Doctors often have to switch a patient from antibiotic to antibiotic until one is found that can get rid of the bacteria. They also have to wait for results from the bacterial cultures to know exactly the type of antibiotic they should use.
There is no fast way to know if an infection is bacterial or viral.
I’ve seen some Doctors that identify Andy’s type of infection by the smell of the affected area.
Recently I heard of a Swiss study where they used a blood test to identify a protein called “procalcitonin” which would be expected with bacterial (not viral) infections.