Plaque enhancement of enteroviruses by magnesium chloride, cysteine, and pancreatin.

Wallis, Craig (Baylor University College of Medicine, Houston, Tex.), Fred Morales, Joycelyn Powell, and Joseph L. Melnick. Plaque enhancement of enteroviruses by magnesium chloride, cysteine, and pancreatin. J. Bacteriol. 91:1932-1935. 1966.-Plaque formation of 21 echoviruses (types 1-6, 9, 13, 15-19, 23-26, 29-32) and 8 coxsackieviruses (B1-6, A7, and A9) was enhanced by increased concentrations of MgCl(2), l-cysteine, and pancreatin in agar overlay medium. In most cases, cationic and anionic polymers (diethylaminoethyl dextran, dextran sulfate, or protamine sulfate) were ineffective. All strains of poliovirus and group B coxsackieviruses were enhanced under agar by MgCl(2). Five of the eight coxsackieviruses tested were also enhanced by cysteine or pancreatin. Certain enteroviruses, which have been difficult to assay by plaque method, can now be quantified effectively by incorporation of additives such as MgCl(2), cysteine, or pancreatin into the overlay medium.