Comparison of growth rates between hyperinfectious and conventionally virulent salmonellae grown under in vitro conditions that are permissive for hypervirulence.

<p>An equivalent dose of hyperinfectious <i>S.</i> Choleraesuis χ3246 and conventionally virulent <i>S.</i> Typhimurium reference strain 14028 (5×10⁷ CFU/ml) were co-cultured in either permissive (LB; open boxes) or nonpermissive (LPM pH 5.5 medium; closed boxes) conditions for the hypervirulent phenotype, following prior growth individually in the same medium. Cell aliquots were sampled for CFU at the cell generation (cell doubling) indicated. Bacterial cells were obtained from, and maintained in, exponential phase cultures diluted periodically such that the cell number was constant at each sampling point. The in vitro competition index is the relative ratio of test strain/reference wild-type strain recovered from the co-culture divided by the input ratio. The values represent the relative ratio of <i>S.</i> Choleraesuis/<i>S.</i> Typhimurium obtained from 3 independent cultures with the standard error bars designated.