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

Efficacy, safety, and therapeutic drug monitoring of polymyxin B sulfate and colistin sulfate in critically ill patients: a real-world retrospective study

Background

Polymyxin B sulfate (PBS) and colistin sulfate (CS) are the last-line treatments for infections caused by multidrug-resistant Gram-negative bacteria, but their efficacy and safety have not been validated. The aims of the current study were to (1) determine their efficacy and safety among critically ill patients and the influencing factors, and (2) determine the relationships of drug exposure with efficacy and safety, to provide evidence for the precision dosing.

Method

This retrospective study included 100 critically ill patients treated with PBS and 80 treated with CS. The efficacy outcomes were clinical efficacy and 30-day mortality, while the safety indicator was acute kidney injury (AKI) incidence.

Result

There was no significant difference between the two drugs in clinical efficacy, 30-day mortality, or overall AKI incidence, but the incidence of stage 3 AKI was significantly higher in the PBS cohort than the CS cohort. Therapeutic drug monitoring (TDM) and trough concentration (Cmin) were significantly associated with clinical efficacy and AKI in both cohorts. Classification and regression tree analysis revealed that Cmin values of ≥0.91 mg/L for PBS and Cmin ≥ 0.53 mg/L for CS were associated with higher clinical efficacy.

Conclusion

There is basically no significant difference in the efficacy and safety of PBS and CS. TDM can significantly improve the clinical efficacy of both drugs and reduce the incidence of AKI. TDM is therefore recommended to improve the clinical efficacy while reducing the adverse reactions.

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

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

Comparative study of polymyxin B and colistin sulfate in the treatment of severe comorbid patients infected with CR-GNB

BACKGROUND

With the difficulties in choosing colistin sulfate and polymyxin B sulfate (PBS) for carbapenem-resistant gram-negative bacteria (CR-GNB), we compared the efficacy and safety of these two old polymyxins in treatment of critically ill patients infected with CR-GNB infection.

METHODS

One hundred four patients infected with CR-GNB in ICU were retrospectively grouped by PBS (68 patients) or colistin sulfate (36 patients). Clinical efficacy including symptoms, inflammatory parameters, defervescence, prognosis and microbial efficacy were analyzed. Hepatotoxicity, nephrotoxicity, and hematotoxicity were evaluated by TBiL, ALT, AST, creatinine, and thrombocytes.

RESULTS

Demographic characteristics between colistin sulfate and PBS were not significantly different. Most of the CR-GNB were cultured in respiratory tract (91.7% vs 86.8%), and almost all were polymyxin-sensitive (98.2% vs 100%, MIC ≤ 2 μg/ml). The microbial efficacy in colistin sulfate (57.1%) was significantly higher than PBS (30.8%) (p = 0.022), however, no significant difference in clinical success was seen in both groups (33.8% vs 41.7%), as well as mortality, defervescence, imaging remission, days in the hospital, microbial reinfections, and prognosis, and almost all patients defervesce within 7 days (95.6% vs 89.5%).

CONCLUSIONS

Both polymyxins can be administrated in critically ill patients infected with CR-GNB and colistin sulfate is superior to PBS in microbial clearance. These results highlight the necessity of identifying CR-GNB patients who may benefit from polymyxin and who are at higher risk of mortality.

An area under the concentration-time curve threshold as a predictor of efficacy and nephrotoxicity for individualizing polymyxin B dosing in patients with carbapenem-resistant gram-negative bacteria

BACKGROUND

Evidence supports therapeutic drug monitoring of polymyxin B, but clinical data for establishing an area under the concentration-time curve across 24 h at steady state (AUC_ss,24 h) threshold are still limited. This study aimed to examine exposure-response/toxicity relationship for polymyxin B to establish an AUC_ss,24 h threshold in a real-world cohort of patients.

METHODS

Using a validated Bayesian approach to estimate AUC_ss,24 h from two samples, AUC_ss,24 h threshold that impacted the risk of polymyxin B-related nephrotoxicity and clinical response were derived by classification and regression tree (CART) analysis and validated by Cox regression analysis and logical regression analysis.

RESULTS

A total of 393 patients were included; acute kidney injury (AKI) was 29.0%, clinical response was 63.4%, and 30-day all-cause mortality was 35.4%. AUC_ss,24 h thresholds for AKI of > 99.4 mg h/L and clinical response of > 45.7 mg h/L were derived by CART analysis. Cox and logical regression analyses showed that AUC_ss,24 h of > 100 mg h/L was a significant predictor of AKI (HR 16.29, 95% CI 8.16-30.25, P < 0.001) and AUC_ss,24 h of ≥ 50 mg h/L (OR 4.39, 95% CI 2.56-7.47, P < 0.001) was independently associated with clinical response. However, these exposures were not associated with mortality. In addition, the correlation between trough concentration (1.2-2.8 mg/L) with outcomes was similar to AUC_ss,24 h.

CONCLUSIONS

For critically ill patients, AUC_ss,24 h threshold of 50-100 mg h/L was associated with decreased nephrotoxicity while assuring clinical efficacy. Therapeutic drug monitoring is recommended for individualizing polymyxin B dosing.