The new test targets the genetic sequences in the bacteria that cause Lyme, which is highly sensitive, and detects only one bacterial cell in the blood sample.
For those who live in a tick infested area, the risk of contracting Lyme disease can overshadow the joy of spring and summer. These bloodsucking spiders can transfer bacteria into their unsuspecting host’s bloodstream, causing disease. Early treatment is necessary, but current tests are not usually sensitive enough to detect disease in patients in its early stages. A recent study in the Journal of Open Access Frontiers in Microbiology It unveils a new test for Lyme disease and is the first to reliably distinguish between early and late stage patients. The test detects the genetic sequence left by the virus in the bacteria that cause Lyme, and it can detect only one bacterial cell in a small blood sample.
Lyme disease is the most common tick-borne infection, affecting nearly 500,000 people in the United States each year. Symptoms include fever, fatigue, joint pain, and a characteristic rash, but if left untreated, the disease can cause paralysis and even death. As such, early diagnosis is important but difficult.
“Early diagnosis of Lyme disease is very vital in reducing suffering, because early Lyme disease can be treated, but late Lyme treatment is very difficult,” said Dr. Jinyu Chan of the University of Leicester, the lead author of the study. “Current tests usually cannot detect low numbers of bacteria in a patient’s blood samples in the early stage. Our goal was to design a highly sensitive test to help clinicians identify Lyme disease as soon as possible.”
The Shan test is based on polymerase chain reaction, or PCR, which works by amplifying small amounts of a specific genetic material so that it can be detected. So far, this technique has not been particularly helpful in detecting Lyme-causing bacteria in the blood. These bacteria often reside in tissues, and they may not be present in blood in large numbers. Additionally, many of the gene sequences targeted by PCR have only one copy within each cell, making them difficult to find and amplify enough for detection.
Chan and colleagues recognized that there was another potential target for PCR in Lyme-causing bacteria. These targets are called prophages, which are genetic sequences inserted into bacteria by a virus. Fortunately, such genetic material can escape from bacteria and thus are more likely to be detectable in blood, and multiple copies exist in individual bacterial cells.
The researchers evaluated their new test directed at Prophage by adding small amounts of Lyme-causing bacteria to their blood samples. They found that the test was very sensitive, detecting only one bacterial cell in 0.3 ml of blood. This means that the test is sensitive enough to be used with human samples, as people infected with the bacteria that cause Lyme usually have between 1 and 100 bacterial cells per ml of blood.
Based on these promising results, the researchers used the PCR test to analyze blood samples from healthy volunteers and patients with Lyme disease in its early or late stages. Remarkably, the test can successfully distinguish healthy, early and late-stage Lyme disease samples, and is the first technique to achieve this with success. “The test can also be very helpful in the rapid exclusion of a person with Lyme disease,” Chan said.
This technique may also be applicable in diagnostic tests for other bacterial infections, if researchers can determine an appropriate prophylaxis sequence for such bacteria. The technology will need to be further developed before it becomes suitable for clinical use, but researchers are already starting to lay the groundwork for it. “We are currently working with a business partner, investigating regulatory issues and a possible clinical trial of this technology,” said Chan.
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