An illness has been slowly spreading throughout the inhabitants of my agrarian society, decimating villages. The first sign of infection is the excessive production of slimy yellow saliva, and since it is in excess, they have no choice other than spit it out (and risk being found out), or swallow it (a long and painful process). Those infected are tied to trees outside of inhabited regions in order to lower the spread of disease. As their illness progresses, their abdomens become bloated, until the point of eruption. Upon eruption, they die, and their bodies (particularly their slimy yellow abdominal cavity) become a hub for infection.
What is this bacteria producing that is so sickly yellow? The only thing I can think of is sulfur, yet there would be no reason for sulfur to exist in the bodies of these farmers (and I'm not looking for a reason). What compounds, in particular, are causing this, and how does it relate to a bacterial infection?
Extra Credit - How does it relate the bloating and explosion of the abdomen?
EDIT - I do not mean to find an actual illness that has these symptoms, nor do I mean for you to design one - I am asking what sort of yellow substances could be produced by a bacteria while in a host.