Novel Method Developed to Diagnose Buruli Ulcer

A Buruli ulcer is a subcutaneous skin disease listed among the neglected tropical diseases, and early case detection and management is very important to reduce morbidity and the accompanied characteristic disfiguring nature of the disease.

The diagnosis of Buruli ulcer (BU) is based on clinical evidence that can lead to misdiagnosis, and microbiological confirmation is essential to reduce abuse of drugs, since the anti-mycobacterial drugs are also used for the treatment of tuberculosis.

Scientists associated with the University of Ghana (Accra, Ghana) developed a method to diagnose BU using aptamers that bind to the lipid particle mycolactone, which is produced by the causative agent Mycobacterium ulcerans. The team collected swabs and fine needle aspirations from 41 patients suspected of having BU. The samples were analyzed by polymerase chain reaction for the IS2404 sequence repeat, culture, and an enzyme-linked oligonucleotide assay (ELONA). Aptamers that bind to mycolactone were isolated by the systematic evolution of ligands by exponential enrichment (SELEX) process. To measure their affinity and specificity to mycolactone, the selected aptamers were screened by means of isothermal titration calorimetry. The ELONA assays measured at absorbance 450 nm using a MultiSkan Go plate reader (Thermo Fisher Scientific, Waltham MA, USA).

The investigators found that five out of the nine selected aptamers bound significantly to mycolactone, of these, three were able to distinguish between mycolactone producing mycobacteria, M. marinum and other bacteria whilst two others also bounded significantly to M. smegmatis. Their dissociation constants were in the micro-molar range. Fourteen swab samples tested positive for both culture and IS2404 PCR whilst positivity observed among the aptamers ranged from one to seven. The aptamer-based assay was used in a case control study and had a sensitivity of 50% and a specificity of 100%.

The aptamer-based test had a sensitivity of 50%, which is comparable to that of microscopy and culture, whilst the specificity is comparable to that of the IS2404 PCR. The authors concluded that their preliminary proof-of-concept indicates that diagnosis of Buruli Ulcer Disease with ribonucleic acid (RNA) aptamers is feasible and can be used as point of care upon incorporation into a diagnostic platform. The study was published on October 24, 2016, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
University of Ghana
Thermo Fisher Scientific