Alli use in itself has not been associated with UTIs.
Increased bowels movements, with the increased need to wipe may be why some women have been experiencing UTI as a matter of hygiene. A change in diet is a secondary cause, as different foods can change the Ph levels which affect bacterial growth. Be sure to keep yourself hydrated, which flushes out the kidneys and urinary tract. Also keep the urine acidic such as drinking some cranberry juice or supplements.
Hope this helps.
Sophia De Monte RPh