Incidence, impact and natural history of Klebsiella species infections in cystic fibrosis: A longitudinal single center study

INTRODUCTION: Non-classical pathogens including Klebsiella spp. have been observed infrequently as part of large cystic fibrosis (CF) cohort studies, but there are sparse data regarding their impact on clinical outcomes. OBJECTIVES: This study was conducted to elucidate the clinical impact of Klebsiella species infections in CF patients. METHODS: Adult patients attending a Canadian CF clinic with Klebsiella spp. positive sputum cultures from 1978-2013 were assessed. Infection was categorized as transient or prolonged (>= 50% positive cultures in one year). Rates of pulmonary exacerbations (PEx) at incident infection and risk factors for developing prolonged infections were determined. Isolates were genotyped and tested for antibiotic susceptibility and hypermucoviscosity. RESULTS: Thirty unique infections among 25 patients (8% of clinic population) were detected, in which 9 K. pneumoniae, 17 K. oxytoca and 4 K. ozaenae species were identified. Four patients developed prolonged infection, however, all but one subsequently cleared. Incident infection was associated with increased risk of PEx compared to clinic visits before but not after isolation. Patients progressing to prolonged infections did not differ in demographics, comorbidities or treatments, compared to transiently infected individuals. Hypermucoviscosity and multi-drug resistance were uncommon. Individuals were infected with only single strains of Klebsiella at a time and no evidence of cross infection was observed. CONCLUSIONS: Klebsiella infections are rare at any individual time point in CF. However, they are observed in almost 10% of a patient cohort followed longitudinally and are not clearly associated with either acute or sub-acute clinical deterioration.