Breakpoints for predicting Pseudomonas aeruginosa susceptibility to inhaled tobramycin in cystic fibrosis patients: use of high-range Etest strips

Mucus polymer concentration and in vivo adaptation converge to define the antibiotic response of Pseudomonas aeruginosa during chronic lung infection

The airway milieu of individuals with muco-obstructive airway diseases (MADs) is defined by the accumulation of dehydrated mucus due to hyperabsorption of airway surface liquid and defective mucociliary clearance. Pathological mucus becomes progressively more viscous with age and disease severity due to the concentration and overproduction of mucin and accumulation of host-derived extracellular DNA (eDNA). Respiratory mucus of MADs provides a niche for recurrent and persistent colonization by respiratory pathogens, including Pseudomonas aeruginosa, which is responsible for the majority of morbidity and mortality in MADs. Despite high concentration inhaled antibiotic therapies and the absence of antibiotic resistance, antipseudomonal treatment failure in MADs remains a significant clinical challenge. Understanding the drivers of antibiotic tolerance is essential for developing more effective treatments that eradicate persistent infections. The complex and dynamic environment of diseased airways makes it difficult to model antibiotic efficacy in vitro. We aimed to understand how mucin and eDNA concentrations, the two dominant polymers in respiratory mucus, alter the antibiotic tolerance of P. aeruginosa. Our results demonstrate that polymer concentration and molecular weight affect P. aeruginosa survival post antibiotic challenge. Polymer-driven antibiotic tolerance was not explicitly associated with reduced antibiotic diffusion. Lastly, we established a robust and standardized in vitro model for recapitulating the ex vivo antibiotic tolerance of P. aeruginosa observed in expectorated sputum across age, underlying MAD etiology, and disease severity, which revealed the inherent variability in intrinsic antibiotic tolerance of host-evolved P. aeruginosa populations.

IMPORTANCE

Antibiotic treatment failure in Pseudomonas aeruginosa chronic lung infections is associated with increased morbidity and mortality, illustrating the clinical challenge of bacterial infection control. Understanding the underlying infection environment, as well as the host and bacterial factors driving antibiotic tolerance and the ability to accurately recapitulate these factors in vitro, is crucial for improving antibiotic treatment outcomes. Here, we demonstrate that increasing concentration and molecular weight of mucin and host eDNA drive increased antibiotic tolerance to tobramycin. Through systematic testing and modeling, we identified a biologically relevant in vitro condition that recapitulates antibiotic tolerance observed in ex vivo treated sputum. Ultimately, this study revealed a dominant effect of in vivo evolved bacterial populations in defining inter-subject ex vivo antibiotic tolerance and establishes a robust and translatable in vitro model for therapeutic development.

[CF Lung Disease - a German S3 Guideline: Pseudomonas aeruginosa]

Cystic Fibrosis (CF) is the most common autosomal recessive genetic multisystemic disease. In Germany, it affects at least 8000 people. The disease is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene leading to dysfunction of CFTR, a transmembrane chloride channel. This defect causes insufficient hydration of the airway epithelial lining fluid which leads to reduction of the mucociliary clearance.Even if highly effective, CFTR modulator therapy has been available for some years and people with CF are getting much older than before, recurrent and chronic infections of the airways as well as pulmonary exacerbations still occur. In adult CF life, Pseudomonas aeruginosa (PA) is the most relevant pathogen in colonisation and chronic infection of the lung, leading to further loss of lung function. There are many possibilities to treat PA-infection.This is a S3-clinical guideline which implements a definition for chronic PA-infection and demonstrates evidence-based diagnostic methods and medical treatment in order to give guidance for individual treatment options.

Mucus polymer concentration and in vivo adaptation converge to define the antibiotic response of Pseudomonas aeruginosa during chronic lung infection

The airway milieu of individuals with muco-obstructive airway diseases (MADs) is defined by the accumulation of dehydrated mucus due to hyperabsorption of airway surface liquid and defective mucociliary clearance. Pathological mucus becomes progressively more viscous with age and disease severity due to the concentration and overproduction of mucin and accumulation of host-derived extracellular DNA (eDNA). Respiratory mucus of MADs provides a niche for recurrent and persistent colonization by respiratory pathogens, including Pseudomonas aeruginosa , which is responsible for the majority of morbidity and mortality in MADs. Despite high concentration inhaled antibiotic therapies and the absence of antibiotic resistance, antipseudomonal treatment failure in MADs remains a significant clinical challenge. Understanding the drivers of antibiotic recalcitrance is essential for developing more effective treatments that eradicate persistent infections. The complex and dynamic environment of diseased airways makes it difficult to model antibiotic efficacy in vitro . We aimed to understand how mucin and eDNA concentrations, the two dominant polymers in respiratory mucus, alter the antibiotic tolerance of P. aeruginosa . Our results demonstrate that polymer concentration and molecular weight affect P. aeruginosa survival post antibiotic challenge. Polymer-driven antibiotic tolerance was not explicitly associated with reduced antibiotic diffusion. Lastly, we established a robust and standardized in vitro model for recapitulating the ex vivo antibiotic tolerance of P. aeruginosa observed in expectorated sputum across age, underlying MAD etiology, and disease severity, which revealed the inherent variability in intrinsic antibiotic tolerance of host-evolved P. aeruginosa populations.

Importance

Antibiotic treatment failure in Pseudomonas aeruginosa chronic lung infections is associated with increased morbidity and mortality, illustrating the clinical challenge of bacterial infection control. Understanding the underlying infection environment, as well as the host and bacterial factors driving antibiotic tolerance and the ability to accurately recapitulate these factors in vitro , is crucial for improving antibiotic treatment outcomes. Here, we demonstrate that increasing concentration and molecular weight of mucin and host eDNA drive increased antibiotic tolerance to tobramycin. Through systematic testing and modeling, we identified a biologically relevant in vitro condition that recapitulates antibiotic tolerance observed in ex vivo treated sputum. Ultimately, this study revealed a dominant effect of in vivo evolved bacterial populations in defining inter-subject ex vivo antibiotic tolerance and establishes a robust and translatable in vitro model for therapeutic development.

The Status of Carbapenem Resistance in Cystic Fibrosis: A Systematic Review and Meta-Analysis

Background: Antibiotic resistance in cystic fibrosis (CF) is a well-known phenomenon. However, the comprehensive epidemiological impact of antibiotic resistance in CF is not clearly documented. So, this meta-analysis evaluated the proportion rates of carbapenem resistance (imipenem, meropenem, and doripenem) in CF based on publication date (1979-2000, 2001-2010, and 2011-2021), continents, pathogens, and antimicrobial susceptibility testing (AST). Methods: We searched studies in PubMed, Scopus, and Web of Science (until April 2021). Statistical analyses were conducted using STATA software (version 14.0). Results: The 110 studies included in the analysis were performed in 25 countries and investigated 13,324 pathogens associated with CF. The overall proportion of imipenem, meropenem, and doripenem resistance in CF were 43% (95% CI 36-49), 48% (95% CI 40-57), 28% (95% CI 23-33), and 45% (95% CI 32-59), respectively. Our meta-analysis showed that trends of imipenem, meropenem, and doripenem-resistance had gradual decreases over time (1979-2021). This could be due to the limited clinical effectiveness of these antibiotics to treat CF cases over time. Among the opportunistic pathogens associated with CF, the highest carbapenem resistance rates were shown in Stenotrophomonas maltophilia, Burkholderia spp., Pseudomonas aeruginosa, and Staphylococcus aureus. The highest and lowest carbapenem resistance rates among P. aeruginosa in CF patients were shown against meropenem (23%) and doripenem (39%). Conclusions: We showed that trends of carbapenem resistance had decreased over time (1979-2021). This could be due to the limited clinical effectiveness of these antibiotics to treat CF cases over time. Plans should be directed to fight biofilm-associated infections and prevent the emergence of mutational resistance. Systematic surveillance for carbapenemase-producing pathogens in CF by molecular surveillance is necessitated.

Establishing antimicrobial susceptibility testing methods and clinical breakpoints for inhaled antibiotic therapy

Inhaled antibiotics are a common and valuable therapy for patients suffering from chronic lung infection, with this particularly well demonstrated for patients with cystic fibrosis. However, in vitro tests to predict patient response to inhaled antibiotic therapy are currently lacking. There are indications that antimicrobial susceptibility testing (AST) may have a role in guidance of therapy, but which tests would correlate best still needs to be researched in clinical studies or animal models. Applying the principles of European Committee on Antimicrobial Susceptibility Testing methodology, the analysis of relevant and reliable data correlating different AST tests to patients’ outcomes may yield clinical breakpoints for susceptibility, but these data are currently unavailable. At present, we believe that it is unlikely that standard determination of minimum inhibitory concentration will prove the best predictor.

Defining antimicrobial resistance in cystic fibrosis

Antimicrobial resistance (AMR) can present significant challenges in the treatment of cystic fibrosis (CF) lung infections. In CF and other chronic diseases, AMR has a different profile and clinical consequences compared to acute infections and this requires different diagnostic and treatment approaches. This review defines AMR, explains how it occurs, describes the methods used to measure AMR as well as their limitations, and concludes with future directions for research and development in the area of AMR in CF.

Evolution of the Pseudomonas aeruginosa Aminoglycoside Mutational Resistome In Vitro and in the Cystic Fibrosis Setting

Inhaled administration of high doses of aminoglycosides is a key maintenance treatment of Pseudomonas aeruginosa chronic respiratory infections in cystic fibrosis (CF). We analyzed the dynamics and mechanisms of stepwise high-level tobramycin resistance development in vitro and compared the results with those of isogenic pairs of susceptible and resistant clinical isolates. Resistance development correlated with fusA1 mutations in vitro and in vivo. pmrB mutations, conferring polymyxin resistance, were also frequently selected in vitro In contrast, mutational overexpression of MexXY, a hallmark of aminoglycoside resistance in CF, was not observed in in vitro evolution experiments.

Relevance of multidrug-resistant Pseudomonas aeruginosa infections in cystic fibrosis

Multidrug-resistant (MDR) Pseudomonas aeruginosa is an important issue for physicians who take care of patients with cystic fibrosis (CF). Here, we review the latest research on how P. aeruginosa infection causes lung function to decline and how several factors contribute to the emergence of antibiotic resistance in P. aeruginosa strains and influence the course of the infection course. However, many aspects of the practical management of patients with CF infected with MDR P. aeruginosa are still to be established. Less is known about the exact role of susceptibility testing in clinical strategies for dealing with resistant infections, and there is an urgent need to find a tool to assist in choosing the best therapeutic strategy for MDR P. aeruginosa infection. One current perception is that the selection of antibiotic therapy according to antibiogram results is an important component of the decision-making process, but other patient factors, such as previous infection history and antibiotic courses, also need to be evaluated. On the basis of the known issues and the best current data on respiratory infections caused by MDR P. aeruginosa, this review provides practical suggestions to optimize the diagnostic and therapeutic management of patients with CF who are infected with these pathogens.

Inhaled Antibiotics for Gram-Negative Respiratory Infections

Gram-negative organisms comprise a large portion of the pathogens responsible for lower respiratory tract infections, especially those that are nosocomially acquired, and the rate of antibiotic resistance among these organisms continues to rise. Systemically administered antibiotics used to treat these infections often have poor penetration into the lung parenchyma and narrow therapeutic windows between efficacy and toxicity. The use of inhaled antibiotics allows for maximization of target site concentrations and optimization of pharmacokinetic/pharmacodynamic indices while minimizing systemic exposure and toxicity. This review is a comprehensive discussion of formulation and drug delivery aspects, in vitro and microbiological considerations, pharmacokinetics, and clinical outcomes with inhaled antibiotics as they apply to disease states other than cystic fibrosis. In reviewing the literature surrounding the use of inhaled antibiotics, we also highlight the complexities related to this route of administration and the shortcomings in the available evidence. The lack of novel anti-Gram-negative antibiotics in the developmental pipeline will encourage the innovative use of our existing agents, and the inhaled route is one that deserves to be further studied and adopted in the clinical arena.

Antimicrobial activity of mul-1867, a novel antimicrobial compound, against multidrug-resistant Pseudomonas aeruginosa

Background

There is an urgent need for new antimicrobial compounds to treat various lung infections caused by multidrug-resistant Pseudomonas aeruginosa (MDR-PA).

Methods

We studied the potency of Mul-1867 against MDR-PA isolates from patients with cystic fibrosis, chronic obstructive pulmonary disease, and ventilator-associated pneumonia. The minimal inhibitory concentrations (MICs) and minimum biofilm eliminating concentrations (MBECs), defined as the concentrations of drug that kill 50 % (MBEC₅₀), 90 % (MBEC₉₀), and 100 % (MBEC₁₀₀) of the bacteria in preformed biofilms, were determined by using the broth macrodilution method.

Results

Mul-1867 exhibited significant activity against MDR-PA and susceptible control strains, with MICs ranging from 1.0 to 8.0 µg/mL. Mul-1867 also possesses anti-biofilm activity against mucoid and non-mucoid 24-h-old MDR-PA biofilms. The MBEC₅₀ value was equal to onefold the MIC. The MBEC₉₀ value ranged from two to fourfold the MIC. Moreover, Mul-1867 completely eradicated mature biofilms at the concentrations tested, with MBEC₁₀₀ values ranging between 16- and 32-fold the MIC. Mul-1867 was non-toxic to Madin-Darby canine kidney (MDCK) cells at concentrations up to 256 µg/mL.

Conclusion

Overall, these data indicate that Mul-1867 is a promising locally acting antimicrobial for the treatment and prevention of P. aeruginosa infections.

Pharmacokinetic and pharmacodynamic implications in inhalable antimicrobial therapy

Inhaled antimicrobials provide a promising alternative to the systemically delivered drugs for the treatment of acute and chronic lung infections. The delivery of antimicrobials via inhalation route decreases the systemic exposure while increasing the local concentration in the lungs, enabling the use of antimicrobials with severe systemic side effects. The inhalation route of administration has several challenges in pharmacokinetic (PK) and pharmacodynamic (PD) assessments. This review discusses various issues that need to be considered during study, data analysis, and interpretation of PK and PD of inhaled antimicrobials. Advancements overcoming the challenges are also discussed.

Evidence of inhaled tobramycin in non-cystic fibrosis bronchiectasis

There is currently less experience with inhaled tobramycin in non-cystic fibrosis bronchiectasis than in cystic fibrosis (CF). Intravenous formulation and solution for inhalation (TSI) have been studied in non-CF bronchiectasis patients with chronic P. aeruginosa bronchial infection. An improvement in clinical parameters and a reduction in bacterial density have been shown with both inhaled solutions in these patients. However, further trials are needed to determine the most effective dose and administration protocol in these patients. Based on the current evidence, recommendations cannot be made regarding the use of TSI to treat exacerbations. Although no systemic toxicity has been reported in studies specifically investigating this treatment, patients with known kidney disease or ear disorders should be treated with caution. Adverse respiratory effects are reported to be more common in non-CF patients than in CF patients, who tend to be non-smokers and younger. Research is being conducted into the possibility of combining tobramycin with other antibiotics to increase its antibacterial activity. In this review we will present and discuss the published evidence regarding the use of inhaled tobramycin in non-CF bronchiectasis.

Azithromycin may antagonize inhaled tobramycin when targeting Pseudomonas aeruginosa in cystic fibrosis

RATIONALE

Recent studies of inhaled tobramycin in subjects with cystic fibrosis (CF) find less clinical improvement than previously observed. Nonhuman data suggest that in some strains of Pseudomonas aeruginosa, azithromycin can antagonize tobramycin.

OBJECTIVES

We tested the hypothesis that concomitant azithromycin use correlates with less improvement in key outcome measures in subjects receiving inhaled tobramycin while not affecting those receiving a comparative, nonaminoglycoside inhaled antibiotic.

METHODS

We studied a cohort of 263 subjects with CF enrolled in a recent clinical trial comparing inhaled tobramycin with aztreonam lysine. We performed a secondary analysis to examine key clinical and microbiologic outcomes based on concomitant, chronic azithromycin use at enrollment.

MEASUREMENTS AND MAIN RESULTS

The cohort randomized to inhaled tobramycin and reporting azithromycin use showed a significant decrease in the percent predicted FEV1 after one and three courses of inhaled tobramycin when compared with those not reporting azithromycin use (28 d: -0.51 vs. 3.43%, P < 0.01; 140 d: -1.87 vs. 6.07%, P < 0.01). Combined azithromycin and inhaled tobramycin use was also associated with earlier need for additional antibiotics, lesser improvement in disease-related quality of life, and a trend toward less reduction in sputum P. aeruginosa density. Subjects randomized to inhaled aztreonam lysine had significantly greater improvement in these outcome measures, which were unaffected by concomitant azithromycin use. Outcomes in those not using azithromycin who received inhaled tobramycin were not significantly different from subjects receiving aztreonam lysine. Azithromycin also antagonized tobramycin but not aztreonam lysine in 40% of P. aeruginosa clinical isolates tested in vitro.

CONCLUSIONS

Oral azithromycin may antagonize the therapeutic benefits of inhaled tobramycin in subjects with CF with P. aeruginosa airway infection.

Long-term efficacy and safety of aerosolized tobramycin 300 mg/4 ml in cystic fibrosis

INTRODUCTION

Aerosolized tobramycin is a standard of care for chronic Pseudomonas aeruginosa (Pa) infection in patients with cystic fibrosis (CF).

OBJECTIVES

The long-term safety and efficacy of intermittent (28-day "on"/"off" cycles) inhaled tobramycin nebulization solution 300 mg/4 ml (TNS4, Bramitob(®)/Bethkis(®)) was assessed over 56 weeks in CF patients aged ≥6 years having baseline 1 sec forced expiratory volume (FEV(1)) 40-80% predicted.

METHODS

Patients were initially randomized in an 8-week open-label trial (core phase) to compare TNS4 (N = 159) and tobramycin 300 mg/5 ml (TNS5, TOBI(®)) (N = 165). A subset of patients continued in a 48-week, single-arm extension receiving TNS4 only. The primary endpoint of the core phase was to demonstrate the non-inferiority of TNS4 compared to TNS5 in terms of absolute change from baseline to week 4 in FEV(1) % predicted. The assessment of long-term safety was the primary purpose of the extension phase. Throughout all phases of the study, microbiological assessments, adverse events, and audiometry findings were also evaluated.

RESULTS

In the core phase (N = 321), FEV(1) (% predicted) increased from baseline (absolute change) following a single on-treatment cycle for both TNS4 (7.0%) and TNS5 (7.5%) and the non-inferiority between treatments was met [difference between treatments of -0.5 (95% CI: -2.6; 1.6)]. These improvements were maintained throughout the extension phase (N = 209), ranging throughout the study between 5.1% (95% CI: 3.2; 6.9) and 8.1% (95% CI: 6.8; 9.4) compared to baseline. Pa sputum count reductions ranged between 0.6 (95% CI: 0.2; 0.9) to 2.3 (95% CI: 2.0; 2.6) log10 CFU/g throughout the 56 weeks. No remarkable safety issues were identified throughout both study phases, with similar percentages of patients reporting adverse events in the two treatment groups during the 8-week core phase [TNS4 (31.4%); TNS5 (28.0%)].

CONCLUSIONS

Overall, TNS4 demonstrated short-term clinical benefits similar to TNS5 which were maintained during the long-term use of TNS4 and was also associated with a favorable tolerability profile.

Pharmacokinetics and pharmacodynamics of aerosolized antibacterial agents in chronically infected cystic fibrosis patients

Bacteria adapt to growth in lungs of patients with cystic fibrosis (CF) by selection of heterogeneously resistant variants that are not detected by conventional susceptibility testing but are selected for rapidly during antibacterial treatment. Therefore, total bacterial counts and antibiotic susceptibilities are misleading indicators of infection and are not helpful as guides for therapy decisions or efficacy endpoints. High drug concentrations delivered by aerosol may maximize efficacy, as decreased drug susceptibilities of the pathogens are compensated for by high target site concentrations. However, reductions of the bacterial load in sputum and improvements in lung function were within the same ranges following aerosolized and conventional therapies. Furthermore, the use of conventional pharmacokinetic/pharmacodynamic (PK/PD) surrogates correlating pharmacokinetics in serum with clinical cure and presumed or proven eradication of the pathogen as a basis for PK/PD investigations in CF patients is irrelevant, as minimization of systemic exposure is one of the main objectives of aerosolized therapy; in addition, bacterial pathogens cannot be eradicated, and chronic infection cannot be cured. Consequently, conventional PK/PD surrogates are not applicable to CF patients. It is nonetheless obvious that systemic exposure of patients, with all its sequelae, is minimized and that the burden of oral treatment for CF patients suffering from chronic infections is reduced.

Tobramycin Inhalation Powder (TIP): An Efficient Treatment Strategy for the Management of Chronic Pseudomonas Aeruginosa Infection in Cystic Fibrosis

Repeated bouts of acute and chronic lung infections are responsible for progressive pulmonary function decline in individuals with cystic fibrosis (CF), ultimately leading to respiratory failure and death. Pseudomonas aeruginosa is the archetypical CF pathogen, causes chronic infection in 70% of individuals, and is associated with an accelerated clinical decline. The management of P. aeruginosa in CF has been revolutionized with the development and widespread use of inhaled antibiotics. Aerosol delivery of antimicrobial compounds in CF enables extremely high concentrations of antibiotics to be reached directly at the site of infection potentially overcoming adaptive resistance and avoiding the potential for cumulative systemic toxicities. Tobramycin inhalation powder (TIP) represents the first dry powder inhaled (DPI) antibiotic available for use in CF. DPIs are notable for a markedly reduced time for administration, ease of portability, and increased compliance. TIP has been developed as a therapeutic alternative to tobramycin inhalation solution (TIS), the standard of care for the past 20 years within CF. Relative to TIS 300 mg nebulized twice daily in on-and-off cycles of 28 days duration, TIP 112 mg twice daily via the T-326 inhaler administered on the same schedule is associated with marked time savings, increased patient satisfaction, and comparable clinical end points. TIP represents an innovative treatment strategy for those individuals with CF and holds the promise of increased patient compliance and thus the potential for improved clinical outcomes.

New advances in the therapy of non-cystic fibrosis bronchiectasis

Non-cystic fibrosis bronchiectasis remains a common and important respiratory disease to date. It is a chronic pathology and consequently the patients usually require continuous treatment. In recent decades therapies that do not have scientific evidence of their benefits have been commonly used in non-cystic fibrosis bronchiectasis. Cystic fibrosis has provided the experience to extrapolate therapeutic approaches to other bronchiectasis patients. Finally, in the last few years some trials have been carried out specifically in non-cystic fibrosis bronchiectasis which aim to assess the efficacy of some of the treatments which are commonly used but sometimes without clear indication. This review will discuss the recent results from these trials, namely mucoactive, anti-inflammatory and antibiotic therapy. Several trials are ongoing and we hope they will be able to add clarification to the management of these patients.

Global fluoroquinolone resistance epidemiology and implictions for clinical use

This paper on the fluoroquinolone resistance epidemiology stratifies the data according to the different prescription patterns by either primary or tertiary caregivers and by indication. Global surveillance studies demonstrate that fluoroquinolone resistance rates increased in the past years in almost all bacterial species except S. pneumoniae and H. influenzae, causing community-acquired respiratory tract infections. However, 10 to 30% of these isolates harbored first-step mutations conferring low level fluoroquinolone resistance. Fluoroquinolone resistance increased in Enterobacteriaceae causing community acquired or healthcare associated urinary tract infections and intraabdominal infections, exceeding 50% in some parts of the world, particularly in Asia. One to two-thirds of Enterobacteriaceae producing extended spectrum β-lactamases were fluoroquinolone resistant too. Furthermore, fluoroquinolones select for methicillin resistance in Staphylococci. Neisseria gonorrhoeae acquired fluoroquinolone resistance rapidly; actual resistance rates are highly variable and can be as high as almost 100%, particularly in Asia, whereas resistance rates in Europe and North America range from <10% in rural areas to >30% in established sexual networks. In general, the continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some guidelines, for example, treatment of urinary tract, intra-abdominal, skin and skin structure infections, and traveller's diarrhea, or even precludes the use in indications like sexually transmitted diseases and enteric fever.

Challenges with current inhaled treatments for chronic Pseudomonas aeruginosa infection in patients with cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa (Pa) is the predominant pathogen infecting the airways of patients with cystic fibrosis (CF). Initial colonization is usually transient and associated with non-mucoid strains, which can be eradicated if identified early. This strategy can prevent, or at least delay, chronic Pa infection, which eventually develops in the majority of patients by their late teens or early adulthood. This article discusses the management and latest treatment developments of Pa lung infection in patients with CF, with a focus on nebulized antibiotic therapy.

METHODS

PubMed was searched to identify English language articles published up until August 2011 using combinations of the following key words: 'antibiotics', 'chronic', 'cystic fibrosis', 'eradication', 'exacerbations', 'guidelines', 'inhaled', 'intravenous', 'lung infection', 'burden', 'adherence', 'patient segregation', 'pseudomonas aeruginosa' and 'resistance'.

FINDINGS

Antibiotics form a central part of the treatment regimens for chronic Pa lung infection. Current treatment guidelines recommend that patients with chronic pulmonary infection with Pa should receive long-term inhaled anti-pseudomonal therapy to preserve lung function, and to reduce the frequency of pulmonary exacerbations and hospital admissions. While antibiotic resistance seems to increase with frequent antibiotic use, this does not appear to impact on clinical outcome. Negative aspects of therapy include the time needed for drug administration and subsequent cleaning of the equipment. These factors cause a significant treatment burden and impact on adherence. The availability of more convenient formulations and delivery vehicles for anti-pseudomonal antibiotics may help overcome some of these challenges.

CONCLUSIONS

Current challenges in the management of CF patients with chronic Pa lung infection are numerous. The availability of novel anti-pseudomonal antibiotic formulations/devices is anticipated to improve treatment adherence in patients with CF, and could improve clinical outcomes. Thus, there is hope for improved survival in individuals with CF suffering from chronic pulmonary infection with Pa.

Outpatient treatment of Pseudomonas aeruginosa bronchial colonization with long-term inhaled colistin, tobramycin, or both in adults without cystic fibrosis

STUDY OBJECTIVE

To compare clinical and microbiologic outcomes in adults without cystic fibrosis who had Pseudomonas aeruginosa bronchial colonization and were receiving inhaled colistin or colistin plus tobramycin with those who were receiving inhaled tobramycin as outpatient treatment.

DESIGN

Prospective, observational cohort study.

SETTING

Referral pneumology service at a tertiary university care hospital.

PATIENTS

Eighty-one Caucasian adults without cystic fibrosis who received 97 courses of inhaled colistin alone, colistin plus tobramycin, or inhaled tobramycin alone as outpatient treatment of P. aeruginosa bronchial colonization between January 2004 and December 2008.

MEASUREMENTS AND MAIN RESULTS

The frequency and duration of hospitalizations for respiratory exacerbations were the primary outcomes compared among treatment groups. Secondary outcomes were emergence of bacterial resistance, antibiotic use during admission, emergence of other opportunistic microorganisms, achievement of sustained P. aeruginosa eradication in the airways, and mortality, as well as safety and changes in respiratory function. No significant differences between colistin and tobramycin were found in the mean number of hospital admissions, duration of hospitalizations, duration of antibiotic treatment, adverse events, mortality, or emergence of other opportunistic microorganisms. Emergence of resistance to colistin was lower than resistance to tobramycin (hazard ratio 0.09, 95% confidence interval [CI] 0.03-0.32). Patients treated with both inhaled antibiotics had fewer days of hospitalization and fewer days of antibiotic use than those treated with tobramycin alone (relative risk [RR] 0.33, 95% CI 0.10-1.12, and RR 0.27, 95% CI 0.08-0.93, respectively).

CONCLUSION

Results with colistin were similar to those with tobramycin for inhaled treatment of P. aeruginosa colonization in this population; however, combined use of colistin and tobramycin appeared to be associated with fewer days of hospitalization and shorter duration of antibiotic treatment. Prospective, double-blind, placebo-controlled trials of outpatient nebulized antibiotics, especially colistin plus tobramycin, should be performed to ascertain the efficacy of this therapy for treatment of P. aeruginosa colonization in patients without cystic fibrosis.

Early Pseudomonas aeruginosa infection in individuals with cystic fibrosis: is susceptibility testing justified?

OBJECTIVES

To test the presumption that Pseudomonas aeruginosa isolates responsible for initial lung infection in individuals with cystic fibrosis (CF) are invariably susceptible to antipseudomonal agents.

METHODS

Antibiotic susceptibility was determined (MIC and Etest) in two populations of P. aeruginosa associated with initial lung infection. Population 1: environmental isolates (n=78). Population 2: clinical isolates responsible for first infection in previously non-infected patients (85 isolates from 85 patients). Susceptibility or resistance was determined using current BSAC guidelines; ninth version (2009).

RESULTS

The majority (≥ 90%) of isolates in both bacterial populations were susceptible to the front-line antipseudomonal agents; colistin, ciprofloxacin, tobramycin, ceftazidime, amikacin and meropenem. Up to 10% of isolates were resistant to one or more antibiotics. A single isolate from each population would be defined as resistant to tobramycin based on a breakpoint (>128 mg/L) that has been suggested for use in patients receiving inhaled therapy.

CONCLUSIONS

The high prevalence of susceptibility found in P. aeruginosa isolates associated with initial infection contrasts with the high prevalence of resistance found in isolates from chronic CF lung infection. However, susceptibility in early isolates cannot be presumed. Until further data are obtained from clinically based studies, susceptibility tests should continue to be performed to assist the choice of antibiotics for treatment of early infection.

Inhaled therapeutics for prevention and treatment of pneumonia

The lungs are the most common site of serious infection owing to their large surface area exposed to the external environment and minimum barrier defense. However, this architecture makes the lungs readily available for topical therapy. Therapeutic aerosols include those directed towards improving mucociliary clearance of pathogens, stimulation of innate resistance to microbial infection, cytokine stimulation of immune function and delivery of antibiotics. In our opinion inhaled antimicrobials are underused, especially in patients with difficult-to-treat lung infections. The use of inhaled antimicrobial therapy has become an important part of the treatment of airway infection with Pseudomonas aeruginosa in cystic fibrosis and the prevention of invasive fungal infection in patients undergoing heart and lung transplantation. Cytokine inhaled therapy has also been explored in the treatment of neoplastic and infectious disease. The choice of pulmonary drug delivery systems remains critical as air-jet and ultrasonic nebulizer may deliver sub-optimum drug concentration if not used properly. In future development of this field, we recommend an emphasis on the study of the use of aerosolized hypertonic saline solution to reduce pathogen burden in the airways of subjects infected with microbes of low virulence, stimulation of innate resistance to prevent pneumonia in immunocompromised subjects using cytokines or synthetic pathogen-associated molecular pattern analogues and more opportunities for the use of inhaled antimicrobials. These therapeutics are still in their infancy but show great promise.

Unorthodox long-term aerosolized ampicillin use for methicillin-susceptible Staphylococcus aureus lung infection in a cystic fibrosis patient

Staphylococcus aureus is a significant cause of pulmonary colonization in cystic fibrosis (CF) patients. The optimal strategy of therapy in chronically infected patients with this pathogen is not yet established. We report a successful long-term aerosolized ampicillin treatment of a 14-year-old girl with chronic symptomatic S. aureus lung infection.

[Microbiological diagnosis of bronchopulmonary colonization-infection in cystic fibrosis]

Cystic fibrosis (CF), a condition produced by mutations in the gene that encodes the cystic fibrosis transmembrane conductance regulator, is the most prevalent autosomal-recessive hereditary disease in caucasian populations. Among other repercussions, this defect leads to an alteration of respiratory secretions and determines a predisposition for chronic bronchopulmonary colonization-infection, which is the main driver of the high morbidity and early mortality of CF patients. Colonization by Staphylococcus aureus and Haemophilus influenzae is frequent in children younger than 10 years, but mucoid Pseudomonas aeruginosa is by far the most relevant pathogen in adults with CF and is responsible for the progressive bronchopulmonary deterioration. As a consequence of repeated, long-lasting antimicrobial treatments and deterioration of lung function, colonization by multidrug-resistant Gram-negative bacilli, such as Stenotrophomonas maltophilia, Achromobacter spp. and Burkholderia cepacia complex, is also frequent in adult CF patients. The special characteristics of the pathologic process and the microorganisms implicated in CF make it advisable to consider microbiological follow-up of chronic bronchopulmonary colonization-infection in these patients a specific diagnostic entity.

Microbiological diagnostic procedures in respiratory infections: suppurative lung disease

Pursuing a microbiological diagnosis in suppurative lung disease can enable focused antibiotic therapy, identify pathogens of potential concern for infection control, and in some cases delineate a specific pathological process. Suppurative lung disease can be categorized as acute or chronic. Acute disease most commonly consists of lung abscess or parapneumonic empyema. The vast majority of chronic suppurative lung disease in childhood is due to cystic fibrosis. Samples from the respiratory tract offer the most useful information for diagnosis and management, but adjunctive information can also be obtained from serological methods, blood cultures and molecular techniques. The quality of respiratory tract samples is vital to aid accurate interpretation of results, and this varies according to the technique of collection. Antibiotic sensitivity testing is of particular importance in an era of evolving antibiotic resistance and can be problematical in cystic fibrosis.

Tobramycin solution for inhalation in cystic fibrosis patients: a review of the literature

Cystic fibrosis patients suffer increased sputum production and a notable decline in respiratory function throughout the progression of their disease. Patients are left vulnerable to respiratory colonization/infection from a number of pathogens, including Pseudomonas aeruginosa. At present, the only antibiotic formulation that is FDA approved for aerosolized delivery is tobramycin solution for inhalation (TSI). TSI allows for targeted antibiotic delivery to the lungs and is indicated for maintenance therapy in cystic fibrosis patients infected with P. aeruginosa. Studies demonstrate that cyclical treatment with TSI is associated with an increase in respiratory function and a decrease in sputum density in cystic fibrosis patients. Additional benefits include fewer hospitalizations and a decreased need for systemic antibiotics. However, because of the need for chronic administration, issues such as emergence of resistant organisms and toxicity are a potential concern and have also been evaluated. This review details the pharmacology of TSI and literature involving its use in cystic fibrosis patients.