As a group dual KO mice were extremely frail, necessitating a modified study design; whereas AOM treatment was started in six-week-old Chrm3-/- and Chrm1-/- mice, AOM treatment was delayed in dual KO mice until they were 11 to 12-weeks-old and better able to tolerate AOM treatment [24]. This evidence concerns the gene CHRM1 and infectious otitis media.