections: a systematic review and meta-analysis

OBJECTIVE

Carbapenem-resistant Enterobacteriaceae (CRE) pose a significant threat to human health and have emerged as a major public health concern. We aimed to compare the efficacy and the safety of ceftazidime-avibactam (CAZ-AVI) and polymyxin in the treatment of CRE infections.

METHODS

A systematic review and meta-analysis was performed by searching the databases of EMBASE, PubMed, and the Cochrane Library. Published studies on the use of CAZ-AVI and polymyxin in the treatment of CRE infections were collected from the inception of the database until March 2023. Two investigators independently screened the literature according to the inclusion and exclusion criteria, evaluated the methodological quality of the included studies and extracted the data. The meta-analysis was performed using RevMan 5.4 software.

RESULTS

Ten articles with 833 patients were included (CAZ-AVI 325 patients vs Polymyxin 508 patients). Compared with the patients who received polymyxin-based therapy, the patients who received CAZ-AVI therapy had significantly lower 30-days mortality (RR = 0.49; 95% CI 0.01-2.34; I2 = 22%; P < 0.00001), higher clinical cure rate (RR = 2.70; 95% CI 1.67-4.38; I2 = 40%; P < 0.00001), and higher microbial clearance rate (RR = 2.70; 95% CI 2.09-3.49; I2 = 0%; P < 0.00001). However, there was no statistically difference in the incidence of acute kidney injury between patients who received CAZ-AVI and polymyxin therapy (RR = 1.38; 95% CI 0.69-2.77; I2 = 22%; P = 0.36). In addition, among patients with CRE bloodstream infection, those who received CAZ-AVI therapy had significantly lower mortality than those who received polymyxin therapy (RR = 0.44; 95% CI 0.27-0.69, I2 = 26%, P < 0.00004).

CONCLUSIONS

Compared to polymyxin, CAZ-AVI demonstrated superior clinical efficacy in the treatment of CRE infections, suggesting that CAZ-AVI may be a superior option for CRE infections.

Drug Combination of Ciprofloxacin and Polymyxin B for the Treatment of Multidrug–Resistant Acinetobacter baumannii Infections: A Drug Pair Limiting the Development of Resistance

Polymyxins are considered as last–resort antibiotics to treat infections caused by Acinetobacter baumannii. However, there are increasing reports of resistance in A. baumannii to polymyxins. In this study, inhalable combinational dry powders consisting of ciprofloxacin (CIP) and polymyxin B (PMB) were prepared by spray–drying. The obtained powders were characterized with respect to the particle properties, solid state, in vitro dissolution and in vitro aerosol performance. The antibacterial effect of the combination dry powders against multidrug–resistant A. baumannii was assessed in a time–kill study. Mutants from the time–kill study were further investigated by population analysis profiling, minimum inhibitory concentration testing, and genomic comparisons. Inhalable dry powders consisting of CIP, PMB and their combination showed a fine particle fraction above 30%, an index of robust aerosol performance of inhaled dry powder formulations in the literature. The combination of CIP and PMB exhibited a synergistic antibacterial effect against A. baumannii and suppressed the development of CIP and PMB resistance. Genome analyses revealed only a few genetic differences of 3–6 SNPs between mutants and the progenitor isolate. This study suggests that inhalable spray–dried powders composed of the combination of CIP and PMB is promising for the treatment of respiratory infections caused by A. baumannii, and this combination can enhance the killing efficiency and suppress the development of drug resistance.

Pharmacokinetics/pharmacodynamics of polymyxin B in patients with bloodstream infection caused by carbapenem-resistant Klebsiella pneumoniae

Introduction: Polymyxin B is a last-line therapy for carbapenem-resistant microorganisms. However, a lack of clinical pharmacokinetic/pharmacodynamic (PK/PD) data has substantially hindered dose optimization and breakpoint setting. Methods: A prospective, multi-center clinical trial was undertaken with polymyxin B [2.5 mg/kg loading dose (3-h infusion), 1.25 mg/kg/12 h maintenance dose (2-h infusion)] for treatment of carbapenem-resistant K. pneumoniae (CRKP) bloodstream infections (BSI). Safety, clinical and microbiological efficacy were evaluated. A validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was applied to determine the concentrations of polymyxin B in blood samples. Population pharmacokinetic (PK) modeling and Monte Carlo simulations were conducted to examine the susceptibility breakpoint for polymyxin B against BSI caused by CRKP. Results: Nine patients were enrolled and evaluated for safety. Neurotoxicity (5/9), nephrotoxicity (5/9), and hyperpigmentation (1/9) were recorded. Blood cultures were negative within 3 days of commencing therapy in all 8 patients evaluated for microbiological efficacy, and clinical cure or improvement occurred in 6 of 8 patients. C_max and C_min following the loading dose were 5.53 ± 1.80 and 1.62 ± 0.41 mg/L, respectively. With maintenance dosing, AUC_ss,24 h was 79.6 ± 25.0 mg h/L and C_ss,avg 3.35 ± 1.06 mg/L. Monte Carlo simulations indicated that a 1 mg/kg/12-hourly maintenance dose could achieve >90% probability of target attainment (PTA) for isolates with minimum inhibitory concentration (MIC) ≤1 mg/L. PTA dropped substantially for MICs ≥2 mg/L, even with a maximally recommended daily dose of 1.5 mg/kg/12-hourly. Conclusion: This is the first clinical PK/PD study evaluating polymyxin B for BSI. These results will assist to optimize polymyxin B therapy and establish its breakpoints for CRKP BSI.

Evaluation of phenotypic methods for detection of polymyxin B-resistant bacteria

Determination of sensitivity to polymyxins has always been a challenge, especially in clinical laboratory routines. This study evaluated two rapid, simple, and inexpensive phenotypic methods to test polymyxin B (PMB) susceptibility in Enterobacterales and non-fermenting Gram-negative bacilli. One hundred isolates were used in the tests. The isolates were collected in three hospitals in southern and southeastern Brazil from 1995 to 2019. We compared broth microdilution (reference method) with the broth disk elution test and modified drop test, using polymyxin B -disk or PMB -powder in 2 concentrations (12 and 16 μg/ml). For the broth disk elution and modified drop test with the concentration of 12 μg/ml, categorical agreement values exceeded 90%. The modified drop test with a concentration of 12 μg/ml and broth disk elution may be excellent for initial screening of polymyxin-resistance in laboratory routines. Moreover, these methods are simple and use inexpensive supplies, and may optimize therapeutic decisions.

Ceftolozane-tazobactam versus colistin for the treatment of infections due to drug-resistant Pseudomonas aeruginosa. A multicenter cohort study

BACKGROUND

The aim of this study was to compare the safety and effectiveness of ceftolozane-tazobactam (C-T) to colistin-based regimen for treating infections caused by multidrug-resistant (MDR) P. aeruginosa.

METHOD

This was a retrospective, multicenter, observational cohort study of inpatients who received either C-T or intravenous colistin for treating infections caused by MDR P. aeruginosa. The study was conducted in 5 tertiary care hospitals in Saudi Arabia. Main study outcomes included clinical cure at end of treatment, in-hospital mortality, and acute kidney injury (AKI). Univariate analysis and multivariate logistic regression model were conducted to evaluate the independent effect of C-T on the clinical outcome.

RESULT

A total of 184 patients were included in the study: 82 patients received C-T and 102 patients received colistin-based regimen. Clinical cure (77% vs 57%; P = 0.005; OR, 2.52; 95% CI, 1.32-4.79) was significantly more common in patients who received C-T. After adjusting the difference between the two groups, treatment with C-T is independently associated with clinical cure (adjusted OR, 2.47; 95% CI, 1.16-5.27). In-hospital mortality (39% vs 49%; P = 0.175; OR, 0.67; 95% CI, 0.37-1.20) was lower in patients who received C-T but the difference was not significant. AKI (15% vs 41%; P < 0.001; OR, 0.25; 95% CI, 0.12-0.51) was significantly less common in patients who received C-T.

CONCLUSION

C-T is associated with higher rate of clinical cure and lower rate of AKI compared to colistin. Our findings support the preferential use of C-T over colistin-based regimen for treating these infections.

Ceftazidime-Avibactam versus Colistin for the Treatment of Infections Due to Carbapenem-Resistant Enterobacterales: A Multicenter Cohort Study

Background

The aim of this study was to compare the safety and effectiveness of ceftazidime-avibactam (CAZ-AVI) to colistin-based regimen in the treatment of infections caused by carbapenem-resistant Enterobacterales (CRE).

Methods

This was a retrospective, multicenter, observational cohort study of inpatients who received either CAZ-AVI or intravenous colistin for treatment of infections due to CRE. The study was conducted in 5 tertiary care hospitals in Saudi Arabia. Main study outcomes included in-hospital mortality, clinical cure at end of treatment, and acute kidney injury (AKI). Univariate analysis and multivariate logistic regression model were conducted to assess the independent impact of CAZ-AVI on the clinical outcome.

Results

A total of 230 patients were included in this study: 149 patients received CAZ-AVI and 81 patients received colistin-based regimen. Clinical cure (71% vs 52%; P = 0.004; OR, 2.29; 95% CI, 1.31–4.01) was significantly more common in patients who received CAZ-AVI. After adjusting the difference between the two groups, treatment with CAZ-AVI is independently associated with clinical cure (adjusted OR, 2.75; 95% CI, 1.28–5.91). In-hospital mortality (35% vs 44%; P = 0.156; OR, 0.67; 95% CI, 0.39–1.16) was lower in patients who received CAZ-AVI but the difference was not significant. AKI (15% vs 33%; P = 0.002; OR, 0.37; 95% CI, 0.19–0.69) was significantly less common in patients who received CAZ-AVI.

Conclusion

CAZ-AVI is associated with higher rate of clinical cure and lower rate of AKI compared to colistin. Our findings support the preferential use of CAZ-AVI over colistin-based regimen for treating these infections.

Effects of sub-lethal antimicrobial photodynamic therapy mediated by haematoporphyrin monomethyl ether on polymyxin-resistant Escherichia coli clinical isolate

BACKGROUND AND AIM

It is generally believed that bacteria can not develop resistance to antimicrobial photodynamic therapy (aPDT). This work employed a polymyxin-resistant Escherichia coli clinical isolate (E15017) to study whether it could become resistant to aPDT mediated by haematoporphyrin monomethyl ether (HMME) via consecutive photodynamic treatments at sub-lethal condition.

METHODS

The sub-lethal and lethal photodynamic treatment conditions for E15017 were determined by colony forming units (CFU) assay. Bacterial cells of E15017 were treated with 20 cycles of repeated sub-lethal HMME-mediated aPDT, and subsequently subjected to aPDT at lethal condition. The antibiotic susceptibility, zeta-potential and membrane integrity of sub-lethal aPDT treated E15017 cells were also investigated.

RESULTS

After 20 cycles of repeated HMME-mediated aPDT treatments at sub-lethal condition, E15017 cells didn't become more resistant to aPDT. Sub-lethal HMME-mediated aPDT decreased the MIC values of E15017 to ceftazidime and polymyxin E by 4 and 2-fold, respectively, and increased the electronegativity of bacterial surface and affected the bacterial membrane integrity.

CONCLUSIONS

The results obtained in this study confirmed that antibiotic-resistant bacteria could not develop resistance to aPDT, and HMME-mediated aPDT is an attractive potential treatment for MDR E. coli caused infections.