Middle ear with purulent effusion, bulging tympanum, Haemophilus influenzae bacteria. Otitis media acute. Frontal cut of the auditory apparatus passing through the outer ear and the middle ear, bulging tympanum with a purulent effusion in the middle ear and inflammation of the mucosa. Below, zoom in on the mucosa with a Haemophilus influenzae bacteria seen in section allowing to see the different layers of the wall with the betalactamases of the periplasmic space and the PBPs of the cytoplasmic membrane bacterial DNA with the ribosomes.