OBJECTIVETo compare the sensitivities of two different serotypes of Streptococcus pneumoniae in acute otitis media of C57BL/6 mice.

METHODSThe middle ear cavity of C57BL/6 mice were inoculated via intratympanic injection of Streptococcus pneumoniae TIGR4 or 6B 1×10(8) CFU, and the control group were inoculated equivalent phosphate buffered solution (PBS). The incidence of mice, development of otitis media and the middle ear lavage fluid pathological changes by HE staining, as well as cell counts and cytokine levels were investigated.

RESULTSAfter inoculated with Streptococcus pneumoniae TIGR4, 6B and PBS, the survival rate of 6B group was significantly less than TIGR4 group and PBS control group (P < 0.01). Inflammatory cells in the middle ear cavity were mainly neutrophils, and the inflammatory cells recruitment in TIGR4 group were more than 6B group; The levels of IL-6 and TNF-α in the middle ear lavage fluid in TIGR4 group and 6B group were significantly increased compared with PBS control group, while the TIGR4 group were significantly increased compared with 6B group;6B group had delayed bacterial clearance in the middle ear.

CONCLUSIONThe study implied that Streptococcus pneumoniae 6B had higher pathogenicity for acute otitis media in C57BL/6 mice than TIGR4.