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Bacteria were isolated from a high percentage of the effusions from patients with otitis media with effusion (OME, serous otitis media). In an attempt to determine if the isolated bacteria were involved in the disease process, we analyzed the serum and effusion of 25 OME patients for the presence of antibacterial antibodies by the indirect immunofluorescence antibody method. Specific antibody activity was detected in 20 of 25 effusions (80%) and 19 of 22 sera (86%). IgG antibodies were the most frequently found class of antibodies in both sera and effusions, but IgA antibodies were detected more frequently in the effusions than in the sera. Hemophilus influenzae, Streptococcus pneumoniae, and diphtheroids were the most frequently isolated organisms, and antibody activity to all bacterial species isolated was detected. The results support the concept that the isolated bacteria are not contaminants but are actively involved in the disease process.

To investigate the possible role of allergy in otitis media with effusion (OME), the immunoglobulin E (IgE) content of 138 middle ear effusions (MEE) and paired serum samples from patients with chronic otitis media with effusion was determined. The initial 62 paired specimens were assayed for IgE by the radioimmunosorbent test (RIST), while the later 76 paired specimens were assayed for IgE by the paper radioimmunosorbent test (PRIST). When the results obtained by these two techniques were compared, it was noted that the PRIST procedure gave significantly lower IgE values for effusions than the RIST method. When the effusion-to-serum ratios (E/S ratios) were computed from the PRIST data, the E/S ratio was less than one, while RIST data gave an E/S ratio greater than one. The results obtained with the PRIST procedure were confirmed by double antibody radioimmunoassay for IgE. Thus, the PRIST procedure appears to measure the IgE content of MEE more accurately, and the results obtained by this procedure fail to support the concept of allergy as a major causative factor in OME.

Eighty-two bacterial isolates recovered from the middle ear effusions (192) of children with otitis media with effusion (OME) were tested for antibiotic sensitivity. Nearly 50% of all bacteria isolated were found to be resistant to penicillin, and in particular, 61% of the Haemophilus isolates were penicillin-resistant; 48% of the Haemophilus isolates were ampicillin-resistant. In addition, we we compared the bacterial recovery rate from effusions of patients who were receiving antibiotics with those who were not. Among patients who were receiving antibiotics, 33% of the effusions were culture positive, while 82% of the effusions were culture positive in the patients who were not given antibiotics. These results are discussed with respect to the possible role of bacteria in the pathogenesis of OME.

Otitis media was induced in chinchillas by intrabullar injection of type 3 Streptococcus pneumoniae. It was found that the severity of a primary infection was related to the dose of bacteria injected, and animals that had recovered from a primary infection were resistant to reinfection with type 3 S pneumoniae. Middle ear effusions from infected animals contained antibodies to type 3 pneumococcal polysaccharide, whereas the sera of these animals lacked this antibody, suggesting that resistance to reinfectin was due to local immune mechanisms. This idea was tested by immunizing chinchillas by various routes. Animals immunized with formalin-killed type 3 S pneumoniae by intramuscular injection (to stimulate the systemic immune system) or by intranasal inoculation (to stimulate the secretory immune system) were found to be susceptible to infection with type 3 pneumonococcus, while animals immunized by inoculation of bacterial suspension directly into the middle ear were resistant to infection. In addition, we found that ampicillin treatment of a primary infection blocks the development of resistance since antibiotic-treated animals were susceptible to reinfection with the type 3 pneumococcus. These results indicate that chinchillas develop an immunity to pneumococcal otitis media following recovery from primary infection and that this immunity is mediated primarily by local immune mechanisms rather than systemic immune responses.