COMPARATIVE-EVALUATION OF CULTURE AND PCR FOR THE DETECTION AND DETERMINATION OF PERSISTENCE OF BACTERIAL STRAINS AND DNAS IN THE CHINCHILLA-LANIGER MODEL OF OTITIS-MEDIA

This study was designed to determine the persistence of culturable bac teria versus DNA in the presence of a middle ear effusion in a chinchi lla model of otitis media. Cohorts of animals were either infected wit h an ampicillin-resistant Haemophilus influenzae strain or injected wi th a tripartite inoculum consisting of freeze-thawed Streptococcus pne umoniae; pasteurized Moraxella catarrhalis; and DNA from H influenzae. The H influenzae-infected animals displayed culture positivity and po lymerase chain reaction positivity through day 35. In the chinchillas infected with the low-copy number inocula of S pneumoniae, DNA was not detectable after day 1 from the co-inoculated pasteurized M catarrhal is bacteria or the purified H influenzae DNA; however, amplifiable DNA from the live low-copy number bacteria persisted through day 21 even though they were not culture-positive past day 3. These results demons trate that DNA, and DNA from intact but nonviable bacteria, does not p ersist in an amplifiable form for more than a day in the presence of a n effusion; however, live bacteria, while not culturable, persist in a viable state for weeks.