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

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