Of course there are myelopathy cases that do not involve spinal cord compression but those cases are rare. Most cases of myelopathy are caused by canal compression resulting in direct injury to the cord. I am unaware of myelopathy symptoms being caused or aggravated by antibiotics. Of course Cipro and some other floxacins can cause ligament damage, typically extremity problems but I would imagine that the spine would not be immune to that condition. Nonetheless, I have never seen spinal involvement with antibiotics.
I did do a simple Google search and found no relation between myelopathy and antibiotics.