Doc, TMZ is used more to treat a protozoan bacterial infection, like E coli, Coccidia etc. While pyo is bacterial and e coli is present it's the hormonal imbalance that induces it along with the alkalinity of the uterus. Check the link understanding antibiotics.

I'd use Metronidazole myself, I actually had an ah ha moment and thought about metronidazole and asked my vet, he said he'd never used it but it should work. Then I saw Jack mentioned using it as well. I believe Jack has information here about treating pyometra but I was unable to locate it. Maybe he'll share that info or if someone finds it please post.

Related info: http://veterinarymedicine.dvm360.com...tment-pyometra

http://www.thepitbullbible.com/forum...ng-Antibiotics

S_B