The importance of bacterial and viral infections associated with adult asthma exacerbations in clinical practice.

Motoyasu Iikura,Ayano Sato,Jin Takasaki,Haruhito Sugiyama,Haruna Masaki,Nobuyuki Kobayashi,Junko Hirashima,Haruka Chino,Sho Watanabe,Sachiko Yamaguchi,Rikiya Koketsu,Satoru Ishii,Masayuki Hojo,Go Naka,Shinyu Izumi,Shoki Ro,Susumu Nakae,Oliver Schildgen

doi:10.1371/journal.pone.0123584

Abstract

BackgroundViral infection is one of the risk factors for asthma exacerbation. However, which pathogens are related to asthma exacerbation in adults remains unclear.ObjectiveThe relation between various infections and adult asthma exacerbations was investigated in clinical practice.MethodsThe study subjects included 50 adult inpatients due to asthma exacerbations and 20 stable outpatients for comparison. The pathogens from a nasopharyngeal swab were measured by multiplex PCR analysis.ResultsAsthma exacerbations occurred after a common cold in 48 inpatients. The numbers of patients with viral, bacterial, or both infections were 16, 9, and 9, respectively. The dominant viruses were rhinoviruses, respiratory syncytial virus, influenza virus, and metapneumovirus. The major bacteria were S. pneumoniae and H. influenzae. Compared to pathogen-free patients, the patients with pathogens were older and non-atopic and had later onset of disease, lower FeNO levels, lower IgE titers, and a higher incidence of comorbid sinusitis, COPD, or pneumonia. Compared to stable outpatients, asthma exacerbation inpatients had a higher incidence of smoking and comorbid sinusitis, COPD, or pneumonia. Viruses were detected in 50% of stable outpatients, but a higher incidence of rhinovirus, respiratory syncytial virus, and metapneumovirus infections was observed in asthma exacerbation inpatients. H. influenzae was observed in stable asthmatic patients. Other bacteria, especially S. pneumoniae, were important in asthma exacerbation inpatients.ConclusionViral or bacterial infections were observed in 70% of inpatients with an asthma exacerbation in clinical practice. Infection with S. pneumoniae was related to adult asthma exacerbation.

Highlights

Inhaled antigens including house dust mite are known to be the major cause of asthma exacerbation
Asthma exacerbation inpatients had a higher incidence of smoking and comorbid sinusitis, chronic obstructive pulmonary disease (COPD), or pneumonia
Viruses were detected in 50% of stable outpatients, but a higher incidence of rhinovirus, respiratory syncytial virus, and metapneumovirus infections was observed in asthma exacerbation

Summary

Results

Fifty patients were admitted to our hospital for asthma exacerbations Asthma exacerbation inpatients had higher incidences of smoking and comorbid sinusitis, COPD, and pneumonia. Co-infections of virus and bacteria were detected in 9 patients with no associations with specific viruses and specific bacteria (Table 2). Compared to pathogen-free patients, the infected patients were older and non-atopic and had later onset of disease, lower FeNO levels, higher IgE titers, and a higher incidence of comorbid sinusitis, COPD, and pneumonia (Table 3). Compared to bacteria-free patients, the bacteria-detected patients were high incidence of comorbid sinusitis and pneumonia (Table 3). Pathogen comparison between stable outpatients and asthma exacerbation patients There was no difference in the pathogen detection rate between inpatients and outpatients (Table 1). Other bacteria other than H. influenzae, especially S. pneumoniae, were important in asthma exacerbation inpatients (Table 4)

Introduction

Ethics statement

Study design

Discussion