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

Abstract

Transmissible strains of Pseudomonas aeruginosa have been described for cystic fibrosis (CF) and may be associated with a worse prognosis. Using a comprehensive strain biobank spanning 3 decades, we sought to determine the prevalence and stability of chronic P. aeruginosa infection in an adult population. P. aeruginosa isolates from sputum samples collected at initial enrollment in our adult clinic and at the most recent clinic visit were examined by a combination of pulsed-field gel electrophoresis and multilocus sequence typing and compared against a collection of established transmissible and local non-CF bronchiectasis (nCFB) isolates. A total of 372 isolates from 107 patients, spanning 674 patient-years, including 66 patients with matched isolates from initial and final encounters, were screened. A novel clone with increased antibacterial resistance, termed the prairie epidemic strain (PES), was found in 29% (31/107 patients) of chronically infected patients referred from multiple prairie-based CF centers. This isolate was not found in those diagnosed with CF as adults or in a control population with nCFB. While 90% (60/66 patients) of patients had stable infection over a mean of 10.8 years, five patients experienced strain displacement of unique isolates, with PES occurring within 2 years of transitioning to adult care. PES has been present in our cohort since at least 1987, is unique to CF, generally establishes chronic infection during childhood, and has been found in patients at the time of transition of patients from multiple prairie-based CF clinics, suggesting broad endemicity. Studies are under way to evaluate the clinical implications of PES infection.

Prevalence and Outcomes of Achromobacter Species Infections in Adults with Cystic Fibrosis: a North American Cohort Study

“…The reason for spontaneous clearance of infection after prolonged carriage is not immediately clear and may simply reflect the natural pattern of infection for Achromobacter, the organism being overtaken by another pathogen, or immune clearance by the patient. Regardless, this highlights how the natural history of novel infections in CF airways may differ from that of P. aeruginosa, suggesting a need for unique terminology to account for these fundamental differences (7,36). Additionally, it demonstrates the difficulty of short-term studies and the value of long-term follow-up.…”

“…To investigate the presence of clonality, strains underwent pulsed-field gel electrophoresis (PFGE) according to established protocols adapted from the work of Parkins et al (36). SpeI (New England BioLabs)-digested samples were run in 1% SeaKem Gold agarose.…”

Carbapenem-Resistant Non-Glucose-Fermenting Gram-Negative Bacilli: the Missing Piece to the Puzzle

“…Most worrisome are reports of clonal outbreaks of P. aeruginosa between persistently colonized cystic fibrosis patients (38)(39)(40). As a result, some centers now spatially segregate patients colonized with clonal strains, which has proven effective at preventing transmission (41).…”

Development and Validation of a PCR Assay To Detect the Prairie Epidemic Strain of Pseudomonas aeruginosa from Patients with Cystic Fibrosis

“…Furthermore, its prevalence has been unchanged through 3 decades of patients who transitioned to the CACFC. PES is more likely to be antibiotic resistant than are unique strains of P. aeruginosa, and infection with PES has been associated with increased rates of lung function decline, pulmonary exacerbation frequency, and progression to death and/or transplantation (7,8).The importance of identifying epidemic P. aeruginosa strains in CF has long been recognized. Typing strategies that are commonly currently employed include pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and random amplified polymorphic DNA PCR (RAPD-PCR) (7, 9, 10).…”

“…Many of these strains are associated with a poor prognosis, manifesting as increased rates of lung function decline, exacerbation frequency, and treatment burden; decreased quality of life; and hastened progression to end-stage lung diseases (5,6). We recently described a novel epidemic P. aeruginosa strain, the prairie epidemic strain (PES) (multilocus sequence type 192) (7). PES was found in one-quarter of patients attending the Calgary Adult CF Clinic (CACFC) and from patients who were transferred from other Prairie-based clinics, suggesting broad endemicity in western Canada.…”