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.

Acute Disease ; Animals ; Cytokines ; immunology ; Female ; Male ; Mice ; Mice, Inbred C57BL ; Otitis Media ; immunology ; microbiology ; Streptococcus pneumoniae ; classification ; pathogenicity

OBJECTIVETo develop a mouse model for acute otitis media (AOM) via transbullar injection method and evaluate its feasibility and practicability.

METHODSThe middle ears (ME) of C57BL/6 mice were inoculated via transbullar injection method with 5 µl streptococcus pneumoniae (S.pn) 19F suspension (1×10(7) CFU/ml), and the control group was inoculated equivalent phosphate buffered solution (PBS). Behavior changes were observed daily following inoculation. The ME tissues for histological examination and the middle ear lavage fluid (MELF) for total cells quantification, S.pn load determination and cytokines measurement were collected at 12 h, day 1, 2, 3, 5, 7 after inoculation, respectively.

RESULTSWithin 24 hours after instillation, the density of S.pn and the level of acute inflammatory cytokines in ME cavity increased rapidly, some mucosal hyperplasia was evident and leukocytic infiltration (primarily neutrophils) began. The level of ME inflammatory response reached maximal at 2-3 days after inoculation, with extensive effusion, leukocytic infiltration and mucosal thickening. Meanwhile, the density of S.pn decreased gradually. Bacterial clearance was completed by day 5 with extensive resolution of ME inflammation, although mucosal hyperplasia did not resolute until day 7.

CONCLUSIONA mouse model for AOM is successfully established via transbullar injection method, laying foundation for future study of AOM.

Acute Disease ; Animals ; Cytokines ; Disease Models, Animal ; Ear, Middle ; Injections ; Mice ; Mice, Inbred C57BL ; Otitis Media ; Otitis Media with Effusion