In the second part of this study, 10 subjects will be recruited for the Exacerbation Cohort. Subjects will provide at least 1 gram of expectorated sputum and 40-ml of blood within 72 hours of hospital admission. Sputum and blood will be processed and analyzed as described above. Sputum and blood also will be obtained at the end of treatment (within 72 hours of completion of IV antibiotics) when the subject is at his or her baseline as determined by the managing physician. Clinical data will be captured from the subject's hospitalization records including lung function measures and clinical culture results.