It comes as lyophilized powder. You reconstitute the drug yourself and follow WHO sterility guidelines (reconstitute with bacteriostatic water, alcohol wipe ampoule top before accessing, keep it in the fridge, and throw it out if you havent finished it within 30 days). I know a dozen people doing this for the last year and none of them have had any sign of even superficial infection.
I think the way it works when you get bacteria into your blood is either you have no noticeable symptoms, or you get a high fever and almost die from sepsis.
People with minimal training drew up billions of doses of covid vaccines from multi-use vials and administered them intramuscularly (deeper and therefore potentially more risky than subcutaneous ozempic/mounjaro) and I never heard of anyone getting an infection from this
Those are wise safety procedures, not that's not sterile compounding. EVERYTHING needs to be sterile. The needles used for mixing, the air in the room, the hood you're mixing it in, everything. The room or hood has to be in positive pressure, and the ampule needs to be at a partial vacuum.
What you're describing is a adequate for immediate use. Not use and storage.
Wiping the bottle before use is just standard practice to prevent contamination after compounding.