Efficacy and Safety of High Loading Dose of Colistin in Multidrug-Resistant Acinetobacter baumannii: A Prospective Cohort Study

Treatment of infections caused by carbapenem-resistant Acinetobacter baumannii

Patients with severe carbapenem-resistant Acinetobacter baumannii (CRAB) infections currently face significant treatment challenges. When patients display signs of infection and the clinical suspicion of CRAB infections is high, appropriate treatment should be immediately provided. However, current treatment plans and clinical data for CRAB are limited. Inherent and acquired resistance mechanisms, as well as host factors, significantly restrict options for empirical medication. Moreover, inappropriate drug coverage can have detrimental effects on patients. Most existing studies have limitations, such as a restricted sample size, and are predominantly observational or non-randomized, which report significant variability in patient infection severity and comorbidities. Therefore, a gold-standard therapy remains lacking. Current and future treatment options of infections due to CRAB were described in this review. The dose and considerable side effects restrict treatment options for polymyxins, and high doses of ampicillin-sulbactam or tigecycline appear to be the best option at the time of initial treatment. Moreover, new drugs such as durlobactam and cefiderocol have substantial therapeutic capabilities and may be effective salvage treatments. Bacteriophages and antimicrobial peptides may serve as alternative treatment options in the near future. The advantages of a combination antimicrobial regimen appear to predominate those of a single regimen. Despite its significant nephrotoxicity, colistin is considered a primary treatment and is often used in combination with antimicrobials, such as tigecycline, ampicillin-sulbactam, meropenem, or fosfomycin. The Infectious Diseases Society of America (IDSA) has deemed high-dose ampicillin-sulbactam, which is typically combined with high-dose tigecycline, polymyxin, and other antibacterial agents, the best option for treating serious CRAB infections. A rational combination of drug use and the exploration of new therapeutic drugs can alleviate or prevent the effects of CRAB infections, shorten hospital stays, and reduce patient mortality.

Impact of clinical pharmacist's interventions on clinical outcomes in appropriate use of colistin: a prospective pre-post intervention study

This study aims to evaluate the clinical pharmacist's contribution impact on the appropriate use of colistin. Our study was conducted prospectively in patients in the Internal Diseases Intensive Care Unit of Gazi University Medical Faculty Hospital for eight months. The first four months of the study were with the observation group, while the next four months were with the intervention group. The study determined how the active participation of clinical pharmacists had affected the appropriateness of colistin use. The results showed that the appropriate use of colistin was higher in the intervention group than in the observational group; furthermore, incidence of nephrotoxicity was lower. The difference between both groups was statistically significant (p < 0.001, p < 0.05), respectively. This study showed that the clinical pharmacist's active intervention by following the patients increased the frequency and percentage of the appropriate use of colistin. This decreased the incidence of nephrotoxicity, colistin's most important side effect.

Antibiotic-Resistant ESKAPE Pathogens and COVID-19: The Pandemic beyond the Pandemic

Antibacterial resistance is a renewed public health plague in modern times, and the COVID-19 pandemic has rekindled this problem. Changes in antibiotic prescribing behavior, misinformation, financial hardship, environmental impact, and governance gaps have generally enhanced the misuse and improper access to antibiotics during the COVID-19 pandemic. These determinants, intersected with antibacterial resistance in the current pandemic, may amplify the potential for a future antibacterial resistance pandemic. The occurrence of infections with multidrug-resistant (MDR), extensively drug-resistant (XDR), difficult-to-treat drug-resistant (DTR), carbapenem-resistant (CR), and pan-drug-resistant (PDR) bacteria is still increasing. The aim of this review is to highlight the state of the art of antibacterial resistance worldwide, focusing on the most important pathogens, namely Enterobacterales, Acinetobacter baumannii, and Klebsiella pneumoniae, and their resistance to the most common antibiotics.

Risk factors for early mortality in patients with carbapenem-resistant Acinetobacter baumannii bacteraemia

OBJECTIVES

Although many deaths due to carbapenem-resistant Acinetobacter baumannii (CRAB) bacteraemia occur within a few days after the onset of bacteraemia, risk factors for early mortality (EM) have not been deeply investigated. We aimed to determine the risk factors for EM and the difference between risk factors associated with EM and late mortality (LM) in CRAB bacteraemia.

METHODS

Clinical information on all patients with CRAB bacteraemia in 10 hospitals during a 1-year period was collected. Among the cases with mortality within 30 days, EM and LM were defined as death within 3 and more than 5 calendar days from the first positive blood culture, respectively.

RESULTS

In total, 212 CRAB bacteraemia cases were included in the analysis. Of 122 (57.5%) patients with 30-day mortality, EM was observed in 75 (61.5%) patients and LM in 39 (32.0%) patients. The proportion of severe sepsis or septic shock, Pitt score, and Sequential Organ Failure Assessment (SOFA) score was significantly higher in patients with EM than those with LM. Although urinary tract infection as the site of infection and the severity of illness were independent predictors of LM, only factors representing the severity of illness were independent risk factors for EM.

CONCLUSION

Our results suggest that a large proportion of CRAB bacteraemia with high severity progresses to a rapidly fatal course, regardless of the underlying diseases or source of infection. Further studies might be needed to investigate the microbiological factors associated with CRAB and pathogen-host interaction in patients with EM.

Bactericidal and Anti-Biofilm Activity of the FtsZ Inhibitor C109 against Acinetobacter baumannii

In the last few years, Acinetobacter baumannii has ranked as a number one priority due to its Multi Drug Resistant phenotype. The different metabolic states, such as the one adopted when growing as biofilm, help the bacterium to resist a wide variety of compounds, placing the discovery of new molecules able to counteract this pathogen as a topic of utmost importance. In this context, bacterial cell division machinery and the conserved protein FtsZ are considered very interesting cellular targets. The benzothiadiazole compound C109 is able to inhibit bacterial growth and to block FtsZ GTPase and polymerization activities in Burkholderia cenocepacia, Pseudomonas aeruginosa, and Staphylococcus aureus. In this work, the activity of C109 was tested against a panel of antibiotic sensitive and resistant A. baumannii strains. Its ability to inhibit biofilm formation was explored, together with its activity against the A. baumannii FtsZ purified protein. Our results indicated that C109 has good MIC values against A. baumannii clinical isolates. Moreover, its antibiofilm activity makes it an interesting alternative treatment, effective against diverse metabolic states. Finally, its activity was confirmed against A. baumannii FtsZ.

Antimicrobial safety considerations in critically ill patients: part I: focused on acute kidney injury

INTRODUCTION

Antibiotic prescription is a challenging issue in critical care settings. Different pharmacokinetic and pharmacodynamic properties, polypharmacy, drug interactions, and high incidence of multidrug-resistant microorganisms in this population can influence the selection, safety, and efficacy of prescribed antibiotics.

AREAS COVERED

In the current article, we searched PubMed, Scopus, and Google Scholar for estimating renal function in acute kidney injury, nephrotoxicity of commonly used antibiotics, and nephrotoxin stewardship in intensive care units.

EXPERT OPINION

Early estimation of kidney function with an accurate method may be helpful to optimize antimicrobial treatment in critically ill patients. Different antibiotic dosing regimens may be required for patients with acute kidney injury. In many low-resource settings, therapeutic drug monitoring is not available for antibiotics. Acute kidney injury may influence treatment effectiveness and patient outcome.

Colistin Monotherapy versus Colistin plus Meropenem Combination Therapy for the Treatment of Multidrug-Resistant Acinetobacter baumannii Infection: A Meta-Analysis

(1) Introduction: Colistin combination therapy with other antibiotics is a way to enhance colistin activity. The purpose of this meta-analysis was to compare the efficacy and safety of treatment with colistin monotherapy versus colistin plus meropenem combination therapy in patients with drug-resistant Acinetobacter baumannii infection. (2) Methods: All studies were included if they reported one or more of the following outcomes: clinical improvement, complete microbiological response, 14-day mortality, hospital mortality, or nephrotoxicity. (3) Results: Three randomized controlled trials and seven retrospective studies were included in the meta-analysis. Colistin monotherapy has similar rates of clinical improvement, 14-day mortality, hospital mortality, and nephrotoxicity as colistin plus meropenem combination therapy. Regarding complete microbiological response, the colistin plus meropenem combination was better than colistin monotherapy. (4) Discussion: Previous meta-analyses demonstrated heterogeneity in study quality and a lack of evidence supporting the use of colistin-based combination therapy. Our meta-analysis clearly showed that colistin combined with meropenem was not superior to colistin monotherapy for the treatment of Acinetobacter baumannii infection. (5) Conclusions: The efficacy and safety of treatment with colistin monotherapy and that of colistin plus meropenem combination therapy in patients with drug-resistant Acinetobacter baumannii infection were comparable. The majority of the evidence was obtained from nonrandomized studies, and high-quality randomized controlled trials are needed to confirm the role of colistin plus meropenem combination therapy in the treatment of multidrug-resistant Acinetobacter baumannii infection.

Colistin Loading Dose in Septic Patients with Gram Negative Infections

Purpose

Intravenous (IV) colistin is commonly used to treat multidrug-resistant gram-negative infections. It is primarily eliminated renally and may induce acute kidney injury (AKI) at a rate of up to 53%. Consequently, septic patients who require colistin administration have an additional risk of developing AKI. The aim of this study is to investigate clinical failure and AKI predictors for septic patients treated with IV colistin.

Methods

This retrospective cohort study was conducted at a tertiary teaching hospital in Saudi Arabia. Adult septic patients with suspected or confirmed gram-negative infections who received colistin admitted to the hospital between May 2016 and December 2020 were screened after obtaining IRB approval. AKI was defined based on the AKI Network criteria. We investigated the incidence of clinical failure based on colistin dosing and AKI risk factors, such as the development of septic shock, severity of illness, and medication co-administration using a multiple logistic regression model.

Results

After screening 163 patients, 103 patients were included in the analysis. No difference was observed between the colistin dosing strategies for clinical failure. Of the included predictors, development of septic shock (OR: 3.75; 95% CI 1.18-13.15), carbapenem co-administration (OR, 3.96; 95% CI, 1.134-15.57) were associated with an increased risk of AKI. The other factors were not significant predictors.

Conclusion

Clinical failure was not affected by colistin dosing strategies in our cohort of patients with sepsis. Moreover, the co-administration of carbapenems and the development of septic shock may increase the risk of inducing AKI in adult septic patients treated with IV colistin. Further studies are required to confirm these findings.

The necessity of a loading dose when prescribing intravenous colistin in critically ill patients with CRGNB-associated pneumonia: a multi-center observational study

Background

The importance or necessity of a loading dose when prescribing intravenous colistin has not been well established in clinical practice, and approximate one-third to half of patients with carbapenem-resistant gram-negative bacteria (CRGNB) infection did not receive the administration of a loading dose. The aim of this study is to investigate the efficacy and risk of acute kidney injury when prescribing intravenous colistin for critically ill patients with nosocomial pneumonia caused by CRGNB.

Methods

This was a multicenter, retrospective study that recruited ICU-admitted patients who had CRGNB-associated nosocomial pneumonia and were treated with intravenous colistin. Then, we classified the patients into colistin loading dose (N = 85) and nonloading dose groups (N = 127). After propensity-score matching for important covariates, we compared the mortality rate, clinical outcome and microbiological eradication rates between the groups (N = 67).

Results

The loading group had higher percentages of patients with favorable clinical outcomes (55.2% and 35.8%, p = 0.037) and microbiological eradication rates (50% and 27.3%, p = 0.042) at day 14 than the nonloading group. The mortality rates at days 7, 14 and 28 and overall in-hospital mortality were not different between the two groups, but the Kaplan–Meier analysis showed that the loading group had a longer survival time than the nonloading group. Furthermore, the loading group had a shorter length of hospital stay than the nonloading group (52 and 60, p = 0.037). Regarding nephrotoxicity, there was no significant difference in the risk of developing acute kidney injury between the groups.

Conclusions

The administration of a loading dose is recommended when prescribing intravenous colistin for critically ill patients with nosocomial pneumonia caused by CRGNB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03947-9.

Investigation of Effect of the Colistin Loading Dosage on the clinical, Microbiological, and Laboratory Results in Acinetobacter baumannii Ventilator-Associated Pneumonia /Pneumonia

MATERIALS AND METHODS

Adult patients administered colistin with and without LD for MDR Acinetobacter baumannii VAP/pneumonia in intensive care units (ICUs) in a tertiary teaching hospital between 1 January 2018 and 31 December 2019 were included in this retrospective cohort study. The primary endpoint was an assessment of clinical and microbiological success between treatment groups. Secondary endpoints included 14- and 30-day mortality and development of nephrotoxicity.

RESULTS

A total of 101 patients were included (colistin with LD, n = 57; colistin without LD, n = 44). No significant difference in clinical success was observed between groups (73.7% versus 77.3%; p=0.670). In patients receiving colistin with LD, the microbiological success rate increased from 65.9% to 71.9%, but there was no statistically significantly difference (p=0.510). In terms of using combination therapies with carbapeneme and/or tigecycline, there was no significant difference between treatment groups (p=0.30). The rates of 14- and 30-day mortality were similar between groups. The colistin with LD group had a higher rate of nephrotoxicity compared to the other group (52.6% versus 20.5% p=0.001). The clinical and microbiological response times were found significantly higher in the colistin with LD group (p=0.001; p=0.017).

CONCLUSION

Colistin with LD was associated with a higher risk of nephrotoxicity and was not related to clinical success, microbiological success, and prolonged survival. Randomized comparative studies are needed to confirm the efficacy of LD colistin regimen on MDR Acinetobacter infection.

Colistin-Induced Acute Kidney Injury and the Effect on Survival in Patients with Multidrug-Resistant Gram-Negative Infections: Significance of Drug Doses Adjusted to Ideal Body Weight

Background

Colistin is a lifesaving treatment for multidrug-resistant Gram-negative bacterial (MDR-GNB) infections along with its well-known nephrotoxicity. The controversy of colistin-induced acute kidney injury (AKI) on mortality is noted. This study aimed to determine the risk factors and impact of AKI on the survival and significance of colistin dosage.

Methods

A retrospective cohort study was performed in adult patients who received intravenous colistin for MDR-GNB treatment between June 2015 and June 2017. Factors influencing colistin-induced AKI and survival were evaluated by Cox regression analysis. Cut-off levels of the colistin dose per ideal body weight (IBW) that significantly affected clinical outcomes were assessed with linearity trends and receiver operating characteristic analyses.

Results

AKI occurred in 68.5% of 412 enrolled patients with an incidence rate of 10.6 per 100 patients-days and a median time was 6 (3–13) days. Stages I–III of AKI were 38.3, 24.5, and 37.2%. Factors associated with colistin-induced AKI were advanced age, high serum bilirubin, AKI presented before colistin administration, increased daily colistin doses per IBW, and concomitant use of nephrotoxic drugs. Colistin-induced AKI was related to mortality (HR 1.74, 95% CI 1.06–2.86, p=0.028). In the non-AKI before colistin usage subgroup, the total dose and total dose/IBW were >1,500–2,000 mg and 30–35 mg/kg to benefit mortality reduction but were <2,500–3,000 mg and 45–50 mg/kg for risk reduction of AKI. A daily colistin dose/IBW >4.5 mg/kg/day also increased the risk of AKI. In the AKI developed before colistin subgroup, the cut-off values of total colistin dose >1250–1350 mg and total dose/IBW >23.5–24 mg/kg demonstrated significant risks of AKI.

Conclusion

The incidence of AKI after colistin administration was high and impacted mortality. Prevention and early correction of these related factors are mandatory. Careful use of colistin was also both beneficial in mortality and AKI reductions.

Clinical Efficacy and Nephrotoxicity of the Loading Dose Colistin for the Treatment of Carbapenem-Resistant Acinetobacter baumannii in Critically Ill Patients

Carbapenem-resistant Acinetobacter baumannii (CRAB) is one of the most common causes of nosocomial infections in critically ill patients. Colistin methanesulfonate (CMS), an inactive prodrug, has been considered as a last-resort treatment for CRAB infection in critically ill patients. The objective of this study was to assess 30-day survival and nephrotoxicity in critically ill patients who received non-loading dose (LD) versus LD of CMS for CRAB infection treatment. Between 2012 and 2017, this retrospective cohort analysis was performed at Chiang Mai University Hospital (CMUH), focusing on critically ill patients with CRAB infection who received either non-LD or LD of CMS. A total of 383 patients met the criteria for inclusion. At the 30th day of treatment, the survival rate of patients in the LD CMS group was 1.70 times (adjusted HR) of those in the non-LD group (95% CI = 1.17-2.50, p = 0.006). Clinical response was significantly higher in the LD CMS group than non-LD CMS group (aHR, 1.35, 95% CI, 1.01-1.82, p = 0.046). In addition, a microbiological response-eradication of pre-treatment isolated pathogens in post-treatment cultures-in patients with LD CMS was 1.57 times that of patients with non-LD CMS (95% CI, 1.15-2.15, p = 0.004). Additionally, there was a significant difference in nephrotoxicity between LD CMS and non-LD CMS (aHR, 1.57, 95% CI, 1.14-2.17, p = 0.006). Based on these results, LD CMS should be used to increase the opportunity of patients to achieve favourable outcomes. However, LD CMS was found associated with an increase in nephrotoxicity, so renal function should be closely monitored when LD colistin was administered.

Systematic review on estimated rates of nephrotoxicity and neurotoxicity in patients treated with polymyxins

BACKGROUND

Nephrotoxicity and neurotoxicity are commonly associated with polymyxin treatment; however, the emergence of multidrug-resistant Gram-negative bacteria with limited therapeutic options has resulted in increased use of polymyxins.

OBJECTIVES

To determine the rates of nephrotoxicity and neurotoxicity during polymyxin treatment and whether any factors influence these.

DATA SOURCES

Medline, Embase and Cochrane Library databases were searched on 2 January 2020.

STUDY ELIGIBILITY CRITERIA

Studies reporting nephrotoxicity and/or neurotoxicity rates in patients with infections treated with polymyxins were included. Reviews, meta-analyses and reports not in English were excluded.

PARTICIPANTS

Patients hospitalized with infections treated with systemic or inhaled polymyxins were included. For comparative analyses, patients treated with non-polymyxin-based regimens were also included.

METHODS

Meta-analyses were performed using a random-effects model; subgroup meta-analyses were conducted where data permitted using a mixed-effects model.

RESULTS

In total, 237 reports of randomized controlled trials, cohort and case-control studies were eligible for inclusion; most were single-arm observational studies. Nephrotoxic events in 35,569 patients receiving polymyxins were analysed. Overall nephrotoxicity rate was 0.282 (95% confidence interval (CI) 0.259-0.307). When excluding studies where >50% of patients received inhaled-only polymyxin treatment or nephrotoxicity assessment was by methods other than internationally recognized criteria (RIFLE, KDIGO or AKIN), the nephrotoxicity rate was 0.391 (95% CI 0.364-0.419). The odds of nephrotoxicity were greater with polymyxin therapies compared to non-polymyxin-based regimens (odds ratio 2.23 (95% CI 1.58-3.15); p < 0.001). Meta-analyses showed a significant effect of polymyxin type, dose, patient age, number of concomitant nephrotoxins and use of diuretics, glycopeptides or vasopressors on the rate of nephrotoxicity. Polymyxin therapies were not associated with a significantly different rate of neurotoxicity than non-polymyxin-based regimens (p 0.051). The overall rate of neurotoxicity during polymyxin therapy was 0.030 (95% CI 0.020-0.043).

CONCLUSIONS

Polymyxins are associated with a higher risk of nephrotoxicity than non-polymyxin-based regimens.

Comparative efficacy and safety of combination therapy with high-dose sulbactam or colistin with additional antibacterial agents for multiple drug-resistant and extensively drug-resistant Acinetobacter baumannii infections: A systematic review and network meta-analysis

OBJECTIVES

This study aimed to compare the efficacy and safety of combination therapy with high-dose sulbactam or colistin with additional antibacterial agents for treating multidrug-resistant or extensively drug-resistant Acinetobacter baumannii (MDR-AB or XDR-AB) infections.

METHODS

We systematically searched PubMed, Embase, Cochrane, and Web of Science (through March 30, 2020) for studies that examined high-dose sulbactam or colistin with additional antibacterial agents as therapy for patients with infections with MDR-AB and XDR-AB. Through a network meta-analysis (NMA), using both direct and indirect evidence, we determined risk ratios and 95% confidence intervals. Primary outcomes included clinical improvement, clinical cure, microbiological eradication, and mortality from any cause. Secondary outcomes included nephrotoxicity.

RESULTS

The NMA included 18 studies and 1835 patients. We found that high-dose sulbactam (≥6 g per day), combined with another single antibacterial agent (levofloxacin or tigecycline), which were the highest ranking in clinical improvement and clinical cure. Still colistin-based combination in drug-resistant Acinetobacter baumannii therapy occupied the main position (the number of studies and patients) in most studies. Colistin combined with additional antibacterial agents was associated with a higher risk of nephrotoxicity.

CONCLUSIONS

Therapeutic regimens including high-dose sulbactam in combination with additional antibacterial agents (including colistin) might be one of the promising options for the treatment of MDR-AB or XDR-AB infections and high-quality study will be needed to confirm clinical efficacy.

Inhalation with intravenous loading dose of colistin in critically ill patients with pneumonia caused by carbapenem-resistant gram-negative bacteria

Background:

Despite the increasing use of colistin in clinical practice, the optimal dosing, and administration route have not been established. This study aimed to evaluate the clinical outcome and safety of intravenous (IV) colistin with a loading dose (LD) and adjunctive aerosolized (AS) colistin administration in critically ill patients with hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP) caused by carbapenem-resistant gram-negative bacteria (CRGNB).

Methods:

We retrospectively reviewed 191 critically ill patients who received colistin for the treatment of HAP or VAP caused by CRGNB. Patients were divided into three groups: non-LD IV (patients received only IV colistin without LD), LD IV (patients received only IV colistin with LD), and AS–LD (patients received IV colistin with LD and adjunctive AS colistin).

Results:

There was no difference in clinical response between the three groups. However, the rate of microbiological eradication was significantly higher in the AS–LD group (60%) than in the non-LD IV (31%), and LD IV (33%) groups (p = 0.010). Patients treated with adjunctive AS colistin in combination with LD IV had significantly lower 30-day mortality rates than patients treated with IV colistin alone (p = 0.027). After adjusting for potential confounding factors, adjunctive AS colistin was still significantly associated with lower mortality (adjusted OR 0.338, CI 95% 0.132–0.864, p = 0.024). However, nephrotoxicity did not change according to the use of LD regimen and AS colistin administration (p = 0.100).

Conclusions:

Adjunctive AS colistin in combination with IV colistin with LD was related to an improved 30-day mortality and microbiological outcome without an increase in nephrotoxicity in critically ill patients with HAP and VAP caused by CRGNB.

The reviews of this paper are available via the supplemental material section.

Efficacy and safety of colistin loading dose: a meta-analysis

Objectives

Colistin represents a polypeptide used for the treatment of MDR microorganisms, although the optimal dosing strategy is under investigation. The present meta-analysis aims to determine whether the administration of a colistin loading dose in patients receiving high-dose maintenance regimens changes the rates of treatment success and the risk of nephrotoxicity.

Methods

Medline, Scopus, CENTRAL, Clinicaltrials.gov and Google Scholar were systematically searched from inception to 18 November 2019. Studies were considered eligible if they reported clinical outcomes among patients receiving high-dose colistin therapy with and without the administration of a loading dose. Meta-analysis was performed by fitting a random-effects model.

Results

Eight (three prospective and five retrospective cohort) studies were included, comprising 1115 patients. The administration of a colistin loading dose was associated with significantly higher microbiological [risk ratio (RR) = 1.23, 95% CI = 1.10–1.39] but not clinical (RR = 1.04, 95% CI = 0.87–1.24) success. No significant associations were calculated for nephrotoxicity (RR = 1.31, 95% CI = 0.90–1.91) and mortality (RR = 1.03, 95% CI = 0.82–1.29) risk. The results remained stable after adjustments for small sample size, credibility ceilings, publication bias and risk of bias.

Conclusions

Observational evidence suggests that the administration of a colistin loading dose in patients receiving high maintenance dosage regimens is significantly associated with higher rates of microbiological response, but does not change clinical cure, mortality or nephrotoxicity risk. The dosing regimen that would provide the optimal balance between treatment efficacy and safety needs to be determined by future randomized controlled trials.

A Randomized Clinical Trial Evaluating the Efficacy of Colistin Loading Dose in Critically Ill Children

Objective:

Pharmacokinetic and clinical studies recommend applying loading dose of colistin for the treatment of severe infections in the critically ill adults. Pharmacokinetic studies of colistin in children also highlight the need for a loading dose. However, there are no clinical studies evaluating the effectiveness of colistin loading dose in children.

Methods:

In a randomized trial, children with ventilator-associated pneumonia or central line-associated bloodstream infection (CLABSI) for whom colistin was initiated, were enrolled. Patients were randomized into two groups; loading dose and conventional dose treatment arms. In the conventional treatment arm, colistimethate sodium was initiated with maintenance dose. In the loading dose group, colistimethate sodium was commenced with a loading dose of 150,000 international unit/kg, then on the maintenance dose. Both treatment arms also received meropenem as combination therapy. Primary outcomes were overall efficacy, clinical improvement and microbiological cure. Secondary outcomes were colistin-induced nephrotoxicity and development of resistance.

Findings:

Thirty children completed this study. There was a significantly higher overall efficacy in the group received loading dose (42.9 vs. 6.3%, P = 0.031). There weren’t any significant differences in the clinical and microbiological endpoints. In the subgroup of children with CLABSI, results illustrated a trend toward (though statistically nonsignificant) better clinical cure for patients receiving loading dose.

Conclusion:

This preliminary study suggests that colistin loading dose might have some benefits in critically ill children, specifically in children with CLABSI. Further trials are required to elucidate colistin best dosing strategy in critically ill children with severe infections.

Differences in Colistin Administration and Bacterial and Treatment Outcomes in Critically Ill Patients

The desired target steady-state average colistin concentration (C_ss,avg) to balance between therapeutic effectiveness and nephrotoxicity is largely unclear. The objective of this study was to evaluate the effect of the desired target colistin C_ss,avg on the effectiveness and safety of IV colistin therapy in critically ill patients. Overall, 153 critically ill patients (71% males) receiving IV colistin were retrospectively analyzed. The desired target colistin C_ss,avg was estimated based on the daily colistin dose and creatinine clearance of each patient. No significant predictor for clinical cure was identified. However, microbiological outcome was significantly associated with pneumonia compared to bacteremia (odds ratio [OR] 0.092, 95% confidence interval [CI] [0.033-0.251], P < 0.001) and the use of IV colistin loading dose (OR 2.783, 95% CI [1.126-6.880], P = 0.027). Colistin-associated nephrotoxicity was significantly less likely to occur in patients who received inhaled colistin close to the time of IV colistin therapy (OR 0.331, CI [0.119-0.925], P = 0.035). The desired target C_ss,avg of colistin was not associated with treatment outcomes or the risk of nephrotoxicity. Loading dose and inhaled colistin use near the time of IV colistin therapy may be considered to maximize therapeutic effectiveness and minimize the risk of colistin-associated nephrotoxicity, respectively.

Intravenous Colistin Monotherapy versus Combination Therapy against Carbapenem-Resistant Gram-Negative Bacteria Infections: Meta-Analysis of Randomized Controlled Trials

This meta-analysis aims to compare intravenous colistin monotherapy and colistin-based combination therapy against carbapenem-resistant gram-negative bacteria (GNB) infections. PubMed, Embase, and Cochrane databases were searched up to July 2018. Only randomized controlled trials (RCTs) evaluating colistin alone and colistin-based combination therapy in the treatment of carbapenem-resistant GNB infections were included. The primary outcome was all-cause mortality. Five RCTs including 791 patients were included. Overall, colistin monotherapy was associated with a risk ratio (RR) of 1.03 (95% confidence interval (CI), 0.89–1.20, I² = 0%) for all-cause mortality compared with colistin-based combination therapy. The non-significant difference was also detected in infection-related mortality (RR, 1.23, 95% CI, 0.91–1.67, I² = 0%) and microbiologic response (RR, 0.86, 95% CI, 0.72–1.04, I² = 62%). In addition, no significant difference was observed in the subgroup analysis—high or low dose, with or without a loading dose, carbapenem-resistant Acinetobacter baumannii infections, and in combination with rifampicin. Finally, colistin monotherapy was not associated with lower nephrotoxicity than colistin combination therapy (RR, 0.98; 95% CI, 0.84–1.21, I² = 0%). Based on the analysis of the five RCTs, no differences were found between colistin monotherapy and colistin-based combination therapy against carbapenem-resistant GNB infections, especially for A. baumannii infections.