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Narciss Okhravi, Peter Adamson, Nora Carroll, Anthony Dunlop, Melville M. Matheson, Hamish M. A. Towler, Susan Lightman; PCR-Based Evidence of Bacterial Involvement in Eyes with Suspected Intraocular Infection. Invest. Ophthalmol. Vis. Sci. 2000;41(11):3474-3479.
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purpose. To assess the usefulness of polymerase chain reaction (PCR) in
detection of bacteria in ocular samples.
methods. Thirty-seven samples (aqueous and vitreous) were collected from 25 eyes
showing typical symptoms and clinical signs of bacterial
endophthalmitis. Ocular samples were also collected from 38 eyes that
underwent routine surgery and from 15 eyes with intraocular
inflammation due to nonbacterial causes. Panbacterial PCR was performed
with a nested pair of 16S rRNA gene primers. Subsequent bacterial
identification was completed for 18 paired samples (nine eyes) using
restriction fragment length polymorphism (RFLP) and DNA sequencing.
results. A 100% concordance was obtained between PCR and culture-positive
samples. A PCR product was amplified from all 37 intraocular samples
from eyes with suspected infection, whereas only 15 of 22 vitreous
samples and 5 of 15 aqueous samples were culture positive.
Culture-negative PCR-positive samples contained a preponderance of
gram-negative bacterial sequences. Cloning and DNA analysis revealed 30
DNA sequences and included eight bacterial 16S rDNA, which currently
remain unidentifiable. The presence of bacterial DNA was associated
with an inflammatory response suggestive of infection and not
colonization. All 15 samples from inflamed eyes with diverse uveitis
diagnoses were PCR negative. The false-positive rate, due to
contamination during sampling, was 5%.
conclusions. Bacterial DNA was detected in all patients with typical clinical signs
of endophthalmitis. Gram-negative organisms seem to play a much more
important role in the pathogenesis of this disease than previously
thought. PCR-based techniques have great value in the confirmation of
the diagnosis of bacterial endophthalmitis especially in
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