Rapid Identification of the Coxsackievirus A24 Variant by Molecular Serotyping in an Outbreak of Acute Hemorrhagic Conjunctivitis

We evaluated the clinical applicability of a molecular serotyping method for determination of the cause of epidemic acute hemorrhagic conjunctivitis. Seventy conjunctival swab specimens from individuals involved in a nationwide acute hemorrhagic conjunctivitis outbreak were tested. Viral culture and a molecular biology-based assay were compared by directly using clinical specimens. On the one hand, virus culture was done to isolate the enteroviruses, and serotyping was done by a coxsackievirus A24 variant-specific PCR. On the other hand, the original clinical specimens were directly screened for enterovirus by reverse transcription (RT)-PCR with panenterovirus-specific primers. Enterovirus screening-positive specimens were subjected to RT-PCR for detection of the VP1 region of enterovirus, and the amplicons were sequenced. Molecular serotyping was done by calculating the pairwise identity scores for the sequences with the maximum identities to the sequences of known prototype enteroviruses. Thirty-two specimens (45.7%) were culture positive, whereas 37 specimens (52.8%) were screening PCR positive (P < 0.001). The VP1 regions were amplified from 21 of the 37 specimens (56.8%), and the products amplified from 9 specimens were appropriately sequenced. These nine sequences were homologous with the sequence of the coxsackievirus A24 variant. Molecular serotyping by direct use of clinical specimens without cell culture could be applied for the rapid identification of the causative agent of epidemic acute hemorrhagic conjunctivitis.