Let’s say you go to the doctor because you have a sore throat. The doctor takes a throat sample and allows it to
potentially grow on nutrient agar in a Petri dish. After about 24 hours you get a call from the doctor – she
informs you that you do not have a bacterial infection (such as strep throat), since no colonies of Streptococcus
grew on the agar. Instead, the doctor indicates your sore throat is caused by a virus. How could the doctor know,
since no viral colonies grew on the agar?