Lysed BCG vaccines. 1. Observations on optimal conditions for BCG growth and lysis

As a first step towards the production of a lysed BCG vaccine that would have reduced toxicity and allergenicity and yet be immunogenic, the growth and lysis of BCG bacilli under strictly controlled conditions have been studied.BCG grown in both Dubos and Aldridge liquid media showed an arithmetic linear growth, preceded by a very short logarithmic phase. This suggested that some of the cell population became metabolically inactive at a very early stage, possibly owing to suboptimal conditions of growth.Glycine, lysozyme and lithium chloride initiated lysis of BCG growth in the aforementioned media 24-48 hours after inoculation. After 2 weeks' incubation approximately 50% of the original BCG culture was lysed and the viable count had fallen 1000-fold. The autolytic pattern of BCG in a nitrogen-deficient, chemically defined Aldridge medium is also described.