Haemophilus influenzae in acute otitis media.

We studied the occurrence of Haemophilus influenzae (Hi) in 2625 middle ear fluid (MEF) specimens obtained from 523 children with otitis media, aged 3 months to 6 years, between October 1977 and May 1979. In clinically acute cases 12.3% of the MEFs grew Hi; 6.3% (13/206) of the strains were of type b and 4.9% (10/206) were beta-lactamase producing. In the very first acute case of a child 8.0% (21/263) of the MEFs grew Hi, but in acute recurrences it was cultured in 17.0% (184/1082) (p less than 0.001). In non-acute persistent MEFs obtained during control visits Hi was found in no less than 21.7% (198/913); as many as 12.6% (25/198) of them were beta-lactamase producing. Both of these figures, but not the proportion of type b strains (8.6%), were significantly (p less than 0.001 and p less than 0.01, respectively) greater than in clinically acute MEFs. Hi was grown in 13.1% of the acute MEFs taken from children less than 4 years old, but in only 8.6% of the older children (p less than 0.05). The annual survey of all the 1816 Hi strains isolated from the MEFs of acute or subacute cases of otitis media in one laboratory in 1976-81 showed the proportion of beta-lactamase producing strains of all Hi strains to be gradually increasing from 8.0% (17/212) in 1976 to 15.2% (16/105) in 1981 (p less than 0.05).