I only remember a few things from when I studied such things a lifetime ago.

Not sure how any of this Directly applies to Boas.

It seems to show up when immune systems are compromised. Which is why you don't want anyone around with Asthma, they have compromised immune systems. When an asthma attack happens, that is an immune response, whether physical, chemical, or bacterial/viral bugs.

I would not think it is good at all for a snake to have this, especially in their lungs or worse if systemic (whole body). It is highly gram negative which means GENERALLY it is harder to kill than most gram positive bugs.

The good thing going here is that your Vet has isolated it, which means he can treat more successful with the RIGHT medicine. Another way to put it is he is going with a rifle approach as opposed to a shotgun approach.

Hope this helps