Pneumonic and non-pneumonic exacerbations in bronchiectasis: Clinical and microbiological differences

Exacerbations of bronchiectasis

Bronchiectasis presents a significant challenge due to its rising prevalence, associated economic burden and clinical heterogeneity. This review synthesises contemporary understanding and literature of bronchiectasis exacerbations, addressing the transition from stable state to exacerbations, underlining the importance of early and precise recognition, rigorous severity assessment, prompt treatment, and prevention measures, as well as emphasising the need for strategies to assess and improve early and long-term patient outcomes. The review highlights the interplay between stable state phases and exacerbations in bronchiectasis, introducing the concept of "exogenous and endogenous changes in airways homeostasis" and the "adapted island model" with a particular focus on "frequent exacerbators", a group of patients associated with specific clinical characteristics and worse outcomes. The pathophysiology of exacerbations is explored through the lens of microbial and nonmicrobial triggers and the presence and the activity of comorbidities, elaborating on the impact of both exogenous insults, such as infections and pollution, and endogenous factors such as inflammatory endotypes. Finally, the review proposes a multidisciplinary approach to care, integrating advancements in precision medicine and biomarker research, paving the way for tailored treatments that challenge the traditional antibiotic paradigm.

Biomarkers in bronchiectasis

Bronchiectasis is a heterogeneous disease with multiple aetiologies and diverse clinical features. There is a general consensus that optimal treatment requires precision medicine approaches focused on specific treatable disease characteristics, known as treatable traits. Identifying subtypes of conditions with distinct underlying biology (endotypes) depends on the identification of biomarkers that are associated with disease features, prognosis or treatment response and which can be applied in clinical practice. Bronchiectasis is a disease characterised by inflammation, infection, structural lung damage and impaired mucociliary clearance. Increasingly there are available methods to measure each of these components of the disease, revealing heterogeneous inflammatory profiles, microbiota, radiology and mucus and epithelial biology in patients with bronchiectasis. Using emerging biomarkers and omics technologies to guide treatment in bronchiectasis is a promising field of research. Here we review the most recent data on biomarkers in bronchiectasis.

Clinical relevance of bronchiectasis in patients with community-acquired pneumonia

BACKGROUND

Data regarding the clinical characteristics and treatment outcomes of patients with community-acquired pneumonia (CAP) and bronchiectasis (BE) are rare. This study aims to elucidate the clinical relevance of BE in patients with CAP.

METHODS

Patients hospitalized with CAP in a single center were retrospectively analyzed and divided into significant BE (BE with ≥ 3 lobes or cystic BE on computed tomography) and control groups. Clinical and microbiological characteristics were compared between the two groups.

RESULTS

In the final analysis, 2112 patients were included, and 104 (4.9%) had significant BE. The significant BE group exhibited a higher prevalence of sputum production, dyspnea, and complicated parapneumonic effusion or empyema than the control group. Pseudomonas aeruginosa was more frequently isolated in the significant BE group than in the control group, whereas Mycoplasma pneumoniae was less commonly identified. Length of hospital stay (LOS) was significantly longer in the significant BE group than the control group (12 [8-17] days vs. 9 [6-13] days, p < 0.001). In contrast, 30-day and in-hospital mortality rates did not significantly differ between the two groups. Furthermore, significant BE was an independent predictor of prolonged hospitalization in two models based on CURB-65 and pneumonia severity index.

CONCLUSIONS

Significant BE occurred in approximately 5% of patients with CAP and was more likely to be associated with sputum, dyspnea, complicated parapneumonic effusion or empyema, and isolation of P. aeruginosa. Significant BE was an independent predictor of LOS in patients with CAP.

How and when to manage respiratory infections out of hospital

Lower respiratory infections include acute bronchitis, influenza, community-acquired pneumonia, acute exacerbation of COPD and acute exacerbation of bronchiectasis. They are a major cause of death worldwide and often affect the most vulnerable: children, elderly and the impoverished. In this paper, we review the clinical presentation, diagnosis, severity assessment and treatment of adult outpatients with lower respiratory infections. The paper is divided into sections on specific lower respiratory infections, but we also dedicate a section to COVID-19 given the importance of the ongoing pandemic. Lower respiratory infections are heterogeneous entities, carry different risks for adverse events, and require different management strategies. For instance, while patients with acute bronchitis are rarely admitted to hospital and generally do not require antimicrobials, approximately 40% of patients seen for community-acquired pneumonia require admission. Clinicians caring for patients with lower respiratory infections face several challenges, including an increasing population of patients with immunosuppression, potential need for diagnostic tests that may not be readily available, antibiotic resistance and social aspects that place these patients at higher risk. Management principles for patients with lower respiratory infections include knowledge of local surveillance data, strategic use of diagnostic tests according to surveillance data, and judicious use of antimicrobials.

The role of viral infections in pulmonary exacerbations of patients with non-cystic fibrosis bronchiectasis: A systematic review

BACKGROUND

Bronchiectasis is a cause of increased morbidity of the respiratory system. Exacerbations among patients with non-CF (cystic fibrosis) bronchiectasis result in reduced pulmonary function and poor quality of life. While the role of bacteria in triggering exacerbations in patients with non- CF bronchiectasis has been well studied, little is known about viral infections in these patients. We aimed to review the evidence on the role of respiratory viruses in the exacerbations of non-CF bronchiectasis.

METHODS

Relevant literature was searched on the MEDLINE/PubMed database. Seven studies satisfied the criteria and were included in this review.

RESULTS

According to the included articles, respiratory viruses are often identified in exacerbations of patients with non-CF bronchiectasis with the most frequent being human rhinovirus and influenza viruses. When a virus is isolated during an exacerbation patients have more symptoms from the upper respiratory tract. One study showed that detection of Epstein- Barr virus among patients with non-CF bronchiectasis is correlated with faster reduction of pulmonary function and progression of the disease.

CONCLUSION

Viruses seem to have a role in the exacerbation of patients with non-CF bronchiectasis. However, the exact nature and importance of this role remain elusive. Viruses are also isolated during the stable period of the disease. Further well-designed studies are necessary to clarify this complex issue.

Molecular Mechanisms of Lipid Metabolism Disorders in Infectious Exacerbations of Chronic Obstructive Pulmonary Disease

Exacerbations largely determine the character of the progression and prognosis of chronic obstructive pulmonary disease (COPD). Exacerbations are connected with changes in the microbiological landscape in the bronchi due to a violation of their immune homeostasis. Many metabolic and immune processes involved in COPD progression are associated with bacterial colonization of the bronchi. The objective of this review is the analysis of the molecular mechanisms of lipid metabolism and immune response disorders in the lungs in COPD exacerbations. The complex role of lipid metabolism disorders in the pathogenesis of some infections is only beginning to be understood, however, there are already fewer and fewer doubts even now about its significance both in the pathogenesis of infectious exacerbations of COPD and in general in the progression of the disease. It is shown that the lipid rafts of the plasma membranes of cells are involved in many processes related to the detection of pathogens, signal transduction, the penetration of pathogens into the cell. Smoking disrupts the normally proceeded processes of lipid metabolism in the lungs, which is a part of the COPD pathogenesis.

Bronchiectasis Exacerbations: Definitions, Causes, and Acute Management

Pulmonary exacerbations (PExs) are events in the course of bronchiectasis which are defined as an increase in disease symptoms lasting a period of a few days. It is established that the tendency toward having PEx is stable throughout the course of the disease. Certain conditions were found to be associated with an increased risk of developing a PEx. Among these are chronic airway infection with Pseudomonas aeruginosa or Aspergillus species, concomitant airway diseases (asthma, chronic obstructive pulmonary disease, and chronic rhinosinusitis), genetic factors such as primary ciliary dyskinesia, and nutritional factors. The immediate events underlying the onset of a PEx are less clearly determined. Although acute changes in bacterial airway composition have been the paradigm for decades, recent microbiome-focused research has not uniformly established such acute changes at the onset of PEx. Other acute changes such as air pollution, viral infection, and changes in bacterial metabolic activity have also been implicated as causes of a PEx. Despite these gaps in our knowledge of the biology of PEx, antimicrobial therapy directed against the identified pathogens in sputum is currently the recommended therapeutic strategy. Various long-term therapies, including antimicrobial and anti-inflammatory strategies, have been proven effective in reducing the frequency of PEx, leading to a recommendation for the use of these strategies in people with frequent PEx.

[Multidisciplinary Management of Non-cystic-fibrosis Bronchiectasis - State of the Art]

Bronchiectasis is a mostly irreversible bronchial dilatation induced by a destruction of elastic and muscular fibers of the bronchial wall. Radiological criteria of bronchiectasis are met, when the inner diameter of the bronchial wall surpasses the outer diameter of the accompanying pulmonary artery. Its incidence increases with age, even though it often lacks true clinical signs of disease. Only when it is accompanied by cough, expectorations and recurring bronchopulmonary infections, it can be considered a true bronchiectatic disease. Cystic fibrosis (CF) is one of its preeminent triggers, but certainly plays a particular role in this entity, which is why the terminus of "non-CF-bronchiectasis" was coined in the first place.Multidisciplinary management consists in extensive diagnostic work-up, treatment of potential triggers of bronchiectasis and supportive care in form of vaccination programs, secretolysis and pulmonary rehabilitation, as well as antibiotic treatment of pulmonary exacerbations.Surgical treatment has to be considered a last resort in case of hemoptysis, recurring severe pneumonia or secondary aspergilloma with complete resection of all pathological findings, ideally by minimally-invasive approach.

Respiratory pathogens in patients with acute exacerbation of non-cystic fibrosis bronchiectasis from a developing country

Bronchiectasis unrelated to cystic fibrosis (non-CF bronchiectasis) has become a major respiratory disease in developing nations. The dilated mucus filled airways promote bacterial overgrowth followed by chronic infection, bronchial inflammation, lung injury and re-infection. Accurate pathogen identification and antimicrobial susceptibility allowing appropriate treatment, in turn, may break this vicious cycle.  This study aimed to gain kowledge about the spectrum and antimicrobial spectrum of pathogen yielded from respiratory specimens in adult patients with acute exacerbation of non-cystic fibrosis (CF) bronchiectasis. This cross-sectional study was performed at the pulmonology clinics of the Aga Khan University, Karachi, Pakistan from 2016-2019. Respiratory specimens were collected from adult patients with acute exacerbation of non-CF bronchiectasis presenting in pulmonology clinics. Microbial cultures were performed using standard methodology. Susceptibility testing was performed and interpreted using Clinical Laboratory Standard Institute criteria.  A total of 345 positive cultures from 160 patients presenting with acute exacerbation were evaluated. The most frequent organisms were Pseudomonas aeruginosa (n=209) followed by Hemophilus influenzae (n=40) and Staphylococcus aureus (n=24). High rates of antimicrobial resistance were found in all these pathogens. Proportion of Pseudomonas aeruginosa strains resistant to ciprofloxacin, imipenem, ceftazidime and piperacillin-tazobactam were 27.1%, 16.8%, 14.8% and 13.1% respectively. 65% of Hemophilus influenzae strains were resistant to cotrimoxazole and ciprofloxacin and 66.7% of Staphylococcus aureus strains were resistant to methicillin. High antimicrobial resistance in non-CF bronchiectasis patients against commonly used antimicrobials is a concern and highlight need for urgent community level interventions to improve clinical outcome in these patients.

Antimicrobial Resistance in Common Respiratory Pathogens of Chronic Bronchiectasis Patients: A Literature Review

Non-cystic fibrosis bronchiectasis is a chronic disorder in which immune system dysregulation and impaired airway clearance cause mucus accumulation and consequent increased susceptibility to lung infections. The presence of pathogens in the lower respiratory tract causes a vicious circle resulting in impaired mucociliary function, bronchial inflammation, and progressive lung injury. In current guidelines, antibiotic therapy has a key role in bronchiectasis management to treat acute exacerbations and chronic infection and to eradicate bacterial colonization. Contrastingly, antimicrobial resistance, with the risk of multidrug-resistant pathogen development, causes nowadays great concern. The aim of this literature review was to assess the role of antibiotic therapy in bronchiectasis patient management and possible concerns regarding antimicrobial resistance based on current evidence. The authors of this review stress the need to expand research regarding bronchiectasis with the aim to assess measures to reduce the rate of antimicrobial resistance worldwide.

Hospitalizations for Community-Acquired and Non-Ventilator-Associated Hospital-Acquired Pneumonia in Spain: Influence of the Presence of Bronchiectasis. A Retrospective Database Study

To examine and compare in-hospital mortality (IHM) of community-acquired pneumonia (CAP) and non-ventilator hospital-acquired pneumonia (NV-HAP) among patients with or without bronchiectasis (BQ) using propensity score matching. A retrospective observational epidemiological study using the Spanish Hospital Discharge Records, 2016–17. We identified 257,455 admissions with CAP (3.97% with BQ) and 17,069 with NV-HAP (2.07% with BQ). Patients with CAP and BQ had less comorbidity, lower IHM, and a longer mean length of hospital stay (p < 0.001) than non-BQ patients. They had a higher number of isolated microorganisms, including Pseudomonas aeruginosa. In patients with BQ and NV-HAP, no differences were observed with respect to comorbidity, in-hospital mortality (IHM), or mean length of stay. P. aeruginosa was more frequent (p = 0.028). IHM for CAP and NV-HAP with BQ was 7.89% and 20.06%, respectively. The factors associated with IHM in CAP with BQ were age, comorbidity, pressure ulcers, surgery, dialysis, and invasive ventilation, whereas in NV-HAP with BQ, the determinants were age, metastatic cancer, need for dialysis, and invasive ventilation. Patients with CAP and BQ have less comorbidity, lower IHM and a longer mean length of hospital stay than non-BQ patients. However, they had a higher number of isolated microorganisms, including Pseudomonas aeruginosa. In patients with BQ and NV-HAP, no differences were observed with respect to comorbidity, in-hospital mortality, or mean length of stay, but they had a greater frequency of infection by P. aeruginosa than non-BQ patients. Predictors of IHM for both types of pneumonia among BQ patients included dialysis and invasive ventilation.

Bronchiectasis phenotypes

PURPOSE OF REVIEW

Bronchiectasis is a chronic respiratory disease with heterogeneous clinical manifestations and outcomes. Identifying clinical phenotypes could help in managing bronchiectasis patients and hopefully improve disease prognosis by adopting personalized treatment. We review the current literature on clinical phenotypes of bronchiectasis and try to highlight priorities for future research.

RECENT FINDINGS

Different studies have tried to stratify bronchiectasis patients according to cause, microbiology, or associated conditions. In consideration of the huge heterogeneity of bronchiectasis different cluster analyses in bronchiectasis have also been performed. Unfortunately classification by cause is clinically meaningful only in a few conditions in which specific treatment is available or a specific management is recommended. This is the case, for instance, of allergic bronchopulmonary aspergillosis, immunodeficiencies or chronic airways comorbidities of bronchiectasis, such as chronic obstructive pulmonary disease and asthma. From a clinical perspective, the microbiological cluster stratification proposed by Aliberti et al. seems the most profitable one but still so a number of host-related factors have an unpredictable effect on clinical manifestations and outcomes of bronchiectasis.

SUMMARY

Although numerous attempts to identify clinical phenotypes in bronchiectasis have been performed, currently there is need to further investigate the host-related factors (endotypes) that surely play a determinant role in disease severity.

The biology of pulmonary exacerbations in bronchiectasis

Bronchiectasis is a heterogeneous chronic disease. Heterogeneity characterises bronchiectasis not only in the stable state but also during exacerbations, despite evidence on clinical and biological aspects of bronchiectasis, exacerbations still remain poorly understood.Although the scientific community recognises that bacterial infection is a cornerstone in the development of bronchiectasis, there is a lack of data regarding other trigger factors for exacerbations. In addition, a huge amount of data suggest a primary role of neutrophils in the stable state and exacerbation of bronchiectasis, but the inflammatory reaction involves many other additional pathways. Cole's vicious cycle hypothesis illustrates how airway dysfunction, airway inflammation, infection and structural damage are linked. The introduction of the concept of a "vicious vortex" stresses the complexity of the relationships between the components of the cycle. In this model of disease, exacerbations work as a catalyst, accelerating the progression of disease. The roles of microbiology and inflammation need to be considered as closely linked and will need to be investigated in different ways to collect samples. Clinical and translational research is of paramount importance to achieve a better comprehension of the pathophysiology of bronchiectasis, microbiology and inflammation both in the stable state and during exacerbations.

Microbiological Progress in Patients with Bronchial Infection with <b><i>Pseudomonas aeruginosa</i></b> Treated with Nebulised Colistin

<b><i>Background:</i></b> Inhaled antibiotics allow the delivery of higher drug concentrations at the site of infection without the systemic adverse effects observed with the use of parenteral or oral antibiotics. These antibiotics have shown to decrease the number of exacerbations, reduce bacterial load or improve pulmonary function in several chronic respiratory conditions. <b><i>Objectives:</i></b> The aim of this study was to describe changes in the bacteriology of sputum in patients with chronic bronchial infection with <i>Pseudomonas aeruginosa</i> treated with nebulised colistin. <b><i>Material and Methods:</i></b> All patients with chronical infection with <i>P. aeruginosa</i> treated with nebulised colistin attending a day care unit during a 5-year (January 2010 to December 2014) period were included. Repeated-measures <i>t</i> tests were used to assess whether the introduction of colistin was associated with changes in the number of exacerbations or the length of the hospitalisations. <b><i>Results:</i></b> Treatment with colistin was associated with a decrease in the number of ambulatory exacerbations (1.87–1.1, <i>p</i> = 0.007), of hospital exacerbations (1.3–0.7, <i>p</i> = 0.010) and of length of stay (15.7–8.6 days, <i>p</i> = 0.005). There was no linear trend in the proportion of isolate Enterobacteriaceae, gram-positive cocci, <i>Haemophilus influenzae</i> or fungi. Isolation of Enterobacteriaceae within 1 year after the beginning of the treatment with nebulised colistin was associated with an increase in the number of ambulatory exacerbations (incidence rate ratio 1.99, 95% CI 1.05–3.79). <b><i>Conclusions:</i></b> Nebulised colistin was effective in the treatment of chronic infection with <i>P. aeruginosa,</i> and no significant changes in the microbiological evolution were observed. Isolation of Enterobacteriaceae within 1 year after the beginning of the treatment with nebulised colistin was associated with an increase in the number of exacerbations.

Paediatric and adult bronchiectasis: Vaccination in prevention and management

Bronchiectasis has received increased attention recently, including an emphasis on preventing infective exacerbations that are associated with disease progression and lung function decline. While there are several bacteria and viruses associated with bronchiectasis, licensed vaccines are only currently available for Streptococcus pneumoniae, Haemophilus influenzae (H. influenzae protein D as a conjugate in a pneumococcal vaccine), Mycobacterium tuberculosis, Bordetella pertussis and influenza virus. The evidence for the efficacy and effectiveness of these vaccines in both preventing and managing bronchiectasis in children and adults is limited with the focus of most research being on other chronic lung disorders, such as chronic obstructive pulmonary diseases, asthma and cystic fibrosis. We review the existing evidence for these vaccines in bronchiectasis and highlight the existing gaps in knowledge. High-quality experimental and non-experimental studies using current state-of-the-art microbiological methods and validated, standardised case definitions are needed across the depth and breadth of the vaccine development pathway.

The Interplay Between Immune Response and Bacterial Infection in COPD: Focus Upon Non-typeable Haemophilus influenzae

Chronic obstructive pulmonary disease (COPD) is a debilitating respiratory disease and one of the leading causes of morbidity and mortality worldwide. It is characterized by persistent respiratory symptoms and airflow limitation due to abnormalities in the lower airway following consistent exposure to noxious particles or gases. Acute exacerbations of COPD (AECOPD) are characterized by increased cough, purulent sputum production, and dyspnea. The AECOPD is mostly associated with infection caused by common cold viruses or bacteria, or co-infections. Chronic and persistent infection by non-typeable Haemophilus influenzae (NTHi), a Gram-negative coccobacillus, contributes to almost half of the infective exacerbations caused by bacteria. This is supported by reports that NTHi is commonly isolated in the sputum from COPD patients during exacerbations. Persistent colonization of NTHi in the lower airway requires a plethora of phenotypic adaptation and virulent mechanisms that are developed over time to cope with changing environmental pressures in the airway such as host immuno-inflammatory response. Chronic inhalation of noxious irritants in COPD causes a changed balance in the lung microbiome, abnormal inflammatory response, and an impaired airway immune system. These conditions significantly provide an opportunistic platform for NTHi colonization and infection resulting in a "vicious circle." Episodes of large inflammation as the consequences of multiple interactions between airway immune cells and NTHi, accumulatively contribute to COPD exacerbations and may result in worsening of the clinical status. In this review, we discuss in detail the interplay and crosstalk between airway immune residents and NTHi, and their effect in AECOPD for better understanding of NTHi pathogenesis in COPD patients.