Hi Al, im very sorry to hear about your loss

Peritonitis is technically an inflammation of the peritoneum, which is a thin layer of tissue that lines all the organs inside the abdomen. Sometimes it is caused by fluids leaking from some of the organs in the abdomen, such as the stomach, intestines, or bladder, but the main cause of peritonitis is actually liver disease, which seems to be fairly common as a cause of illness/death n gliders. Do you know if your vet sent off liver samples to a lab for histology? When you talk about poisoning of the blood stream, that is actually something different and is called septicaemia.
Unless the cause is infectious I think your other gliders should be fine, i would just closely monitor them and make sure you keep the cage clean, feed a good diet and make sure they do not have access to any chemicals which they could eat/lick (such as unsuitable disinfectants).
I hope that has helped a little. Sorry again to hear about your loss.
