Lyme Disease Testing

Recently one of my close friends from my undergrad years was tested for Lyme Disease. As most of you know, the causative agent for Lyme disease is Borrelia burgdorferi (more specifically Borrelia burgdorferi sensu strict). Luckily her test was negative, but I came across an article that discussed the evolution of Borrelia serology testing which I found interesting. This post will give a brief background on B. burgdorferi, and how testing as improved since it was discovered. 

Borrelia burgdorferi is a spirochete, which is a spiral shaped bacterium. As stated earlier, it responsible for Lyme disease. A distinctive feature of Lyme disease is a bull’s eye rash. It is transmitted by ticks, which means you should listen to your parents about being cautious when spending time in the woods. The organism is difficult to grow in culture, and often it is diagnosed through serology tests. Serology tests detect the antibodies made in response to the bacterium, not the actual bacterium itself.

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Past Protocols

The first standard protocol for testing this came about in 1994. The first cases of Lyme disease were in mid-to-late 1970s. This is quite a large time gap where there was not a set standard on testing. The first protocol was referred to as the “Two-Tier Test Protocol” and followed the normal progression of the majority of tests today: screening test followed by a confirmatory test. The screening test had high sensitivity and detected IgG and IgM antibodies to B. burgodrferi. The portion of testing was usually an Enzyme-linked immunosorbent assay (ELISA) or indirect fluorescent assay (IFA). 

ELISA

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 IFA

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If a patient tested positive on the screening test, then a confirmatory test was performed. This test consisted of separate IgG and IgM antibody immunoblots. This type of testing runs the purified sample through a gel and adds B. burgdorferi antigen by blotting. If a precipitate or band forms, the antibody is present to that antigen. This test has a high specificity. If the patient receives a positive result, an official positive is reported. If the patient receives a negative for either the screening or confirmatory test, an official negative is reported. 

Current Protocols

Fast forward in time to 2001, and the testing progression has not changed. The antigens used however have improved from whole cell antigens to utilizing single, synthetic antigen: 26 mer synthetic peptide on invariable region 6 of Vmp-like sequence lipoprotein. In 2003 scientists researched other antigens for testing: recombinant V1sE1, synthetic C6, and synthetic pepC10. The names may sound like jibberish to most, but these purified antigens allowed for a higher specificity of 98% and higher sensitivity than the “Two-Tier Test Protocol” in patients with acute Lyme disease. This resulted in more accurate diagnosis for patients. The article concluded that testing with the combination of the rV1sE1 IgG (or C6 IgG) in conjunction with pepC10 IgM is superior to testing the each antigen alone. Using this information, they developed a multiplex immunoassay in addition to an ELISA test that utilized both antigens in a solid phase. Now testing is much easier to decipher and provides more accurate results.

Article reference:

Kopnitsky MJ. The evolution of Borrelia serology tests. Medical Laboratory Observer. June 2013; 46.6: 24-25

Keep An Eye Out For Fungus Conclusion

As the title implies, the causative organism in the last post was Aspergillus terreus. Once the causative agent was identified, the patient was prescribed natamycin and Voriconazole eyedrops in addition to his other prescriptions for 10 days. Normally amphotericin B (AMB) is prescribed to fungal infections, but Aspergillus terreus has intrinsic resistance to this antibiotic. Triazoles show promising treatment for Aspergillus terreus infections. When the treatment regimen was completed, the patient underwent a photo-therapeutic keratectomy (PTK) to remove dense corneal scarring caused by this infection.

Infections caused by this organism can be classified as invasive, saprophytic or allergic, and can be involved in lung disease, allergic bronchopulmonary disease, allergic sinusitis, cutaneous infections, invasive bronchopulmonary disease, intradural spinal biopsy, nosocomial aspergillus peritonitis, and invasive aspergillosis. It is a common cause of fungal infections in hematologic (leukemia) malignant patients and solid-organ or hematopoietic stem-cell transplants patients.

One problem with identifying fungal infections is that identification tests for them are not routinely performed in the hospital laboratory setting. The main reasons for this are the small patient volumes and lack of technical competency in the hospital lab to perform the tests. Often, these samples are sent and processed at reference labs, which is how this patient’s sample was analyzed.

Below is the reference to the article “Aspergillus terreus Recovered from a Corneal Scraping”

Campbell Suzanna, Aspergillus terreus Recovered from a Corneal Scraping. ASCLS. Spring 2014 . 27: 67-71.