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Molecular techniques improve organism identification from pleural fluid in empyema
  1. T H Chapman
  1. Senior Clinical Fellow, Royal Free Hospital, London, UK;

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This study compares a broad range molecular technique with bacterial culture for the detection of organisms from pleural fluid in 32 children with empyema. The concordance of organisms identified and influence of prior antibiotic treatment was also investigated. There was a median duration of 8 (1–42) days antibiotic therapy before pleural fluid aspiration.

The molecular assay is an established and validated broad range 16S rDNA PCR technique. This is based on bacterial ribosomal (r)DNA with sequencing of the PCR product to reveal the source organism. Significant organisms were detected in 19% of cases by culture, whilst 69% of cases were PCR positive. Of the six culture positive samples, five were PCR positive and the organism identified was identical using both techniques. The organism not detected by PCR was grown only after enrichment culture and was present at levels below the PCR detection limit. The presence of organisms detected by PCR but not culture was probably because of prior antibiotic treatment. The PCR negative cases had also all received antibiotic therapy, causing organism death and DNA degradation.

Molecular (non-culture) techniques improve organism identification from pleural fluid in children with empyema, even after commencement of antibiotics, but should be considered complementary to culture. This assay produces a result in 48 hours, allowing appropriate alterations in management soon within the inpatient stay.

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