Evidence of bacterial metabolic activity in culture-negative otitis media with effusion
M G Rayner1, Y Zhang, M C Gorry
1Department of Pathology, University of Pittsburgh School of Medicine, Pa, USA.
Context:
Otitis media with effusion (OME) can lead to significant hearing loss in children. Although previous studies have shown that bacterial DNA is present in a significant percentage of effusions sterile by culture, whether the DNA represents viable organisms or "fossilized remains" is unknown.
Objective:
To determine if bacterial messenger RNA (mRNA), as detected by a reverse transcriptase-polymerase chain reaction (RT-PCR)-based assay, is present in chronic pediatric middle ear effusions that contain bacterial DNA but are sterile by standard cultural methods. Bacterial mRNAs have a half-life measured in seconds to minutes; therefore, detection of bacteria-specific mRNAs would be evidence that metabolically active organisms are present.
Design:
Blinded comparative study.
Patients:
A total of 93 effusions from pediatric outpatients seen for myringotomy and tube placement for chronic (>3 months) OME (median age of children, 17 months).
Setting:
Tertiary care pediatric hospital.
Main Outcome Measures:
Percentage of positive test results for RT-PCR-based assays compared with culture for Haemophilus influenzae and concordance between RT-PCR and PCR-based findings for bacterial nucleic acids.
Results:
Eleven (11.8%) of the 93 specimens tested positive by culture, PCR, and RT-PCR for H influenzae. A total of 29 specimens (31.2%) were positive by PCR but negative by culture for H influenzae. All 29 specimens were positive by RT-PCR for H influenzae-specific mRNA.
Conclusions:
The RT-PCR-based assay system can detect the presence of bacterial mRNA in a significant percentage of culturally sterile middle ear effusions, establishing the presence of viable, metabolically active, intact organisms in some culture-negative OME.
