Something else unmentioned is that 70-80% of hospital acquired infections are related to medical devices that are susceptible to the formation of biofilms where the bacteria create a protective layer that antibiotics can't penetrate.
For example antibiotic resistant urinary tract infections caused by the use of catheters. Effective antibiotics simply don't work when they can't reach the infection.
Nothing can be _completely_ sterile all the time. Urinary catheters also tend to move a bit when inserted, so they tend to slowly transport bacteria from the outside into the inside.
That's the packaging. Once you break the seal, it's contaminated from the surrounding air. But that's not even relevant. When the catheter is inserted, it picks up bacteria from the genitals. No washing and disinfection can remove all of them. Also, like @cyberax said, the catheter can move. The longer it's kept in place, the more bacteria gets upstream.
For example antibiotic resistant urinary tract infections caused by the use of catheters. Effective antibiotics simply don't work when they can't reach the infection.