Infection With Transmissible Strains of Pseudomonas aeruginosa and Clinical Outcomes in Adults With Cystic Fibrosis

Abstract

SEUDOMONAS AERUGINOSA IS A gram-negative bacterium that causes chronic endobronchial infections in 60% to 70% of adult patients with cystic fibrosis (CF). 1 Infection with P aeruginosa is associated with increased morbidity and mortality for patients with CF, irrespective of lung function. 2,3 However, there is heterogeneity in the type and timing of outcome among those who are infected with P aeruginosa; some patients experience a rapid decline in pulmonary function after infection and others harbor the organism for extended periods without any obvious adverse effects. 4 The marked difference in prognosis among patients with P aeruginosa has not been adequately explained , but it may be due in part to differences among infecting strains. 5 P aeruginosa transmissible strains are genetically identical strains that infect Author Affiliations are listed at the end of this article.

Twenty-Five-Year Outbreak of Pseudomonas aeruginosa Infecting Individuals with Cystic Fibrosis: Identification of the Prairie Epidemic Strain

“…Because our entire clinic cohort was not assessed (i.e., we excluded those without P. aeruginosa infection), this number overestimates the true measure of incident infections. These low rates of acquisition are in accord with the work of Aaron et al during their 3-year prospective study involving 446 CF adults in Ontario, as they observed an incidence of 7 cases per 1,000 person-years (9).…”

“…Only strain A (LES), strain B, Houston-1, and now PES have been described to date in North America (9,31,32). The mechanisms by which these strains are capable of being transmitted from one patient to another are poorly understood, but cough aerosol is the most commonly presumed mechanism (16,33).…”

“…Pulsed-field gel electrophoresis (PFGE) was used as the primary screening procedure for all isolates, using a protocol modified from the work of Aaron et al (9). Gels were electrophoresed using a Chef Mapper XA system (Bio-Rad, Hercules, CA) under the following conditions: buffer temperature, 10°C; voltage, 6.0 V/cm; run time, 20 h; included angle, 120°; initial switch time, 5 s; and final switch time, 45 s. Strains that had banding patterns that were Ն80% identical were considered related, conforming to the Tenover criteria, in which isolates with 1 to 3 band differences are still considered related (20,21).…”

“…The acquisition of this organism and its conversion to a hyper-alginate-producing mucoid phenotype are associated with deteriorating clinical status, increased treatment requirements, and progression to end-stage disease (4)(5)(6)(7)(8). P. aeruginosa, which is ubiquitous in the environment (9)(10)(11), was initially presumed to be acquired from each patient's local environment and not transmitted among patients (12). However, multiple local, national, and transcontinental epidemic strains of P. aeruginosa have now been described.…”

“…However, multiple local, national, and transcontinental epidemic strains of P. aeruginosa have now been described. Several of these strains are associated with an accelerated clinical deterioration notable for increased treatment burden (13,14), increased exacerbation frequency (14), and progression to respiratory failure (9). For further information on transmissible strains of P. aeruginosa in CF, the reader is referred to a recent review by Fothergill et al (15).…”