Outcomes of Adults with Cystic Fibrosis Infected with Antibiotic-Resistant Pseudomonas aeruginosa

Inhaled antibiotics: A promising drug delivery strategies for efficient treatment of lower respiratory tract infections (LRTIs) associated with antibiotic resistant biofilm-dwelling and intracellular bacterial pathogens

Antibiotic-resistant bacteria associated with LRTIs are frequently associated with inefficient treatment outcomes. Antibiotic-resistant Streptococcus pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, and Staphylococcus aureus, infections are strongly associated with pulmonary exacerbations and require frequent hospital admissions, usually following failed management in the community. These bacteria are difficult to treat as they demonstrate multiple adaptational mechanisms including biofilm formation to resist antibiotic threats. Currently, many patients with the genetic disease cystic fibrosis (CF), non-CF bronchiectasis (NCFB) and chronic obstructive pulmonary disease (COPD) experience exacerbations of their lung disease and require high doses of systemically administered antibiotics to achieve meaningful clinical effects, but even with high systemic doses penetration of antibiotic into the site of infection within the lung is suboptimal. Pulmonary drug delivery technology that reliably deliver antibacterials directly into the infected cells of the lungs and penetrate bacterial biofilms to provide therapeutic doses with a greatly reduced risk of systemic adverse effects. Inhaled liposomal-packaged antibiotic with biofilm-dissolving drugs offer the opportunity for targeted, and highly effective antibacterial therapeutics in the lungs. Although the challenges with development of some inhaled antibiotics and their clinicals trials have been studied; however, only few inhaled products are available on market. This review addresses the current treatment challenges of antibiotic-resistant bacteria in the lung with some clinical outcomes and provides future directions with innovative ideas on new inhaled formulations and delivery technology that promise enhanced killing of antibiotic-resistant biofilm-dwelling bacteria.

Ceftolozane-Tazobactam against Pseudomonas aeruginosa Cystic Fibrosis Clinical Isolates in the Hollow-Fiber Infection Model: Challenges Imposed by Hypermutability and Heteroresistance

Pseudomonas aeruginosa remains a challenge in chronic respiratory infections in cystic fibrosis (CF). Ceftolozane-tazobactam has not yet been evaluated against multidrug-resistant hypermutable P. aeruginosa isolates in the hollow-fiber infection model (HFIM). Isolates CW41, CW35, and CW44 (ceftolozane-tazobactam MICs of 4, 4, and 2 mg/L, respectively) from adults with CF were exposed to simulated representative epithelial lining fluid pharmacokinetics of ceftolozane-tazobactam in the HFIM. Regimens were continuous infusion (CI; 4.5 g/day to 9 g/day, all isolates) and 1-h infusions (1.5 g every 8 hours and 3 g every 8 hours, CW41). Whole-genome sequencing and mechanism-based modeling were performed for CW41. CW41 (in four of five biological replicates) and CW44 harbored preexisting resistant subpopulations; CW35 did not. For replicates 1 to 4 of CW41 and CW44, 9 g/day CI decreased bacterial counts to <3 log10 CFU/mL for 24 to 48 h, followed by regrowth and resistance amplification. Replicate 5 of CW41 had no preexisting subpopulations and was suppressed below ~3 log10 CFU/mL for 120 h by 9 g/day CI, followed by resistant regrowth. Both CI regimens reduced CW35 bacterial counts to <1 log10 CFU/mL by 120 h without regrowth. These results corresponded with the presence or absence of preexisting resistant subpopulations and resistance-associated mutations at baseline. Mutations in ampC, algO, and mexY were identified following CW41 exposure to ceftolozane-tazobactam at 167 to 215 h. Mechanism-based modeling well described total and resistant bacterial counts. The findings highlight the impact of heteroresistance and baseline mutations on the effect of ceftolozane-tazobactam and limitations of MIC to predict bacterial outcomes. The resistance amplification in two of three isolates supports current guidelines that ceftolozane-tazobactam should be utilized together with another antibiotic against P. aeruginosa in CF.

Novel Applications of Biomarkers and Personalized Medicine in Cystic Fibrosis

As routine care in cystic fibrosis (CF) becomes increasingly personalized, new opportunities to further focus care on the individual have emerged. These opportunities are increasingly filled through research in tools aiding drug selection, drug monitoring and titration, disease-relevant biomarkers, and evaluation of therapeutic benefits. Herein, we will discuss such research tools presently being translated into the clinic to improve the personalization of care in CF.

Adaptation and Evolution of Pathogens in the Cystic Fibrosis Lung

As opposed to acute respiratory infections, the persistent bacterial infections of the lung that characterize cystic fibrosis (CF) provide ample time for bacteria to evolve and adapt. The process of adaptation is recorded in mutations that accumulate over time in the genomes of the infecting bacteria. Some of these mutations lead to obvious phenotypic differences such as antibiotic resistance or the well-known mucoid phenotype of Pseudomonas aeruginosa. Other mutations may be just as important but harder to detect such as increased mutation rates, cell surface changes, and shifts in metabolism and nutrient acquisition. Remarkably, many of the adaptations occur again and again in different patients, signaling that bacteria are adapting to solve specific challenges in the CF respiratory tract. This parallel evolution even extends across distinct bacterial species. This review addresses the bacterial systems that are known to change in long-term CF infections with a special emphasis on cross-species comparisons. Consideration is given to how adaptation may impact health in CF, and the possible evolutionary mechanisms that lead to the repeated parallel adaptations.

Recipient Management before Lung Transplantation

Lung transplantation is considered a viable treatment option for patients with end-stage lung disease. Recent decades have seen a gradual increase in the number of lung transplantation patients worldwide, and in South Korea, the case number has increased at least 3-fold during the last decade. Furthermore, the waiting list time is becoming longer, and more elderly patients (>65 years) are undergoing lung transplantation; that is, the patients placed on the waiting list are older and sicker than in the past. Hence, proper management during the pre-transplantation period, as well as careful selection of candidates, is a key factor for transplant success and patient survival. Although referring and transplant centers should address many issues, the main areas of focus should be the timing of referral, nutrition, pulmonary rehabilitation, critical care (including mechanical ventilation and extracorporeal membrane oxygenation), psychological support, and the management of preexisting comorbid conditions (coronary artery disease, diabetes mellitus, gastroesophageal reflux disease, osteoporosis, malignancy, viral infections, and chronic infections). In this context, the present article reviews and summarizes the pre-transplantation management strategies for adult patients listed for lung transplantation.

The Use of Tobramycin for Pseudomonas aeruginosa: A Review

INTRODUCTION

Pseudomonas aeruginosa is a common respiratory pathogen that contributes to chronic pulmonary infection in individuals with cystic fibrosis. Guidelines recommend early intervention upon positive P. aeruginosa culture. Tobramycin has in vitro activity against Gram-negative bacteria, including P. aeruginosa, and TOBI Podhaler is indicated for the management of individuals with cystic fibrosis with P. aeruginosa infection. The dry powder inhaler formulation decreases the time required for treatment compared with nebulized solution and therefore may improve quality of life and adherence, which have a positive impact on disease progression.

AREAS COVERED

In this review, we discuss the safety and efficacy of tobramycin inhaled powder and provide insights into appropriate individuals who might benefit from a dry powder inhaler, keeping in mind that patient preference is an important consideration for therapy selection.

EXPERT OPINION

Providing a less burdensome alternative to delivering inhaled antibiotics that is more portable with a significantly shorter administration time may help improve adherence, and therefore improve outcomes. Continued development of new antibiotics to add to current regimens for eradication and control of airway microbiology, combined with more efficient delivery systems such as tobramycin inhaled powder, will help evolve the treatment of patients with CF.

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.

Bacterial infections in lung transplantation

Lung transplantation has lower survival rates compared to other than other solid organ transplants (SOT) due to higher rates of infection and rejection-related complications, and bacterial infections (BI) are the most frequent infectious complications. Excess morbidity and mortality are not only a direct consequence of these BI, but so are subsequent loss of allograft tolerance, rejection, and chronic lung allograft dysfunction due to bronchiolitis obliterans syndrome (BOS). A wide variety of pathogens can cause infections in lung transplant recipients (LTRs), including a number of nosocomial pathogens and other multidrug-resistant (MDR) pathogens. Although pneumonia and intrathoracic infections predominate, LTRs are at risk of a number of types of infections. Risk factors include altered anatomy and function of airways, impaired immunity, the microbial flora of the donor and recipient, underlying medical conditions, and genetic factors. Further work on immune monitoring has the potential to improve outcomes. The infecting agents can be derived from the donor lung, pre-existing recipient flora, or acquired from the environment over time. Certain infections may preclude lung transplantation, but this varies from center to center, and more recent studies suggest fewer patients should be disqualified. New molecular methods allow microbiome studies of the lung, gut, and other sites that may further our knowledge of how airway colonization can result in infection and allograft loss. Surveillance, early diagnosis, and aggressive antimicrobial therapy of BI is critical in LTRs. Antibiotic resistance is a major barrier to successful management of these infections. The availability of new agents for MDR Gram-negatives may improve outcomes. Other new therapies, such as bacteriophage therapy, show promise for the future. Finally, it is important to prevent infections through peri-transplant prophylaxis, vaccination, and infection control measures.

The determinants of survival among adults with cystic fibrosis-a cohort study

BACKGROUND

Cystic fibrosis (CF) is one of the most common autosomal recessive diseases. Factors contributing to disease exacerbations and survival rate of CF patients are type of mutation in the CFTR gene, poor nutritional status, lung failure, and infection development by Pseudomonas aeruginosa. The study aimed to evaluate the relationship between the severity of mutation, nutritional status, lung function, and Pseudomonas aeruginosa prevalence and survival rate in adult patients with cystic fibrosis.

METHODS

A study of 124 (68 ♀ and 56 ♂) adults with CF aged 18-51 years were evaluated for (a) type of mutation in the CFTR gene, (b) nutritional status (BMI), (c) lung function (FEV₁%), and (d) Pseudomonas aeruginosa prevalence. For statistical calculations, Kaplan-Meier analysis of survival, chi-squared test for multiple samples, and logistic regression were used.

RESULTS

The type of mutation (χ² = 12.73, df = 3, p = 0.005), FEV₁% (χ² = 15.20, df = 2, p = 0.0005), Pseudomonas aeruginosa prevalence (χ² = 11.48, df = 3, p = 0.009), and BMI (χ² = 31.08, df = 4, p < 0.000) significantly differentiated the probability of survival of patients with CF. The shortest life expectancy was observed in patients with a severe type of mutation on both alleles, FEV₁% < 40, subjects in whom Pseudomonas culture was extensively drug-resistant or pandrug-resistant, and patients whose BMI was lower than 18.5 kg/m². The period from 30 to 40 years of age was the most critical in CF adults' lifespan. The risk of adults with CF death doubled with Pseudomonas aeruginosa prevalence (OR = 2.06, 95% CI 1.29; 2.28) and eightfold when the bacteria acquired antibiotic resistance (OR = 8.11, 95% CI 1.67; 38.15).

CONCLUSIONS

All factors included in the study were significantly related to the survival rate of patients with cystic fibrosis.

Duration of intravenous antibiotic treatment for acute exacerbations of cystic fibrosis: A systematic review: Duration of treatment for acute exacerbations of cystic fibrosis

BACKGROUND

Acute exacerbations of Cystic Fibrosis (AECF) are associated with significant morbidity. Recommendations are to treat for 2-3 weeks despite limited data. Spirometry is a measure of clinical response yet appears to plateau at 7-10 days. While durations <9 days have been associated with poorer outcomes, a duration of 10 days may be as effective as 14 days, potentially conferring advantages in terms of cost and adverse events. A 2019 Cochrane review by Abbott et al. did not identify any randomised controlled trials (RCT) comparing durations of treatment. Utilising data from non-randomised studies (NRS), we report a systematic review of intravenous antibiotic treatment, exploring changes in FEV₁ (Forced Expiratory Volume in 1 second), CRP (C-reactive protein) and peripheral WBC (white blood cell) count in studies with different treatment durations.

STUDY DESIGN AND METHODS

Systematic review of published literature following a search of MEDLINE, Embase, CINAHL and the Cochrane Clinical Trials register. Guidelines from the Preferred Reporting items for Systematic reviews and Meta-Analysis (PRISMA) and reporting Meta-analysis of Observational studies (MOOSE) statement were followed.

RESULTS

No randomised controlled trials were identified that specifically examined duration of treatment during AECF. This study included all relevant RCTs and also NRS, grouping according to study characteristics, such as length of treatment, location, year, and also characteristics of the patient population. 52 studies, comprising 79 subgroups, and 1,597 patients, were identified. Mean change (95%CI) in ppFEV₁ was 10.13 (9.21-11.05). There was no significant difference in change in ppFEV₁ for studies treating for 10-12 days; 8.85 (7.47-10.23), vs 13-15 days; 10.68 (9.53-11.82). Similar changes in CRP and WBC were seen irrespective of treatment duration.

CONCLUSION

This systematic review provides evidence that shorter durations of treatment may be associated with similar changes in FEV₁, CRP and WBC compared with longer durations.

Impact of Socioeconomic Position on Access to the U.S. Lung Transplant Waiting List in a Matched Cystic Fibrosis Cohort

Rationale: Referrals for lung transplant and transplant rates in the United States are lower than in Canada for patients with advanced cystic fibrosis (CF) lung disease. Further study of factors limiting access are needed to optimize referral and transplant for this population.Objectives: To determine the effect of socioeconomic position, while accounting for disease severity, on the likelihood of wait-listing for lung transplant in the United States.Methods: A case-control study of 3,110 patients (1,555 wait-listed, 1,555 never wait-listed) in the linked CF Foundation Patient Registry/Scientific Registry of Transplant Recipients was performed with 1:1 matching for age, forced expiratory volume in 1 second, and year. Logistic regression was performed with univariate and multivariate analyses accounting for eight clinical factors (sex, oxygen use, body mass index, hemoptysis, forced vital capacity, methicillin-resistant Staphylococcus aureus, multidrug-resistant Pseudomonas aeruginosa, and i.v. antibiotic days) and six socioeconomic factors (race, marital status, education, health insurance, median zip code income, and distance to transplant program). The CF Health Score and Socioeconomic Barrier Score were created based on summation of variables. Interactions between scores were calculated.Results: We found an inverse relationship between the probability of wait-listing and CF Health Score and Socioeconomic Barrier Score. As the CF Health Score decreased (less healthy), the probability of wait-listing increased by 69.3% from a score of 7 to 2. As the Socioeconomic Barrier Score decreased (fewer barriers), the probability of wait-listing increased by 31.7% from a score of ≥5 to 1). Regardless of illness severity, socioeconomic barriers presented an impediment to wait-listing. Individuals with higher Socioeconomic Barrier Scores accessed transplant about half as often as those with lower scores at the same level of medical severity. Analysis of interactions demonstrated a higher probability of wait-listing for individuals with moderate health severity and fewer social barriers compared with sicker individuals with more socioeconomic barriers.Conclusions: Accrual of socioeconomic barriers limits access to lung transplant irrespective of disease severity, a finding of substantial concern for patients with CF and for transplant providers. Future interventions can focus on this at-risk population early in the disease course.

Polymicrobial Interactions in the Cystic Fibrosis Airway Microbiome Impact the Antimicrobial Susceptibility of Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most dominant pathogens in cystic fibrosis (CF) airway disease and contributes to significant inflammation, airway damage, and poorer disease outcomes. The CF airway is now known to be host to a complex community of microorganisms, and polymicrobial interactions have been shown to play an important role in shaping P. aeruginosa pathogenicity and resistance. P. aeruginosa can cause chronic infections that once established are almost impossible to eradicate with antibiotics. CF patients that develop chronic P. aeruginosa infection have poorer lung function, higher morbidity, and a reduced life expectancy. P. aeruginosa adapts to the CF airway and quickly develops resistance to several antibiotics. A perplexing phenomenon is the disparity between in vitro antimicrobial sensitivity testing and clinical response. Considering the CF airway is host to a diverse community of microorganisms or 'microbiome' and that these microorganisms are known to interact, the antimicrobial resistance and progression of P. aeruginosa infection is likely influenced by these microbial relationships. This review combines the literature to date on interactions between P. aeruginosa and other airway microorganisms and the influence of these interactions on P. aeruginosa tolerance to antimicrobials.

Association Between Number of Intravenous Antipseudomonal Antibiotics and Clinical Outcomes of Pediatric Cystic Fibrosis Pulmonary Exacerbations

BACKGROUND

Pulmonary exacerbations (PEx) in people with cystic fibrosis (PwCF) are associated with significant morbidity. While standard PEx treatment for PwCF with Pseudomonas aeruginosa infection includes two IV antipseudomonal antibiotics, little evidence exists to recommend this approach. This study aimed to compare clinical outcomes of single versus double antipseudomonal antibiotic use for PEx treatment.

METHODS

Retrospective cohort study using the linked CF Foundation Patient Registry-Pediatric Health Information System dataset. PwCF were included if hospitalized between 2007-2018 and 6-21 years of age. Regression modeling accounting for repeated measures was used to compare lung function outcomes between single versus double IV antipseudomonal antibiotic regimens using propensity-score weighting to adjust for relevant confounding factors.

RESULTS

Among 10,660 PwCF in the dataset, we analyzed 2,578 PEx from 1,080 PwCF, of which 455 and 2,123 PEx were treated with 1 versus 2 IV antipseudomonal antibiotics, respectively. We identified no significant differences between PEx treated with 1 versus 2 IV antipseudomonal antibiotics either in change between pre- and post-PEx percent predicted forced expiratory volume in one second (ppFEV1) (-0.84%, [95% CI -2.25, 0.56]; p=0.24), odds of returning to ≥90% of baseline ppFEV1 within 3 months following PEx (Odds Ratio 0.83, [95% CI 0.61, 1.13]; p=0.24) or time to next PEx requiring IV antibiotics (Hazard Ratio 1.04, [95% CI 0.87, 1.24]; p=0.69).

CONCLUSION

Use of 2 IV antipseudomonal antibiotics for PEx treatment in young PwCF was not associated with greater improvements in measured respiratory and clinical outcomes compared to treatment with 1 IV antipseudomonal antibiotic.

New Sequence Type ST3449 in Multidrug-Resistant Pseudomonas aeruginosa Isolates from a Cystic Fibrosis Patient

Pseudomonas aeruginosa is one of the most critical bacterial pathogens associated with chronic infections in cystic fibrosis patients. Here we show the phenotypic and genotypic characterization of five consecutive multidrug-resistant isolates of P. aeruginosa collected during a month from a CF patient with end-stage lung disease and fatal outcome. The isolates exhibited distinct colony morphologies and pigmentation and differences in their capacity to produce biofilm and virulence potential evaluated in larvae of Galleria mellonella. Whole genome-sequencing showed that isolates belonged to a novel sequence type ST3449 and serotype O6. Analysis of their resistome demonstrated the presence of genes bla_OXA-396, bla_PAO, aph(3')-IIb, catB, crpP and fosA and new mutations in chromosomal genes conferring resistance to different antipseudomonal antibiotics. Genes exoS, exoT, exoY, toxA, lasI, rhlI and tse1 were among the 220 virulence genes detected. The different phenotypic and genotypic features found reveal the adaptation of clone ST3449 to the CF lung environment by a number of mutations affecting genes related with biofilm formation, quorum sensing and antimicrobial resistance. Most of these mutations are commonly found in CF isolates, which may give us important clues for future development of new drug targets to combat P. aeruginosa chronic infections.

Emergence and impact of oprD mutations in Pseudomonas aeruginosa strains in cystic fibrosis

BACKGROUND

Antimicrobial resistance in cystic fibrosis (CF) Pseudomonas aeruginosa airway infection is complex and often attributed to chromosomal mutations. How these mutations emerge in specific strains or whether particular gene mutations are clinically informative is unclear. This study focused on oprD, which encodes an outer membrane porin associated with carbapenem resistance when it is downregulated or inactivated.

AIM

Determine how mutations in oprD emerge in two prevalent Australian shared CF strains of P. aeruginosa and their clinical relevance.

METHODS

The two most common shared CF strains in Queensland were investigated using whole genome sequencing and their oprD sequences and antimicrobial resistance phenotypes were established. P. aeruginosa mutants with the most common oprD variants were constructed and characterised. Clinical variables were compared between people with or without evidence of infection with strains harbouring these variants.

RESULTS

Frequently found nonsense mutations arising from a 1-base pair substitution in oprD evolved independently in three sub-lineages, and are likely major contributors to the reduced carbapenem susceptibility observed in the clinical isolates. Lower baseline FEV₁ %predicted was identified as a risk factor for infection with a sub-lineage (odds ratio=0.97; 95% confidence interval 0.96-0.99; p<0.001). However, acquiring these sub-lineage strains did not confer an accelerated decline in FEV₁ nor increase the risk of death/lung transplantation.

CONCLUSIONS

Sub-lineages harbouring specific mutations in oprD have emerged and persisted in the shared strain populations. Infection with the sub-lineages was more likely in people with lower lung function, but this was not predictive of a worse clinical trajectory.

Approaches to Targeting Bacterial Biofilms in Cystic Fibrosis Airways

The treatment of lung infection in the context of cystic fibrosis (CF) is limited by a biofilm mode of growth of pathogenic organisms. When compared to planktonically grown bacteria, bacterial biofilms can survive extremely high levels of antimicrobials. Within the lung, bacterial biofilms are aggregates of microorganisms suspended in a matrix of self-secreted proteins within the sputum. These structures offer both physical protection from antibiotics as well as a heterogeneous population of metabolically and phenotypically distinct bacteria. The bacteria themselves and the components of the extracellular matrix, in addition to the signaling pathways that direct their behaviour, are all potential targets for therapeutic intervention discussed in this review. This review touches on the successes and failures of current anti-biofilm strategies, before looking at emerging therapies and the mechanisms by which it is hoped they will overcome current limitations.

Pulmonary Exacerbations in Adults With Cystic Fibrosis: A Grown-up Issue in a Changing Cystic Fibrosis Landscape

Pulmonary exacerbations (PExs) are significant life events in people with cystic fibrosis (CF), associated with declining lung function, reduced quality of life, hospitalizations, and decreased survival. The adult CF population is increasing worldwide, with many patients surviving prolonged periods with severe multimorbid disease. In many countries, the number of adults with CF exceeds the number of children, and PExs are particularly burdensome for adults as they tend to require longer courses and more IV treatment than children. The approach to managing PExs is multifactorial and needs to evolve to reflect this changing adult population. This review discusses PEx definitions, precipitants, treatments, and the wider implications to health-care resources. It reviews current management strategies, their relevance in particular to adults with CF, and highlights some of the gaps in our knowledge. A number of studies are underway to try to answer some of the unmet needs, such as the optimal length of treatment and the use of nonantimicrobial agents alongside antibiotics. An overview of these issues is provided, concluding that with the changing landscape of adult CF care, the definitions and management of PExs may need to evolve to enable continued improvements in outcomes across the age spectrum of CF.

Management and prophylaxis of bacterial and mycobacterial infections among lung transplant recipients

Bacterial and mycobacterial infections are associated with morbidity and mortality in lung transplant recipients. Infectious complications are categorized by timing post-transplant: <1, 1–6, and >6 months. The first month post-transplant is associated with the highest risk of infection. During this period, infections are most commonly healthcare-associated, and include infections related to surgical complications. The lungs and bloodstream are common sites of infections. Common healthcare-associated organisms include methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative bacilli such as Pseudomonas aeruginosa, and Clostridioides difficile. More than 1-month post-transplant, opportunistic infections can occur. Tuberculosis occurs in 0.8–10% of lung transplant recipients which reflects variation in background prevalence. The majority of post-transplant tuberculosis stems from reactivation of untreated or undiagnosed latent tuberculosis. Most post-transplant tuberculosis occurs in the lungs and develops within a year of transplant. Non-tuberculous mycobacteria commonly colonize the lungs of lung transplant candidates and are often hard to eradicate even with prolonged courses of antimycobacterial agents. Drug interactions between antimycobacterial agents and calcineurin and mTOR inhibitors also complicates treatment post-transplant. Given that infection adversely impacts outcomes after lung transplant, and that anti-infective therapy is often less effective after transplant, infection prevention is key to long-term success. A comprehensive approach that includes pre-transplant evaluation, perioperative prophylaxis, long-term antimicrobial prophylaxis, immunization, and safer living at home and in the community, should be employed to minimize the risk of infection.

Ultrasmall TPGS-PLGA Hybrid Nanoparticles for Site-Specific Delivery of Antibiotics into Pseudomonas aeruginosa Biofilms in Lungs

Inhaled antibiotic treatment of cystic fibrosis-related bacterial biofilm infections is challenging because of the pathological environment of the lungs. Here, we present an "environment-adaptive" nanoparticle composed of a solid poly lactic-co-glycolic acid (PLGA) core and a mucus-inert, enzymatically cleavable shell of d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) for the site-specific delivery of antibiotics to bacterial biofilms via aerosol administration. The hybrid nanoparticles with ultrasmall size were self-assembled via a nanoprecipitation process by using a facile microfluidic method. The interactions of the nanoparticles with the biological barriers were comprehensively investigated by using cutting-edge techniques (e.g., quartz crystal microbalance with dissipation monitoring, total internal reflection fluorescence microscopy-based particle tracking, in vitro biofilm model cultured in a flow-chamber system, and quantitative imaging analysis). Our results suggest that the mucus-inert, enzymatically cleavable TPGS shell enables the nanoparticles to penetrate through the mucus, accumulate in the deeper layer of the biofilms, and serve as sustained release depot, thereby improving the killing efficacy of azithromycin (a macrolide antibiotic) against biofilm-forming Pseudomonas aeruginosa. In conclusion, the ultrasmall TPGS-PLGA hybrid nanoparticles represent an efficient delivery system to overcome the multiple barriers and release antibiotics in a sustained manner in the vicinity of the biofilm-forming bacteria.

Serum-Associated Antibiotic Tolerance in Pediatric Clinical Isolates of Pseudomonas aeruginosa

BACKGROUND

When grown in human serum, laboratory isolates of Pseudomonas aeruginosa exhibit tolerance to antibiotics at inhibitory concentrations. This phenomenon, known as serum-associated antibiotic tolerance (SAT), could lead to clinical treatment failure of pseudomonal infections. Our purpose in this study was to determine the prevalence and clinical impact of SAT in Pseudomonas isolates in hospitalized children.

METHODS

The SAT phenotype was assessed in patients aged <18 years admitted with respiratory or blood cultures positive for P. aeruginosa. The SAT phenotype was a priori defined as a ≥2-log increase in colony-forming units when grown in human serum compared with Luria-Bertani medium in the presence of minocycline or tobramycin.

RESULTS

SAT was detected in 29 (64%) patients. Fourteen patients each (34%) had cystic fibrosis (CF) and tracheostomies. Patient demographics and comorbidities did not differ by SAT status. Among CF patients, SAT was associated with longer duration of intravenous antibiotics (10 days vs 5 days; P < .01).

CONCLUSIONS

This study establishes that SAT exists in P. aeruginosa from human serum and may be a novel factor that contributes to differences in clinical outcomes. Future research should investigate the mechanisms that contribute to SAT in order to identify novel targets for adjunctive antimicrobial therapies.

Activity of hypothiocyanite and lactoferrin (ALX-009) against respiratory cystic fibrosis pathogens in sputum

Objectives

To determine the antimicrobial activity of ALX-009, a combination of bovine lactoferrin and hypothiocyanite, in sputum against Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc), key pathogens causing infection in the lungs of cystic fibrosis (CF) patients.

Methods

The antimicrobial activity of ALX-009 against clinical respiratory P. aeruginosa isolates was determined by time-kill assay. Sputum from CF patients was treated with ALX-009, either alone or in combination with tobramycin, and the effect on P. aeruginosa, Bcc and total sputum density was determined.

Results

Time-kill assay indicated that ALX-009 was bactericidal at 24 h against 4/4 P. aeruginosa isolates under aerobic conditions, and against 3/4 isolates under anaerobic conditions. ALX-009 was also bactericidal against P. aeruginosa in sputum samples at 6 h (n = 22/24 samples) and 24 h (n = 14/24 samples), and demonstrated significantly greater activity than tobramycin at both timepoints. Activity against Bcc in sputum samples (n = 9) was also demonstrated, but the magnitude of change in Bcc density was less than for P. aeruginosa. To determine the effect of treating sputum with two doses of ALX-009, similar to current regimens for inhaled antibiotics, aliquots of a further 10 sputum samples positive for P. aeruginosa were treated with one (t = 0 h) or two doses (t = 0 h, t = 12 h) of ALX-009; treatment with two doses resulted in bactericidal activity in 7/10 samples at 34 h compared with only 3/10 samples when treatment was with one dose.

Conclusions

ALX-009 demonstrates promise as a novel antimicrobial that could be used to decrease P. aeruginosa density in the lungs of people with CF.

Duration of intravenous antibiotic therapy in people with cystic fibrosis

BACKGROUND

Progressive lung damage from recurrent exacerbations is the major cause of mortality and morbidity in cystic fibrosis. Life expectancy of people with cystic fibrosis has increased dramatically in the last 40 years. One of the major reasons for this increase is the mounting use of antibiotics to treat chest exacerbations caused by bacterial infections. The optimal duration of intravenous antibiotic therapy is not clearly defined. Individuals usually receive intravenous antibiotics for 14 days, but treatment may range from 10 to 21 days. A shorter duration of antibiotic treatment risks inadequate clearance of infection which could lead to further lung damage. Prolonged courses of intravenous antibiotics are expensive and inconvenient. The risk of systemic side effects such as allergic reactions to antibiotics also increases with prolonged courses and the use of aminoglycosides requires frequent monitoring to minimise some of their side effects. However, some organisms which infect people with cystic fibrosis are known to be multi-resistant to antibiotics, and may require a longer course of treatment. This is an update of previously published reviews.

OBJECTIVES

To assess the optimal duration of intravenous antibiotic therapy for treating chest exacerbations in people with cystic fibrosis.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises references identified from comprehensive electronic database searches, handsearches of relevant journals, abstract books and conference proceedings. Most recent search of the Group's Cystic Fibrosis Trials Register: 30 May 2019.We also searched online trials registries. Most recent search of the ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) portal: 06 January 2019.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing different durations of intravenous antibiotic courses for acute respiratory exacerbations in people with CF, either with the same drugs at the same dosage, the same drugs at a different dosage or frequency or different antibiotics altogether, including studies with additional therapeutic agents.

DATA COLLECTION AND ANALYSIS

No eligible trials were identified for inclusion. A trial looking at the standardised treatment of pulmonary exacerbations is currently ongoing and will be included when the results are published.  MAIN RESULTS: No eligible trials were included.

AUTHORS' CONCLUSIONS

There are no clear guidelines on the optimum duration of intravenous antibiotic treatment. Duration of treatment is currently based on unit policies and response to treatment. Shorter duration of treatment should improve quality of life and adherence, result in a reduced incidence of drug reactions and be less costly. However, the shorter duration may not be sufficient to clear a chest infection and may result in an early recurrence of an exacerbation. This systematic review identifies the need for a multicentre, randomised controlled trial comparing different durations of intravenous antibiotic treatment as it has important clinical and financial implications. The currently ongoing STOP2 trial is expected to provide some guidance on these questions when published.

How does Pseudomonas aeruginosa affect the progression of bronchiectasis?

BACKGROUND

Pseudomonas aeruginosa is one of the most common pathogens isolated from respiratory tract specimen in patients with bronchiectasis. It is considered highly responsible for pathogenicity, progression and clinical outcomes of bronchiectasis.

AIMS

To summarize existing evidence on how different factors of Pseudomonas aeruginosa affect the pathogenicity, progression and clinical outcomes of bronchiectasis, so as to provide possible insights for clinical practice and related research in the future.

SOURCES

PubMed was searched for studies pertaining to bronchiectasis and P. aeruginosa published to date, with no specific inclusion or exclusion criteria. Reference lists of retrieved reviews were searched for additional articles.

CONTENT

This review focused on non-cystic fibrosis bronchiectasis and also provided some data on cystic fibrosis when studies in bronchiectasis were limited. We discussed various factors in relation to P. aeruginosa: virulence factors, drug resistance, regulatory systems, genomic diversity and transmission of P. aeruginosa, as well as treatment for P. aeruginosa. Their impacts on bronchiectasis and its management were discussed.

IMPLICATIONS

The impact of P. aeruginosa on bronchiectasis is definite, although conclusions in some aspects are still vague. Faced with the worrying drug-resistance status and treatment bottleneck, individualized management and novel therapies beyond the classic pathway are most likely to be a future trend. To confirm the independent or integrated impact of various factors of P. aeruginosa on bronchiectasis and to figure out all the problems mentioned, larger randomized control trials are truly needed in the future.

Antimicrobial susceptibility testing (AST) and associated clinical outcomes in individuals with cystic fibrosis: A systematic review

BACKGROUND

Antimicrobial susceptibility testing (AST) is a cornerstone of infection management. Cystic fibrosis (CF) treatment guidelines recommend AST to select antimicrobial treatments for CF airway infection but its utility in this setting has never been objectively demonstrated.

METHODS

We conducted a systematic review of primary published articles designed to address two PICO (patient, intervention, comparator, outcome) questions: 1) "For individuals with CF, is clinical response to antimicrobial treatment of bacterial airways infection predictable from AST results available at treatment initiation?" and 2) "For individuals with CF, is clinical response to antimicrobial treatment of bacterial airways infection affected by the method used to guide antimicrobial selection?" Relationships between AST results and clinical response (changes in pulmonary function, weight, signs and symptoms of respiratory tract infection, and time to next event) were assessed for each article and results were compared across articles when possible.

RESULTS

Twenty-five articles describing the results of 20 separate studies, most of which described Pseudomonas aeruginosa treatment, were identified. Thirteen studies described pulmonary exacerbation (PEx) treatment and seven described 'maintenance' of chronic bacterial airways infection. In only three of 16 studies addressing PICO question #1 was there a suggestion that baseline bacterial isolate antimicrobial susceptibility was associated with clinical response to treatment. None of the four studies addressing PICO question #2 suggested that antimicrobial selection methods influenced clinical outcomes.

CONCLUSIONS

There is little evidence that AST predicts the clinical outcome of CF antimicrobial treatment, suggesting a need for careful consideration of current AST use by the CF community.

Persistence and Microevolution of Pseudomonas aeruginosa in the Cystic Fibrosis Lung: A Single-Patient Longitudinal Genomic Study

Background: During its persistence in cystic fibrosis (CF) airways, P. aeruginosa develops a series of phenotypic changes by the accumulation of pathoadaptive mutations. A better understanding of the role of these mutations in the adaptive process, with particular reference to the development of multidrug resistance (MDR), is essential for future development of novel therapeutic approaches, including the identification of new drug targets and the implementation of more efficient antibiotic therapy. Although several whole-genome sequencing studies on P. aeruginosa CF lineages have been published, the evolutionary trajectories in relation to the development of antimicrobial resistance remain mostly unexplored to date. In this study, we monitored the adaptive changes of P. aeruginosa during its microevolution in the CF airways to provide an innovative, genome-wide picture of mutations and persistent phenotypes and to point out potential novel mechanisms allowing survival in CF patients under antibiotic therapy. Results: We obtained whole genome sequences of 40 P. aeruginosa clinical CF strains isolated at Trentino Regional Support CF Centre (Rovereto, Italy) from a single CF patient over an 8-year period (2007-2014). Genotypic analysis of the P. aeruginosa isolates revealed a clonal population dominated by the Sequence Type 390 and three closely related variants, indicating that all members of the population likely belong to the same clonal lineage and evolved from a common ancestor. While the majority of early isolates were susceptible to most antibiotics tested, over time resistant phenotypes increased in the persistent population. Genomic analyses of the population indicated a correlation between the evolution of antibiotic resistance profiles and phylogenetic relationships, and a number of putative pathoadaptive variations were identified. Conclusion: This study provides valuable insights into the within-host adaptation and microevolution of P. aeruginosa in the CF lung and revealed the emergence of an MDR phenotype over time, which could not be comprehensively explained by the variations found in known resistance genes. Further investigations on uncharacterized variations disclosed in this study should help to increase our understanding of the development of MDR phenotype and the poor outcome of antibiotic therapies in many CF patients.

Understanding the impact of antibiotic therapies on the respiratory tract resistome: a novel pooled-template metagenomic sequencing strategy

Determining the effects of antimicrobial therapies on airway microbiology at a population-level is essential. Such analysis allows, for example, surveillance of antibiotic-induced changes in pathogen prevalence, the emergence and spread of antibiotic resistance, and the transmission of multi-resistant organisms. However, current analytical strategies for understanding these processes are limited. Culture- and PCR-based assays for specific microbes require the a priori selection of targets, while antibiotic sensitivity testing typically provides no insight into either the molecular basis of resistance, or the carriage of resistance determinants by the wider commensal microbiota. Shotgun metagenomic sequencing provides an alternative approach that allows the microbial composition of clinical samples to be described in detail, including the prevalence of resistance genes and virulence traits. While highly informative, the application of metagenomics to large patient cohorts can be prohibitively expensive. Using sputum samples from a randomised placebo-controlled trial of erythromycin in adults with bronchiectasis, we describe a novel, cost-effective strategy for screening patient cohorts for changes in resistance gene prevalence. By combining metagenomic screening of pooled DNA extracts with validatory quantitative PCR-based analysis of candidate markers in individual samples, we identify population-level changes in the relative abundance of specific macrolide resistance genes. This approach has the potential to provide an important adjunct to current analytical strategies, particularly within the context of antimicrobial clinical trials.

In vitro activity of β-lactams in combination with avibactam against multidrug-resistant Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Achromobacter xylosoxidans isolates from patients with cystic fibrosis

The in vitro activity of anti-pseudomonal β-lactams in combination with avibactam was evaluated against 54 multidrug-resistant non-fermenting Gram-negative bacilli isolated from cystic fibrosis patients. Avibactam increased and/or restored the antibacterial activities of ceftazidime and aztreonam against Pseudomonas aeruginosa and Stenotrophomonas maltophilia, respectively. No β-lactam-avibactam combination was active against Achromobacter xylosoxidans.

Unmet needs in cystic fibrosis: the next steps in improving outcomes

INTRODUCTION

Cystic fibrosis (CF) outcomes and survival have improved over the last century primarily due to advancements in antibiotics, nutritional, and pulmonary therapies. Reviewed here are the significant unmet needs that exist for individuals with CF. Areas covered: With the recent development of medications that address the underlying defect in the CF protein, there is hope that there will be continued improvement in CF outcomes. However, there remains a need to prevent or stop progression of CF-related complications, as the CF protein is important to several body systems. As end stage lung disease is the primary cause of mortality in CF, a need exists for advancements in pulmonary therapies to reduce time burden, identification of best practices for the treatment of pulmonary exacerbations, further development of anti-infective and anti-inflammatory therapies, and appropriately timed referral for lung transplantation at end-stage lung disease. Extra-pulmonary complications are increasingly recognized and better understanding of such problems as CF related liver disease is needed. Expert commentary: While CFTR modulators are available for the majority of CF patients, there remains a need for effective therapies to address infection, inflammation, irreversible lung disease, and extrapulmonary complications of CF.

How can the cystic fibrosis respiratory microbiome influence our clinical decision-making?

PURPOSE OF REVIEW

Almost 15 years have now passed since bacterial community profiling techniques were first used to analyse respiratory samples from people with cystic fibrosis. Since then, many different analytical approaches have been used to try to better understand the contribution of the cystic fibrosis lung microbiota to disease, with varying degrees of success. We examine the extent to which cystic fibrosis respiratory microbiome research has been successful in informing clinical decision-making, and highlight areas that we believe have the potential to yield important insight.

RECENT FINDINGS

Recent research on the cystic fibrosis lung microbiome can be broadly divided into efforts to better characterize microbiota composition, particularly relative to key clinical events, and attempts to understand the cystic fibrosis lung microbiology as an interactive microbial system. The latter, in particular, has led to the development of a number of models in which microbiome-mediated processes precipitate clinical events.

SUMMARY

Growing technological sophistication is enabling increasingly detailed microbiological data to be generated from cystic fibrosis respiratory samples. However, translating these data into clinically useful measures that accurately predict outcomes and guide treatments remains a formidable challenge. The development of systems biology approaches that enable the integration of complex microbiome and host-derived data provide an exciting opportunity to address this goal.

Antibiotic duration and changes in FEV1 are not associated with time until next exacerbation in adult cystic fibrosis: a single center study

Background

Pulmonary exacerbations (PEx) are a major driver of morbidity and mortality in cystic fibrosis and reducing their frequency by extending the time between them is an important therapeutic goal. Although treatment decisions for exacerbations are often made based on dynamic changes in lung function, it is not clear if these changes truly impact future exacerbation risk. We analyzed adults with chronic Pseudomonas aeruginosa infection to determine whether changes in FEV₁ or duration of intravenous antibiotic therapy were associated with time to the next pulmonary exacerbation.

Methods

Medical records and Cystic Fibrosis Foundation Patient Registry data were examined retrospectively to assess whether various patient-specific demographic factors and exacerbation-specific characteristics were associated with time until next exacerbation using the Andersen-Gill model in order to control for previous exacerbation frequency history.

Results

We examined 59 patients with 221 CF pulmonary exacerbations over a 3-year study period. Mean age was 28.2 years and mean baseline FEV₁ was 62% predicted. In our univariable model, fall in FEV₁ at onset of exacerbation (median absolute −3% predicted change), recovery of FEV₁ with treatment (median absolute +3% predicted change) and duration of IV antibiotics (median 16 days) were not associated with time to next exacerbation (median 93.5 days). Paradoxically each one-year increase in age was associated with a reduction in hazard of PEx by 3% (HR 0.97, P = 0.03, 95% CI 0.95–1.00).

Conclusions

FEV1 drop and recovery associated with onset and treatment of a CF pulmonary exacerbation or duration of intravenous antibiotics were not predictive of time until next exacerbation. Our finding that older age may be associated with decreased hazard of exacerbation is likely due to a healthy survivor effect and should be controlled for in clinical trials of pulmonary exacerbations.

The emergence of multidrug-resistant Pseudomonas aeruginosa in cystic fibrosis patients on inhaled antibiotics

INTRODUCTION

Multidrug-resistant Pseudomonas aeruginosa (MDR-PA) is an important and growing issue in the care of patients with cystic fibrosis (CF), and a major cause of morbidity and mortality.

OBJECTIVE

The objective of the study was to describe the frequency of MDR-PA recovered from the lower respiratory samples of pediatric and adult CF patients, and its antibiotic resistance pattern to commonly used antimicrobial agents including β-lactams, aminoglycosides, and fluoroquinolones.

MATERIALS AND METHODS

The lower respiratory isolates of P. aeruginosa were obtained from inpatients and outpatients CF clinics from a tertiary care teaching hospital for the period from October 2014 to September 2015. The identification and antimicrobial susceptibility for all the isolates were performed by using the BD Phoenix™ and E-test in compliance with Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

A total of 61 P. aeruginosa samples were isolated from thirty CF patients from twenty families. Twelve sputum samples were positive for MDR-PA (seven nonmucoid and five mucoid isolates) from five CF patients (five families) with moderate-to-very severe lung disease given MDR-PA frequency of 19.7%. The median age of the study group was 20 (range 10-30) years. Three CF patients were on chronic inhaled tobramycin and two on nebulized colistin. The antimicrobial patterns of isolates MDR-PA showed the highest rate of resistance toward each gentamycin, amikacin, and cefepime (100%), followed by 91.7% to ciprofloxacin, 75% to tobramycin, 58.3% to meropenem, and 50% to piperacillin-tazobactam. None of the isolates were resistant to colistin during the study period.

CONCLUSION

The study results emphasize that the emergence of a significant problem in the clinical isolates of P. aeruginosa in CF patients that dictate appropriate attention to the antibiotic management after proper surveillance.

Phagocytes, Antibiotics, and Self-Limiting Bacterial Infections

Most antibiotic use in humans is to reduce the magnitude and term of morbidity of acute, community-acquired infections in immune competent patients, rather than to save lives. Thanks to phagocytic leucocytes and other host defenses, the vast majority of these infections are self-limiting. Nevertheless, there has been a negligible amount of consideration of the contribution of phagocytosis and other host defenses in the research for, and the design of, antibiotic treatment regimens, which hyper-emphasizes antibiotics as if they were the sole mechanism responsible for the clearance of infections. Here, we critically review this approach and its limitations. With the aid of a heuristic mathematical model, we postulate that if the rate of phagocytosis is great enough, for acute, normally self-limiting infections, then (i) antibiotics with different pharmacodynamic properties would be similarly effective, (ii) low doses of antibiotics can be as effective as high doses, and (iii) neither phenotypic nor inherited antibiotic resistance generated during therapy are likely to lead to treatment failure.

In Vitro Activity of Ceftolozane-Tazobactam against Multidrug-Resistant Nonfermenting Gram-Negative Bacilli Isolated from Patients with Cystic Fibrosis

Ceftolozane-tazobactam was tested against 58 multidrug-resistant nonfermenting Gram-negative bacilli (35 Pseudomonas aeruginosa, 11 Achromobacter xylosoxydans, and 12 Stenotrophomonas maltophilia isolates) isolated from cystic fibrosis patients and was compared to ceftolozane alone, ceftazidime, meropenem, and piperacillin-tazobactam. Ceftolozane-tazobactam was the most active agent against P. aeruginosa but was inactive against A. xylosoxydans and S. maltophilia In time-kill experiments, ceftolozane-tazobactam had complete bactericidal activity against 2/6 clinical isolates (33%).

Draft Genome Sequences of 40 Pseudomonas aeruginosa Clinical Strains Isolated from the Sputum of a Single Cystic Fibrosis Patient Over an 8-Year Period

We report draft genome sequences of 40 Pseudomonas aeruginosa strains, isolated from the sputum of a single cystic fibrosis patient over eight years. Analyses indicated a correlation between multidrug-resistant phenotypes and population structure. Our data provide new insights into the mechanisms leading to acquisition of antibiotic resistance in P. aeruginosa.

Managing Pseudomonas aeruginosa respiratory infections in cystic fibrosis

PURPOSE OF REVIEW

The current guidelines and recent clinical research in the management of Pseudomonas aeruginosa respiratory infections in cystic fibrosis (CF) are reviewed. Areas where further research is required will also be highlighted.

RECENT FINDINGS

P. aeruginosa is a key respiratory pathogen in CF. Inhaled tobramycin or colistin is recommended for early eradication to prevent establishment of chronic infection. Other antibiotic options are currently being investigated. The long-term success of eradication strategies is also now being assessed. The use of inhaled antibiotics in the management of chronic P. aeruginosa infection is an area of active investigation. Acute pulmonary exacerbations are still a major cause of morbidity and mortality. Guidelines continue to recommend combination intravenous therapy but further research is required to clarify the advantage of this approach. Multidrug resistance is common and potentially more effective antipseudomonal antibiotics may soon become available.

SUMMARY

The management of P. aeruginosa respiratory infection in CF remains a challenging area, especially in the setting of multidrug resistance. The role of inhaled antibiotics continues to be expanded. Further research is required in the key areas of eradication and management of chronic infection and acute pulmonary exacerbations to identify those treatments that optimize long-term, clinical benefits.

Duration of intravenous antibiotic therapy in people with cystic fibrosis

BACKGROUND

Respiratory disease is the major cause of mortality and morbidity in cystic fibrosis. Life expectancy of people with cystic fibrosis has increased dramatically in the last 40 years. One of the major reasons for this increase is the mounting use of antibiotics to treat chest exacerbations caused by bacterial infections. The optimal duration of intravenous antibiotic therapy is not clearly defined. Individuals usually receive intravenous antibiotics for 14 days, but treatment may range from 10 to 21 days. A shorter duration of antibiotic treatment risks inadequate clearance of infection which could lead to further lung damage. Prolonged courses of intravenous antibiotics are expensive and inconvenient and the incidence of allergic reactions to antibiotics also increases with prolonged courses. The use of aminoglycosides requires frequent monitoring to avoid some of their side effects. However, some organisms which infect people with cystic fibrosis are known to be multi-resistant to antibiotics, and may require a longer course of treatment. This is an update of previously published reviews.

OBJECTIVES

To assess the optimal duration of intravenous antibiotic therapy for treating chest exacerbations in people with cystic fibrosis.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises references identified from comprehensive electronic database searches, handsearches of relevant journals, abstract books and conference proceedings.Most recent search of the Group's Cystic Fibrosis Trials Register: 05 May 2016.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing different durations of intravenous antibiotic courses for acute respiratory exacerbations in people with CF, either with the same drugs at the same dosage, the same drugs at a different dosage or frequency or different antibiotics altogether, including studies with additional therapeutic agents.

DATA COLLECTION AND ANALYSIS

No eligible trials were identified.

MAIN RESULTS

No eligible trials were identified.

AUTHORS' CONCLUSIONS

There are no clear guidelines on the optimum duration of intravenous antibiotic treatment. Duration of treatment is currently based on unit policies and response to treatment. Shorter duration of treatment should improve quality of life and compliance; result in a reduced incidence of drug reactions; and be less costly. However, this may not be sufficient to clear a chest infection and may result in an early recurrence of an exacerbation. This systematic review identifies the need for a multicentre, randomised controlled trial comparing different durations of intravenous antibiotic treatment as it has important clinical and financial implications.

Aminoglycoside resistance of Pseudomonas aeruginosa in cystic fibrosis results from convergent evolution in the mexZ gene

RATIONALE

Aminoglycoside (AG) resistance of Pseudomonas aeruginosa in cystic fibrosis (CF) is associated with poorer clinical outcomes and is usually due to overexpression of the efflux pump MexXY. MexXY is regulated by mexZ, one of the most commonly mutated genes in CF P. aeruginosa isolates. Little is known about the evolutionary relationship between AG resistance, MexXY expression and mexZ mutations.

OBJECTIVES

To test the hypothesis that AG resistance in P. aeruginosa develops in parallel with higher MexXY expression and mexZ mutations.

METHODS

CF P. aeruginosa isolates were compared for chronically infected (CI) adults, CI children and children with new infection.

MEASUREMENTS

One P. aeruginosa isolate from each patient was analysed for mexZ mutations, mexY mRNA expression and amikacin resistance.

MAIN RESULTS

56 patients with CF were enrolled: 21 children with new P. aeruginosa infection, 18 CI children and 17 CI adults. Amikacin resistance and mexY mRNA expression were higher in cohorts with longer P. aeruginosa infection. The prevalence of non-conservative mexZ mutations was 0%, 33% and 65% in children with new infection, CI children and CI adults, respectively. The same trend was seen in the ratio of non-conservative to non-synonymous mexZ mutations. Of isolates with non-conservative mexZ mutations, 59% were amikacin-resistant compared with 18% of isolates with non-synonymous mutations. The doubling rate of amikacin resistance and non-conservative mexZ mutations was approximately 5 years.

CONCLUSIONS

P. aeruginosa mexZ mutations undergo positive selection resulting in increased mexY mRNA expression and amikacin resistance and likely play a role in bacterial adaption in the CF lung.

Pseudomonas aeruginosa antibiotic resistance in Australian cystic fibrosis centres

BACKGROUND AND OBJECTIVE

In cystic fibrosis (CF), chronic Pseudomonas aeruginosa infection is associated with increased morbidity, antibiotic treatments and mortality. By linking Australian CF registry data with a national microbiological data set, we examined the association between where treatment was delivered, its intensity and P. aeruginosa antibiotic resistance.

METHODS

Sputa were collected from paediatric and adult CF patients attending 18 Australian CF centres. P. aeruginosa antibiotic susceptibilities determined by local laboratories were correlated with clinical characteristics, treatment intensity and infection with strains commonly shared among Australian CF patients. Between-centre differences in treatment and antibiotic resistance were also compared.

RESULTS

Large variations in antibiotic usage, maintenance treatment practices and multi-antibiotic resistant P. aeruginosa (MARPA) prevalence exist between Australian CF centres, although the overall proportions of MARPA isolates were similar in paediatric and adult centres (31% vs 35%, P = 0.29). Among paediatric centres, MARPA correlated with intravenous antibiotic usage and the Australian state where treatment was delivered, while azithromycin, reduced lung function and treating state predicted intravenous antibiotic usage. In adult centres, body mass index (BMI) and treating state were associated with MARPA, while intravenous antibiotic use was predicted by gender, BMI, dornase-alpha, azithromycin, lung function and treating state. In adults, P. aeruginosa strains AUST-01 and AUST-02 independently predicted intravenous antibiotic usage.

CONCLUSION

Increased treatment intensity in paediatric centres and the Australian state where treatment was received are both associated with greater risk of MARPA, but not worse clinical outcomes.

Differential outcome of an antimicrobial stewardship audit and feedback program in two intensive care units: a controlled interrupted time series study

BACKGROUND

Antimicrobial decision making in intensive care units (ICUs) is challenging. Unnecessary antimicrobials contribute to the development of resistant pathogens, Clostridium difficile infection and drug related adverse events. However, inadequate antimicrobial therapy is associated with mortality in critically ill patients. Antimicrobial stewardship programs are increasingly being implemented to improve antimicrobial prescribing, but the optimal approach in the ICU setting is unknown. We assessed the impact of an audit and feedback antimicrobial stewardship intervention on antimicrobial use, antimicrobial costs, clinical outcomes and microbiologic outcomes in two ICUs with different patient populations.

METHODS

The audit and feedback intervention was implemented in a trauma and neurosurgery ICU (TNICU) and a medical surgical ICU (MSICU) at a 465-bed teaching hospital in Toronto, Canada. ICU patients were reviewed Monday to Friday by a physician and pharmacist with infectious diseases training. Recommendations related to appropriate antimicrobial use were presented to ICU teams during a dedicated daily meeting. A controlled interrupted time series analysis was used to compare outcomes in the 12 months before and after the intervention. Cardiovascular and coronary care ICUs served as control units.

RESULTS

Mean total monthly antimicrobial use in defined daily doses (DDD) per 1000 patient days was reduced 28% in the TNICU (1433 vs. 1037) but increased 14% in the MSICU (1705 vs. 1936). In the time series analysis, total monthly antimicrobial use in the TNICU decreased by 375 DDD per 1000 patient days (p < 0.0009) immediately following the intervention, followed by a non-significant downward trend in use of -9 DDD per 1000 patient days (p = 0.56). No significant changes in antimicrobial use were identified in the MSICU. Antimicrobial use temporarily increased in one control unit and remained unchanged in the other. There were no changes in mortality, length of stay, readmission rate, incidence of C. difficile infection or resistance patterns of E. coli and P. aeruginosa in either intervention unit.

CONCLUSIONS

Audit and feedback antimicrobial stewardship programs can lead to significant reductions in total antimicrobial use in the ICU setting. However, this effect may be context-dependent and further work is needed to determine the ingredients necessary for success.

Pseudomonas aeruginosa biofilm infections: from molecular biofilm biology to new treatment possibilities

Bacteria in natural, industrial and clinical settings predominantly live in biofilms, i.e., sessile structured microbial communities encased in self-produced extracellular matrix material. One of the most important characteristics of microbial biofilms is that the resident bacteria display a remarkable increased tolerance toward antimicrobial attack. Biofilms formed by opportunistic pathogenic bacteria are involved in devastating persistent medical device-associated infections, and chronic infections in individuals who are immune-compromised or otherwise impaired in the host defense. Because the use of conventional antimicrobial compounds in many cases cannot eradicate biofilms, there is an urgent need to develop alternative measures to combat biofilm infections. The present review is focussed on the important opportunistic pathogen and biofilm model organism Pseudomonas aeruginosa. Initially, biofilm infections where P. aeruginosa plays an important role are described. Subsequently, current insights into the molecular mechanisms involved in P. aeruginosa biofilm formation and the associated antimicrobial tolerance are reviewed. And finally, based on our knowledge about molecular biofilm biology, a number of therapeutic strategies for combat of P. aeruginosa biofilm infections are presented.

The problems of antibiotic resistance in cystic fibrosis and solutions

Chronic respiratory infection is the main cause of morbidity and mortality in cystic fibrosis (CF) patients. One of the hallmarks of these infections, led by the opportunistic pathogen Pseudomonas aeruginosa, is their long-term (lifelong) persistence despite intensive antimicrobial therapy. Antimicrobial resistance in CF is indeed a multifactorial problem, which includes physiological changes, represented by the transition from the planktonic to the biofilm mode of growth and the acquisition of multiple (antibiotic resistance) adaptive mutations catalyzed by frequent mutator phenotypes. Emerging multidrug-resistant CF pathogens, transmissible epidemic strains and transferable genetic elements (such as those encoding class B carbapenemases) also significantly contribute to this concerning scenario. Strategies directed to combat biofilm growth, prevent the emergence of mutational resistance, promote the development of novel antimicrobial agents against multidrug-resistant strains and implement strict infection control measures are thus needed.

Antimicrobial resistance in the respiratory microbiota of people with cystic fibrosis

Cystic fibrosis is characterised by chronic polymicrobial infection and inflammation in the airways of patients. Antibiotic treatment regimens, targeting recognised pathogens, have substantially contributed to increased life expectancy of patients with this disease. Although the emergence of antimicrobial resistance and selection of highly antibiotic-resistant bacterial strains is of major concern, the clinical relevance in cystic fibrosis is yet to be defined. Resistance has been identified in recognised cystic fibrosis pathogens and in other bacteria (eg, Prevotella and Streptococcus spp) detected in the airway microbiota, but their role in the pathophysiology of infection and inflammation in chronic lung disease is unclear. Increased antibiotic resistance in cystic fibrosis might be attributed to a range of complex factors including horizontal gene transfer, hypoxia, and biofilm formation. Strategies to manage antimicrobial resistance consist of new antibiotics or localised delivery of antimicrobial agents, iron sequestration, inhibition of quorum-sensing, and resistome analysis. Determination of the contributions of every bacterial species to lung health or disease in cystic fibrosis might also have an important role in the management of antibiotic resistance.

Pseudomonas aeruginosa infection in patients with cystic fibrosis: scientific evidence regarding clinical impact, diagnosis, and treatment

Evidence-based techniques have been increasingly used in the creation of clinical guidelines and the development of recommendations for medical practice. The use of levels of evidence allows the reader to identify the quality of scientific information that supports the recommendations made by experts. The objective of this review was to address current concepts related to the clinical impact, diagnosis, and treatment of Pseudomonas aeruginosa infections in patients with cystic fibrosis. For the preparation of this review, the authors defined a group of questions that would be answered in accordance with the principles of PICO-an acronym based on questions regarding the Patients of interest, Intervention being studied, Comparison of the intervention, and Outcome of interest. For each question, a structured review of the literature was performed using the Medline database in order to identify the studies with the methodological design most appropriate to answering the question. The questions were designed so that each of the authors could write a response. A first draft was prepared and discussed by the group. Recommendations were then made on the basis of the level of scientific evidence, in accordance with the classification system devised by the Oxford Centre for Evidence-Based Medicine, as well as the level of agreement among the members of the group.

Effects of green tea compound epigallocatechin-3-gallate against Stenotrophomonas maltophilia infection and biofilm

We investigated the in vitro and in vivo activities of epigallocatechin-3-gallate (EGCg), a green tea component, against Stenotrophomonas maltophilia (Sm) isolates from cystic fibrosis (CF) patients. In vitro effects of EGCg and the antibiotic colistin (COL) on growth inhibition, survival, and also against young and mature biofilms of S. maltophilia were determined. Qualitative and quantitative changes on the biofilms were assessed by confocal laser scanning microscopy (CLSM). Further, in vivo effects of nebulized EGCg in C57BL/6 and Cftr mutant mice during acute Sm lung infection were evaluated. Subinhibitory concentrations of EGCg significantly reduced not only biofilm formation, but also the quantity of viable cells in young and mature biofilms. CLSM showed that EGCg-exposed biofilms exhibited either a change in total biofilm biovolume or an increase of the fraction of dead cells contained within the biofilm in a dose depended manner. Sm infected wild-type and Cftr mutant mice treated with 1,024 mg/L EGCg by inhalation exhibited significantly lower bacterial counts than those undergoing no treatment or treated with COL. EGCg displayed promising inhibitory and anti-biofilm properties against CF Sm isolates in vitro and significantly reduced Sm bacterial counts in an acute infection model with wild type and CF mice. This natural compound may represent a novel therapeutic agent against Sm infection in CF.