Description and evaluation of a simple method for microbiological studies on otitis externa.

A simple cultural method for identification of the bacteria and yeasts likely to cause external otitis in divers is described. The method employs a commercial dip-slide system (Urotube) in which ear swabs are rolled onto the three agar surfaces, spread by a loop, and then incubated for a period of 18 h or more at 37 degrees C. The method was compared with traditional culture methodology on agar plates. Use of reference strains of bacteria and stored clinical isolates of bacteria and yeasts from ear infections showed stable patterns of growth for each species. Semiquantitative investigation of growth showed that there was a constant relationship between amount of growth on agar plates as compared to the dip-slide. Results were reproducible and were not affected by prolonged incubation. Directly inoculated swabs from normal ear canals and clinically infected ear canals showed identical findings by the traditional culture and Urotube methods. The Urotube method has also been evaluated in practical situations offshore with favorable experience. The Urotube method thus provides a rapid and simple way of identifying the causes of external otitis in divers in isolated areas where laboratory facilities are not readily available. This can have consequences for speed and choice of therapy in isolated environments.