For decades, investigators have been searching for one of the Holy Grails of acute otitis media (AOM)—that is, an easy non-invasive marker that would identify or even suggest the specific pathogen causing AOM. Antibiotic selection by clinicians for almost all episodes of AOM is empirical. Most episodes of AOM usually result from congestion of the eustachian tube by an antecedent virus infection, which then allows one or two of the four typical aerobic bacteria, such as Streptococcus pneumoniae, Haemophilus influenzae, Moraxiella catarrhalis or Streptococcus pyogenes, to ascend into the middle ear space, causing the painful purulent effusion of AOM. Viruses seem to be an uncommon aetiology of AOM, as positive cultures for viruses being the sole pathogen of AOM occur in only 5–6% of cases.^1,2

How commonly do bacteria cause AOM? Many multicentre studies report bacterial culture-positive rates between 55% and 75% of children, depending on whether the study is multinational or from a single country or region.^3–7 But, the devil is in the details—that is, the culture methods. Consequently, when microbiologically rigorous clinical studies use a single tympanocentesis with optimal bacterial culture techniques in children with AOM, a bacterial pathogen is obtained in 87–95% of tympanocentesis aspirates.^5–7 Thus, AOM itself is most always found to be caused by bacteria—when stringent criteria to diagnose AOM are used and highly experienced investigators carry out tympanocentesis.

Can any dataset show the Holy Grail of AOM? Can any physical or symptom markers differentiate bacterial from non-bacterial AOM, or Streptococcus pneumoniae from H influenzae or M catarrhalis? Can any set of clinical or otological scores evaluating …