The phrase "to indicate an infection" means that it gives a sign or shows that a person has a disease caused by harmful microorganisms invading their body. Full definition
It's possible to find a strange odor coming from your dog's ears which also indicates an infection. (allstarpetresort.com)
Because of this, it is important to be on the watch for any signs indicating an infection, such as head shaking or scratching, and know how to clean their ears carefully. (terrificpets.com)
Since you don't see signs of infection (the ear is inflamed but dry — not inflamed with exudate which usually indicates infection as well as inflammation). (vetinfo.com)