i would seek out a lawyer as it seems its your word against the vets. i think its terrible that your dog has had to go through a big operation and then catch mrsa from their premises. its always the way,vets love to take your money but never seem to want to fork out when they are in the wrong. is your dog insured? if so i would contact them to find out what the situation is with them regarding this,also would contact your vet to explain that you are not willing to pay the money as feel there was lack and care on their behalf regarding the operation taking place on your dog and now contracting the bug. so therefore will take it further by seeking proffessional help. dont rant and rave on the phone. talk it out as calmly as you can as you are more likely to get somewhere.