Co-infection of primary human adenoid epithelial cells with Influenza A and Streptococcus pneumoniae

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Human adenoid epithelial cells (HAEC) from adenoids were used as a model for exploring potential viral/bacterial synergy. Methods: HAEC were grown on a collagen, matrix-coated tissue culture plate until the monolayer became confluent. A differentiated cell population with secretory component, mucin production, and ciliary activity was seen with histochemical staining. Cells were infected with Influenza A/Beijing/H3N2 at an MOI of 0.01 PFU for 24 h. The monolayer was washed and 10 7 Streptococcus pneumoniae added. After a 3-h pneumococcal infection, pneumococci were titered in the supernatant, in the cells after washing (adherent and intracellular bacteria) and in cells treated with antibiotics to destroy adherent bacteria followed by lysis (intracellular bacteria). Results: Over the 3-h infection period, neither pneumococci type 14 (encapsulated) and R6× (unencapsulated) influenced the titer of influenza released nor did influenza affect the bacterial growth. Co-localization of pneumococcal and influenza infection in individual cells was not evident. The capacity varied of pneumococcal strains to adhere and invade the epithelial surface. Encapsulated type 14 from the bloodstream was less invasive than an unencapsulated laboratory strain R6×. Conclusion: The propensity for bacterial superinfection, based on increased adherence or invasion of pneumococci to influenza-infected epithelial cells, could not be explained in the HAEC model.