Binding of S. pneumoniae TIGR4 and G54 to D562 cells infected with HPIV3 (A) or RSV (B). The number of bacteria adhering to mock-infected cells (gray) and to viral-infected cells (black) is shown. The number of bacteria is calculated as the mean (± SEM) number of colony forming units observed in at least 3 replicate wells. Adhesion of pneumococci to viral-infected cells vs. mock-infected at varying viral doses is noted with a star (p < 0.05, Student’s test). Since the primary comparison in this figure is between mock-infected and virus-infected cells, the Y-axis scales for the two bacterial strains are different.