Any encouragement about getting over a citrobacter koseri uti?

My dear elderly mom has struggled for several months with several UTIs, most have been E. Coli. All involved antibiotics (and plenty of pro-biotics). But this result is the first time she's had citrobacter koseri, which sounds scary and, according to the internet, is hard to beat. Does anyone have any success stories or suggestions? Mom has worn disposable briefs for these months, but now we're switching to good ol' cotton panties. She knows all about wiping the right way. She's currently on Keflex.