RESUMEN
INTRODUCTION: Between 20% and 50% of middle ear effusions in otitis media with effusion test positive for bacteria, i.e. H. influenzae, M. catarrhalis and S. pneumoniae. In one study 48% of effusions that tested negative by culture wre positive by polymerase chain reaction (PCR).1 This has been advanced as evidence for the presence of bacterial biofilms, as agents leading to the persistence of glue ear. There is, however, the possibility that the DNA detected is the fossilized remains of bacteria from previously cleared infections. If this is the case, then the effusioin must in some way be protecting the DNA from breakdown by DNases. METHODS: Here we demonstrate, using a viscosity assay, that middle ear effusions taken from children during myringotomy inhibit the breakdown of DNA in a concentration-dependent manner. Middle ear effusion homogenates 0.5-3.0 ml (1 : 10 Vol. vol/effusion: PBS) were incubated with 3 ml of DNA (0.5 mg/ml in PBS) plus 0.2 ml of DNase 1 (500 Kunitz) at 37 degrees C for 24 h. Viscosity measurements were taken at regular intervals and the changes in viscosity expressed as a percentage of time 0. DNase activity was inhibited by 1.5 ml and 3.0 ml of effusion 48% and 91%, respectively, after 30 min incubation. CONCLUSION: This study demonstrated that effusions have the ability to inhibit nuclease activity, and the reported presence of non-culturable bacteria based on DNA detection by PCR could still represent fossilized remains and not viable bacteria. The same could also be true of recent reports of bacterial mRNA.2
RESUMEN
INTRODUCTION: Glucocorticoids have been used in the treatment of otitis media with effusion with promising but inconsistent resluts. The HT29-MTX cell line is a completely differentiated and almost exclusively mucous secreting cell line, which therefore has the potential to act as an ideal model for the study of mucus-secreting epithelia. To assess this potential of steroids in suppressing mucin secretion we have studied the response of the cell culture to prednisolone. METHODS: Confluent cell cultures were trypsinized, subcultured in six-well plates and incubated with four doses of prednisolone from 10-5 M to 10-11 M and over varying time courses from 12 to 36 h. ELISA was performed using a monoclonal mouse antibody to human gastric mucin by dot-blot ELISA. RESULTS: Prednisolone caused a reduction in mucin production from the cell line consistently. Media control values ranged from 3495 to 3559 compared with untreated controls of 18 998-27 176 and steroid treatment values of 12 244-27 792. Increasing concentrations of prednisolone result in increasing suppression of MUC5AC (P = 0.005). There was no independent time-related effect. CONCLUSION: There does appear to be a genuine suppression of mucus production by prednisolone and this appears to be dose-dependent but not time-dependent at the times studied. The effect size was small.
