Tennessee permits a plaintiff to rely on the res ipsa loquitor doctrine in medical negligence cases when appropriate under the facts. For the most recent Tennessee case on the issue see Flowers v. H.C.A. Health Care Services of Tennessee, Inc., 2006 WL 627183 ((Tenn. Ct. App. Mar. 14, 2006).
But take a look at this case out of Missouri. It holds that a plaintiff can rely on res ipsa in a case where the plaintiff got an E. coli infection after back surgery.
The Missouri Court noted that "Plaintiffs have alleged that all defendants were in control or had a right of control of the instrumentalities from which her infection was obtained, that the infection in the surgical site itself is one that does not occur in the absence of negligence, that the defendants all were negligent, that she was unconscious and has no knowledge of how the infection occurred, and that the defendants have superior knowledge of how it occurred." The plaintiff had an expert to support this position but who could not say how the infection actually occurred.