Systemic colistin use in children without cystic fibrosis: a systematic review of the literature

Colistin induced acute kidney injury in critically ill children: a prospective study utilizing RIFLE criteria

BACKGROUND

Colistin is one of the last resort antibiotic options for resistant gram-negative pathogens. Renal injury is the most common side effect of colistin. Characteristics of nephrotoxicity are well described in adults. However, this data is sparse in children.

OBJECTIVES

In this study we evaluated the incidence, severity, time course and risk factors of colistin nephrotoxicity in a pediatric population.

METHODS

In a prospective study over a 9-month period, children who received intravenous colistin for at least 48 h were evaluated for renal side effect by utilizing Risk-Injury-Failure-Loss-End Stage Kidney Disease (RIFLE) criteria. Children receiving renal replacement therapy (RRT) or received a repeated course of colistin were excluded.

RESULTS

Thirty-seven children were included. Median age of participants was 4.5 months. Overall, 48.6% of the cases developed AKI and consisted 56% in the Risk, 33% in the Injury and 11% in the Failure categories of RIFLE criteria. AKI was reversible while colistin continued and no one required RRT. Mean ± SD time to AKI development was 10.94 ± 7.51 days. Multivariate logistic regression analysis demonstrated that total cumulative dose of colistin was an independent predictor of nephrotoxicity (standardized ß = 1.024, P = 0.034).

CONCLUSION

AKI is a common side effect of colistin therapy in critically ill children developing in nearly half of recipients. However, with the dosage range utilized in this study, in the majority of children, renal injury seemed to be mild to moderate in nature. Given the limited treatment options available in critically ill children with resistant gram-negative pathogens, colistin remains a marvelous therapeutic option. Further studies are required to fully elucidate the risk factors and clinical pictures of colistin-induced nephrotoxicity.

No increased acute kidney injury rate through giving an intravenous colistin loading dose in pediatric patients

OBJECTIVES

A colistin loading dose is required to achieve adequate drug exposure for the treatment of multidrug-resistant Gram-negative bacteria. However, data on acute kidney injury (AKI) rates associated with this approach in children have been unavailable. The aim of this study was to examine AKI rates in children who were prescribed a colistin loading dose.

METHODS

A retrospective study was conducted in patients aged 1 month to 18 years who had received intravenous colistin for ≥48 h. Loading dose (LD) was defined as colistin methanesulfonate at 4-5 mg of colistin base activity/kg/dose. AKI was defined according to KDIGO serum creatinine (SCr) criteria - SCr ≥ 1.5 times the baseline, measured 3-7 days after colistin initiation. Augmented renal clearance (ARC) was defined as an estimated glomerular filtration rate (eGFR) >150 mL/min/1.73 m². The rates of AKI were compared between children receiving or not receiving an LD, and between different eGFR groups.

RESULTS

In total, 181 children were enrolled. The mean age was 4.3 years (95% confidence interval [CI], 3.6-4.9 years). Ninety-five of the subjects (52.5%) were male. There were 157 children with a baseline eGFR of ≥ 80 mL/min/1.73 m². The overall AKI rate within the first week in this group was 20.4% (95% CI, 14.4-27.6%): LD, 16.1% vs no LD, 23.2% (p = 0.29). Subgroup analysis, excluding patients with ARC, showed a lower AKI rate of 12.8% (95% CI, 6.8-21.3%): LD, 9.7% vs no LD, 14.3% (p = 0.53).

CONCLUSIONS

AKI rate was not different among children who received an intravenous colistin loading dose. This approach should be implemented to ensure the necessary drug exposure required for good treatment outcomes.

Intravenous colistin use for infections due to MDR Gram-negative bacilli in critically ill paediatric patients: a systematic review and meta-analysis

BACKGROUND

Data are limited regarding the clinical effectiveness and safety of intravenous colistin for treatment of infections due to MDR Gram-negative bacilli (GNB) in paediatric ICUs (PICUs).

METHODS

Systematic review of intravenous colistin use in critically ill paediatric patients with MDR-GNB infection in PubMed, Scopus and EMBASE (up to 31 January 2018).

RESULTS

Out of 1181 citations, 7 studies were included on the use of intravenous colistin for 405 patients in PICUs. The majority of patients were diagnosed with lower respiratory tract infections, Acinetobacter baumannii being the predominant pathogen. Colistin dosages ranged between 2.6 and 18 mg/kg/day, with only one case reporting a loading dose. Emergence of colistin resistance during treatment was reported in two cases. Nephrotoxicity and neurotoxicity were reported in 6.1% and 0.5%, respectively, but concomitant medications and severe underlying illness limited our ability to definitively associate use of colistin with nephrotoxicity. Crude mortality was 29.5% (95% CI = 21.7%-38.1%), whereas infection-related mortality was 16.6% (95% CI = 12.2%-21.5%).

CONCLUSIONS

While the reported incidence of adverse events related to colistin was low, reported mortality rates for infections due to MDR-GNB in PICUs were notable. In addition to severity of disease and comorbidities, inadequate daily dosage and the absence of a loading dose may have contributed to mortality. As the use of colistin for treatment of MDR-GNB infections increases, it is imperative to understand whether optimal dosing of colistin in paediatric patients differs across different age groups. Thus, future studies to establish the pharmacokinetic properties of colistin in different paediatric settings are warranted.

mcr-Colistin Resistance Genes Mobilized by IncX4, IncHI2, and IncI2 Plasmids in Escherichia coli of Pigs and White Stork in Spain

Colistin has become the last-line antimicrobial for the treatment of multidrug resistant (MDR) Enterobacterales in human medicine. To date, several colistin resistance genes have been described. Of them mcr-1 is disseminated worldwide in Escherichia coli of human and animal origin. The aim of this study was to characterize mcr-mediated resistance plasmids from E. coli of animal origin in Spain. From our strain collection, 70 E. coli of pig origin collected between 2005 and 2014 (10 per year, except for years 2009–2010–2013) were randomly selected and screened for the presence of mcr-genes. Additionally, 20 E. coli isolated in 2011 from white storks (Ciconia ciconia) from the same urban household waste landfill associated colony were also included. Whole genome sequencing of mcr-positive isolates was carried out on a MiSeq (Illumina). Hybrid whole genome sequencing strategy combining nanopore and Illumina technologies were performed in a selection of isolates to close the genomes and plasmids and identify the presence of antimicrobial resistance genes. Minimum inhibitory concentration (MIC) was used to assess the susceptibility to colistin. Mating experiments were carried out to evaluate transferability of the mcr-genes. A total of 19 mcr-1 and one mcr-4 positive isolates were detected, 15 from pigs distributed during the study period, and five from storks collected in 2011. No other mcr-variants were found. The MICs for colistin ranged between 4 and >4 mg/L. High diversity of STs were detected among the mcr-1 positive E. coli isolates, with only ST-10 shared between pigs and white storks. Except for one isolate, all were genotypic and phenotypically MDR, and five of them also harbored cephalosporin resistance genes (bla_CTX–M–14, bla_SHV–12, and three bla_CMY–2). mcr-1 genes were mobilizable by conjugation, associated with IncX4, IncHI2, and IncI2 plasmids. In our study, mcr-1 genes have been circulating in pig farms since 2005 harbored by a variety of E. coli clones. Its persistence may be driven by co-selection since plasmids containing mcr-1 also exhibit resistance to multiple drugs used in veterinary medicine. Furthermore, this is the first report of the presence of mcr-1 gene in isolates from white storks in Spain. This finding highlights the potential importance of wildlife that forage at urban household waste landfills in the transmission and spread of colistin resistance genes.

Mechanisms of antimicrobial-induced nephrotoxicity in children

Drug-induced nephrotoxicity is responsible for 20% to 60% of cases of acute kidney injury in hospitalized patients and is associated with increased morbidity and mortality in both children and adults. Antimicrobials are one of the most common classes of medications prescribed globally and also among the most common causes of nephrotoxicity. A broad range of antimicrobial agents have been associated with nephrotoxicity, but the features of kidney injury vary based on the agent, its mechanism of injury and the site of toxicity within the kidney. Distinguishing nephrotoxicity caused by an antimicrobial agent from other potential inciting factors is important to facilitate both early recognition of drug toxicity and prompt cessation of an offending drug, as well as to avoid unnecessary discontinuation of an innocuous therapy. This review will detail the different types of antimicrobial-induced nephrotoxicity: acute tubular necrosis, acute interstitial nephritis and obstructive nephropathy. It will also describe the mechanism of injury caused by specific antimicrobial agents and classes (vancomycin, aminoglycosides, polymyxins, antivirals, amphotericin B), highlight the toxicodynamics of these drugs and provide guidance on administration or monitoring practices that can mitigate toxicity, when known. Particular attention will be paid to paediatric patients, when applicable, in whom nephrotoxin exposure is an often-underappreciated cause of kidney injury.

Use of Colistin in Critically Ill Patients

Due to lack of better therapeutic options, colistin use for extensively drug-resistant Gram-negative organisms was revived in the past two decades, including in patients in intensive-care units (ICU). There are multiple knowledge gaps pertaining to the clinical use and utility of colistin in critically-ill patients, but due to lack of options, it is used in these high risk patients. In this chapter, we critically review the various topics pertaining to colistin use in critically-ill patients, while highlighting the (lack of) controlled evidence supporting common current practices pertaining to colistin use by clinicians.

Infection with gram-negative bacteria among children in a tertiary pediatric hospital in Egypt

BACKGROUND

Patients in pediatric intensive care units (PICUs) are susceptible to infections with gram-negative bacteria (GNB).

METHODS

A prospective observational study was conducted in 2 PICUs at Cairo University Hospitals to determine the incidence and outcome of GNB infections over 1 year. Variables of interest included age, gender, isolated organism, susceptibility to antibiotics, and final outcome.

RESULTS

During the study period, 1420 patients were admitted to the PICU; of these, 291 developed GNB infections. The median age of the studied GNB patients was 50 months (interquartile range [IQR], 22-80 months). The mortality rate was 37.1%. Organisms were isolated from blood in the majority (86.6%) of patients, with Klebsiella (36.0%) being the most frequently isolated organism. Among patients with GNB infection, 235 patients, one had a multidrug-resistant (MDR) infection. The length of hospital stay was statistically significantly longer in the MDR group (25 days; IQR, 20-30) than in the non-MDR group (15 days; IQR, 10-20) (P < .01). Mortality was similar in both groups (37.4% vs 35.7% in the MDR and non-MDR groups, respectively; P = .88).

CONCLUSION

This study highlights high rates of pediatric MDR-GNB infections and emphasizes the need for a continuous surveillance system in the management of these critically ill children.

Colistin use in critically ill neonates: A case-control study

BACKGROUND

The aim of this study was to assess the safety and efficacy of colistin use in critically ill neonates.

METHODS

This was a case-control study that included newborn infants with proven or suspected nosocomial infections between January 2012 and October 2015, at two centers in Diyarbakir, Turkey. The clinical and laboratory characteristics and outcomes of patients who received colistin therapy were reviewed and compared to patients who were treated with antimicrobial agents other than colistin during the same period.

RESULTS

Forty-seven cases who received intravenous colistin (colistin group) and 59 control patients (control group) were included. There were no significant differences between the groups regarding outcomes and nephrotoxicity, including acute renal failure. Colistin therapy was associated with significantly reduced serum magnesium (1.38 ± 0.39 mg/dL vs. 1.96 ± 0.39 mg/dL, p < 0.001) and hypokalemia (46.8% vs. 25.4%, p = 0.026). The patients who received colistin also had longer hospital stays (43 (32-70) days vs. 39 (28-55) days, p = 0.047), a higher rate of previous carbapenem exposure (40.4% vs. 11.9%, p = 0.001), and a higher age at the onset of infection (13 (10-21) days vs. 11 (9-15) days, p = 0.03).

CONCLUSION

This study showed that colistin was both effective and safe for treating neonatal infections caused by multidrug-resistant gram-negative bacteria. However, intravenous colistin use was significantly associated with hypomagnesemia and hypokalemia.

An audit of colistin use in neonatal sepsis from a tertiary care centre of a resource-limited country

Background & objectives:

Sepsis due to multidrug-resistant Gram-negative pathogens is a challenge for clinicians and microbiologists and has led to use of parenteral colistin. There is a paucity of data regarding safety and efficacy of intravenous colistin use in neonates. The objective of this retrospective analysis was to study the efficacy and safety of intravenous colistin in the treatment of neonatal sepsis.

Methods:

An audit of the data from neonates, admitted to a neonatal intensive care unit of a tertiary care hospital during January 2012 to December 2012, and who received intravenous colistin was carried out.

Results:

Sixty two neonates received intravenous colistin (52 preterm and 10 term) for the treatment of pneumonia, bloodstream infections and meningitis. The isolated pathogens in decreasing order of frequency were Acinetobacter baumannii, Klebsiella pneumonia and Pseudomonas aeruginosa. Of the total 62 neonates, 41 (66.12%) survived and 21 (33.87%) died. Significantly higher mortality was observed in neonates with lower body weights (P < 0.05). A significant association of mortality was found in those with sepsis due to Klebsiella species. Only one of seven with this infection survived as against 15 of the 23 who grew other organisms [P = 0.03; crude odds ratio = 11.25 (1.2, 110.5)]. None of the neonates developed neurotoxicity or nephrotoxicity.

Interpretation & conclusions:

This retrospective study in neonates with sepsis showed that intravenous colistin was safe and effective in the treatment of neonatal sepsis. Further, well–controlled, prospective clinical trials need to be done to corroborate these findings.

Clinical and Bacterial Risk Factors for Mortality in Children With Carbapenem-resistant Enterobacteriaceae Bloodstream Infections in India

BACKGROUND

Carbapenem-resistant Enterobacteriaceae (CRE) are an increasing cause of nosocomial infection in hospitalized children worldwide. Few studies have investigated risk factors for mortality in children with CRE bloodstream infection (BSI). Data are particularly scarce in areas where NDM and OXA carbapenemases predominate. Here, we investigate mortality rates, clinical and microbiologic risk factors for mortality in 50 pediatric patients with CRE BSI in India.

METHODS

Children younger than 17 years old with meropenem-resistant Klebsiella pneumoniae or Escherichia coli isolated from blood culture in 2014 and 2015 were identified from laboratory records. Clinical records were systematically reviewed for each child to establish mortality at 30 days and clinical details. Bacterial isolates were subjected to meropenem E test and multiplex polymerase chain reaction to determine carbapenemase gene. Data were analyzed to establish clinical and bacterial risk factors for mortality.

RESULTS

All CRE BSI were hospital-acquired or associated with healthcare. A total of 84% of children had an underlying comorbidity and 46% had a malignancy. K. pneumoniae was the most common bacteria isolated; NDM was the most common carbapenemase gene detected. The mortality rate was 52%. Significant risk factors for mortality included intensive care admission, intubation, inotropic support and respiratory source. Failure to clear bacteremia and a minimum inhibitory concentration > 8 mg/L for the isolate was associated with a statistically significant increase in mortality. Mortality rates were significantly lower when two or more effective drugs were used in combination.

CONCLUSIONS

CRE BSI affects children with multiple comorbidities and repeated admissions to hospital. The mortality rate is high; combination therapy may be beneficial.

Use of Colistin in a Neonatal Intensive Care Unit: A Cohort Study of 65 Patients

BACKGROUND The emergence of infections related to multidrug-resistant Gram-negative bacilli (MDR-GNB) reintroduced the use of colistin, an antibiotic that was previously abandoned due to adverse effects. However, because of its limited use in neonatal intensive care units, there is very little data about the effectiveness and safety of colistin in children and newborns. In this study, which will be the largest case study in the literature, we aimed to evaluate the effectiveness and safety of colistin in full-term and preterm newborns. MATERIAL AND METHODS The study included patients admitted into 2 level 3 neonatal intensive care units between January 2013 and June 2015. The medical records of patients diagnosed with sepsis, meningitis, pneumonia, and urinary tract infection based on the diagnostic culture results and treated with colistin were analyzed retrospectively. The patients whose infections were not verified were excluded from the study. RESULTS The study included 65 patients (18 term, 47 preterm). The most frequently isolated pathogens were Klebsiella pneumoniae and Acinetobacter baumannii followed by Pseudomonas aeruginosa and Enterobacter cloacae. Mean colistin treatment time was 15±3.5 days. All patients treated with colistin were being treated with at least 1 other antibiotic. While a complete clinical response was achieved in 51 (72.3%) patients, 14 (21.5%) patients died during treatment. Four (7.7%) patients died during as a result of another infection. Three patients developed renal toxicity, another 3 patients had seizures, and apnea was observed in 3 patients. CONCLUSIONS Colistin was found to be effective and safe for treatment of MDR-GNB infections in preterms and infants with very low birth weight. Given the severity of the infection, the adverse effects of colistin were at acceptable levels.

Intravenous Colistin Use for Multidrug-Resistant Gram-Negative Infections in Pediatric Patients

BACKGROUND

The emergence of infections due to multidrug-resistant Gram-negative bacilli (MDR-GNB) has led to the resurrection of colistin use. The data on colistin use and drug-related adverse effects in children are scarce.

AIMS

In this study, we aimed to evaluate the clinical efficacy and safety of colistin use in critically ill pediatric patients.

STUDY DESIGN

This study has a retrospective study design.

METHODS

Sixty-one critically ill children were identified through the department's patient files archive during the period from January 2011 to November 2014.

RESULTS

Twenty-nine females and thirty-two males with a mean±standard deviation (SD) age of 61±9 months (range 0-216, median 12 months) received IV colistin due to MDR-GNB infections. Bacteremia (n=23, 37.7%) was the leading diagnosis, followed by pneumonia (n=19, 31%), clinical sepsis (n=7, 11.4%), wound infection (n=6, 9.8%), urinary tract infection (n=5, 8.1%) and meningitis (n=1, 1.6%). All of the isolates were resistant to carbapenems; however, all were susceptible to colistin. The isolated microorganisms in decreasing order of frequency were: Acinetobacter baumanni (n=27, 44.2%), Pseudomonas aeruginosa (n=17, 27.8%), Klebsiella pneumoniae (n=6, 9.8%), K. pneumoniae and Stenotrophomonas maltophilia (n=1, 1.6%), K. pneumoniae and A. baumanni (n=1, 1.6%), K. oxytoca (n=1, 1.6%) and Enterobacter cloacae (n=1, 1.6%). In seven patients, no microorganisms were detected; however, five of these patients were colonized by carbapenem-resistant K. pneumoniae. The mean duration of colistin therapy was 12 days (range 3-45). Colistin was administered concomitantly with one of the following antibiotics: carbapenem (n=50, %82), ampicillin-sulbactam (n=5, 8%), quinolones (n=5, 8%), rifampicin (n=1, 1.6%). Carbapenem was the most frequently used antibiotic. Nephrotoxicity was observed in only 1 patient, and we did not observe neurotoxicity in this study. All the patients received intravenous colistin (colisthimethate) at a dosage of 5 mg/kg daily by dividing it in three equal doses. Seven (11.4%) patients died during the study period.

CONCLUSION

Colistin appears to be a safe and efficacious drug for treating MDR-GNB infections in children.

Is colistin effective in the treatment of infections caused by multidrug-resistant (MDR) or extremely drug-resistant (XDR) gram-negative microorganisms in children?

The increasing incidence of infections caused by multidrug-resistant (MDR) or extremely drug-resistant (XDR) gram-negative organisms has led to the reemergence of colistin use. Clinical and demographic data were collected on 94 pediatric patients diagnosed with MDR or XDR gram-negative infections and treated with either a colistin-containing regimen (colistin group) or at least one antimicrobial agent other than colistin (noncolistin group). The overall clinical response rates were 65.8% in the colistin group and 70.0% in the noncolistin group (P = 0.33). The infection-related mortality rates were 11% in the colistin group and 13.3% in the noncolistin group (P = 0.74). There was no statistically significant difference in nephrotoxicity in the colistin and noncolistin groups. Colistin therapy was at least as effective and as safe as beta-lactam antibiotics or quinolones, with or without aminoglycosides, in the treatment of infections caused by gram-negative organisms and may be a therapeutic option in children.

The safety of polymyxin antibiotics

INTRODUCTION

The emergence of multidrug-resistant gram-negative bacteria has led to the increasing use of polymyxins. Nephrotoxicity and, to a lesser degree, neurotoxicity occur often during systemic polymyxin therapy. Scientific evidence regarding safety associated with polymyxins remains limited.

AREAS COVERED

Case reports/case series, observational studies and clinical trials assessing safety and toxicity of polymyxins were critically reviewed.

EXPERT OPINION

Polymyxins are drugs with a narrow therapeutic range. Nephrotoxicity is associated with both host factors and polymyxin exposure, and recent studies suggest that the relative risk of nephrotoxicity is similar for colistin and polymyxin B. Studies that have examined the safety of polymyxins have several limitations. Considering the available evidence, toxicities that may develop while on polymyxin therapy most often are mild to moderate in magnitude and reversible in nature. Strategies to minimize toxicity associated with polymyxins have evolved and include avoidance of toxic medications, careful dosing, use of critical care, therapeutic drug monitoring and development of polymyxin derivatives. However, given that polymyxin use has re-emerged in an era of increased antimicrobial resistance, the presence of other treatment modalities may be limited. Therefore, clinicians must consider overall risk to benefit ratio of continuing versus stopping polymyxin treatment and optimize minimization strategies to reduce polymyxin-induced toxicities.

Safety and Efficacy of Intravenous Colistin in Neonates With Culture Proven Sepsis

Background:

Although it is well described among adults, intravenous colistin use and its associated toxicities in newborns are poorly understood.

Objectives:

We present our experience of efficacy and safety of intravenous colistin in the treatment of sepsis in term and preterm neonates.

Patients and Methods:

The records of neonates who received colistin between January 2013 and February 2014 were retrospectively reviewed. All neonates with culture proven nosocomial infections due to multidrug resistant organisms and treated continuously with colistin for more than 72 hours were included in the study.

Results:

Patients were evaluated for clinical and microbiological response to the drug and its and side effects. Twelve newborn infants with mean 31.8 ± 3.5 weeks gestational age and median 1482 (810 - 3200) gram birth weight were included. 11/12 (91.7%) patients showed microbiological clearance with intravenous colistin. One patient who had recurrent cerebrospinal fluid positive culture was treated with intraventricular colistin. The major side effects observed was hyponatremia and hypokalemia in 2 (16.6%) patients, all infants required magnesium supplementation.

Conclusions:

Intravenous colistin administration appears to be safe and efficacious for multidrug-resistant gram-negative infections in neonates, including preterm infants. However, we believe that large prospective controlled studies are needed to confirm its efficacy and safety in neonates.

Colistin inhalation monotherapy for ventilator-associated pneumonia of Acinetobacter baumannii in prematurity

BACKGROUND

Ventilator-associated pneumonia (VAP) caused by Acinetobacter baumannii is increasing. It has a high mortality rate but experience in using inhaled colistin as monotherapy for VAP in children, especially pre-term infants, is limited. This study presents experiences using aerosolized colistin as monotherapy for VAP due to A. baumannii infection in pre-term infants.

METHODS

Eight pre-term infants (gestational age 25-36 weeks) admitted to the neonatal intensive care unit (NICU) of Kaohsiung Chang Gung Memorial Hospital in Taiwan from January 2006 to December 2010 who received inhaled colistin as monotherapy for VAP due to A. baumannii infection were retrospectively evaluated. Of the isolated microorganisms, five were multi-drug resistant strains of A. baumannii (MDR-AB) but all were sensitive to colistin. All patients received inhaled colistin at a dose of 1,000,000 IU (33.4 mg) twice daily for an average of 9.1 days (range, 4-22 days).

RESULTS

All pre-term infants were cured, with A. baumannii eradicated from airway secretions. There were no clinical or laboratory adverse events related to colistin use.

CONCLUSIONS

Aerosolized colistin may be used as monotherapy for VAP due to A. baumannii infection in pre-term infants. A larger controlled study is warranted to corroborate the findings.

Anti-infective use in children and pregnancy: current deficiencies and future challenges

There are a number of challenges to using anti-infective agents in children and pregnant women. There is limited understanding of the altered pharmacokinetics of anti-infectives in these populations and as a result, optimized dosing regimens are yet to be established. The potential adverse effects of the drug on pregnancy outcome and the developing foetus is a major consideration, and the long term implications of drug side effects must be taken into account when drug exposure occurs early in life. These factors hinder research and licensing of new anti-infective drugs in these populations. We describe the current deficiencies and future challenges of anti-infective use in children and pregnant women, providing specific examples.

Colistin use in pediatric intensive care unit for severe nosocomial infections: experience of an university hospital

Background

The aim of this study was to investigate the efficacy and safety of colistin therapy in pediatric patients with severe nosocomial infections in pediatric intensive care unit.

Methods

The medical records of patients treated with colistin at a 200-bed university children hospital were reviewed.

Result

Thirty-one patients (male/female = 22/9; median age, 3 years; range, 3 months-17 years) received forty-one courses of colistin. The average dose of colistin was 4.9 ± 0.5 mg/kg/day and average treatment duration was 19.8 ± 10.3 days. Three patients who received concomitant nephrotoxic agent with colistin developed nephrotoxicity. Colistin treatment was well tolerated in other patients, and neurotoxicity was not seen in any patient. Favourable outcome was achieved in 28 (68.3%) episodes. Twelve patients died during the colistin therapy. Six of these patients died because of primary underlying disease. The infection-related mortality rate was found 14.6% in this study.

Conclusion

In our study, colistin therapy was found to be acceptable treatment option for the severe pediatric nosocomial infections caused by multi-drug resistant bacteria. However, the use of concomitant nephrotoxic drugs with colistin must be avoided and renal function test should be closely monitored.

Colistin is relatively safe in hematological malignancies and hematopoietic stem cell transplantation patients

PURPOSE

Colistin is increasingly used as the last-resort treatment option against infections caused by multidrug-resistant (MDR) Gram-negative pathogens, but its nephrotoxicity is of concern, especially in severely ill patients. The aim of this study was to analyze the toxicity of colistin therapy in adults and children with hematological malignancies (HM) and hematopoietic stem cell transplantation (HSCT) recipients.

METHODS

Data on HSCT recipients and HM patients, treated with intravenous colistin (2.5-5 mg/kg/day in children and 3-6 million international units (IU) in adults, adjusted to renal function) during the period 2008-2011 in our center, were retrospectively collected and analyzed. Nephrotoxicity was defined according to the RIFLE criteria (Risk, Injury, Failure, Loss, and End-stage kidney disease).

RESULTS

Twenty-nine children and adults received 38 courses of intravenous colistin (2.5-5 mg/kg/day in children and 3-6 × 10(6) IU in adults, adjusted to renal function) [allogeneic HSCT (22 courses) and HM (16 courses)] for 3-28 days (median 10 days) for empirical therapy for nosocomial clinical sepsis (28) or local infection (6), and bacteremia with MDR Gram-negative rods (4). Nephrotoxicity was observed at the end of 4 (10.5%) courses. In 32 (84%) courses, nephrotoxic medications were concomitantly administered. Two patients had convulsions, probably unrelated to colistin. Seven patients (18%) died while on colistin therapy. No death was attributed to an adverse effect of colistin.

CONCLUSIONS

Treatment with intravenous colistin, with dosage adjusted to renal function, was relatively safe for HM/HSCT patients, even with concomitantly administered nephrotoxic medications. Concern about nephrotoxicity should not justify a delay in initiating empirical colistin treatment in situations where infection with MDR Gram-negative rods is likely.

The use of intravenous colistin among children in the United States: results from a multicenter, case series

BACKGROUND

A rapid increase in multidrug-resistant Gram-negative infections has led to a reemergence of colistin use globally. Although it is well described among adults, colistin use and its associated toxicities in children are poorly understood. We report findings from the largest case series of pediatric colistin use to date.

METHODS

We queried pediatric infectious diseases specialists from the Emerging Infections Network to identify members who had prescribed intravenous colistin within the past 7 years. We collected relevant demographic and clinical data. Bivariate analyses and multivariable logistic regression were performed.

RESULTS

Two hundred twenty-nine pediatric infectious diseases specialists completed the survey (84% response); 22% had prescribed colistin to children. Among respondents, 92 cases of colistin use from 25 institutions were submitted. The most commonly targeted organisms were multidrug-resistant Pseudomonas (67.4%), multidrug-resistant Acinetobacter -baumanii (11.9%), carbapenemase-producing Enterobacteriaceae (13.0%) and extended-spectrum β-lactamase producing Enterobacteriaceae (5.4%). Development of resistance to colistin was observed in 20.5% of patients. Additional antimicrobial therapy was administered to 84% of patients, and 22% of children experienced nephrotoxicity (not associated with dosage or interval of colistin prescribed). Renal function returned to baseline in all patients. Children aged ≥13 years had approximately 7 times the odds of developing nephrotoxicity than younger children, even after controlling for receipt of additional nephrotoxic agents (odds ratio 7.16; 95% confidence interval: 1.51-14.06; P = 0.013). Four children exhibited reversible neurotoxicity.

CONCLUSIONS

Most pediatric infectious diseases specialists have no experience prescribing colistin. Colistin use in children has been associated primarily with nephrotoxicity and, to a lesser extent, neurotoxicity, both of which are reversible. Emergence of resistance to colistin is concerning.

Clinical and microbiological efficacy and toxicity of colistin in patients infected with multidrug-resistant gram-negative pathogens

Polymyxins have recently again become important because of multidrug-resistant (MDR) gram-negative pathogens. The aim of this study was to evaluate the clinical and microbiological efficacy and toxicity of different dosages of colistin in patients infected with MDR microorganisms that were sensitive only to colistin. The study was conducted in the 1,200-bed Ankara Numune Training and Research Hospital. Patients with normal renal function who received colistin for 48 h or more were retrospectively evaluated. Clinical response was defined as resolution of fever and clinical and laboratory findings. Microbiological response was defined as bacteriological eradication from the infection site. Nephrotoxicity was defined as at least two consecutive serum creatinine measurements with an increase of 0.5 mg/dl from baseline at least 24 h apart after 2 or more days of colistin therapy. Twenty-four patients were included in the study: total clinical response was obtained in 17 of 24 (70.8 %) patients and microbiological response in 15 of 24 (62.5 %) patients. Patients were grouped according to colistin dosage of 3 × 1 million units (MU) versus 3 × 2 MU. Clinical response rates were 69.2 % and 72.7 %, respectively (p = 0.65). Microbiological response rate was similar (p = 0.62). Nephrotoxicity was revealed in 1 of 13 patients (7.7 %) for the 3 × 1 MU group and 2 of 11 patients (18.2 %) in the 3 × 2 MU group (p = 0.57). The nephrotoxicity rate was greater with higher dosages of colistin, but the difference was not statistically significant. Renal function of patients receiving higher dosages of colistin should be more closely monitored.

Old agent, new experience: colistin use in the paediatric Intensive Care Unit--a multicentre study

Nosocomial infections caused by multidrug-resistant (MDR) microorganisms are a common problem around the world, especially in Intensive Care Units. The aim of this study was to investigate the efficacy and safety of colistin therapy in paediatric patients with severe nosocomial infections caused by MDR Gram-negative bacteria. There were 87 episodes in 79 paediatric Intensive Care Unit patients in five different hospitals; each patient was treated intravenously with colistin and evaluated. Of the 79 patients, 54.4% were male and the median age was 30 months. The most commonly isolated microorganism was Acinetobacter baumannii, the most common isolation site was tracheal aspirate fluid and the most common type of infection was ventilator-associated pneumonia. The mean colistin dose in patients without renal failure was 5.4 ± 0.6 mg/kg/day, the mean therapy duration was 17.2 ± 8.4 days and the favourable outcome rate was 83.9%. Serious side effects were seen in four patient episodes (4.6%) during therapy; two patients suffered renal failure and the others had convulsive seizures. Other patients tolerated the drug well. The infection-related mortality rate was 11.5% and the probability of death within the first 9 days of treatment was 10 times higher than after the first 9 days. In conclusion, this study suggests that colistin is effective in the treatment of severe nosocomial infections caused by MDR Gram-negative bacteria and is generally well tolerated by patients, even after relatively long-term use.

Outcome of ventilator-associated pneumonia due to multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa treated with aerosolized colistin in neonates: a retrospective chart review

Multidrug-resistant (MDR) gram-negative bacteria-related nosocomial infections and ventilator-associated pneumonia (VAP) presents an emerging challenge to clinicians. Older antimicrobial agents such as colistin have become life-saving drugs because of the susceptibility of these pathogens. We report our experience with aerosolized colistin in two preterm and one term neonate with Acinetobacter baumannii and Pseudomonas aeruginosa-related VAP who were unresponsiveness to previous antimicrobial treatment. All pathogens were isolated from tracheal aspirate. We used 5 mg/kg (base activity) aerosolized colistin methanesulfonate sodium in every 12 h as an adjunctive therapy for VAP. VAP was treated by 14, 14, and 16-day courses of aerosolized colistin in these patients, respectively. No adverse effect such as nephrotoxicity or neurotoxicity was observed. We found that aerosolized colistin was tolerable and safe, and it may be an adjunctive treatment option for MDR gram-negative bacterial VAP in neonates. Further studies are needed to determine appropriate doses for aerosolized colistin and its eligibility as an alternative treatment choice in newborns.

Intravenous colistin administration in neonates

BACKGROUND

Nosocomial infection due to multidrug-resistant Gram-negative pathogens in intensive care units is a challenge for clinicians and microbiologists, and has led to resurgence of parenteral colistin use in the last decade. Safety and efficacy data regarding intravenous colistin (colistimethate) use in neonates is sparse. We present our experience of efficacy and safety of colistimethate in the treatment of sepsis in critically sick term and preterm neonates.

METHODS

The records of the neonates who received colistimethate in a neonatal intensive care unit of a tertiary care center from January 2009 to December 2009 were reviewed.

RESULTS

Eighteen critically sick neonates (10 term and 8 preterm) received 21 courses of colistimethate (dose ranging from 50,000 to 75,000 IU/kg/d) for treatment of pneumonia, blood stream infections, meningitis, and empyema thoracis. The isolated pathogens in decreasing order of frequency were Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonos aeruginosa, and Enterobacter. Mean duration of colistimethate was 13.1 days/course (range: 5-21 days). At least one other antibiotic was coadministered in all courses. A favorable clinical outcome occurred in 16 of 21 (76%) courses, 5 patients died due to severe sepsis with multiple organ dysfunction. Microbiologic clearance was documented in 17 courses. Increase in serum creatinine by > 0.5 mg/dL above baseline in 2 babies was associated with the presence of multiple organ dysfunction syndrome in both and coadministration of netilmicin in one.

CONCLUSIONS

Colistimethate intravenous administration appears to be safe and efficacious for multidrug-resistant Gram-negative infections in neonates, including preterm and extremely low birth weight neonates.

Safety in treatment of ventilator-associated pneumonia due to extensive drug-resistant Acinetobacter baumannii with aerosolized colistin in neonates: a preliminary report

BACKGROUND

Infections caused by extensive drug-resistant Acinetobacter baumannii (XDR-AB) have been increasingly observed and are associated with a high mortality rate. We present our experience using aerosolized colistin for the treatment of ventilator-associated pneumonia (VAP) due to XDR-AB in neonates.

METHODS

The clinical data of neonates who received aerosolized 4 mg per kg of colistin base twice daily as an adjunctive therapy for VAP caused by XDR-AB between July 2008 and September 2009 were retrospectively reviewed. The outcomes were compared with the neonates with VAP from XDR-AB in October 2006-September 2007 who did not receive aerosolized colistin.

RESULTS

During the study period, eight neonates (three preterm and five term neonates) with VAP caused by XDR-AB received aerosolized colistin. All isolated pathogens from the tracheobronchial specimens of the eight patients were XDR-AB susceptible to colistin only. Six patients received aerosolized colistin without concomitant intravenous colistin. All children were cured with eradication of XDR-AB from respiratory secretions. Seven patients survived and were discharged from the hospital, and one died from bacterial sepsis unrelated to the VAP episode. There were no clinical or laboratory adverse events related to aerosolized colistin. Compared to the seven neonates in the earlier period, the neonates who received aerosolized colistin had higher birth weight and gestational age, and lower mortality rate (13% vs. 71%, P=0.04).

CONCLUSIONS

Aerosolized colistin may be a useful adjunctive therapy in VAP due to XDR-AB. The use of aerosolized colistin in neonates should be investigated in a larger controlled study.

Orally administered colistin leads to colistin-resistant intestinal flora and fails to prevent faecal colonisation with extended-spectrum β-lactamase-producing enterobacteria in hospitalised newborns

Colonisation and infection with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) is an emerging problem. The aim of this study was to investigate whether colistin, which is reported to be effective against multiresistant enterobacteria, prevents ESBL-E colonisation in neonates. For prophylaxis of necrotising enterocolitis, oral gentamicin (15 mg/kg/day) is routinely used in all neonates hospitalised at the Neonatal Intensive Care Unit of University Hospital Graz (Austria). During the study period from May 2005 to September 2007, three ESBL-E outbreaks (total duration 18 months) occurred. During these outbreaks, gentamicin was immediately replaced by oral colistin (8 mg/kg/day) in all hospitalised neonates. All neonates colonised with ESBL-E during the study period were retrospectively analysed with regard to the influence of colistin on ESBL-E colonisation. Genetic relatedness of isolates was assessed by repetitive sequence-based polymerase chain reaction (rep-PCR). During the study period, 30 (4.5%) of 667 neonates were colonised with ESBL-E. Twelve of twenty-one patients colonised with Klebsiella pneumoniae (ESBL-Kp) and one of nine patients colonised with Klebsiella oxytoca (ESBL-Ko) had received oral colistin at time of colonisation with ESBL-E. Amongst ESBL-Kp, the rate of colistin resistance was significantly higher in the colistin group (P=0.0075). Four different clones of ESBL-Kp and three different clones of ESBL-Ko were isolated, indicating the occurrence of patient-to-patient transmission. Colistin-resistant as well as colistin-susceptible isolates were detected within the same clones, indicating induction of resistance. At the dosage used, oral colistin did not prevent colonisation with ESBL-E and appeared to select colistin-resistant strains or to induce colistin resistance.

Inhaled colistin for the treatment of tracheobronchitis and pneumonia in critically ill children without cystic fibrosis

Data regarding the role of inhaled colistin in critically ill pediatric patients without cystic fibrosis are scarce. Three children (one female), admitted to the intensive care unit (ICU) of a tertiary-care pediatric hospital in Athens, Greece, during 2004-2009 received inhaled colistin as monotherapy for tracheobronchitis (two children), and as adjunctive therapy for necrotizing pneumonia (one child). Colistin susceptible Acinetobacter baumannii and Pseudomonas aeruginosa were isolated from the cases' bronchial secretions specimens. All three children received inhaled colistin at a dosage of 75 mg diluted in 3 ml of normal saline twice daily (1,875,000 IU of colistin daily), for a duration of 25, 32, and 15 days, respectively. All three children recovered from the infections. Also, a gradual reduction, and finally total elimination of the microbial load in bronchial secretions was observed during inhaled colistin treatment in the reported cases. All three cases were discharged from the ICU. No bronchoconstriction or any other type of toxicity of colistin was observed. In conclusion, inhaled colistin was effective and safe for the treatment of two children with tracheobronchitis, and one child with necrotizing pneumonia. Further studies are needed to clarify further the role of inhaled colistin in pediatric critically ill patients without cystic fibrosis.

[Colimycin: an old antibiotic which has to be learnt to know]

The emergence of Pseudomonas aeruginosa, Acinetobacter baumanii, and Enterobacteriaceae strains resistant to all beta-lactams (including carbapemenases producing strains), quinolones, aminoglycosides and no new antibiotics have led to reconsider the colimycin use. This antibiotic known since the 50s, had been completely abandoned, in one hand due to poor clinical activity and in other hand because of its toxicity (renal and neurological). The colimycin is an antibiotic complex like no other (until now, we have more questions than answers) and extremely difficult to use. It should be prescribed only when absolutely necessary and only after isolation of the strain responsible of the infection and determination of the in vitro susceptibility tests confirming both resistance to other antibiotics and sensitivity to colimycin. Even if the strain is resistant to other antibiotics, a synergy can be observed with many antibiotics. Monotherapy is not recommended because it promotes rapid development of resistance. Because of low serum concentrations, very close to MICs of targeted bacteria, the dosages are necessarily high.

Colistin administration to pediatric and neonatal patients

Emergence of multidrug-resistant Gram-negative nosocomial pathogens has led to resurgence of colistin use. Safety and efficacy data regarding colistin use in pediatric patients are sparse, while optimal dosage has not been defined. We present a case series of neonates and children without cystic fibrosis treated with various doses of colistin intravenously. The records of patients who received colistin in a tertiary-care hospital from January 2007 to March 2009 were reviewed. Thirteen patients (median age 5 years, range 22 days to 14 years) received 19 courses of colistin as treatment of pneumonia, central nervous system infection, bacteremia, or complicated soft tissue infection. The isolated pathogens were Acinetobacter baumannii, Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. Daily dose of colistin (colistimethate) ranged between 40,000 and 225,000 IU/kg. Duration of administration ranged from 1 to 133 days. Other antimicrobials were co-administered in 18/19 courses. Increase of serum creatinine in one patient was associated with co-administration of colistin and gentamicin. Sixteen of 19 courses had a favorable outcome, and only two of the three deaths were infection-related. Colistin intravenous administration appears well tolerated even at higher than previously recommended doses and of prolonged duration.

Serum and cerebrospinal fluid levels of colistin in pediatric patients

Using a liquid chromatography-tandem mass spectrometry method, the serum and cerebrospinal fluid (CSF) concentrations of colistin were determined in patients aged 1 months to 14 years receiving intravenous colistimethate sodium (60,000 to 225,000 IU/kg of body weight/day). Only in one of five courses studied (a 14-year-old receiving 225,000 IU/kg/day) did serum concentrations exceed the 2 microg/ml CLSI/EUCAST breakpoint defining susceptibility to colistin for Pseudomonas and Acinetobacter. CSF colistin concentrations were <0.2 microg/ml but increased in the presence of meningitis (approximately 0.5 microg/ml or 34 to 67% of serum levels).

Colistin in the 21st century

PURPOSE OF REVIEW

Colistin is a 50-year-old antibiotic that is being used increasingly as a 'last-line' therapy to treat infections caused by multidrug-resistant Gram-negative bacteria, when essentially no other options are available. Despite its age, or because of its age, there has been a dearth of knowledge on its pharmacological and microbiological properties. This review focuses on recent studies aimed at optimizing the clinical use of this old antibiotic.

RECENT FINDINGS

A number of factors, including the diversity in the pharmaceutical products available, have hindered the optimal use of colistin. Recent advances in understanding of the pharmacokinetics and pharmacodynamics of colistin, and the emerging knowledge on the relationship between the pharmacokinetics and pharmacodynamics, provide a solid base for optimization of dosage regimens. The potential for nephrotoxicity has been a lingering concern, but recent studies provide useful new information on the incidence, severity and reversibility of this adverse effect. Recent approaches to the use of other antibiotics in combination with colistin hold promise for increased antibacterial efficacy with less potential for emergence of resistance.

SUMMARY

Because few, if any, new antibiotics with activity against multidrug-resistant Gram-negative bacteria will be available within the next several years, it is essential that colistin is used in ways that maximize its antibacterial efficacy and minimize toxicity and development of resistance. Recent developments have improved use of colistin in the 21st century.

Multidrug-resistant Gram-negative infections: what are the treatment options?

The emergence of multidrug-resistant (MDR) Gram-negative bacilli creates a challenge in the treatment of nosocomial infections. While the pharmaceutical pipeline is waning, two revived old antibacterials (colistin and fosfomycin), a newer one (tigecycline) and an 'improved' member of an existing class (doripenem) are the only therapeutic options left. The class of polymyxins, known since 1947 and represented mostly by polymyxin B and polymyxin E (colistin), has recently gained a principal role in the treatment of the most problematic MDR Gram-negative pathogens (such as Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae and Stenotrophomonas maltophilia). Future prospective studies are needed to answer important clinical questions, such as the possible benefit of combination with other antimicrobials versus monotherapy, the efficacy of colistin in neutropenic hosts and the role of inhaled colistin. As new pharmacokinetic data emerge, clarification of the pharmacokinetic/pharmacodynamic (PK/PD) profile of colistin as well as appropriate dosing seems urgent, while development of resistance must be carefully monitored. Fosfomycin tromethamine, a synthetic salt of fosfomycin discovered in 1969, has regained attention because of its in vitro activity against extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and MDR P. aeruginosa. Although in use for decades in oral and parenteral formulations for a variety of infections without significant toxicity, its clinical utility in MDR infections remains to be explored in future studies. Tigecycline, the first representative of the new class of glycylcyclines, holds promise in infections from MDR K. pneumoniae (K. pneumoniae carbapenemase [KPC]- and ESBL-producing strains) and Enterobacteriaceae with various mechanisms of resistance. The in vitro activity of tigecycline against A. baumannii makes it a tempting option, as it is currently the most active compound against MDR strains along with colistin. However, the usual minimum inhibitory concentration values of this pathogen are approximately 2 mg/L and compromise clinical outcomes based on PK/PD issues. Its advantageous penetration into various tissues is useful in infections of the skin and soft tissues as well as intra-abdominal infections (official indications), whereas low serum concentrations compromise its use in bloodstream infections. Therefore, prospective studies with dose escalation are urgently needed, as well as clarification of its role in nosocomial pneumonia, after poor results in the study of ventilator-associated pneumonia. Finally, doripenem, the recently licensed member of the carbapenems (without significant spectrum alterations from the ascendant members) seems to possess a lower potential for resistance selection and a more favourable pharmacokinetic profile when given as an extended infusion. The latter strategy could prove helpful in overcoming low level resistance of A. baumannii and P. aeruginosa strains.