Had nephrectomy when i was 7 yrs old, now im 22 alrdy, had urinalysis, and showed few bacterias, is it true that im prone to uti coz i lack one kdney?

Not really : It's not that you are more prone to urinary tract infections as much as it is that you have to avoid any injury, including infection, to your solitary kidney.

Not necessarily: Few bacteria in a urinalysis are more likely than not to be contamination rather than uti, particularly if you have no symptoms. Without knowing the reason for the nephrectomy and your entire medical history, cannot tell you that you are not at risk, but it is not likely. Talk to the doctor who ordered the urinalysis. Good luck.