Detection of Human Adenovirus from Clinical Samples of Conjunctivitis by Real-time PCR: A Cross-sectional Descriptive Study

Abstract

Introduction: Human Adenoviruses (HAdV) have been implicated in a variety of infections, including conjunctivitis, respiratory tract infections, genitourinary infections and gastroenteritis. Epidemic Keratoconjunctivitis (EKC) is a severe ocular surface infection strongly associated with HAdV, known to occur in widespread outbreaks. HAdV species B, D and E are associated with ocular manifestations ranging from simple follicular conjunctivitis (types 3, 4, 7) and pharyngoconjunctival fever (types 3, 7, 14) to the more severe EKC (types 8, 19, 37, 53, 54, 56 and 64). Viral cell cultures of conjunctival specimens help confirm adenovirus infection through the characteristic Cytopathic Effect (CPE) and Polymerase Chain Reaction (PCR) is the best standard method to diagnose viral conjunctivitis due to its sensitivity, accuracy and rapidity. Aim: To diagnose HAdV in clinically suspected cases of viral conjunctivitis using real-time PCR. To isolate HAdV in viral cell culture and confirm it by observing its characteristic CPE and performing adenoviral real-time PCR. Materials and Methods: A cross-sectional descriptive study was conducted from July 2023 to September 2023 at the state-level Virus Research and Diagnostic Laboratory (VRDL) at Bangalore Medical College and Research Institute (BMCRI), Bengaluru, Karnataka, India. A total of 45 conjunctival swab samples from patients with suspected viral conjunctivitis, who attended the Ophthalmology Outpatient Department (OPD) or were admitted to the wards, were included in the study. Conjunctival swab samples collected in Viral Transport Medium (VTM) were centrifuged at 3000 rpm for five minutes at 4°C. Real-time PCR was performed and samples positive for HAdV by real-time PCR were taken up for viral cell culture. Confirmatory PCR was conducted for samples showing CPEs in the cell line. The data collected were analysed using descriptive statistics. Results: The majority of patients in the present study were in the age group of 18-45 years, comprising 25 (56%) of the total patients. Out of 45 conjunctival samples tested, 8 samples were positive in adenovirus real-time PCR. All eight PCR-positive samples showed a CPE in viral cell culture on the A549 cell line. The study found PCR positivity in 8 samples (17.7%), while adenoviral recovery from cell culture was observed in 6 samples (13.3%). Conclusion: Real-time PCR has become the standard diagnostic procedure for detecting adenovirus conjunctivitis. Rapid and accurate diagnosis is key to interrupting the contagious spread of adenoviral conjunctivitis, along with timely treatment.