Thank you for your query,
usually not seen in throats and it doesn' cause infection in normal children.
It cause disease in immunocompromised, hospitalised patients and in patients with cystic fibrosis
It may be detected in your child throat sample because of contamination while taking or handling the sample. This is the reason for asking for the repition of the test.
As your doctor said the cough
may be due to allergy
The bacteria wont cause isolated cough.
Hope I have answered your query.