Could 50, 000 cfu/ml lactobacillus in urine culture indicate a uti? if so, what antibiotic do you suggest?

Doubtful: Lactobacillus is an unusual bacteria for a bladder infection. It is a typical bacteria of the vagina, so this most likely represents a contaminated urine sample.

Vaginal contaminant: Lactobacillus is typically a vaginal contaminant. The threshold for a UTI on clean catch is 100, 000 cpu/ml so this culture should not be considered positive. If you have UTI symptoms repeat the urine with a good clean catch.