Actually, the bleeding tendency from cefoperazone/sulbactam is due to just thiomethyl tetrazole (MTT) ring of cefoperazone. This MTT is present in cefoperazone, cefamandole, cefotetan, and moxalactam. It acts as a competitive inhibitor of the vitamin K-dependent carboxylase responsible for converting clotting factors II, VII, IX, and X to active forms.
The indications for supplement vitamin K to patients with cefoperazone treatment are ones with increased risk such as malnutrition, advanced age, recent surgery of GI tract, and renal failure etc.