Popeye /Exophthalmial

[Fishquake]

I understand that Popeye is a opportunistic bacterial infection, widely believed to be cause by poor water conditions. However, if the water conditions are considered optimal for Discus, can there be any additional causative agents, such as physical injury to the fish, (such as dashing around the tank when frightened), thus providing an entry point for the bacteria? Is this bacteria generally present in all aquarium water, whereas a stressed fish (such a newly introduced Discus) becomes more susceptible to it? Also, can cross-contamination be an issue from say a tank of Asian Discus, where the same spoon may have been used to feed them as well Stendkers in another tank in an other room?