Persistence and variability of Stenotrophomonas maltophilia in cystic fibrosis patients, Madrid, 1991-1998

During 1991 to 1998 at least one Stenotrophomonas maltophilia pulmonary infection was observed in 25 (24%) of 104 cystic fibrosis patients at the same unit of our hospital in Spain. Ribotyping and pulse-field gel electrophoresis (PFGE) characterization of 76 S. maltophilia isolates from these patients indicated an overall clonal incidence of 47.1%, reflecting new strains in 44% of patients with repeated positive cultures for S. maltophilia. Six patients with repeated episodes were persistently colonized (greater than or equal to6 months) with the same strain. S. maltophilia bacterial counts were higher (geometric mean, 2.9 x 10(8) cfu/mL) in patients with repeated episodes than in those with a single episode (8.4 x 10(4) cfu/mL, p<0.01). Single episodes of S. maltophilia occurred in patients <10 years of age (43% [6/14]), whereas chronic colonization occurred more frequently in older patients (>16 years of age).