I read that pleco's can be back for bichirs because the suck the slime coat off of the fish and can kill them. But that bristlenose (or bushynose I don't remember) are ok and compatible for them. How come they don't suck off the slime coat?
As long as you keep it well fed you shouldn't have a problem. But make sure you separate the two as soon as you notice it. I had a similar problem a long time ago with a pleco that found a new craving for my Florida Gar's slime coat.
My father keeps bristle nose plecos with his bichir. Bristle nose plecos are almost exclusively plant eaters. Many plecos are omnivores and some are carnivores.