Detection of Alloiococcus otitis in mixed bacterial populations from middle-ear effusions of patients with otitis media

Background Otitis media is a potentially serious disorder, since there is a risk of permanent hearing loss. Culture methods are not useful in characterisation of populations of bacteria in the middle ear. We have used a PCR-based method that does not depend on prior knowledge of the bacteria identified by culture. Methods Middle-ear effusion fluid was obtained from 12 patients with chronic otitis media with effusion. Total DNA was extracted from the samples, and the hypervariable regions of bacterial 16S rRNA genes were amplified by means of broad-range PCR primers. Individual PCR products were segregated by cloning to allow analysis of mixed bacterial populations. Findings Many bacterial species were detected by PCR, whereas with culture-based approaches, no bacterial growth was detected for ten of the 12 patients. The gram-positive bacterium Alloiococcus otitis (A otitidis) was detected by 16S rDNA amplification in six of the twelve samples, but not by culture techniques. Interpretation The method may have general usefulness in characterising bacterial populations at the site of infection and may indicate, from small sample numbers, organisms that are candidates for further investigation.