There’s no question that some materials (because of their surface charge and structure) are “not great” at resisting microbes and subsequent biofilm formations. Once a biofilm community (monomicrobial, or worse, polymicrobial) is set up, it becomes almost impossible to eradicate the infection on the device or in tissue. Diagnostics for most preliminary infections (gram-positive likely suspects) are not widely available yet.
My interview with Dr. Tom Webster at Brown University was almost entirely about your questions, so I’ll do my best to make some of this information available next month (but no promises). It was a 50 minute on-camera interview, covering these subjects:
1. Prosthetic designs and device failures
2. Orthopedic device infections
3. Types of bacterial infections
4. Bone turnover & osteoporosis
5. Osteoporosis medications & efficacy
6. Bacterial biofilms on orthopedic devices
7. Biofilms defined
8. Biofilms and antibiotic resistance
9. Challenges in biofilm eradication
10. Deploying nanotechnology: antibacterial design
11. Enzymes and electromagnetic fields for biofilm eradication
12. Beating biofilms
Sorry I can’t work more quickly to make this information available; but I’ve been working on these issues for the past year. I need resources, people, money or miracles. Any of these will do nicely, thank you. 
Any way, a small excerpt from this informative video interview:
Dr. Tom Webster -- Brown University:
“…biofilms are extremely detrimental, even the presence of some bacteria on an implant surface is detrimental, because that keeps bone from growing next to the implant. If you have something I the way like bacteria that will keep the bone or the appropriate tissue from growing. What bacteria will try to do is, try to stick to that foreign object if that environment is appropriate, and proliferate much faster than any bone cell could ever proliferate, until it reaches a state of biofilm formation, until multi-layers are formed and it kind of, a good way to think about it, it sequesters that area of the implant from the rest of the body.
So you really have an impenetrable area that has formed next to the implant and this is why pharmaceutical agents no longer matter once you reach that point is because that agent or drug cannot penetrate the biofilm to expose themselves to then kill bacteria, so there is really a so called sweet spot in which you can begin to kill bacteria once you pass, once the bacteria pass that, you cannot kill them through conventional means. The other things that happen underneath a biofilm, if it has formed on something like this titanium, is you get a very aggressive degradation of the metal, or a polymer, or if it was a polymer and because of the environment inside of a biofilm, you will have a lot of corrosive events, which would occur, which would just lead you down this cascade of failure of this negative release of metal ions, to even promote more bacteria to grow, or promote more inflammatory cells to come to the implant surface, etc…”
CP: Please add a signature to your profile. CP, see the User CP link?! Made just for you!