Sphingobacterium respiratory tract infection in patients with cystic fibrosis

Abstract

Background: Bacteria that belong to the genus Sphingobacterium are Gram-negative, non-fermentative bacilli, ubiquitous in nature and rarely involved in human infections. The aims of this study were to evaluate the epidemiology of infection by Sphingobacterium in a cohort of patients affected by Cystic Fibrosis (CF), the antibiotic susceptibility and the DNA fingerprinting of the isolated strains and to analyze some clinical outcomes of the infected patients.

Findings: Between January 2006 and June 2008, patients (n = 332) attending the Regional CF Unit in Naples, Italy, were enrolled. Sputum samples were processed for microscopic, cultural, phenotypic identification and antibiotic susceptibility testing. DNA fingerprinting was performed by pulsed-field gel electrophoresis (PFGE). A total of 21 strains of Sphingobacterium were isolated from 7 patients (13 of S. spiritovorum, 8 of S. multivorum). S. multivorum isolates were more resistant than those of S. spiritovorum. PFGE profiles were in general heterogeneous, which suggested independent circulation.

Conclusions: This is the first Italian report about respiratory tract infections by Sphingobacterium in CF patients. In our cohort, these infections were not associated with a deterioration of pulmonary function during the follow-up period. Although the exact role of this microorganism in CF lung disease is unknown and the number of infected patients was small, this study could represent an important starting-point for understanding the epidemiology and the possible pathogenic role of Sphingobacterium in CF patients.

Figure 1

PFGE profiles of genomic DNA digested with ApaI of Sphingobacterium strains. From lanes 1 to 4: S. spiritovorum strains from A to D profiles, respectively. From lanes 5 to 7: S. multivorum strains from E to G profiles, respectively. Molecular size markers (a ladder of lambda phage DNA concatemers) were run in lanes St. Sizes are indicated in kilobases.