Infection Breakthrough at Rothman | Orthopedics This Week

Infection Breakthrough at Rothman

Scanning electron micrograph of Streptococcus pyogenese bacteria (yellow) bound to a human neutrophil (blue) / Source: Wikimedia Commons and NIH

Javad Parvizi, M.D., orthopedic surgeon at Rothman and one of the most prolific infection researchers in orthopedics, has made a significant and very novel breakthrough in the understanding and treatment of infections.

As he described the problem to OTW:  “Traditionally, diagnosing infection from bacterial cultures has come with the downside of false positives and false negatives. These rather crude efforts are giving way to the field of genomics, an interdisciplinary field where we use next generation sequencing to pinpoint the organism(s) in patients with periprosthetic joint infection (PJI).”

“What makes the diagnosis of joint infection particularly difficult is that the organisms are usually in biofilm form—not floating around. Our current detection techniques are only effective 60-70% of the time…and that is a conservative estimate. It’s unfortunate, but we often just don’t know what organism we are dealing with. A surgeon may give a patient an antibiotic and then the patient rightfully asks, ‘How can you choose a medication if you don’t know what I have?’”

In effect, physicians are playing “guess that organism.”

What if there was a nearly fool proof method to identify the infection culprits?

As Dr. Parvizi explains it, he and his team may well have found it.

’23 and me’ for Bacteria?

“In the last few years we have attempted to use a more sensitive process—polymerase chain reaction (PCR). It is a very sensitive tool that essentially amplifies the DNA, enlarging a few pieces of the bacteria. The problem with PCR is that you have to know what organism you are looking for (Staph, E. Coli, etc.). We began to realize that this is not going to cut it.”

“Recently the cost of sequencing DNA has come down drastically. The initial sequencing of the human genome took 13 years and cost $3 billion; now you can do it in a few hours for $200. We are seeing a lot of companies springing up to participate in the DNA analysis market.”

“We began thinking that it would be possible to use a similar type of technology to identify infected organisms. When a company known as MicrogenDx initially approached me about next generation sequencing there was no data on this in orthopedics, so I was skeptical. Several cases changed my mind, however, including one that made it into the Philadelphia Inquirer.”

Parvizi’s Acid Test

Dr. Parvizi told OTW, “The wife of one of my knee replacement patients called me and said that his knee was red and swollen and that he had fever. We aspirated the joint and it was clearly infected…but the culture was negative. We sent the same sample to MicrogenDx and they isolated Streptococcus canis, something I had never heard of until that day.”

“Canis,” as in canine.

“Interesting,” said the patient’s wife. “Our dog scratched my husband’s leg and has been licking his wound.”


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