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 characte risation of populations of bacteria in the middle ear. We have used a PCR-b ased method that does not depend on prior knowledge of the bacteria identif ied by culture. Methods Middle-ear effusion fluid was obtained from 12 patients with chroni c otitis media with effusion. Total DNA was extracted from the samples, and the hypervariable regions of bacterial 16S rRNA genes were amplified by me ans 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 patien ts. The gram-positive bacterium Alloiococcus otitis (A otitidis) was detect ed by 16S rDNA amplification in six of the twelve samples, but not by cultu re techniques. Interpretation The method may have general usefulness in characterising bac terial populations at the site of infection and may indicate, from small sa mple numbers, organisms that are candidates for further investigation.