Clonal relatedness, biofilm formation, and biofilm-associated genotypes of clinical and environmental S. maltophilia strains. The dendrogram was constructed with PFGE profiles by similarity and clustering analysis by the Dice coefficient and the UPGMA. A percent genetic similarity scale is showed above the dendrogram. Isolates showing ≥ 90% of similarity (indicated as a dotted line) were considered genetically related. ID strains, source [non-CF strains are not marked, CF isolates are marked with an asterisk (*), and ENV isolates are indicated with two asterisks (**)], PFGE types and the 3 major PFGE clusters encountered in this study are also indicated. Sm189, Sm190, Sm191, Sm192, Sm193, Sm194, and Sm195 isolates were recovered from the same CF patient. Sm134, Sm135, and Sm136 strains are other consecutive isolates recovered from another CF patient. According to biofilm amount formed, strains were classified as follows: NP (no biofilm producer: OD492 ≤ 0.096), W (weak biofilm producer: 0.096 < OD492 ≤ 0.192), M (moderate biofilm producer: 0.192 < OD492 ≤ 0.384), S (strong biofilm producer: OD492 > 0.384). a BA genotype, Biofilm-associated genotype. ND, not determined.