Abstract

Stenotrophomonas maltophilia is an emerging multidrug-resistant opportunistic pathogen in intensive care units (ICUs) and cystic fibrosis (CF), where biofilm formation may favor persistence, device-associated colonization/infection, and clonal dissemination. This study compared biofilm formation, clonal relatedness, biofilm phenotypes, and motility in 37 ICU-associated and 42 CF-associated S. maltophilia isolates. Biofilm formation on polystyrene was quantified by crystal violet assay and expressed both as absolute biomass and as a growth-normalized Biofilm Index, calculated to account for differences in planktonic growth. Genetic diversity was assessed by pulsed-field gel electrophoresis, while swimming and twitching motility were evaluated using agar-based assays. ICU isolates showed a higher prevalence of biofilm formation, greater biofilm biomass, and higher growth-normalized Biofilm Index values than CF isolates. They also displayed lower genetic diversity and more frequent cross-transmission, supporting the circulation of selected hospital-associated lineages. Conversely, CF isolates showed greater heterogeneity and a more complex biofilm pattern, consistent with adaptation to a distinct chronic airway environment. Motility was not associated with biofilm formation, suggesting that the enhanced biofilm phenotype of ICU isolates is not explained by swimming or twitching alone. Overall, these findings support a setting-specific model in which enhanced biofilm-forming capacity may contribute to S. maltophilia ICU persistence and clonal dissemination, highlighting the need for targeted surveillance and careful device management.

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