Pseudomonas infection signals poor outcome for COPD patients

By Helen Albert

Patients with chronic obstructive pulmonary disease (COPD) who are infected with Pseudomonas aeruginosa have a worse clinical outcome and are more likely to be hospitalized than those without the infection, states recent research.

"Previous studies have shown that infection with P. aeruginosa is more common in patients with more severe COPD [compared with less severe COPD]," said study researcher Sanjay Sethi (University of Buffalo, New York, USA) at the American Thoracic Society International Conference in San Francisco, California in a press statement.

"In this study, we wanted to determine if infection with P. aeruginosa was associated with poorer clinical outcomes, such as hospitalizations, need for intensive care, and greater numbers of exacerbations," he added.

The researchers recruited 110 patients with COPD to take part in their study between March 1994 and January 2011. Once enrolled, the participants visited the clinic monthly and during any exacerbations. Sputum samples were taken at each visit and tested for P. aeruginosa infection.

The participants were followed up for a minimum of 6 months. They were divided into P. aeruginosa infected (n=55; one or more positive sputum tests) and uninfected groups (n=55). If information was available on patients' health status before becoming infected with P. aeruginosa (phase 1), it was compared with their status after being infected (phase 2).

Despite the P. aeruginosa infected and noninfected individuals being well matched in terms of age, gender, pack-years of smoking, and FEV1% predicted, patients infected with P. aeruginosa had a greater risk for hospitalization and a worse outcome than uninfected individuals, although the difference was not statistically significant.

However, there were significantly more hospitalizations, exacerbations, and intensive care admissions in patients who were infected in phase 2 versus phase 1.

"Similar analyses are being performed with other bacterial pathogens identified in our COPD study clinic data to determine if this observation is unique to P. aeruginosa or extends to other bacterial pathogens," said Sethi.

"The possibility exists that, in our study, P. aeruginosa may be simply a 'colonizing bacteria' - a marker for worsening COPD - rather than a cause of the worse clinical outcomes," he added.

"However, we and others have shown that P. aeruginosa behaves as an infectious pathogen in COPD. Also, in related chronic airway diseases, such as cystic fibrosis, Pseudomonas infection is a major cause of morbidity and mortality."

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