Is it a condition of your lease? Is there a limit of the number of pets on your lease? If not, try to hang on keeping everything super-clean for a few weeks, then see what he says.

Explain it's not the number of cats that was the problem, it was a baby-sitter's mistake, which will NOT happen again.

This from the landlord who won't throw out the guy who practically burned the place downnn??????

Do you have a lease, or are you a tenant-at-will (month to month).