Common methods to induce acute or chronic OM in mouse models. Common methods to induce acute or chronic OM in mouse models. Methods shown here are for mouse models (methods to induce acute or chronic otitis media are determined by the model species and the hypothesis under test, and can be combined; for example, inoculating a genetic mutant with bacteria). (A) Inoculation with bacteria. A mouse is inoculated with bacteria, intranasally or by injection directly into the middle ear (bulla). Bacteria commonly used include pneumococcus or NTHi. (B) Surgical methods. The top inset shows surgically induced tympanic membrane perforation, and the lower inset shows surgical ligation of the Eustachian tube. (C) Genetic manipulation. This can be performed via chemical mutagenesis [typically with injection of the chemical mutagen N-ethyl-N-nitrosourea (ENU), as shown] or by targeted genetic mutation. (D) In vitro cell culture, for example of immortalised middle ear epithelial cells or mucosal explants. Following exposure to bacteria, these cell-culture models enable host-pathogen interactions at the epithelial surface to be assessed. Mahmood F. Bhutta et al. Dis. Model. Mech. 2017;10:1289-1300 © 2017. Published by The Company of Biologists Ltd