Ocular Fluids Analyzed for Infectious Pathogens

The measurement of the genomic DNA of ocular infectious pathogens in ocular fluids has been analyzed and correlated with the relevant diseases.

The clinical relevance of ophthalmic pathogens has been analyzed in relation to uveitis, which is an inflammation of middle, pigmented, vascular structures of the eye, and endophthalmitis, an inflammation of the structures of the tissues in the eyeball.

Scientists at the Tokyo Medical and Dental University (Japan) and their colleagues from other institutions performed a prospective clinical case of 500 patients with infectious uveitis and endophthalmitis. Intraocular samples were collected and examined for genomic DNA of bacteria, fungi, parasites, and viruses by comprehensive polymerase chain reaction (PCR). Samples were analyzed first by multiplex PCR and quantitative real-time PCR for Human herpesvirus (HHV) 1 through 8, and Toxoplasma. Subsequently, samples were examined by broad-range real-time PCR for bacterial 16S and fungal 18S/28S ribosomal DNA (rDNA).

From all of the tested infectious uveitis and endophthalmitis patients, the team detected 18 Herpes simplex virus type 1, 4 Herpes simplex virus type 2, 55 Varicella-zoster virus, 17 Epstein-Barr virus (HHV-4), 68 Cytomegalovirus, 2 HHV type 6, 6 Toxoplasma gondii, 33 bacterial 16S, and 11 fungal 18S/28S genomes. Neither HHV type 7 nor HHV type 8 DNA was detected in any of the samples. Of the 21 false-negative results found during the PCR analyses, 12 cases were negative for patients clinically suspected of having bacterial endophthalmitis. Conversely, false-positive results for the comprehensive PCR examinations occurred in only three cases that subsequently were found to have bacterial 16S rDNA. The sensitivity of the PCR assays was 91.3%, and the specificity was 98.8%.

The authors concluded that using a comprehensive PCR assay to examine ocular samples in patients with endophthalmitis and uveitis seems to be clinically useful for detecting infectious antigen DNA. The PCR method was a reliable tool for both diagnosing ocular disorders and further screening of patients for intraocular infections. The study was published on May 7, 2013, in the journal Ophthalmology.

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Tokyo Medical and Dental University