Published online by Cambridge University Press: 15 May 2009
The sensitivity of in vitro- and in vivo-grown strains of S. typhi was determined not only by their antigenic structure, but also by their growth phase. An increased vulnerability to the antibody-complement system has been found in cells during the lag and the early exponential phase, while non-multiplying cells devoid of any nutrient were almost invulnerable to the antibody-complement system. Extracts of organs from normal and infected animals may promote the growth of S. typhi, and, therefore, increase its vulnerability to the antibody-complement system. The majority of extracts from organs of mice infected with strain Ty 2 inhibited markedly the bactericidal action of serum on this strain and, to a lower extent, on strain O 901.