Middle ear fluid bacteriology of acute otitis media in neonates and very young infants.

The middle ear fluid (MEF) bacteriology of 107 attacks of acute otitis media (AOM) in 101 infants less than 3 months old was analyzed. A total of 108 bacteria were isolated from 85 attacks. Major AOM-pathogens, S. pneumoniae (19%), H. influenzae (9%) or B. catarrhalis (7%) were cultured in approximately one-third of all the attacks. S. aureus (17%) and coagulase-negative staphylococci (22%) without the above pathogens were commonly found, whereas gram-negative enteric bacteria were culturable from only 5 attacks. Only 8% of the MEFs were polymicrobial. More than half of all the bacterial strains produced beta-lactamase. The bacteriology of those younger than one month was not different from that of the others. The same was true with attacks of out-patients and in-patients, except for a larger proportion of beta-lactamase producing strains in in-patients. Nasal-nasopharyngeal and MEF samples showed the same bacteriology in only 20% of cases. Two-thirds of AOM attacks were present in infants with perinatal or other concomitant morbidity, but their bacteriology was not different from those without other morbidity. In addition to the examination of ears in infants presenting with any illness before the age of 3 months, the study stresses the importance of bacteriological analysis of MEF in all cases of AOM at this age.