Comparison of three protein A-gold immune electron microscopy methods for detecting rotaviruses

Three immune electron microscopic (IEM) methods employing protein A-colloidal gold (PAG) were compared with direct electron microscopy (DEM) and direct IEM (DIEM) techniques for their abilities to detect simian rotavirus (SA11) and human rotavirus. Using PAG IEM the number of rotavirus particles per grid square was 10 to 50 times and 2 to 5 times higher than observed with DEM and DIEM, respectively. A comparison of sensitivities among the three PAG IEM methods showed that the trapping efficiency for SA11 and human rotavirus was significantly enhanced by a serum-in-agar (SIA) method. The SIA method appeared to be a more reliable and sensitive alternative for detection and quantitation of viral particles.