Infectious Disease Expert Opines On Deep Joint Infection

Jared Firestone

Written by
— Updated on February 11, 2021

Infectious Disease Expert Opines On Deep Joint Infection


Thomas Pipitone and his wife, Bonnie, brought suit against Biomatrix, Inc. (“Biomatrix”), alleging that a product that Biomatrix manufactured, known as Synvisc, caused Mr. Pipitone to develop a salmonella infection in his knee after a physician injected his knee with Synvisc. The district court excluded the testimony of the plaintiffs’ experts, Doctor Coco, under the standard set forth in Daubert. The district court concluded that without the testimony of their witness, the plaintiffs could not establish their case and granted summary judgment in favor of Biomatrix.

Expert Witness:

Dr. Coco specializes in infectious diseases. He is employed by three local hospitals in the area of hospital epidemiology and biostatistics and concentrates in this area as it relates to infectious diseases and the prevention thereof. He has been on the Specialty Board of Infectious Diseases and has written on the subject. For the last twelve years, Dr. Coco has been a Clinical Assistant Professor at Louisiana State University School of Medicine in the Department of Infectious Disease. Dr. Coco drew on this experience when he personally examined Pipitone in January 2000. Based on his experience as an infectious disease specialist and his personal observation of Pipitone and his symptoms, Dr. Coco concluded that the most likely cause of Pipitone’s infection was the Synvisc that had been injected into his knee two days before. Specifically, Dr. Coco based this opinion on the timeliness of the infection (symptoms of which began to appear hours after the Synvisc injection), the source of the Synvisc, the type of organism (salmonella) that infected Pipitone, and the elimination of all other likely alternatives.

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Daubert Challenge:

The Defendants motioned to exclude Dr. Coco’s testimony at the trial level and were granted this motion. The district court grounded its decision to exclude Dr. Coco’s testimony on causation largely because it found that Dr. Coco had identified “many viable alternative sources” of the salmonella infection in Pipitone’s knee.


After a careful review of the summary judgment opinion, the Court decided that the record did not support this statement. Dr. Coco methodically eliminated the alternative sources of the infection as viable possibilities. After doing so, he stated that he was “99.9%” sure that the source of the salmonella was the Synvisc syringe.

One of the alternatives rejected by Dr. Coco was that Pipitone ingested salmonella, the bacteria infected his GI tract (a condition called gastroenteritis), translocated into his bloodstream (a condition called bacteremia), and traveled directly to his knee, causing the infection. Another alternative source was that the salmonella infected his scabbed-over toe, traveled in his bloodstream (also producing bacteremia), and infected his knee. Dr. Coco rejected both of these alternatives, however, on the grounds that Pipitone showed none of the symptoms associated with either gastroenteritis or bacteremia when Dr. Coco examined him in the hospital. Dr. Coco testified that when he examined Pipitone, Pipitone “did not have diarrhea, nausea, or vomiting”, which are the symptoms of gastroenteritis. Dr. Coco also testified that Pipitone was not running a fever at the time of his entry into the hospital, nor did he have chills or severe inflammatory response associated with bacteremia. Dr. Coco also noted that it is nearly impossible to contract salmonella through even an open traumatic wound, much less the scabbed-over surface of Pipitone’s toe. Based on the lack of these symptoms and his specialized knowledge and experience, Dr. Coco ruled out these alternatives.

Another possible cause of the salmonella infection that Dr. Coco rejected as a viable alternative was Dr. Millet’s (the doctor who injected Pipitone with the Synvisc) technique in administering the injection. Dr. Coco interviewed Dr. Millet about the technique he used in giving Pipitone the Synvisc injection. Dr. Coco testified that the alcohol and the antibiotic cleanser that Dr. Millet used to clean Pipitone’s knee before the injection would have killed any salmonella on the skin. Dr. Coco further testified that he learned from Dr. Millet that the injection needle was in a protective sheath until Dr. Millet injected Pipitone. Even if the needle had been removed from the sheath some time before the injection, however, Dr. Coco stated that salmonella does not exist in sufficient quantities on the hands to contaminate an injection needle nor does it exist in saliva in an individual’s mouth. Dr. Coco testified that if unsterile injection technique could cause salmonella infection in a joint, he would have expected to have found reports of such an occurrence in the literature, regardless of the drug being injected. Yet, Dr. Coco’s research revealed no evidence of any injectable causing a salmonella infection in a knee. Given all of this information, Dr. Coco concluded that the content of the Synvisc syringe injected into Pipitone was the most likely source of the salmonella that infected his knee.

Finally, Biomatrix argued that Dr. Coco’s unfamiliarity with the Synvisc manufacturing process and his “inability” to explain the lack of salmonella in the other Synvisc syringes held back from Pipitone’s production lot renders his testimony “unreliable” under Daubert. The Court disagreed with Biomatrix’s characterization of Dr. Coco’s deposition testimony. Dr. Coco stated that while he would have expected other samples of Synvisc in the same manufacturing lot to be contaminated, the absence of salmonella in those few other samples tested did not undermine his conclusion. Dr. Coco explained that only a small number of Salmonella organisms would be required to infect a joint that was directly exposed to the organism. He also stated that in his epidemiological experience, a batch that produces a contaminated sample may contain no other contaminated samples.

The Court believed that the answer to the causation question would depend on which set of predicate facts the fact-finder believes: the plaintiffs’ contention that the content of the Synvisc syringe administered to Pipitone was contaminated or the defendant’s that it was not. It was therefore not the role of the trial court to make this decision, but rather the purpose of the jury in fulfilling its role in the adversary system.
This Court therefore concluded that the standard of reliability that the district court applied to Dr. Coco’s testimony was overly stringent. The fact-finder was entitled to hear Dr. Coco’s testimony and decide whether it should accept or reject that testimony after considering all factors that weigh on credibility, including whether the predicate facts on which Dr. Coco relied are accurate.

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