Role of infection in chronic bronchitis

Oral-lung microbiome interactions in lung diseases

The proximity and continuity of the oral cavity and the lower respiratory tract allows the oropharyngeal microbiome to be a major determinant of the lung microbiome. In addition, host-pathogen interactions related to the oropharyngeal microbiome or its metabolites could propagate systemic inflammation or modulate host defense mechanisms that could affect other organs, including the lung. There is increasing appreciation of the pathophysiologic significance of the lung microbiome, not only in the classical infection-related diseases, pneumonia, bronchiectasis, and cystic fibrosis, but also in chronic noninfectious lung diseases, such as chronic obstructive pulmonary disease, asthma, and pulmonary fibrosis. In this review, we will explore the relationship of the oral microbiome with lung diseases, such as pneumonia, chronic obstructive pulmonary disease, asthma, and cystic fibrosis.

The neutrophil-mobilizing cytokine interleukin-26 in the airways of long-term tobacco smokers

Long-term tobacco smokers with chronic obstructive pulmonary disease (COPD) or chronic bronchitis display an excessive accumulation of neutrophils in the airways; an inflammation that responds poorly to established therapy. Thus, there is a need to identify new molecular targets for the development of effective therapy. Here, we hypothesized that the neutrophil-mobilizing cytokine interleukin (IL)-26 (IL-26) is involved in airway inflammation amongst long-term tobacco smokers with or without COPD, chronic bronchitis or colonization by pathogenic bacteria. By analyzing bronchoalveolar lavage (BAL), bronchail wash (BW) and induced sputum (IS) samples, we found increased extracellular IL-26 protein in the airways of long-term smokers in vivo without further increase amongst those with clinically stable COPD. In human alveolar macrophages (AM) in vitro, the exposure to water-soluble tobacco smoke components (WTC) enhanced IL-26 gene and protein. In this cell model, the same exposure increased gene expression of the IL-26 receptor complex (IL10R2 and IL20R1) and nuclear factor κ B (NF-κB); a proven regulator of IL-26 production. In the same cell model, recombinant human IL-26 in vitro caused a concentration-dependent increase in the gene expression of NF-κB and several pro-inflammatory cytokines. In the long-term smokers, we also observed that extracellular IL-26 protein in BAL samples correlates with measures of lung function, tobacco load, and several markers of neutrophil accumulation. Extracellular IL-26 was further increased in long-term smokers with exacerbations of COPD (IS samples), with chronic bronchitis (BAL samples ) or with colonization by pathogenic bacteria (IS and BW samples). Thus, IL-26 in the airways emerges as a promising target for improving the understanding of the pathogenic mechanisms behind several pulmonary morbidities in long-term tobacco smokers.

Analysis of viral infection and biomarkers in patients with acute exacerbation of chronic obstructive pulmonary disease

OBJECTIVE

To investigate viral infection in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) in Shanghai, and to analyze the clinical characteristics and biomarkers in viral infection.

METHODS

This study included all consecutive patients who were admitted for a diagnosis of AECOPD during June 2013 to May 2015. Thirty-one stable COPD patients and 31 healthy controls were also recruited. Oropharyngeal samples were assessed, PCR for respiratory viruses were performed. Patients were divided into AECOPD virus-positive (+) group and AECOPD virus-negative (-) group according to viral detection. Luminex was used to detect the concentrations of inflammatory cytokines in the serum.

RESULTS

A total of 264 patients were included with a mean age of 75 ± 0.5 years. There were 72 patients (27.3%) identified with viral positive, of whom two patients were detected with double viral infections (FluA + FluB and RSVA + HRV, respectively). The rate of viral detection was associated with season, highest in winter. Comparisons of clinical characteristics showed no significant differences between AECOPD virus+ group and AECOPD virus- group. However, serum concentrations of interferon-inducible protein-10 (IP-10) and interferon-gamma (IFN-γ) in virus+ AECOPD patients were significantly higher than those in the virus- AECOPD, stable COPD and healthy control groups (P < .05).

CONCLUSION

Viral infection was an important pathogen in AECOPD patients; the most common viruses included FluA, HRV and FluB. It was very difficult to diagnose the viral infection according to clinical characteristics. The increased of serum IP-10 and IFN-γ levels might be value to indicate viral infection in AECOPD.

Understanding the role of the microbiome in chronic obstructive pulmonary disease: principles, challenges, and future directions

In the past several years, advances in sequencing platforms and bioinformatics have transformed our understanding of the relationship between microbial ecology and human health. Both the normal and diseased lung are host to hundreds of bacterial genera, blurring the lines between "colonization" and "infection". However, whereas in health the respiratory microbiome is determined primarily by the dynamic balance of immigration and elimination, in chronic disease conditions become much more favorable for the reproduction of resident bacteria. Recent studies demonstrate that the microbiota of the chronic obstructive pulmonary disease (COPD) lung differ from the healthy lung although significant intrasubject and intersubject heterogeneity are still present with variation impacted by factors such as disease stage and inhaled medications. Changes in the relative abundance of specific bacterial taxa during COPD exacerbations have also been noted although further longitudinal analyses are needed to ascertain the malleability and resilience of this ecological system and its role in the occurrence and frequency of exacerbations. Whether patients with a "frequent exacerbator" phenotype possess specific or greater alterations in their airway microbiome that predispose them to recurrent exacerbations as compared with nonfrequent exacerbators needs to be determined. Although recent data suggest that the presence of bacteria has the potential to influence the host immune response, a key challenge in the next few years will be to continue to move beyond descriptive studies to define the clinical relevance of differences in lung microbiota associated with COPD.

Respiratory infectious phenotypes in acute exacerbation of COPD: an aid to length of stay and COPD Assessment Test

Purpose

To investigate the respiratory infectious phenotypes and their impact on length of stay (LOS) and the COPD Assessment Test (CAT) Scale in acute exacerbation of COPD (AECOPD).

Patients and methods

We categorized 81 eligible patients into bacterial infection, viral infection, coinfection, and non-infectious groups. The respiratory virus examination was determined by a liquid bead array xTAG Respiratory Virus Panel in pharyngeal swabs, while bacterial infection was studied by conventional sputum culture. LOS and CAT as well as demographic information were recorded.

Results

Viruses were detected in 38 subjects, bacteria in 17, and of these, seven had both. Influenza virus was the most frequently isolated virus, followed by enterovirus/rhinovirus, coronavirus, bocavirus, metapneumovirus, parainfluenza virus types 1, 2, 3, and 4, and respiratory syncytial virus. Bacteriologic analyses of sputum showed that Pseudomonas aeruginosa was the most common bacteria, followed by Acinetobacter baumannii, Klebsiella, Escherichia coli, and Streptococcus pneumoniae. The longest LOS and the highest CAT score were detected in coinfection group. CAT score was positively correlated with LOS.

Conclusion

Respiratory infection is a common causative agent of exacerbations in COPD. Respiratory coinfection is likely to be a determinant of more severe acute exacerbations with longer LOS. CAT score may be a predictor of longer LOS in AECOPD.

Infections in "noninfectious" lung diseases

Many chronic pulmonary diseases, including those that are not primarily infectious in etiology, have some aspects of their pathogenesis that are influenced by infectious organisms. Microorganisms may contribute to chronic lung diseases, either directly (i.e., overt infection) or indirectly, via the amplification of inflammatory pathways that are critical to host defense. As techniques for detecting and characterizing microorganisms have advanced, investigations of both infecting and colonizing organisms have yielded new insights into mechanisms of pulmonary disease. In addition, changes in patterns of infection and microbial resistance have important implications for treatment. Examples of these infectious-pulmonary associations, including Haemophilus influenzae infection and chronic obstructive pulmonary disease, nontuberculous mycobacteria and bronchiectasis, and human immunodeficiency virus and obstructive lung disease, are reviewed.

Chronic obstructive pulmonary disease and infection. Disruption of the microbiome?

The dynamics of infection in chronic obstructive pulmonary disease (COPD) are complex, and microbiome technology has provided us with a new research tool for its better understanding. There is compartmentalization of the microbiota in the various parts of the lung. Studies of the lower airway lumen microbiota in COPD have yielded confusing results, and additional studies with scrupulous attention to prevent and account for upper airway contamination of bronchoalveolar lavage samples are required. Lung tissue microbiota has been examined in three studies, which also demonstrate varied results based on the site of sampling (bronchial mucosa, lung parenchyma), and this variation extends to sampling sites within a lobe of the lung. The Vicious Circle Hypothesis embodies how an altered lung microbiome could contribute to COPD progression. Relating microbiota composition to airway and systemic inflammation and clinical outcomes are important research questions. Although various obstacles need to be surmounted, ultimately lung microbiome studies will provide new insights into how infection contributes to COPD.

Role of infections

This article represents a review of the current literature on the role of infection in the pathogenesis of chronic obstructive pulmonary disease (COPD), in stable disease, exacerbations, and pneumonia. It outlines the complex interactions between respiratory pathogens and host immune defenses that underlie the clinical manifestations of infection in COPD.

Infectious Mechanisms Regulating Susceptibility to Acute Exacerbations of COPD

Acute exacerbations of COPD (AECOPD) are defined by clinical criteria, outlined in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines [1]. These include an acute increase in one or more of the following cardinal symptoms, beyond day to day variability: dyspnea, increased frequency or severity of cough and increased volume or change in character of sputum, which represent an acute increase in airway inflammation. The role of infection in the pathogenesis of COPD, acute exacerbation and disease progression has been a clinical and research question for many years, and the pendulum has swung from infection as a major cause of acute exacerbation and COPD (British Hypothesis) [2], to infection as an unrelated epiphomenon in acute exacerbation [3–5], and back again to infection as integral in the development of AECOPD and likely an important contributor to COPD progression [6–19]. Upwards of 80 % of AECOPD are driven by infectious stimuli, with 40–50 % associated with bacterial infection and 30–50 % associated with acute viral infection, with some exacerbations having dual bacterial and viral causation [20]. Much of the advancement in our understanding of the role of infection is AECOPD is due to the advancement of clinical and research tools that have allowed researchers to accurately characterize the microbial pathogens, and better understand the host-pathogen interactions (Table 1).

The role of the bacterial microbiome in lung disease

Novel culture-independent techniques have recently demonstrated that the lower respiratory tract, historically considered sterile in health, contains diverse communities of microbes: the lung microbiome. Increasing evidence supports the concept that a distinct microbiota of the lower respiratory tract is present both in health and in various respiratory diseases, although the biological and clinical significance of these findings remains undetermined. In this article, the authors review and synthesize published reports of the lung microbiota of healthy and diseased subjects, discuss trends of microbial diversity and constitution across disease states, and look to the extrapulmonary microbiome for hypotheses and future directions for study.

IL-8 production in response to cigarette smoke is decreased in epithelial cells from COPD patients

Cigarette smoke is the principal cause of chronic obstructive pulmonary disease (COPD), a disorder characterized by airway inflammation. As epithelial cells are the first line of defense against foreign material, the response of normal epithelial cells to smoke has been extensively studied. However, little is known about how epithelial cells derived from COPD patients respond to ongoing smoke exposure. This study was aimed at comparing the intracellular response of normal human bronchial/tracheal epithelial cells (NHBE) and COPD-diseased human bronchial/tracheal epithelial cells (DHBE) to cigarette smoke. NHBE and DHBE cells were treated with cigarette smoke condensate (CSC) for 24 h. IL-8 production was measured by ELISA and western blot was used to measure TLR4 expression. Cells were pretreated with CLI-095, a TLR4 inhibitor, or the signaling pathway inhibitors PD184352, Helenalin, or PI-103, which inhibit the ERK1/2, NF-κB and PI3K pathways, respectively. NHBE cells increased IL-8 production in a dose-dependent manner in response to CSC while DHBE cells did not show any significant difference and had a much lower production of IL-8 in response to CSC compared to NHBE cells. There was no change in TLR4 expression with CSC exposure. CLI-095 and PD184352 attenuated IL-8 secretion, indicating that CSC-induced inflammation is both TLR4- and ERK1/2-dependent. These results demonstrate that NHBE and DHBE cells differentially respond to cigarette smoke. DHBE cells exhibit a dampened IL-8 release, indicating that COPD is associated with a reduced capacity of airway epithelial cells to respond to foreign material.

End-tidal arterial CO2 partial pressure gradient in patients with severe hypercapnia undergoing noninvasive ventilation

BACKGROUND

Patients with severe hypercapnia represent a particularly serious condition in an emergency department (ED), requiring immediate attention. Noninvasive ventilation (NIV) is an integral part of the treatment for acute respiratory failure. The present study aimed to validate the measurement of end-tidal CO2 (EtCO2) as a noninvasive technique to evaluate the effectiveness of NIV in acute hypercapnic respiratory failure.

METHODS

Twenty consecutive patients admitted to the ED with severe dyspnea were enrolled in the study. NIV by means of bilevel positive airway pressure, was applied to the patients simultaneously with standard medical therapy and continued for 12 hours; the arterial blood gases and side-stream nasal/oral EtCO2 were measured at subsequent times: T0 (admission to the ED), T1h (after 1 hour), T6h (after 6 hours), and T12h (after 12 hours) during NIV treatment.

RESULTS

The arterial CO2 partial pressure (PaCO2)-EtCO2 gradient decreased progressively, reaching at T6h and T12h values lower than baseline (P < 0.001), while arterial pH increased during the observation period (P < 0.001). A positive correlation was found between EtCO2 and PaCO2 values (r = 0.89, P < 0.001) at the end of the observation period.

CONCLUSION

In our hypercapnic patients, the effectiveness of the NIV was evidenced by the progressive reduction of the PaCO2-EtCO2 gradient. The measurement of the CO2 gradient could be a reliable method in monitoring the effectiveness of NIV in acute hypercapnic respiratory failure in the ED.

Clinical Aspects of Upper and Lower Respiratory Tract Infections

Respiratory tract infections are among the most common illnesses leading to medical consultation, and are associated with significant mortality. Community-acquired pneumonia is a common illness and, while Streptococcus pneumoniae continues to be the most frequent causative agent, atypical pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella species are now identified as additional common aetiological agents. Since clinical and roentgenographic features poorly predict the aetiological agent in most cases of community-acquired pneumonia, empirical therapy is generally recommended. Nosocomial pneumonia is the second most common hospital-acquired infection and is associated with significant mortality. Aerobic Gram-negative bacilli and Staphylococcus aureus are the predominant causative pathogens. New techniques to improve the diagnosis of nosocomial pneumonia have been introduced, but their role has not been entirely clarified. Therapy directed toward the most likely pathogens (aerobic Gram-negative species and S. aureus) on an empirical basis is recommended until more specific information is obtained. Acute exacerbations of chronic bronchitis should be treated with antimicrobial therapy directed toward S. pneumoniae, Haemophilus influenzae or Moraxella catarrhalis. Because of the emergence of β-lactamase-producing strains of H. influenzae and M. catarrhalis, the choice of an antimicrobial agent has to be carefully considered. Group A β-haemolytic streptococci are the most common cause of bacterial pharyngitis and penicillin remains the drug of choice. Patients suffering from otitis media and sinusitis are infected with the same organisms as those patients with acute exacerbations of chronic bronchitis and antibacterial choices are therefore similar.

Roflumilast, a Novel Phosphodiesterase 4 Inhibitor, for COPD Patients with a History of Exacerbations

Acute exacerbations of COPD (AECOPD) are major clinical events. They are associated with a more rapid decline in lung function, poorer quality of life scores, and an increased risk of dying. Exacerbations that require hospitalization have particular significance. Approximately 40% of the AECOPD patients who require hospitalization will die in the subsequent year. Since many AECOPD require hospitalization, they account for most of the expense of caring for COPD patients. Treatment with long-acting bronchodilators and combination inhaled corticosteroid/long-acting bronchodilator inhalers reduces but does not eliminate AECOPD. Roflumilast, a selective phosphodiesterase 4 (PDE4) inhibitor, is an anti-inflammatory medication that improves lung function in patients with COPD. In patients with more severe airway obstruction, clinical features of chronic bronchitis, and a history of AECOPD, roflumilast reduces the frequency of AECOPD when given in combination with short-acting bronchodilators, long-acting bronchodilators, or inhaled corticosteroids. It is generally well tolerated but the most common adverse effects include diarrhea, nausea, weight loss, and headaches. In clinical trials, patients treated with roflumilast experienced weight loss that averaged just over 2 kg but was primarily due to the loss of fat tissue. Weight loss was least in underweight patients and obese patients experienced the greatest weight loss. An unexpected benefit of treatment with roflumilast was that fasting blood glucose and hemoglobin A1c levels improved in patients with comorbid type 2 diabetes mellitus. Roflumilast, the first selective PDE4 inhibitor to be marketed, is a promising drug for the management of COPD patients with more severe disease.

Impact of bacterial colonization on the severity, and accompanying airway inflammation, of virus-induced wheezing in children

It is reported that bacterial colonization of the airway in neonates affects the likelihood and severity of subsequent wheezing in childhood. This study aimed to explore the impact of bacterial colonization on the severity of virus-induced wheezing, and accompanying airway inflammation. Nasopharyngeal aspirates (NPAs) from 68 hospitalized children with bronchiolitis and 85 children with recurrent wheezing were obtained. Eleven common respiratory viruses were sought by PCR and/or direct fluorescence assay. Bacteria were isolated from NPAs by routine culture methods. Cell numbers and concentrations of cytokines/chemokines in the NPAs were measured, and nucleated cells were characterized. The frequency of bacterial colonization in children with recurrent wheezing was significantly higher than in children with an initial attack of bronchiolitis. Bacterial colonization accompanying virus infection had no effect on clinical manifestations, duration of hospitalization, concentrations of cytokines/chemokines (except interleukin-10 (IL-10)) or cellularity in the children with bronchiolitis; however, among the children with recurrent wheezing, those who had coexistent non-invasive bacterial colonization and virus infection presented more frequent cyanosis, longer duration of hospitalization, a higher concentration of IL-10 and a higher percentage of neutrophils in NPAs than those with virus infection but without bacterial colonization. Bacterial colonization was common in children with virus-induced wheezing, particularly in the situation of recurrent wheezing. To some extent, bacterial colonization accompanying virus infection may contribute to the severity of the wheezing because of its impact on airway inflammation.

Impact of bacterial colonization on the severity, and accompanying airway inflammation, of virus-induced wheezing in children

It is reported that bacterial colonization of the airway in neonates affects the likelihood and severity of subsequent wheezing in childhood. This study aimed to explore the impact of bacterial colonization on the severity of virus-induced wheezing, and accompanying airway inflammation. Nasopharyngeal aspirates (NPAs) from 68 hospitalized children with bronchiolitis and 85 children with recurrent wheezing were obtained. Eleven common respiratory viruses were sought by PCR and/or direct fluorescence assay. Bacteria were isolated from NPAs by routine culture methods. Cell numbers and concentrations of cytokines/chemokines in the NPAs were measured, and nucleated cells were characterized. The frequency of bacterial colonization in children with recurrent wheezing was significantly higher than in children with an initial attack of bronchiolitis. Bacterial colonization accompanying virus infection had no effect on clinical manifestations, duration of hospitalization, concentrations of cytokines/chemokines (except interleukin-10 (IL-10)) or cellularity in the children with bronchiolitis; however, among the children with recurrent wheezing, those who had coexistent non-invasive bacterial colonization and virus infection presented more frequent cyanosis, longer duration of hospitalization, a higher concentration of IL-10 and a higher percentage of neutrophils in NPAs than those with virus infection but without bacterial colonization. Bacterial colonization was common in children with virus-induced wheezing, particularly in the situation of recurrent wheezing. To some extent, bacterial colonization accompanying virus infection may contribute to the severity of the wheezing because of its impact on airway inflammation.

Molecular diagnosis of respiratory tract infection in acute exacerbations of chronic obstructive pulmonary disease

Acute exacerbations are significant events in the course of chronic obstructive pulmonary disease. Modern diagnostic techniques have revealed an infectious cause for the majority of exacerbations. Common respiratory viruses contribute to 25%–50% of exacerbations. Detection of viral nucleic acids in nasopharyngeal swab or sputum samples has become the preferred method to study viral exacerbations instead of viral cultures and serologic examination. Clinical application of such molecular detection requires additional studies to clarify interpretation of a positive result. Bacteria account for 25%–50% of exacerbations. Studies comparing molecular detection of bacteria in sputum with conventional culture techniques have shown that a substantial proportion of bacteria are not detected by the latter method. However, as with molecular viral detection, clinical application of molecular bacterial diagnosis requires additional studies. Although still faced with several challenges and requiring additional development, it is quite likely that molecular methods will become the preferred methods for determining the etiology of exacerbations of chronic obstructive pulmonary disease.

Acute exacerbations in COPD and their control with oral immunization with non-typeable haemophilus influenzae

Chronic obstructive pulmonary disease (COPD) a term based on the demonstration of irreversible airways obstruction, introduced to unify a range of chronic progressive diseases of the airways consequent upon inhalation of toxins. While disease is initiated and progressed by inhaled toxins, an additional pathway of damage has emerged, with particular relevance to acute exacerbations. Exacerbations of disease due to an increase in the level of intrabronchial inflammation have taken on a new significance as their role in determining both acute and chronic outcomes is better understood. This “second pathway” of disease is a consequence of bacterial colonization of damaged airways. Although bacteria have been linked to acute episodes in COPD over 50 years, only recently has quality data on antibiotic usage and the detection of “exacerbation isolates” of non-typeable Haemophilus influenzae (NTHi) provided strong argument in support of a pathogenic role. Yet a poor correlation between detection of colonizing bacteria and clinical status remained a concern in attempts to explain a role for bacteria in a classical infection model. This presentation discusses a hypothesis that acute exacerbations reflect a T cell-dependent hypersensitivity response to colonizing bacteria, with IL-17 dependent accumulation of neutrophils within the bronchus, as the main outcome measure. Critical protection against exacerbations following oral administration of NTHi, an immunotherapy that drives a TH17 T cell response from Peyer’s patches, reduces the load of intrabronchial bacteria while preventing access of inhaled bacteria into small airways. Immunotherapy augments a physiological “loop” based on aspiration of bronchus content into the gut. A second “hypersensitivity” mechanism may cause bronchospasm – in both COPD and treatment-resistant asthma – due to specific IgE antibody directed against colonizing bacteria, as oral NTHi abrogates wheeze in subjects with recurrent “wheezy bronchitis.”

Pathogenesis of Bacterial Exacerbations of COPD

Acute exacerbations are significant events in the course of COPD. The pathogenesis of exacerbations was poorly understood, specifically, the role of bacteria was highly controversial. Recent observations have demonstrated that bacterial infection is involved in about half of the exacerbations. The predominant mechanism of bacterial exacerbation in COPD appears to be acquisition of new strains of bacterial pathogens from the environment that are able to establish infection in the tracheobronchial tree in COPD because of compromised innate lung defenses. These pathogens interact with airway cells, elicit an inflammatory response, which underlies the pathophysiology and symptoms characteristic of exacerbation. An immune response that can be mucosal, systemic or both develops to the infecting bacterial strain. This immune response contains the infectious process, could eradicate the infecting pathogen and prevent re-infection with the same strain. However, because of antigenic diversity among bacterial strains, this immunity tends to be strain-specific rather than widely protective. Other mechanisms, including increase in bacterial load and interaction with other etiologies such as viruses, also could contribute to bacterial exacerbations. Improved understanding of the host-pathogen interaction in the airways in COPD will lead to novel approaches to prevention and treatment of exacerbations.

Exacerbation rate, health status and mortality in COPD--a review of potential interventions

COPD is prevalent in Western society and its incidence is rising in the developing world. Acute exacerbations of COPD, about 50% of which are unreported, lead to deterioration in quality of life and contribute significantly to disease burden. Quality of life deteriorates with time; thus, most of the health burden occurs in more severe disease. COPD severity and frequent and more severe exacerbations are all related to an increased risk of mortality. Inhaled corticosteroids (ICS) have similar effects on quality of life but ICS/long-acting bronchodilator combinations and the long-acting antimuscarinic tiotropium all improve health status and exacerbation rates and are likely to have an effect on mortality but perhaps only with prolonged use. Erythromycin has been shown to decrease the rate of COPD exacerbations. Pulmonary rehabilitation and regular physical activity are indicated in all severities of COPD and improve quality of life. Noninvasive ventilation is associated with improved quality of life. Long-term oxygen therapy improves mortality but only in hypoxic COPD patients. The choice of an inhaler device is a key component of COPD therapy and this requires more attention from physicians than perhaps we are aware of. Disease management programs, characterized as they are by patient centeredness, improve quality of life and decrease hospitalization rates. Most outcomes in COPD can be modified by interventions and these are well tolerated and have acceptable safety profiles.

Bacteraemic pneumococcal pneumonia in COPD patients: better outcomes than expected

The purpose of the study was to compare the clinical characteristics and outcomes of bacteraemic pneumococcal pneumonia (BPP) in chronic obstructive pulmonary disease (COPD) and non-COPD patients. A case-control study was conducted. Cases were any adult with BPP and forced expiratory volume in 1 second (FEV(1)) <80% and FEV(1)/forced expiratory vital capacity (FVC) <70%. Controls were patients with BPP without clinical diagnosis of COPD matched 1:2 by age, gender and date of isolation. Variables included co-morbidities, serotypes, pneumonia severity index (PSI), treatment and mortality. There were 45 cases and 90 controls. No significant differences were found in Charlson scores, antibiotic treatment, serotype distribution and severity. Malignancy, shock and mechanical ventilation were less frequent in COPD patients. One patient died vs 14 controls (p = 0.02). In univariate analysis, shock, multilobar involvement, Charlson score, heart failure and absence of COPD were associated with mortality. After adjustment for the presence of shock there were no differences in mortality. BPP presents less frequently with shock and has a lower mortality rate in COPD patients than in non-COPD patients.

Infections

This chapter reviews the epidemiological evidence implicating infectious pathogens as triggers and will discuss the mechanisms of interaction between the host–pathogen response and preexisting airway pathology that result in an exacerbation. Asthma is a multifaceted syndrome involving atopy, bronchial hyperreactivity, and IgE and non-IgE-mediated acute and chronic immune responses. The asthmatic airway is characterized by an infiltrate of eosinophils and of T-lymphocytes expressing the type 2 cytokines IL-4, IL-5, and IL-13. Trigger factors associated with acute exacerbations of asthma include exposure to environmental allergens, especially animals, molds, pollens and mites, cold, exercise, and drugs. The frequency of exacerbations is a major factor in the quality of life of patients with COPD. The typical clinical features of an exacerbation include increased dyspnea, wheezing, cough, sputum production, and worsened gas exchange. Although noninfectious causes of exacerbations such as allergy, air pollution, or inhaled irritants including cigarette smoke may be important, acute airway infections are the major precipitants. The infection and consequent host inflammatory response result in increased airway obstruction. The success of vaccination to prevent respiratory virus infections has been limited by significant variation within the major virus types causing disease. Currently much of the treatment of infective exacerbations of asthma and COPD is symptomatic, consisting of increased bronchodilators, either short-acting β 2—agonists in inhaled or intravenous form or anticholinergics or theophyllines, or supportive in the form of oxygen and in severe cases noninvasive or invasive ventilatory measures.

Bacterial infection and risk factors in outpatients with acute exacerbation of chronic obstructive pulmonary disease: a 2-year prospective study

BACKGROUND AND OBJECTIVES

Acute exacerbations of COPD (AECOPD) are commonly observed in community-based patients worldwide. The factors causing exacerbation are largely unknown. This study was undertaken to determine the predominant bacterial pathogens cultured from sputum in community-based patients with AECOPD, to assess the risk factors associated with exacerbations and to compare these findings with published studies.

METHODS

Forty-five patients with stable COPD were prospectively followed in the outpatients' clinic of King Abdulaziz University Hospital. At the first visit, personal data, CXR and measurement of baseline PEF were obtained from each patient. In the subsequent visits, sputum culture and CXR were carried out during exacerbations.

RESULTS

Over a period of 24 months, patients made a total of 139 visits for exacerbations, and 69.8% had a positive sputum culture for a single pathogen. Moraxella catarrhalis (25.2%), Pseudomonas aeruginosa (12.2%) and Haemophilus influenzae (11.5%) were the most common isolated organisms. Patients with a lower level of baseline PEF had a significantly increased frequency of exacerbations (r = 0.337, P = 0.024). However, there was a weak correlation between exacerbation frequency and duration of COPD and exposure to cigarette smoking.

CONCLUSION

There was a higher incidence of Moraxella catarrhalis and Pseudomonas aeruginosa than reported in previous studies. These findings should influence antibiotic selection for exacerbations. COPD patients with a low baseline PEF are at a higher risk of having repeated exacerbations and gram-negative pathogens.

Role of nontypeable Haemophilus influenzae in exacerbations and progression of chronic obstructive pulmonary disease

PURPOSE OF REVIEW

Nontypeable Haemophilus influenzae is the most common bacterial pathogen associated with airway infection in chronic obstructive pulmonary disease, both in stable disease and during exacerbations. Past attempts to elucidate its role as a pathogen in this disease yielded confusing and contradictory results, leading to its designation as an 'innocent bystander' with little if any pathogenic role in exacerbations and stable disease. Application of modern understanding of bacterial pathogenesis and of innovative research methodologies, however, has considerably clarified its role.

RECENT FINDINGS

Acquisition of antigenically diverse strains of nontypeable H. influenzae which engender a neutrophilic inflammatory response and strain-specific immunity appears to be the mechanism underlying recurrent exacerbations of chronic obstructive pulmonary disease. In the stable phase of the disease, this pathogen appears to be an inflammatory stimulus in the lower airways with the potential to contribute to progressive airway obstruction that is characteristic of the condition. Several mechanisms may allow the infection to persist in the lower airways of patients with chronic obstructive pulmonary disease, including tissue invasion, antigenic alteration and biofilm formation.

SUMMARY

Though much has been learnt about nontypeable H. influenzae in chronic obstructive pulmonary disease, new therapeutic and preventive approaches require an even greater understanding of this host-pathogen interaction.

Moxifloxacin for the treatment of acute exacerbations of chronic obstructive pulmonary disease

BACKGROUND/PURPOSE

The significant impact of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) is now recognized. This recognition has led to increased efforts to provide evidence-based, appropriate treatment of AECOPD, to minimize its negative impact. This article reviews the bacterial etiology of AECOPD and clinical trials (both placebo-controlled and antibiotic comparison trials) that support the use of antibiotics for AECOPD, with an emphasis on the role of newer fluoroquinolones for the treatment of patients with this condition. A discussion of patient stratification that permits identification of those who require initial aggressive antibiotic therapy is presented.

MAIN FINDINGS

Among the treatment modalities for exacerbations, the role and choice of antibiotics is hotly debated. Current evidence supports the use of antibiotics in the treatment of AECOPD, because bacterial pathogens cause approximately half the exacerbations, and because empirical antibiotics have a significant benefit in most exacerbations. Several recent investigations have aided in the development of a rational antibiotic strategy for AECOPD. These include outcome studies that have identified patients who are likely to have a poor outcome of their exacerbation and, therefore, are candidates for aggressive initial antibiotic therapy. Studies of the new fluoroquinolone agents have shown superior short- and long-term clinical results among patients with AECOPD who are at risk of a poor outcome.

CONCLUSIONS

Theoretical concerns about the emergence of resistance to the fluoroquinolones dictate not only the appropriate use of these drugs but, also, the use of the most-potent agents available in this class, to sustain their usefulness over time. Such selected use of the new fluoroquinolones balances individual benefit with societal concerns regarding the use of these agents for the treatment of AECOPD.

Moraxella catarrhalis in chronic obstructive pulmonary disease: burden of disease and immune response

RATIONALE

Moraxella catarrhalis is frequently present in the sputum of adults with chronic obstructive pulmonary disease (COPD). Little is known about the role of M. catarrhalis in this common disease.

OBJECTIVE

To elucidate the burden of disease, the dynamics of carriage, and immune responses to M. catarrhalis in COPD.

METHODS

Prospective cohort study of 104 adults with COPD in an outpatient clinic at the Buffalo Veterans Affairs Medical Center.

MEASUREMENTS

Clinical information, sputum cultures, molecular typing of isolates, and immunoassays to measure antibodies to M. catarrhalis.

MAIN RESULTS

Over 81 months, 104 patients made 3,009 clinic visits, 560 during exacerbations. Molecular typing identified 120 episodes of acquisition and clearance of M. catarrhalis in 50 patients; 57 (47.5%) of the acquisitions were associated with clinical exacerbations. No instances of simultaneous acquisition of a new strain of another pathogen were observed. The duration of carriage of M. catarrhalis was shorter with exacerbations compared with asymptomatic colonization (median, 31.0 vs. 40.4 days; p = 0.01). Reacquisition of the same strain was rare. The intensity of the serum IgG response was greater after exacerbations than asymptomatic colonization (p = 0.009). Asymptomatic colonization was associated with a greater frequency of a sputum IgA response than exacerbation (p = 0.009).

CONCLUSIONS

M. catarrhalis likely causes approximately 10% of exacerbations of COPD, accounting for approximately 2 to 4 million episodes annually. The organism is cleared efficiently after a short duration of carriage. Patients develop strain-specific protection after clearance of M. catarrhalis from the respiratory tract.

Antibiotic activity of telithromycin and comparators against bacterial pathogens isolated from 3,043 patients with acute exacerbation of chronic bronchitis

Background

Antimicrobial therapy is considered an important component in the medical management of most patients with acute exacerbation of chronic bronchitis (AECB). The three predominant bacterial species isolated are nontypeable Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae. Staphylococcus aureus is also frequently isolated while atypical bacteria are thought to cause up to 10% of exacerbations. Antibacterial resistance is increasing worldwide and little surveillance data exist concerning pathogens isolated from patients with AECB.

Methods

This study examines the prevalence of antibacterial resistance in isolates obtained from patients with clinically diagnosed AECB. A total of 3043 isolates were obtained from 85 centres in 29 countries, between 1999–2003, and were tested against the new ketolide telithromycin and a panel of commonly used antibiotics.

Results and Discussion

Of the S. pneumoniae isolates, 99.9% were susceptible to telithromycin, but only 71% were susceptible to erythromycin and 75.3% to penicillin. Of the H. influenzae isolates, 99.6% were susceptible to telithromycin. 11.7% of these isolates produced β-lactamase. Almost 10% of S. pneumoniae were multidrug-resistant; 99.0% of these isolates were susceptible to telithromycin. Telithromycin also demonstrated good in vitro activity against M. catarrhalis (MIC₉₀ = 0.12 mg/L) and was the most active compound against methicillin-susceptible S. aureus (98.9% susceptible).

Conclusion

Telithromycin demonstrated similar or better activity against the bacterial species investigated than the other agents, with the most complete coverage overall. These species are the predominant causative bacterial pathogens in AECB and thus the spectrum of activity of telithromycin makes it a potential alternative for the empirical treatment of AECB.

Guide to selection of fluoroquinolones in patients with lower respiratory tract infections

Newer fluoroquinolones such as levofloxacin, moxifloxacin, gatifloxacin and gemifloxacin have several attributes that make them excellent choices for the therapy of lower respiratory tract infections. In particular, they have excellent intrinsic activity against Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and the atypical respiratory pathogens. Fluoroquinolones may be used as monotherapy to treat high-risk patients with acute exacerbation of chronic bronchitis, and for patients with community-acquired pneumonia requiring hospitalisation, but not admission to intensive care. Overall, the newer fluoroquinolones often achieve clinical cure rates in > or =90% of these patients. However, rates may be lower in hospital-acquired pneumonia, and this infection should be treated on the basis of anticipated organisms and evaluation of risk factors for specific pathogens such as Pseudomonas aeruginosa. In this setting, an antipseudomonal fluoroquinolone may be used in combination with an antipseudomonalbeta-lactam. Concerns are now being raised about the widespread use, and possibly misuse, of fluoroquinolones and the emergence of resistance among S. pneumoniae, Enterobacteriaceae and P. aeruginosa. A number of pharmacokinetic parameters such as the peak concentration of the antibacterial after a dose (C(max)), and the 24-hour area under the concentration-time curve (AUC24) and their relationship to pharmacodynamic parameters such as the minimum inhibitory and the mutant prevention concentrations (MIC and MPC, respectively) have been proposed to predict the effect of fluoroquinolones on bacterial killing and the emergence of resistance. Higher C(max)/MIC or AUC24/MIC and C(max)/MPC or AUC24/MPC ratios, either as a result of dose administration or the susceptibility of the organism, may lead to a better clinical outcome and decrease the emergence of resistance, respectively. Pharmacokinetic profiles that are optimised to target low-level resistant minor subpopulations of bacteria that often exist in infections may help preserve fluoroquinolones as a class. To this end, optimising the AUC24/MPC or C(max)/MPC ratios is important, particularly against S. pneumoniae, in the setting of lower respiratory tract infections. Agents such as moxifloxacin and gemifloxacin with high ratios against this organism are preferred, and agents such as ciprofloxacin with low ratios should be avoided. For agents such as levofloxacin and gatifloxacin, with intermediate ratios against S. pneumoniae, it may be worthwhile considering alternative dose administration strategies, such as using higher dosages, to eradicate low-level resistant variants. This must, of course, be balanced against the potential of toxicity. Innovative approaches to the use of fluoroquinolones are worth testing in further in vitro experiments as well as in clinical trials.

Role of antimicrobial agents in the management of exacerbations of COPD

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a common occurrence and characterize the natural history of the disease. Over the past decade, new knowledge has substantially enhanced our understanding of the pathogenesis, outcome and natural history of AECOPD. The exacerbations not only greatly reduce the quality of life of these patients, but also result in hospitalization, respiratory failure, and death. The exacerbations are the major cost drivers in consumption of healthcare resources by COPD patients. Although bacterial infections are the most common etiologic agents, the role of viruses in COPD exacerbations is being increasingly recognized. The efficacy of antimicrobial therapy in acute exacerbations has established a causative role for bacterial infections. Recent molecular typing of sputum isolates further supports the role of bacteria in AECOPD. Isolation of a new strain of Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae was associated with a considerable risk of an exacerbation. Lower airway bacterial colonization in stable patients with COPD instigates airway inflammation, which leads to a protracted self-perpetuating vicious circle of progressive lung damage and disease progression. A significant proportion of patients treated for COPD exacerbation demonstrate incomplete recovery, and frequent exacerbations contribute to decline in lung function. The predictors of poor outcome include advanced age, significant impairment of lung function, poor performance status, comorbid conditions and history of previous frequent exacerbations requiring antibacterials or systemic corticosteroids. These high-risk patients, who are likely to harbor organisms resistant to commonly used antimicrobials, should be identified and treated with antimicrobials with a low potential for failure. An aggressive management approach in complicated exacerbations may reduce costs by reducing healthcare utilization and hospitalization.

[ANTEAB: a study of early antibiotic therapy in intensive care management of acute exacerbations of chronic obstructive lung disease]

INTRODUCTION

Intensive Care Unit (ICU) admission for acute exacerbation of chronic obstructive lung disease (COLD) is a major cause of morbidity and mortality in such patients. Although bacterial and/or viral infections are considered as the major precipitating factor, the antibiotic strategy in this setting is unclear. The potential benefit of routine antibiotic therapy in the absence of evidence of overt infection remains controversial, and has not been adequately studied in patients admitted to the ICU. To assess the benefit (or lack thereof) of routine early systemic antibiotic therapy in patients with COLD admitted to the ICU.

METHODS

This is a multicenter, randomized, double-blind controlled trial, comparing amoxicillin-clavulanic acid administered for 7 days to a placebo. Patients included are those with documented or suspected COLD, exclusive of other bronchial or lung disease, and admitted for acute exacerbation, in the absence of overt sepsis or broncho-pneumonia, and having no other organ failure. Patients recently hospitalized, having received antibiotics for > 24 h, or on long-term steroids will not be included. Co-interventions (bronchodilators, steroids) are controlled for. Patients will be administered the antibiotic or placebo within 24 hours of admission.

EXPECTED RESULTS

A 20% reduction of the duration of clinical symptoms of exacerbation is expected. To this end, 520 patients are planned to be included in 15 centers in a 2-year period. Secondary end-points are the incidence of documented infection (lower respiratory tract or other sites), antibiotic use, the proportion of patients having infection with resistant bacteria, the incidence of endotracheal intubation, the duration of stay and mortality in the ICU and the hospital.

Factors Associated With Outcomes of Acute Exacerbations of Chronic Obstructive Pulmonary Disease

The purpose of this article is to provide a general review of the current literature on the factors associated with the outcomes of hospitalizations, survival and health-related quality of life in acute exacerbations of chronic obstructive pulmonary disease (AECOPD), highlighting the limitations and the complexities in interpretation of the results of current studies. There is no consensus definition for AECOPD; onsets may be difficult to define and the determination of duration elusive. The prevalence of acute exacerbations of COPD (AECOPD) in the community appears to be underestimated as exacerbations are underreported by patients and their doctors. Hospitalization for COPD is due mainly to severe AECOPDs which drive the cost of care. There are few longitudinal epidemiological studies on factors associated with hospitalizations for AECOPD. The results of current studies do not allow clear differentiation between associations that are predictors of event, the consequences of the event, or indicators of severity. Strategies to reduce severe exacerbations of COPD include pharmacological treatment, vaccinations, pulmonary rehabilitation, and home care programs. The optimal strategy for the reduction of hospitalization in COPD remains unclear. Long-term interventional studies are needed to provide clearer information for the prevention of exacerbations and hospitalizations in COPD.

Host defense function of the airway epithelium in health and disease: clinical background

Respiratory infection is extremely common and a major cause of morbidity and mortality worldwide. The airway epithelium has an important role in host defense against infection and this is illustrated in this review by considering infection by respiratory viruses. In patients with asthma or chronic obstructive pulmonary disease, respiratory viruses are a common trigger of exacerbations. Rhinoviruses (RV) are the most common virus type detected. Knowledge of the immunopathogenesis of such RV-induced exacerbations remains limited, but information is available from in vitro and from in vivo studies, especially of experimental infection in human volunteers. RV infects and replicates within epithelial cells (EC) of the lower respiratory tract. EC are an important component of the innate-immune response to RV infection. The interaction between virus and the intracellular signaling pathways of the host cell results in activation of potentially antiviral mechanisms, including type 1 interferons and nitric oxide, and in the production of cytokines and chemokines [interleukin (IL)-1 beta, IL-6, IL-8, IL-11, IL-16, tumor necrosis factor alpha, granulocyte macrophage-colony stimulating factor, growth-regulated oncogene-alpha, epithelial neutrophil-activating protein-78, regulated on activation, normal T expressed and secreted, eotaxin 1/2, macrophage-inflammatory protein-1 alpha], which influence the subsequent induced innate- and specific-immune response. Although this is beneficial in facilitating clearance of virus from the respiratory tract, the generation of proinflammatory mediators and the recruitment of inflammatory cells result in a degree of immunopathology and may amplify pre-existing airway inflammation. Further research will be necessary to determine whether modification of EC responses to respiratory virus infection will be of therapeutic benefit.

Chronic obstructive pulmonary disease: role of bacteria and guide to antibacterial selection in the older patient

Chronic obstructive pulmonary disease (COPD) is a common problem in the elderly. The disease is characterised by intermittent worsening of symptoms and these episodes are called acute exacerbations. The best estimate, based on several lines of evidence, is that approximately half of all exacerbations are caused by bacteria. These lines of evidence include studies of lower respiratory tract bacteriology during exacerbations, correlation of airways' inflammation with results of sputum cultures during exacerbations, analysis of immune responses to bacterial pathogens, and the observation in randomised, prospective, placebo-controlled trials that antibacterial therapy is of benefit. The most important bacterial causes of exacerbations of COPD are nontypeable Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae and Chlamydia pneumoniae. In approaching the elderly patient with an exacerbation, it is useful to consider the severity of the exacerbation based on three cardinal symptoms: increased sputum volume, increased sputum purulence and increased dyspnoea compared with baseline. Patients experiencing moderate (two symptoms) or severe (all three symptoms) exacerbations benefit from antibacterial therapy. Consideration of underlying host factors allows for a rational choice of antibacterial agent. Patients are considered to have 'simple COPD' or 'complicated COPD' based on: (i) the severity of underlying lung disease; (ii) the frequency of exacerbations; and (iii) the presence of comorbid conditions. It is proposed that patients with simple COPD are treated with doxycycline, a newer macrolide, or an extended-spectrum oral cephalosporin; and patients with complicated COPD are treated with amoxicillin/clavulanate or a fluoroquinolone. The major goals of antibacterial therapy for exacerbations of COPD are acceleration of symptom resolution and prevention of the complications of exacerbation.

The Role of Antibiotics in Acute Exacerbations of Chronic Obstructive Pulmonary Disease

Our understanding of the pathogenesis and consequences of acute exacerbations of chronic obstructive pulmonary disease (COPD) has increased considerably in the past decade. Several new lines of evidence support bacterial causation of about half the exacerbations. Contrary to previous data, recent studies with improved methodology have demonstrated that exacerbations do contribute to the loss of lung function in COPD. Another interesting new observation is that colonization by bacterial pathogens may not be innocuous, and in fact may lead to airway inflammation and contribute to pathogenesis of COPD. Evidence that bacteria cause exacerbations, that exacerbations contribute to loss of lung function, and that chronic colonization by bacteria may be harmful, has emphasized the potential importance of appropriate antibiotics in the treatment of exacerbations. An unfortunate paucity of data does not allow evidence-based recommendations to be made for optimal choice of antibiotics for exacerbations of COPD. Emerging data that antibiotics differ in unconventional measures of efficacy such as time to next exacerbation, improvement in health-related quality of life, and bacteriologic eradication will help us make concrete recommendations in the future.

A comparison of 5-day courses of dirithromycin and azithromycin in the treatment of acute exacerbations of chronic obstructive pulmonary disease

BACKGROUND

Short-term use of antibiotics has become a common component of the management of acute exacerbations of chronic bronchitis (AECB), particularly in complex cases with productive cough or purulent phlegm. The macrolide antibiotics, particularly second-generation agents such as dirithromycin and azithromycin, are among the antibiotic classes frequently recommended and used to treat upper and lower respiratory infections, including AECB.

OBJECTIVE

This study compared the clinical efficacy and tolerability of 5-day courses of dirithromycin and azithromycin given once daily for the treatment of acute exacerbations of chronic obstructive pulmonary disease (COPD).

METHODS

This randomized, investigator-blinded, parallel-group clinical trial was conducted at 5 centers in the United States. Eligible patients were adult (age >35 years) smokers or ex-smokers (smoking history of at least 10 pack-years) with chronic bronchitis and an acute exacerbation, defined by the occurrence of increased dyspnea and/or productive cough and feverishness within 48 hours of enrollment. Before randomization, an attempt was made to obtain a sputum specimen from each patient for Gram's staining and culture. Patients were randomized to receive dirithromycin 500 mg QD for 5 days or azithromycin 500 mg QD on day 1 and 250 mg QD on days 2 to 5. Clinical efficacy was assessed separately by patients and physicians at early (days 7-10) and late (days 25-35) posttreatment visits.

RESULTS

Eighty-six patients (48 women, 38 men; mean age, 55 years) with a mean smoking history of 31 pack-years were included in the intent-to-treat analysis. Forty-six (54%) patients were randomized to dirithromycin and 40 (47%) patients to azithromycin. Clinical efficacy was reported in a high proportion of patients in both treatment groups, both at the early posttreatment visit (84.8% dirithromycin, 75.7% azithromycin; difference dirithromycin - azithromycin, 9.1%; 95% CI, -8.2 to 26.4) and the late posttreatment visit (95.5% and 86.5%, respectively; difference dirithromycin - azithromycin, 9.0%; 95% CI, -3.7 to 21.6). A similar proportion of patients required a second course of antibiotics over the study period (20.5% dirithromycin, 27.0% azithromycin; difference dirithromycin - azithromycin, -6.6%; 95% CI, -25.2 to 12.1). Only 42 (48.8%) patients were able to produce a sputum sample before receiving study treatment, and of these, only 20 (47.6%) demonstrated a preponderance of neutrophils on Gram's staining. Both treatments were well tolerated.

CONCLUSIONS

The results of this study suggest comparable clinical efficacy between 5-day courses of once-daily dirithromycin and azithromycin in acute exacerbations of COPD. There were insufficient data to permit meaningful comparison of the bacteriologic efficacy of these macrolide antibiotics.

An open-label, randomized, multicenter, comparative study of the efficacy and safety of 7 days of treatment with clarithromycin extended-release tablets versus clarithromycin immediate-release tablets for the treatment of patients with acute bacterial exacerbation of chronic bronchitis

OBJECTIVE

The aim of this study was to compare the efficacy and safety of clarithromycin extended-release (ER) tablets and immediate-release (IR) tablets.

METHODS

This was a Phase III, open-label, randomized, multicenter, comparative study in ambulatory patients with a diagnosis of acute exacerbation of chronic bronchitis (AECB). Eligible patients were randomized 1:1 to receive either 1 clarithromycin ER 500-mg tablet QD for 7 days or 1 clarithromycin IR 250-mg tablet BID for 7 days. Clinical and bacteriologic responses were assessed within 48 hours after the last dose of study drug and at a test-of-cure visit 21 +/- 2 days posttreatment.

RESULTS

Of 233 patients randomized, 162 (86/117 [73.5%] in the ER group and 76/115 [66.1%] in the IR group) completed the study protocol. Compliance did not differ significantly between the treatment groups; however, significantly fewer patients in the ER group reported missing doses of study medication than in the IR group (7/118 [5.9%] vs 16/115 [13.9%]; P = 0.04). The clinical cure rates for the clarithromycin ER and IR groups were 81.0% (68/84) and 82.1% (64/78) and the clinical success (clinical cure plus clinical improvement) rates were 94.0% [79/84] and 89.7% [70/78], respectively. There were insufficient data for analysis of bacteriologic efficacy. However, bacteria were eradicated or presumed eradicated in 71.4% (10/14) and 79.2% (19/24) of patients in the ER and IR groups, respectively. The number of adverse events (AEs) considered to be possibly or probably related to study drug (23.4% [52/222] of patients receiving clarithromycin ER and 24.4% [43/176] of patients receiving clarithromycin IR) was similar between groups, as was the severity of these events (94.2% [49/52] in the ER group classified as mild or moderate vs 93.0% [40/43] in the IR group). Overall, the most commonly reported AEs were diarrhea, nausea, abdominal pain, headache, and taste disturbance.

CONCLUSION

Clarithromycin ER 500-mg tablets QD for 7 days were as effective and well tolerated as clarithromycin IR 250-mg tablets BID for 7 days in treating adults with AECB.

New strains of bacteria and exacerbations of chronic obstructive pulmonary disease

BACKGROUND

The role of bacterial pathogens in acute exacerbations of chronic obstructive pulmonary disease is controversial. In older studies, the rates of isolation of bacterial pathogens from sputum were the same during acute exacerbations and during stable disease. However, these studies did not differentiate among strains within a bacterial species and therefore could not detect changes in strains over time. We hypothesized that the acquisition of a new strain of a pathogenic bacterial species is associated with exacerbation of chronic obstructive pulmonary disease.

METHODS

We conducted a prospective study in which clinical information and sputum samples for culture were collected monthly and during exacerbations from 81 outpatients with chronic obstructive pulmonary disease. Molecular typing of sputum isolates of nonencapsulated Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and Pseudomonas aeruginosa was performed.

RESULTS

Over a period of 56 months, the 81 patients made a total of 1975 clinic visits, 374 of which were made during exacerbations (mean, 2.1 per patient per year). On the basis of molecular typing, an exacerbation was diagnosed at 33.0 percent of the clinic visits that involved isolation of a new strain of a bacterial pathogen, as compared with 15.4 percent of visits at which no new strain was isolated (P<0.001; relative risk of an exacerbation, 2.15; 95 percent confidence interval, 1.83 to 2.53). Isolation of a new strain of H. influenzae, M. catarrhalis, or S. pneumoniae was associated with a significantly increased risk of an exacerbation.

CONCLUSIONS

The association between an exacerbation and the isolation of a new strain of a bacterial pathogen supports the causative role of bacteria in exacerbations of chronic obstructive pulmonary disease.

Infections

Infection, in particular by respiratory viruses, plays an important role in triggering exacerbations and has also been implicated in the etiology of asthma and chronic obstructive pulmonary disease (COPD). This chapter reviews the epidemiological evidence that implicates infectious pathogens as triggers. The chapter also discusses the mechanisms of interaction between the host-pathogen response and preexisting airway pathology resulting in an exacerbation. Much of the treatment of infective exacerbations for both asthma and COPD is symptomatic, consisting of bronchodilators or supportive in the form of oxygen, and in severe cases it includes noninvasive or invasive ventilatory measures. The current therapy for virus-induced exacerbations of asthma and COPD relies on increased treatment of preexisting disease. Antibiotics are indicated for bacterial infections. The effective use of antiviral agents, particularly for influenza viruses, requires viral diagnosis, commencement of treatment early in the course of an exacerbation, or the targeting of high-risk groups for prophylaxis. Alternative strategies for drug development involve the identification of key factors common to exacerbations induced by a range of different viruses. Increased knowledge of the host–virus interaction can help in designing treatments that can increase virus clearance and minimize immunopathology.

Antibiotics

This chapter discusses the bacterial pathogens that cause infective exacerbations, trials of antimicrobial therapy, individual antimicrobial agents, and guidelines for their use in the treatment of both asthma and chronic obstructive pulmonary disease (COPD). The relationship between respiratory tract infection, especially viral infection, and exacerbations of airway diseases is very well established. However, research is required to find new ways to distinguish between the colonization and infective exacerbations of COPD to gain a better understanding of the role of infection in the disease. With advances in molecular biology, the antigenic structures of bacteria and the evaluation of the antibody response to antigens can become the basis for identifying an acute exacerbation of COPD (AECB). Most clinical trials of antibiotics were performed for licensing, and patients with pathogens resistant to different antimicrobials were excluded. Future studies of new antimicrobials should examine clinical efficacy more stringently based on a classification system that would help select patients most likely to benefit from an antibiotic. These studies should also include well-defined prospective economic analyses and quality-of-life assessment to ascertain the cost utility of the antibiotic in question.

Antibacterials and Acute Exacerbation of Chronic Bronchitis

The utility of antibacterials in the management of acute exacerbations of chronic bronchitis (AECB) and the related lung pathology, chronic obstructive pulmonary disease (COPD), has been debated for decades. Data presented in this article document that more expensive antimicrobials may be favored in AECB treatment to prevent adverse outcomes to patients, namely antimicrobial failure and hospitalization. Identified patient-specific variables that may lead to treatment failure include right- or left-sided heart failure and ≥4 exacerbations/year. Risk factors for hospitalization include age ≥65 years and severe pulmonary and nonpulmonary dysfunction. However, these risk factors have never been formally validated in a prospective, randomized trial. Drug-resistant organisms have not been documented to cause antimicrobial failure or hospitalization, however, more data are needed in this growing area.

Optimizing economic outcomes in acute exacerbations of chronic bronchitis

The treatment of community-acquired respiratory tract infections, such as acute exacerbations of chronic bronchitis (AECB), constitutes a huge socioeconomic burden. In most cases, an antimicrobial agent is advocated to lessen morbidity and prevent serious clinical sequelae. Use of antimicrobial agents for AECB, however, is controversial, as it is difficult to distinguish between bacterial and nonbacterial AECB, and only marginal benefits have been reported. Antimicrobial agents, however, have reduced relapse rates, prolonged the time between exacerbations, shortened the duration of symptoms, and reduced the need for hospitalization. Microbiologic resistance and individual patient characteristics play important roles in determining the most appropriate antimicrobial agent for patients with AECB. More research on the effect of resistant bacteria on antimicrobial response rates will enable physicians to prescribe economically rational antimicrobial therapy for this common infection.