Effect of Heat and of pH on Strains of Coxsackie Virus

Abstract

This report describes studies of the thermostability and resistance to pH of three strains of Coxsackie virus of Group A and two strains of Group B. Results of earlier studies of MM and Lansing poliomyelitis virus are included for comparison.

Procedure.Infected mouse brains or leg muscles that had been stored in a dry-ice box were suspended and clarified by centrifugation. Immediately after preparation, 0.5 ml volumes of the suspensions were sealed in 3 ml lyophile bulbs for immersion in units of 3, in the heating bath. Immediately before and after heating they were chilled in an ice and water bath. For each suspension one unit was held without heating. The samples were pooled on the day heated and tested in mice on the following day. To determine the time required for the samples to reach the temperature of the bath, a constantan-nickel thermocouple in 0.5 ml of distilled water in a lyophile bulb was used. The lag time was relatively constant about 60 seconds. The pH values of each original suspension and of a heated sample were determined electro-metrically. The values lay between 6.3 and 7.4, many between 6.9 and 7.2. Heating of a given suspension did not change the pH. Suspensions were prepared in a 10% solution of beef-infusion broth in physiologic salt solution (broth-salt solution) and in distilled water. They were heated for 30 minutes.

Infectivity was tested by intraperitoneal injection of 0.05-ml amounts into 2- to 6-day-old suckling mice of the Albany standard strain; from 6 to 9 for each dilution tested. They were observed for 2 weeks, but only those affected from the second to the seventh day (for those receiving No. 5096 (Group B), from the second to the tenth day) are included in the results reported.∗