Viral and bacterial infection in acute asthma and chronic obstructive pulmonary disease increases the risk of readmission

Abstract

Background and objective: Infection is as an important trigger for acute asthma and chronic obstructive pulmonary disease (COPD). The aim of this article was to determine the prevalence and impact of virus and bacterial infections in acute asthma and COPD.

Methods: Subjects were recruited, within 24 h of hospital admission for acute exacerbations of asthma and COPD. Nose/throat swabs and sputum samples were collected and examined by multiplex polymerase chain reaction for respiratory viruses and cultured for bacteria. The primary outcomes were length of stay (LOS) and readmission to hospital within 60 days.

Results: A total of 199 subjects were recruited (96 had asthma and 103 COPD) for 235 events (36 re-presented). A virus was detected in 79 subjects (40%), bacteria in 41 (21%), and of these, 18 had both. Rhinovirus A was the most frequently isolated virus. A multivariate analysis was performed to control for confounders. It found that detection of a virus, a virus and bacteria, forced expiratory volume in 1 s (FEV(1)) and a diagnosis of COPD were all independent predictors of prolonged LOS, while risk of readmission within 60 days was increased with virus infection alone, virus and bacterial infection, lower FEV(1) and current smoking.

Conclusions: Virus infection, especially in the presence of chronic bacterial infection, is an important determinant of more severe acute exacerbations in both asthma and COPD, and patients with co-infections are more likely to be readmitted to hospital following their exacerbation.

Keywords: asthma; chronic obstructive pulmonary disease; infection and inflammation; respiratory infection; viral infection.

Figure 1

Seasonal distribution of virus. Number of respiratory viruses detected per season between March 2007 and September 2009. Autumn = March–May, Winter = June–August, Spring = September–November and Summer = December–February. CoV, non‐severe acute respiratory syndrome coronavirus; EV, enterovirus; FLU, influenza virus (A and B), hMPV, human metapneumovirus; RSV, respiratory syncytial virus (A and B); RV, rhinovirus. , RV; , EV; , FLU; , CoV; , hMPV; , RSV.

Figure 2

Rhinovirus phylogenetic tree. A phylogenetic tree depicting the relationship between known rhinovirus serotypes and the rhinovirus positives from our study. Published rhinovirus serotypes are designated by ‘HRV’. Sequences identified in this study are designated by molecular code A followed by a number. There are three main rhinovirus species, HRV‐A, HRV‐B and HRV‐C.

Figure 3

Bacteria isolates. Number of bacteria isolates detected between March 2007 and September 2009 for selected prominent bacteria. Haemophilus influenzae followed by Pseudomonas aeruginosa, Moroxella catarrhalis, Streptococcus pneumonia, Staphylycoccus aureus and Stentotrophomonas maltophilia.