this has to be a form of URI and I'm uncertain why the 2 rounds of antibiotics haven't yet worked? you may want to try something inexpensive and nearly as effective as an antibiotic....that is if the infection hasn't spread into the lungs. in any case it won't harm. I order out of iherb.com and use L-lysine an amino acid. this is a human amino acid but is safe for use in cats because this one is wheat,gluten, soy, milk, egg and fish FREE. it is a pure powder so much less is needed than any a Vet clinic would prescribe. Start with just a little under 1/2 teas.(approx 1000mg) daily for one week only, either mixed in the food or liquefied and given via dropper.than reduce down to 1/4 teas thereafter for maintenance, I would discontinue after a month if no relief is seen or at anytime if the kitties should develop diarrhea...
http://www.iherb.com/Now-Foods-L-Lysine-Pure-Powder-1-lb-454-g/653
We have a 15 year old cat that has had sinus problems since day one. We have tried many things, , and he only gets a month or two relief, if that. Our vets are at a loss, and has said that some cats just have this problem all their life and nothing seems to work. I wish you luck
Has this proven contagious to other cats?