I have lost a number of fish to this gram- positive bacteria. As it grows, the fish appears to become obese with abnormal bulges, often just on one side. Eventually, the bacteria breaks the body wall and kills the fish. Larger fish, like goldfish, may survive open sores that look like infected red, cheesy boils for many months whereas all my small fish died as soon as they ruptured. Also, commonly small fish like danios and white clouds that were born normal developed kinked spines from TB as they aged and the TB set in.
Tuberculosis apparently can be in a fish for years without any harm.
If the fish is stressed in any way, the TB may become active. Older fish are prone to infections. Tuberculosis is sometimes killed using tetracyclines or sulfonamides. It is virtually incurable and causes cursing from normally polite aquarists. The first two were as pills in the water but the last was a medicated food.