Organic acids and anaerobic microorganisms in the contents of the cholesteatoma sac.

Organic acids in the contents of the cholesteatoma sac from 28 cases were studied by gas chromatographic technique. Five volatile fatty acids (acetate, propionate, isobutyrate, butyrate and isovalerate) and lactate were detected in large amounts, which may lower the pH of the cholesteatoma content. These acids were considered to be derived from products of anaerobic microorganisms. Therefore, the contents from 12 cases were cultured anaerobically in a glove box. Obligate microorganisms were identified in 92% of the cases and Peptococcus, Bacteroides, and Clostridium species were frequently isolated. In vitro, such obligate anaerobes produced various organic acids from the cholesteatoma content. Facultatives such as Staphylococcus aureus and Proteus mirabilis produced acetate in the content under aerobic and anaerobic conditions, whereas no organic acid was produced by Pseudomonas aeruginosa. Organic acids in the cholesteatoma content could be fermentative products made by the microorganisms, anaerobes and facultatives, which use the content as a substrate for acid production.