Anal sex is the "best way" to get infection in urinary tract, hence the infection has "freeway" to all urogenital organs ,include prostate. Why does it happen ?
Because a rectum,colon - where your penis is penetrating while intercourse, has the pathogenic/Conditionally pathogenic flora that enters your urinary tract.
It is pretty much the same about the mouth.
Nature, didnt "create" anal sex or oral sex - it was only vaginal sex, rectum and mouth were designed for other purpose. Contrariwise - Vagina, especially designed for penis penetration and it has healthy-friendly flora ( i consider usual healthy women , that if you will perform an anal sex on her its a big chance to get infected).
If you both do enjoy anal and oral sex - do it using condoms !
But if a man perform an oral sex on her - it is the same and also has the consequences!
You may infect her vagina by your mouth, and get it back to your penis while regular sex !
It should be done protected.

Sorry , but that's the way it is !