Ocular toxoplasmosis: coinfection and molecular differential diagnosis in immunocompetent patients

A descriptive transversal study was done in a Uveitis Service of an Ophthalmology Reference Center, in Bogotá Colombia, from July 2014 to February 2016. A complete clinical history and ophthalmological examination was performed in all patients. Aqueous humor and/or vitreous fluid, blood and serum samples were collected from consecutive patients suspected of having uveitis of infectious origin at presentation. The diagnosis of OT was confirmed by serum antiblody titers and avidity, quantification of antibodies with the Goldmann–Witmer coefficient (GWC) and by detection of Toxoplasma gondii genome using PCR. Differential diagnosis by PCR in aqueous humor was done for viral origin CMV, HS1, HS2, VZV, EBV; and Mycobacterium tuberculosis when suspected.

From 67 patients with uveitis of presumed infectious origin, 25 (37.3 %) were biologically confirmed as ocular toxoplasmosis and 15 (22.4 %) as other etiologies (VZ, EBV, MBT). Coinfection of Toxoplasma and viral origin was confirmed by qPCR in aqueous humour in 3 patients (2 VZ, 1 CMV+VZ). Viral coinfection is possible in patients with confirmed OT. Additional studies are necessary to analyze how the co-infections impact the therapeutic response and prognosis in this group of patients and the need to include additional tests during management of patients with ocular toxoplasmosis. Either antibodies load in aqueous humor or PCR should be included in any diagnostic algorithm.

This study was conducted according to the tenets of the Declaration of Helsinki, strictly following the Guide for Good Laboratory Procedures. The protocol was ap- proved by the Institutional Ethical Committees (Reference numbers: 5–14-1 from Universidad Tecnológica de Pereira and 030314 from Escuela Superior de Oftalmología - Instituto Barraquer de América) and all participants provided written informed consent.