What is the cause for strep uti? treated with cipro (ciprofloxacin) and it came back. is amoxicillin a good choice and what is the usual dosage for strep uti?

Yes: Streptococcal bacteria can be "normal" flora in the vagina or rectum/gi tract but if they get into the bladder, they can cause problems/utis. Amoxicillin may have better activity against streptococcal bacteria than cipro, (ciprofloxacin) but it depends on the sensitivity. A typical dose is 500mg taken every 8 hours for 3-7days depending on the severity of the infection (eg if kidney involvement is present/suspec.