Your main concern should be rabies. Cat scratch disease and bite-induced infections are not uncommon, but they are quite treatable. Rabies however is not treatable once symptoms appear and it is deadly.
It is a dilemma, because like Sandie said, the cat may very well be euthanized if it has no owner - but if rabies is common where you live, I would say you need to get the shots. There's a good chance that they won't catch the cat anyway.
I've faced a similar dilemma last year. One of my officers (a girl aged 20) was playing with a semi-tamed feral I was feeding next to our office (of course - strictly against military regulations). She didn't know much about cats so when he rolled on his back she assumed he wants a belly rub (like a dog would). Well, the cat bit her quite hard and I was very worried. My first responsibility was for her safety. Yet, military regulations are very clear about this - any biting animal must be captured - dead or alive - to be checked for rabies. She couldn't even go to the doctor, because that would have beem a military doctor and he would have to be told the whole story.... I would have got in serious trouble for being in contact with stray animals and for letting my subordinates do the same...
So, what did I do? I contacted the cat welfare society of Israel for consultation. They told me that there were no documented cases of rabies in the vicinity of Tel Aviv (where the whole thing took place) in the last 50 years. They said that there were practically zero chances that the cat had rabies. That and the fact that he was provoked into the bite, conviced me not to report the incident and so save the cat. The girl was fine and only had a minor infection which was cured with an OTC antibtioc cream.
I must say though, that ever since I ask for ferals to be vaccinated against rabies when we have any spayed/neutered - just to be on the safe side.
So, my advice would be to check and see if there are cases of rabies reported where you live (and if there are wildlife nearby - chances are there is some around). Then go to your doctor and ask to be vaccinated. I'm told it's a relatively simple procedure (no shots in the stomach - just one in your arm) and it will put you our of risk and at ease.