Selection of DNA Aptamers Against Neisseria gonorrhoeae Causing Sexually Transmitted Infection (STI).

Neisseria gonorrhoeae (NG) is the second most common bacterial sexually transmitted infection (STI) worldwide. Gonorrhoea is a very serious infection because if untreated, it can lead to significant ramifications to reproductive, maternal, & newborn health and increase transmission of HIV. Infections are very often asymptomatic and symptoms when present manifest differently in men and women. The cornerstone of gonorrhoea control is to assure rapid diagnosis and prompt treatment of patients to prevent the onward spread of infection. The resource-rich settings are utilizing nucleic acid amplification tests (NAATs) for diagnosis, whereas resource-limited settings like ours where laboratory infrastructure is lacking, reliance is placed on syndromic approach. In view of the limitations of each, there is a compelling need for development of a point of care test (POCT). Aptamers offer such potential. These are short oligonucleotides that bind to its target with high affinity and specificity and therefore can be maneuvred for use in diagnostics. In this study, we performed live cell-SELEX (Systematic Evolution of Ligands by EXponential enrichment) to select 12 single-stranded DNA (ssDNA) aptamers that bind strongly to a cocktail of Neisseria gonorrhoeae strains, with Kd values ranging from 8.58 to 596 nM. Gold nanoparticle (GNP) assay revealed that one of the aptamers, E8 19 was highly specific for Neisseria gonorrhoeae (Kd = 24.5 nM). More importantly, it did not demonstrate any binding to Neisseria meningitidis and commensal Neisseria sp. The identified aptamer holds much promise for the development of a rapid test for diagnosis of gonorrhoea.