FIG 5.

The role of quorum-sensing fratricide in serotype-dependent competition. (A) Pups at 4 days of age were IN inoculated with an even mixture of 6 capsule-switch constructs with colonization density and serotype proportion determined 3 days postinoculation. Where indicated, T4^23F was substituted with T4^23FΔcbpDΔcibABC, which no longer expresses the fratricide effectors. n = 10–16 mice per condition. (B) In “head start” experiments, pups were IN inoculated with a single capsule-switch construct, either the T4¹⁴ or T4¹⁴ΔcbpDΔcibABC, and 6 or 24 h later, as indicated, IN inoculated with an even mixture of the other 5 capsule-switch constructs with colonization density and serotype proportion determined 3 days after the last inoculation. n = 7–9 mice/condition. Differences in serotype proportion were assessed between pups infected with the parent strain and corresponding ΔcbpDΔcibABC construct, with red symbols (*) indicating a significant increase while black symbols (*) represent a significant decrease. Differences in serotype proportion were compared to a hypothetical median of 0 using the Wilcoxon Signed Rank test. *, P < 0.05; **, P < 0.01.