@Fatas - @PunkrockerGirl59 and I have both done our best to explain why changing a catheter is a very hygienic process. It HAS to be, otherwise the person with the catheter can get urinary infections - which pose a very real danger to such patients because they can cause irreparable kidney damage - and their risk is higher because of the catheter.
It is NOT toileting - very little urine is usually drained - if the person has a catheter all the time, urine is constantly draining into the bag (which will be emptied - in a toilet - before the catheter is changed - no-one is going to remove someone’s catheter without emptying the bag), so only a few ml will come out when the new catheter goes in, and this will be caught in a disposable kidney dish, and immediately disposed of in a proper clinical waste bag. Then the area should be properly cleaned - and cleaned to aseptic, clinical standards, which are pretty high.
Likewise, no-one will change a colostomy bag without emptying the old one first - again, in a toilet, not the clinical room, so there will be only a small amount of poo involved - which any half decent nurse/HCA will catch in gauze/tissue, and dispose of safely in a clinical waste bag. Then they will clean the area properly.
Frankly, somewhere that is being cleaned by a nurse or HCA is likely to be cleaner than a normal office, where people may be eating, drinking, sneezing, touching the surfaces after going to the loo and not washing their hands.
And germs cannot leap. Your expressing equipment would have to be in direct contact with a contaminated surface, or you would have to touch a contaminated surface and then touch your expressing equipment for there to be any real risk of contamination. As long as you wipe down the desk with antibacterial wipes, then wash your hands beforehand, and are careful handling the equipment (which you should be anyway) there should be very little risk at all. Nothing is ever totally without risk, but short of expressing in a totally sterile environment, having autoclave your boobs, this is as safe as you can get.