Aerosolized Antibiotics to Manage Ventilator-Associated Infections: A Comprehensive Review

BACKGROUND

Ventilator-associated lower respiratory tract infectious complications in critically ill patients cover a wide spectrum of one disease process (respiratory infection), initiating from tracheal tube and/or tracheobronchial colonization, to ventilator associated tracheobronchitis (VAT) and ventilator-associated pneumonia (VAP). VAP occurence has been associated with increased intensive care unit (ICU) morbidity (ventilator days, as well as length of ICU and hospital stay) and ICU mortality. Therefore, treatments that aim at VAP/VAT incidence reduction are a high priority.

AIM

The aim of the present review is to discuss the current literature concerning two major aspects: (a) can aerosolized antibiotics (AA) administered in a pre-emptive way prevent the occurrence of ventilator-associated infections? and (b) can VAT treatment with aerosolized avert the potential evolution to VAP?

RESULTS

There were identified eight studies that provided data on the use of aerosolized antibiotics for the prevention of VAT/VAP. Most of them report favorable data on reducing the colonisation rate and the progression to VAP/VAT. Another four studies dealt with the treatment of VAT/VAP. The results support the decrease in the incidence to VAP transition and/or the improvement in signs and symptoms of VAP. Moreover, there are concise reports on higher cure rates and microbiological eradication in patients treated with aerosolized antibiotics. Yet, differences in the delivery modality adopted and resistance emergence issues preclude the generalisability of the results.

CONCLUSION

Aerosolized antibiotic therapy can be used to manage ventilator-associated infections, especially those with difficult to treat resistance. The limited clinical data raise the need for large randomized controlled trials to confirm the benefits of AA and to evaluate the impact on antibiotic selection pressure.

The Unfulfilled Promise of Inhaled Therapy in Ventilator-Associated Infections: Where Do We Go from Here?

Respiratory infection is common in intubated/tracheotomized patients and systemic antibiotic therapy is often unrewarding. In 1967, the difficulty in treating Gram-negative respiratory infections led to the use of inhaled gentamicin, targeting therapy directly to the lungs. Fifty-three years later, the effects of topical therapy in the intubated patient remain undefined. Clinical failures with intravenous antibiotics persist and instrumented patients are now infected by many more multidrug-resistant Gram-negative species as well as methicillin-resistant Staphylococcus aureus. Multiple systematic reviews and meta-analyses suggest that there may be a role for inhaled delivery but “more research is needed.” Yet there is still no Food and Drug Administration (FDA) approved inhaled antibiotic for the treatment of ventilator-associated infection, the hallmark of which is the foreign body in the upper airway. Current pulmonary and infectious disease guidelines suggest using aerosols only in the setting of Gram-negative infections that are resistant to all systemic antibiotics or not to use them at all. Recently two seemingly well-designed large randomized placebo-controlled Phase 2 and Phase 3 clinical trials of adjunctive inhaled therapy for the treatment of ventilator-associated pneumonia failed to show more rapid resolution of pneumonia symptoms or effect on mortality. Despite evolving technology of delivery devices and more detailed understanding of the factors affecting delivery, treatment effects were no better than placebo. What is wrong with our approach to ventilator- associated infection? Is there a message from the large meta-analyses and these two large recent multisite trials? This review will suggest why current therapies are unpredictable and have not fulfilled the promise of better outcomes. Data suggest that future studies of inhaled therapy, in the milieu of worsening bacterial resistance, require new approaches with completely different indications and endpoints to determine whether inhaled therapy indeed has an important role in the treatment of ventilated patients.

Spotlight on inhaled ciprofloxacin and its potential in the treatment of non-cystic fibrosis bronchiectasis

Non-cystic fibrosis bronchiectasis (NCFB) is a severe chronic illness characterized by irreversible dilation of airways and thickening of bronchial walls, chronic inflammation, repeated infections, and progressive obstruction of the airways. In contrast to cystic fibrosis bronchiectasis (CFB), which is a well-defined genetic disorder, NCFB is a heterogeneous disease caused by many different medical entities. Inhaled antibiotics are effective for patients with CFB, but their efficacy in NCFB has not been proven. The main pathogens involved in the colonization of patients with bronchiectasis are Haemophilus influenza, Moraxella catarrhalis, Staphylococcus aureus, and Pseudomonas aeruginosa. The latter is associated with increased morbidity and mortality. In addition, in NCFB, P. aeruginosa strains are frequently more resistant than those in CFB. At present, there are no approved inhaled antibiotic therapies for NCFB patients. Inhaled ciprofloxacin has been under investigation in the last few years. In two phase II randomized, double-blind, placebo-controlled trials, the use of inhaled ciprofloxacin was significantly associated with reduction in sputum bacterial density and greater eradication rates. In four phase III randomized, double-blind, placebo-controlled trials, the results regarding the time of the first exacerbation and the rate of exacerbations were inconsistent. Specifically, ORBIT-4 and RESPIRE-1 trials showed clinical benefit (prolongation of the time of the first exacerbation and reduced rate of exacerbations in the treatment group compared to the placebo group), whereas the ORBIT-3 and RESPIRE-2 failed to achieve their primary endpoints. The RESPIRE-1 was the first trial that examined the 14-days on/off course separate from the standard 28-days on/off regimen, which is based on CFB protocol treatments. The current data on the efficacy of inhaled ciprofloxacin are encouraging, but further evaluation is needed to determine the appropriate target group and the ideal duration of treatment.

Nebulized Gentamicin as an Alternative to Nebulized Tobramycin for Tracheitis in Pediatric Patients

OBJECTIVES

Tracheitis is an infection of the lower respiratory tract and is defined by the US Centers for Disease Control and Prevention (CDC) based on signs and symptoms with no radiographic evidence of pneumonia. One method of treatment involves the use of tobramycin given by nebulizer. The purpose of this study was to compare the safety and efficacy of nebulized gentamicin with nebulized tobramycin.

METHODS

This study was conducted in patients under 21 years of age who received greater than or equal to 1 day of gentamicin, 80 mg, or tobramycin, 300 mg, given twice a day by nebulization within the 14-month study period. The primary endpoint was amount of time until the patient no longer met the CDC definition of tracheitis.

RESULTS

There were 19 patients who presented with 60 separate encounters. The average age of the patients within the gentamicin group was 7.2 and 5 years old within the tobramycin group. The average duration of time for the gentamicin treatment encounters to be free of the CDC definition of tracheitis was 3.36 days compared to 3.17 days with tobramycin. No adverse effects were observed that were attributable to aminoglycoside nebulization.

CONCLUSIONS

No differences were detected between the safety and efficacy of intravenous gentamicin administered twice a day by nebulizer and that of tobramycin inhalation solution given twice daily in children without cystic fibrosis.

Can we improve clinical outcomes in patients with pneumonia treated with antibiotics in the intensive care unit?

INTRODUCTION

Pneumonia in the intensive care unit (ICU) is associated with high morbidity, mortality and healthcare costs. However, treatment outcomes with conventional intravenous (IV) antibiotics remain suboptimal, and there is an urgent need for improved therapy options.

AREAS COVERED

We review how clinical outcomes in patients with pneumonia treated in the ICU could be improved; we discuss the importance of choosing appropriate outcome measures in clinical trials, highlight the current suboptimal outcomes in patients with pneumonia, and outline potential solutions. We have included key studies and papers based on our clinical expertise, therefore a systematic literature review was not conducted. Expert commentary: Reasons for poor outcomes in patients with nosocomial pneumonia in the ICU include inappropriate initial therapy, increasing bacterial resistance and the complexities of IV dosing in critically ill patients. Robust clinical trial endpoints are needed to enable an accurate assessment of the success of new treatment approaches, but progress in this field has been slow. In addition, only very few new antimicrobials are currently in development for nosocomial pneumonia; two potential alternative solutions to improve outcomes could therefore include the optimization of pharmacokinetic/pharmacodynamics (PK/PD) and dosing of existing therapies, and the refinement of antimicrobial delivery by inhalation.

Levofloxacin inhalation solution for the treatment of chronic Pseudomonas aeruginosa infection among patients with cystic fibrosis

Chronic pulmonary infections are common among patients with cystic fibrosis. By 10 years of age, Pseudomonas aeruginosa is the predominant pathogen. Inhaled levofloxacin solution (MP-376) is a promising new therapy that exhibits rapid antibacterial activity and excellent biofilm penetration against P. aeruginosa. In the largest trial to date, 151 patients were randomized to receive MP-376 or placebo. At the end of the 28-day treatment period, patients who received MP-376 had decreased P. aeruginosa density in sputum, improved lung function parameters and improved respiratory symptoms. MP-376 also appeared to be safe and well tolerated. The results of two recently completed Phase III trials have not yet been released; however, these data will be critical in determining whether MP-376 is a safe and effective maintenance therapy for chronic pulmonary P. aeruginosa infections among patients with cystic fibrosis.

Development of levofloxacin inhalation solution to treat Pseudomonas aeruginosa in patients with cystic fibrosis

Inhaled therapies allow for the targeted delivery of antimicrobials directly into the lungs and have been widely used in the treatment of cystic fibrosis (CF) acute pulmonary exacerbations. Nebulized levofloxacin solution (MP-376) is a novel therapy that is currently being evaluated in phase I, II, and III clinical trials among patients with stable CF and recent isolation of Pseudomonas aeruginosa from sputum. Phase I studies have investigated the single and multiple-dose pharmacokinetics of MP-376 and shown that it is rapidly absorbed from the lungs and results in low systemic concentrations. A subsequent phase IB study found that MP-376 pharmacokinetics were comparable among adults and children 6-16 years of age. Further phase II studies reported that sputum P. aeruginosa density decreased in a dose-dependent manner among patients who were randomized to MP-376 when compared with patients who received placebo. Improvements in pulmonary function and a decrease in the need for other antipseudomonal antibiotics were also reported for patients who received inhaled levofloxacin. The most common adverse event was dysgeusia (abnormal taste sensation), which was reported by nearly half of the participants who received MP-376. No serious drug-related adverse events were reported. These findings are encouraging; however, data from the two ongoing phase III trials are needed to determine whether MP-376 demonstrates substantial evidence of safety and efficacy as a chronic CF maintenance therapy and therefore may be useful in routine clinical practice.