Effect of apolactoferrin on experimental pneumococcal otitis media

Abstract

Objective: To find the effect of apolactoferrin administration on the middle and inner ears after experimentally induced pneumococcal otitis media.

Design: Histopathologic and morphometric analysis of the middle and inner ears.

Setting: University of Minnesota, Minneapolis.

Subjects: Ten chinchillas.

Interventions: The middle ear cavities of chinchillas were inoculated bilaterally with type 2 wild-type Streptococcus pneumoniae. Twenty-four hours later, the ears of 5 of the animals were injected with phosphate-buffered saline (PBS) and the other 5 with human apolactoferrin. The animals were killed 24 hours after the last injection. Bacterial counts were made of the middle ear effusions, and the cochleae were processed for histologic analysis. The thickness of the round window membranes and bacterial and inflammatory cell infiltration of the round window membranes, and scala tympani and damage of the hair cells and stria vascularis were compared for these 2 groups of animals.

Main outcome measures: Comparison of inflammatory and bacterial cells in the middle and inner ears, and damage to inner ear structures.

Results: Bacterial plate counts of middle ear effusions (P = .005) and the number of inflammatory cells in the round window membrane (P = .047) were significantly lower in the apolactoferrin group compared with the group treated with PBS.

Conclusion: Further investigation of apolactoferrin as a nonantibiotic approach for the treatment of otitis media and its complications is needed to confirm its safety and efficacy.

Figure 1

Inflammation of the round window membrane (RWM) (toluidine blue, original magnification ×600). A, The most severe pathological changes observed in an RWM from the apolactoferrin-treated group, showing a slightly elevated thickness and a small number of inflammatory cells. B, The most severe pathological changes seen in the RWM of the phosphate-buffered saline–treated group, showing a large number of bacteria and inflammatory cells in the RWM and a substantial increasing of its thickness. Bacteria (arrows) are seen within the RWM and adjacent scala tympani (ST). ME indicates middle ear; arrows indicate bacteria.

Figure 2

Inner ear inflammation (toluidine blue; original magnification ×600). A, Inner ear pathological changes were seen in both the apolactoferrin- and phosphate-buffered saline (PBS)-treated groups; however, it was seen more often in the PBS-treated group. There is inflammatory cell infiltration in the scala tympani (ST), severe strial edema, hair cell damage, and bacterial cells (arrow) in this PBS-treated ear. B, Higher magnification shows bacteria (arrows) within the area of the neurofilaments. SM indicates scala media; SV, stria vascularis.

Figure 3

Histogram shows a significant difference between the phosphate-buffered saline (PBS)- and apolactoferrin (ALF)-treated groups of animals. A, Bacterial plate counts of middle ear effusion (P = .005). B, Inflammatory cell infiltration of the round window membrane (RWM) (P = .047). Error bars indicate standard errors.