Inhibition of OM pathogens by alpha-hemolytic streptococci from healthy children, children with SOM and children with rAOM

The present study was undertaken to elucidate the inhibitory activity of th e normal nasopharyngeal flora against the three most common otitis media (O M) pathogens in healthy children, children with secretory otitis media (SOM ) and children with recurrent otitis media (rAOM). Isolates of alpha-hemoly tic streptococci (AHS) and OM pathogens were recovered from the tubal orifi ce in each child. The samples were taken from 20 healthy children under gen eral anesthesia, from 19 children with SOM and 20 children with rAOM. The m ethod used to test the bacterial interference in vitro was a modified agar overlay method. The AHS sampled from the tubal orifice of the healthy child ren were able to inhibit 92% of the S. peumoniae isolates, 74% of the non-t ypable H. influenzae isolates and 89% of the M. catarrhalis isolates. The c orresponding figures for children with SOM and children with rAOM were: 73% of the S. pneumoniae isolates, 58 and 54% of the non-typable H. influenzae isolates and 86 and 89% of the M. catarrhalis isolates. The AHS from child ren with SOM and children with rAOM were significantly less capable of inhi biting the S. peumoniae and the H. influenzae isolates (P < 0.001). There w as no significant difference between the three groups of children regarding inhibitory activity against M. catarrhalis. The results suggest that the i nhibitory activity of the normal bacterial flora at the tubal orifice again st pneumococci and H. influenzae may be reduced in children with SOM and rA OM. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.