Influenza infection induces bacterial shedding at a level high enough to infect infant mice.

<p><b>A–E.</b> Wildtype (A, C, and E) and <i>tlr2^−/−</i> mice (B and D) were infected with either <i>S. pneumoniae</i> and influenza (A, B and E) or <i>S. pneumoniae</i> alone (C and D) as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004339#ppat-1004339-g001" target="_blank">Figure 1A</a>. Each day (starting on day 8), the nose of each mouse was gently pressed onto an agar plate 10 times, exhaled bacteria were spread, and plates were incubated overnight. Each symbol represents the bacterial count from one animal on each day. In panel E, Pam3Cys or PBS alone (vehicle control) was administered on days 8, 10 and 12. Colony counts from days 10 and 11 are combined for comparison. <b>F.</b> Infant (7 day old) and adult (6 week old) mice were inoculated with ∼500 (dotted line) CFU of strain P1121 in PBS. One day post inoculation, the mice were sacrificed, nasal lavage was performed and lavage fluid was serially diluted and plated on selective media to enumerate bacteria.