PCV2 infection in STEC. A Detection of PCV2 infection in STEC by indirect immunofluorescence assay. Green fluorescence indicates that cells were infected with PCV2. Scale bar, 100 μm. B Proliferation of PCV2 in STEC. The cells were infected with PCV2 at MOI 1, the supernatants and cells were frozen and thawed 3 times at 12 h, 24 h, 36 h and 48 h post-infection. Viral DNA were extracted and quantitated by qRT-PCR assay. The results are shown as mean ± SD of three separate experiments.