Prolonged recovery of desiccated adenoviral serotypes 5, 8, and 19 from plastic and metal surfaces in vitro

BACKGROUND: Prevention of the spread of epidemic keratoconjunctivitis (EKC) at eye care facilities (doctors' offices, clinics, hospitals) has been a major public health goal for ophthalmology for more than 50 years. The authors explored a potentially contributing attribute of the adenovirus serotypes that cause EKC. Specifically, they investigated the capacity of different clinical and laboratory ocular serotypes (AD8, 19, and 5) to survive for extended periods of time in a desiccated state. METHODS: Twenty microliters containing 2000 plaque-forming units of different ATCC laboratory adenoviral ocular serotypes (AD8, 19, and 5) and clinical isolates (AD8 Cray, AD19 Kowalski, and AD5 McEwen) were inoculated onto 7-mm plastic disks and 6-mm aluminum foil disks and were allowed to completely desiccate. At weekly intervals up to 7 weeks, eight desiccated virus-inoculated plastic or metal disks per serotype were added to tissue culture medium, and the amount of recoverable virus was determined by plaque assay on A549 cells. RESULTS: Ocular adenoviral serotypes AD8, 19, and 5 could be recovered up to 49 days from plastic, and 35 to 49 days from metal. Sufficient virus concentrations (> 100 plaque-forming units/disk) to be clinically infectious were recovered up to 28 days. Differences in recovery among serotypes (AD19 > AD5, AD8) were demonstrated, but laboratory and clinical isolates of the same serotype were usually comparable. CONCLUSIONS: Ocular isolates of adenovirus that cause EKC are much harder than previously suspected, and the capacity to survive in a desiccated state may possibly play some role in office-based mini-epidemics of EKC.