Pseudomonas aeruginosa infection increases the readmission rate of COPD patients

Choi, Juwhan; Oh, Jee Youn; Lee, Young Seok; Hur, Gyu Young; Lee, Sung Yong; Shim, Jae Jeong; Kang, Kyung Ho; Min, Kyung Hoon

In this study, we analyzed the effect of bacterial or viral identification on readmission of patients with severe AECOPD. A previous study based in London showed that 10.2% of severe AECOPD patients were readmitted within 30 days after discharge and 17.8% were readmitted within 90 days. 13 Other studies of readmission in severe AECOPD have focused on age, comorbidity, inhaler use, and psychological disorders. 11, [14] [15] [16] There is a lack of data on readmission focused on the bacterial or viral identification causing exacerbation. This study is the first to demonstrate that identification of P. aeruginosa correlates with readmission rate in severe AECOPD. P. aeruginosa is a Gram-negative rod bacterium that can cause opportunistic infections. It is the causative agent of infections mainly in immunocompromised or chronic lung disease patients, including patients with cystic fibrosis or COPD. It has become an important pathogen with increases in immunosuppressive treatments, chemotherapy, and use of intensive care units. P. aeruginosa is currently the most common causative agent of nosocomial infection and the second most common causative agent of ventilator-associated pneumonia in the US. 17 P. aeruginosa infections are difficult to treat. First, P. aeruginosa has innate resistance to many of the antimicrobial agents commonly used in the treatment of pneumonia. P. aeruginosa has several broadly specific multidrug efflux systems that provide this innate resistance. 18 Second, P. aeruginosa easily acquires resistance compared to other bacteria. 19 P. aeruginosa strains possess large genomes (∼5-7 Mbp), can produce multiple secondary metabolites and polymers, and has better quorum sensing than other bacteria, which allows spreading of acquired resistance between bacteria. 20 Third, P. aeruginosa secretes virulence factors and impairs the immune system. For example, P. aeruginosa secretes elastase B and escapes phagocytosis. 21 P. aeruginosa also secretes exoenzyme S (ExoS), a bifunctional toxin encoded by the exoS gene, which disrupts the pulmonary vascular barrier, resulting in bacteremia. 22 The identification of P. aeruginosa means that treatment and complete eradication are difficult. Compared to other bacteria, antibiotics are used for longer times, and the duration of hospitalization is greater, often leading to secondary hospital infections and antibiotic side effects.