FIG. 3.

Detection of NLV RNA and internal control RNA by RT-PCR and oligoprobing of 10-fold (−1) and 100-fold (−2) dilutions of RNA extracts from outbreak food samples processed by both methods. (A) Ethidium bromide-stained agarose gel; (B) Southern blot of gel in panel A. Results were obtained with NLV GII capsid primer pair Mon441-Mon443. (C) Southern blot for each food extract dilution from a separate RT-PCR seeded with 50 copies of NV internal standard RNA, using the primer pair NVp35-NVp36 to identify sample inhibition. Other lanes include a negative reagent control (neg) and a digoxigenin-labeled molecular size marker (M). NLV-specific amplicons (268 bp) are seen in lanes 2, 8, and 9 of panel B. Internal standard control-specific amplicons (347 bp) are seen in lanes 2, 4 to 6, and 8 to 13 of panel C. The internal standard control is absent from lanes 1 and 3 of panel C due to sample inhibition.