• To better define risk factors for first isolation of Pa from respiratory culture, as well as for emergence of mucoid Pa and antibiotic-resistant Pa. [ Time Frame: over the two-to-five-year observational period ] [ Designated as safety issue: No ]
  
• To better define clinical outcomes associated with acquisition of Pa, as well as outcomes associated with emergence of mucoid Pa and antibiotic-resistant Pa. [ Time Frame: over the two-to-five-year observational period ] [ Designated as safety issue: No ]
  

• Among subjects who acquire Pa but do not enroll in the EPIC Clinical Trial, to examine the effect of the duration of Pa positive respiratory cultures prior to initiation of anti-pseudomonal therapy and the type and length of anti-pseudomonal therapy. [ Time Frame: over the two-to-five year observational period ] [ Designated as safety issue: No ]
  
• To describe temporal changes in anti-pseudomonal serology and airway microbiology. [ Time Frame: over the two-to-five year observational period ] [ Designated as safety issue: No ]
  
• To better define clinical outcomes associated with isolation of S. aureus from respiratory cultures, as well as outcomes associated with emergence of methicillin-resistant S. aureus (MRSA). [ Time Frame: over the two-to-five year observational period ] [ Designated as safety issue: No ]
  
• To bank Pa and S. aureus isolates and serum samples for future studies to enhance the understanding of early CF lung disease. [ Time Frame: over the two-to-five year observational period ] [ Designated as safety issue: No ]
  
• To use and bank DNA samples for analyses of genetic factors that may be associated with CF pathogenesis, disease progression, and clinical outcomes. [ Time Frame: over the two-to-five year observational period ] [ Designated as safety issue: No ]
  
• For subjects who enroll in EPIC Clinical Trial, to collect ancillary data on risk factors preceding trial enrollment and to provide follow-up for clinical endpoints after trial participation has ended. [ Time Frame: over the two-to-five year observational period ] [ Designated as safety issue: No ]
  
• To provide a cohort of subjects who acquire Pa during the observational study period but who do not enroll in EPIC Clinical Trial and therefore receive non protocol-based anti-pseudomonal therapy. [ Time Frame: over the two-to-five year observational period ] [ Designated as safety issue: No ]
  

The EPIC Observational Study is a longitudinal, prospective, observational study that will be conducted at 59 sites, including the 55 sites of the EPIC Clinical Trial.

The EPIC Observational Study will serve as a freestanding epidemiologic study of the risk factors for and clinical impact of initial Pa acquisition and anti-pseudomonal therapy. Defining the risk factors for Pa acquisition can potentially allow for preventive measures and identification of high-risk populations requiring closer monitoring. Despite rigorous data collection, previous studies have been limited by small sample sizes and by conduct at one or two centers. This study will include a much larger sample size from many more centers than previous studies. It will thus provide for more generalizable results and more precise risk estimates for previously identified risk factors for Pa acquisition, and it will allow for exploration of novel risk factors not included in earlier studies. Better understanding of the clinical outcomes associated with Pa acquisition and the outcomes associated with different types of anti-pseudomonal therapies will inform the development of rational early intervention treatment regimens. Better knowledge about temporal relationships between respiratory signs and symptoms, Pa serology, and CF airway microbiology may lead to improved strategies for early detection of Pa and could have important implications for the timing of interventions aimed at preventing or treating early Pa acquisition. Finally, this study will serve as an important source of Pa and S. aureus isolates, serum samples, and DNA samples that will be used and banked for studies designed to enhance the understanding of the pathogenesis of CF, e.g., microarray investigations of early Pa isolates, investigations to identify proteomic biomarkers of airway inflammation, and investigations to identify genetic factors related to CF disease progression, including early lung disease, and clinical outcomes.