Isolation of XXXX virus from polymerase chain reaction-negative cloacal samples of waterfowl.

@entity1 @entity1573 @entity1323 @entity33105
@entity1323 virus (AIV) is one of the most important zoonotic pathogens because of its potential to cause severe disease outbreaks in avian and @entity1 hosts. Virus isolation in embryonated @entity1573 eggs (ECEs) remains a gold standard technique for AIV detection. However, some laboratories prefer molecular methods, such as real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), for initial sample screening because of their high throughput sample processing and rapid results. Samples found positive on real-time qRT-PCR are then inoculated in ECEs for virus isolation and characterization. This approach is based on the premise that real-time qRT-PCR will detect all AIV-positive samples. The current study aimed to determine if AIV can be isolated from cloacal samples of waterfowl that were initially found to be negative by real-time qRT-PCR screening. Quantitative RT-PCR-negative cloacal samples (1,369) were inoculated for virus isolation in commercial nonspecific pathogen-free ECEs. After 4 days of incubation, the allantoic fluids were harvested and inoculated in fresh ECEs for a second passage. Allantoic fluids from 147 samples were positive for hemagglutination with @entity1573 erythrocytes. Of the 147 hemagglutination-positive allantoic fluids, 82 were AIV positive when confirmed with real-time qRT-PCR. Ten isolates were subtyped as H7N2 (n = 7), H7N1, H1N2, and @entity33105 . In addition, N subtype could be determined for isolates from an additional 25 samples. These results highlight the fact that screening by real-time qRT-PCR may result in some false-negative cloacal samples for AIV.
