Hi there It depends how the sample was collected. A positive urinary bag sample is not confirmatory of infection. Negative report does help to rule out infection. Why you did a urine test ? Is there any symptoms or fever?? If your child is clinically normal with no any urinary symptoms , then get a proper sample ( recommended is catheter sample or suprapubic sample) & confirm the infection before starting antibiotic) . If your child has symptoms - crying while passing urine or fever or passing less urine, then get a suprapubic sample , & there after start antibiotic awaiting report of culture and then to decide whether to cont antibiotic, change antibiotic or need further investigations.

Culture is gold standard test for uti.