Further Studies on the Standardization of Bacterial Vaccines by Photometric Methods

Abstract

In a previous communication1 on the standardization of typhoid vaccine, the reasons for investigation in this field and the technic of the method of photometric estimation were presented. In the present paper we purpose not to deal with these phases of the subject but to proceed at once to a consideration of the results obtained in further experience with the paratyphoid bacilli. The technic has been the same as that previously followed and continued experience with the procedure has made possible more consistent readings, serving further to emphasize the fact that estimation of bacterial vaccines by aid of the photometre is both practicable and accurate. The strains of typhoid and paratyphoid bacilli employed in these studies showed certain differences in form in microscopic examination. The individual organisms of Eberthella typhi appeared somewhat longer and more slender than those of Salmonella schottmiilleri (emend), but the average volume of the individual organisms of the two species appeared equal. In comparison the individual cells of Salmonella paratyphi appeared distinctly larger on the average. The data of the photometric readings are in accord with these observations. The graphs presented for Eberthella typhi and Salmonella schottmulleri are remarkably similar while Salmonella paratyphi exhibits a more marked effect on the light in the same numerical concentrations. Photometric readings would thus appear to be of value in demonstrating volume differences between organisms and also in detecting morphologic differences in the same strain which might arise as a result of alteration in mediums or other environmental influences.