Abstract
Abstract: :
Purpose: Rose bengal is a photosensitive dye that is commonly used as a diagnostic agent in evaluating corneal and external disease including herpes simplex virus (HSV) epithelial keratitis. Rose bengal has antiviral properties both in vivo and vitro and inhibits HSV propagation in cell culture. The current study was designed to determine whether rose bengal affects PCR detection of herpes simplex virus. Methods: Corneal scrapings from eyes where HSV was clinically suspected yet PCR was negative for HSV DNA were evaluated for PCR inhibitory activity. Dacron swabs inoculated with rose bengal, lissamine green, phenyl mercuric acetate (PMA)(the preserve of the former two), and proparacaine were processed as clinical samples, inoculated with 312,500 genome copies of control HSV, and prepared for HSV PCR. Conjunctival swabs of normal volunteers obtained one minute after rose bengal instillation were similarly evaluated. PCR amplification of a 179 bp fragment of the HSV–1 DNA polymerase gene was carried out as described previously (Arch Ophthalmol. 1996 Jul;114(7):834–40)and has a sensitivity of detecting approximately 100 HSV genome copies. The effect of rose bengal on the PCR detection of Varicella Zoster (VZV), Cytomegalovirus (CMV), and Toxoplasma DNA was also evaluated. Results: 1.Corneal scrapings with high clinical suspicion for HSV, from patients in which rose bengal and fluoroscein were used clinically, remained PCR negative for HSV even after inoculation with control HSV DNA, indicating the presence of inhibitory substances in the sample. 2. Rose bengal and lissamine green inhibit PCR detection of HSV. PMA and proparacaine do not inhibit HSV detection. 3. The amount of rose bengal present on bulbar and palpebral conjunctival swabs one minute after clinical administration, was sufficient to inhibit PCR detection of HSV. 4. Inoculation of dacron swabs with concentrations as low as 0.062% inhibited the detection of HSV DNA by PCR. 5. Rose bengal also inhibits PCR detection of VZV, CMV and Toxoplasma DNA indicating that this photosensitive dye may inhibit the PCR reaction itself. Conclusion: Rose bengal inhibits PCR detection of HSV. In cases where the clinical diagnosis is questionable, or in cases where detection of virus (i.e. HSV vs. VZV) will affect treatment choice or duration of treatment, it is recommended that the corneal epithelium be sampled prior to placement of rose bengal stain.
Keywords: cornea: clinical science • cornea: epithelium • herpes simplex virus