Traditional wound cultures are being replaced by molecular diagnostic medicine
Lower extremity wounds and toenail fungus can be a challenge for physicians because they often consist of a complex community of microbes. These microbes consist of bacteria and fungus and prevent the wound from healing. Proper treatment requires identifying the pathogens and administering the right antibiotics. Historically, this is accomplished with a wound culture. The wound is swabbed to collect the pathogens and then smeared onto a growing medium to grow out the bacteria. This technique is often inaccurate because certain organisms thrive in certain types of cultures while others do not. This bias also affects the quantity of bacteria that grows out on the culture medium giving a skewed perspective on which organisms are causing the infection. Traditional cultures are also error prone because they are extremely time and temperature sensitive. There are many false negatives because the organisms die before they can be cultured. This can happen because the swab sits too long waiting for the lab to pick it up. It is also routing practice to place the swabs in a lock box outside of the physician’s office building for ease of pick up by the lab. Temperatures here in Louisiana can easily raise the temperature of the swap to a lethal level, killing any bacteria before it can be cultured. As a result, we are often reduced back to square one when properly identifying the root cause, however, there is an answer to these problems with new technology to diagnose the issue.
Molecular diagnostic testing provides a solution to all these issues. This new technology looks at the DNA on the swab and makes no attempt to grow anything. This means that it doesn’t matter if the organism is alive or dead. It also looks at the quantity of DNA in the sample so it tells you what pathogens are present and in what amount. The culture collection method remains the same, but instead of growing the bacteria on special mediums, the bacteria are put into a PCR machine that sequences the DNA. This DNA is then compared against a national database that contains over 25,000 microbial species. The test is faster than conventional cultures tests because the organism does not need to be grown out. Results of the level one screening are available within 24 hours where the DNA is compared against a dozen of the most likely pathogens and within 3-5 days the complete test comparing the sample to all 25,000 microbes is available. Conventional cultures can take 2 weeks or longer. This new technology not only identifies the particular species of pathogen but also the percentage of each species, which allows the physician to identify the major contributing factors of the infection.
So, if you have been suffering from things like toenail fungus or wounds to your foot that have been traditionally difficult and been resistant to a cure, then the answer may be found through the molecular diagnostic testing. Although this is new, it is being adopted at our offices and the patient recovery and response has been extremely positive in helping us properly diagnose issues that have been stubborn or have been subject to not growing cultures….or Louisiana heat.