antibiotic reaction

Is it common to have two urine sample for culture to have the same organism, same CFU and exactly the same antibiotic reading? I mean the numerical part of antibiotic susceptibility reading?

If you are in doubt about your culture, can you repeat the procedure using the same urine sample? If you want to replete/re test for antibiotic susceptibility,can you use the old plate you inoculated? Thankd