Doctors can refuse to see a patient for any reason, just like when a restaurant refuses to serve someone for not wearing shoes or something. The only exception is when the patient is in an immediately-life-threatening situation, unlike you. Of course, everyone would agree that your situation is odd. But it appears you signaled the idea that you seriously questioned your ID physician's decision, so maybe the other ID physicians shied away out of self-interest. Their doing that isn't malpractice. Just bad form.
I do not think you would have an underlying malpractice claim. You would have to show more than just the fact that IV antibiotics were required. You'd also have to show that the failure to keep you on the IV (rather than oral) meds caused your MRSA to become worse. That's tough. Staph infections are hard to clear even when the best antibiotics are employed in heavy doses.
It is not uncommon for physicians to refuse to take on a new patient in an instance where they fear that they may be attaching themselves to the back end of a malpractice suit against the prior treating physician.
Osteomylelitis is a tough infection to beat into permanent remission. If your primary MD felt that you should get better advice, s/he probably is right. The other two MDs, if "friends" might be hesitant to take you on for any one of several reasons. Apparently, a third one as well. You can get diagnosis and orders from an appropriate MD specialist located away enough where the original MD is unknown, and the treatment can be done locally at your hospital. You can go to Long Island or upstate to get the managing MD specialist and carry everything out in NYC.
With regard to collusion...didn't you ever watch that Seinfeld episode?!
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