I had a very nasty prostate infection about three years ago and subsequently gave up having anal sex with my wife. The doctor never said it was caused by the anal intercourse and I can't really prove that there is a connection. Now my wife would like to resume this, but I am concerned that I may get another infection -- nothing is worth that!
Please don't suggest a condom because it takes me forever to have an orgasm anyway and a condom makes it last so long that my wife gets very sore.
But if the prostatic fluid comes out through the penis, why can't the anal germs go the other way?

I can't see how you penetrating your wife could possibly create a prostate infection. The two areas are not really connected by any major blood vessels, and so anything that got into your blood could have infected your whole body and not just the prostate.

Time for a second opinion I think.