Formations of Host Fibers and Bacteria in Human Temporal Bones With Otitis Media

Abstract

Hypothesis:In temporal bones with otitis media, fibrin and neutrophil extracellular traps (NETs) form a fibrous network with bacteria, which is involved in growth of bacterial clusters/biofilms and chronicity of disease.Background:NETs and fibrin are important in host defense against pathogens; however, their role in otitis media is not well understood.Methods:Eight human temporal bones with serous otitis media, 30 with serous-purulent otitis media, 7 with mucoid otitis media, 23 with mucoid-purulent otitis media (OM), 30 with purulent OM, and 30 with chronic otitis media were selected based on histopathologic findings. Fibrous material with bacteria was detected with hematoxylin-eosin, Gram-Weigert, and propidium iodide stains; and its composition was analyzed with immunohistochemistry.Results:Extensive formations of fibrous material with bacteria were observed in 30% of temporal bones with serous-purulent otitis media, 29% with mucoid otitis media, 50% with mucoid-purulent OM, 57% with purulent OM, and 67% of temporal bones with histological evidence of chronic otitis media. Some of these formations showed large bacterial clusters or biofilms. Immunohistochemical analysis showed that fibrous structures were composed of fibrin or NETs.Conclusions:Formations of fibrous material with bacteria were detected in human temporal bones with different types of otitis media. Inflammatory cells were observed mostly in areas with low presence of fibrous structures. The network of fibrous material seems to prevent clearance of bacteria by phagocytic cells and thus influences growth of bacterial clusters or biofilms. Fibrin and NETs may be important for the recurrences and chronicity of disease, and contribute to clogging of tympanostomy tubes in children.

Chronic Intraocular Leptospiral Infection Relying on Biofilm Formation inside the Vitreous Cavity Leads to Recurrent Uveitis in Horses

“…The formation of NETs and biofilm promote each other [155,156]. Similar to what has been described for otitis media [157], these numerous fibers could be incorporated into the biofilm and help to reinforce the biofilm scaffold, so that therapeutically only mechanical removal is promising.…”

Infectious Uveitis in Horses and New Insights in Its Leptospiral Biofilm-Related Pathogenesis

“…It is conceivable that this network of fibrous material becomes integrated into the leptospiral biofilm, making pathogen elimination increasingly impossible, similar to what has been described for chronic recurrent otitis in children [449]. It is therefore clear why vitrectomy is the most effective treatment option for typical ERU.…”

“…Fibrous material such as NET and fibrin is suggested to prevent the clearance of bacteria by phagocytic cells, and thus promotes the growth of bacterial clusters or biofilms. Fibrin and NETs are discussed to be important for the recurrence and chronicity of otitis media in children [449].…”

“…Biofilms not only confer protection, but also exhibit a potential for homeostasis, thereby reducing maintenance energy [461]. The in vivo biofilm can also harness certain immune responses of the host and integrate them into the biofilm scaffold (e.g., NETs and fibrin fibers) [449].…”

“…Other biofilm-associated diseases include wound infections [496,497], infected implants and bone sequestrum formation [498], osteomyelitis [499][500][501], chronic otitis [449,502], infectious endocarditis [503], and borreliosis [504][505][506]. Whenever possible, mechanical or surgical removal of the biofilm is considered the most effective therapy to eliminate the infection [481,507,508].…”