The Role of Other Bacteria, Fungi, and Viruses in Bronchiectasis

Bronchiectasis, a heterogeneous disease, is characterized by a vicious cycle of airway infection and inflammation that results in structural damage to the airways and the surrounding lung parenchyma [1]. Many microorganisms have been associated with bronchiectasis, both as a complication of the anatomic abnormalities and possibly as a cause of the structural disease as well [2, 3]. Diverse polymicrobial communities are present in the airways of patients with bronchiectasis [4]. Studies using standard microbiologic culture techniques have demonstrated the presence of bacterial, fungal, and viral pathogens in the lungs of bronchiectasis patients both when the patient is clinically stable and when there is an exacerbation of disease [2, 5]. Newer molecular techniques have broadened our understanding of the microbiome in bronchiectasis patients [4, 6]. Pseudomonas aeruginosa has been repeatedly shown to be a problematic pathogen in patients with bronchiectasis and is associated with a worse prognosis [7, 8]. Multiple epidemiologic reports have shown that approximately 20–35% of patients worldwide with bronchiectasis are chronically infected with P. aeruginosa [2, 9, 10]. Several antibiotic trials have been published where the main target of therapy is Pseudomonas aeruginosa [11–17]. (See Chap. 10.1007/978-3-319-61452-6_11 for a full review of P. aeruginosa infections associated with bronchiectasis.) Another problematic group of pathogens, nontuberculous mycobacteria (NTM), is a common infecting organism in bronchiectasis, particularly in the United States and in parts of Asia [2, 18]. NTM infection is fully discussed in Chap. 10.1007/978-3-319-61452-6_13. In this chapter, we will review the role of bacterial pathogens other than P. aeruginosa and the impact of fungal and viral infections in bronchiectasis patients. (See Table 13.1.)