New perspectives in the direct microscopic examination of middle ear effusions.

Detection and identification of bacteria in middle ear effusions from patients with otitis media with effusion requires sensitive bacteriologic techniques. Direct microscopic examination is very important in this respect. Three staining methods--Gram, Giemsa and the fluorescent acridine orange stain--were evaluated and compared by examining 112 middle ear effusions. Purulent effusions showed more bacteria than mucoid, and mucoid effusions showed more bacteria than serous in the direct microscopic examination of the smears. Acridine orange stain proved superior in detecting bacteria compared with Gram and Giemsa stains and distinguished dead from living bacteria. It is even more sensitive in this way than aerobic and anaerobic cultures. Giemsa stain was superior in the identification of inflammatory cells. Acridine orange and Giemsa stains are recommended in the bacteriocytologic examination of middle ear effusions; Gram stain may provide additional information.