thanks all. As I said, I wasn't worried about it. If they were going to 'catch' something from one another , they would have already - long since. It's just that I had never seen this before. And, trust me, I have been to soooooooo many vets with soooooooo many cats over the years. Thought I had seen it all. Even worked with a real 'old timer' for a summer and even he used separate needles and syringes for each animal. Well, I guess in this day of recycling.... and if it does no harm.....
I have to say, I have three very subdued kitties tonight. The rest too (wondering when their time will be?).