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T. Milman, N. Mirani, R. van Gelder, P. Langer; Actinomyces Israelii Endogenous Endophthalmitis with false negative PCR . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4012.
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Purpose:To report the first case in the literature of Actinomyces Israelii endogenous endophthalmitis, as documented by pathologic evaluation and confirmed through polymerase chain reaction (PCR) testing and DNA sequencing. Achieving the final diagnosis was complicated by a false negative PCR result. Methods:Clinical, pathologic, and microbiologic review of one patient with Actinomyces israelii endophthalmitis. Molecular biologic techniques were required to obtain the final diagnosis. Results:A 74 year old diabetic woman experienced acute unilateral visual loss one week after a dental procedure for a chipped tooth. Initial examination revealed endophthalmitis that progressed despite vitrectomies and intravitreal antibiotic injections. When the vision deteriorated to no light perception with the presence of 100% hypopyon and serous retinal detachment, the patient was referred for enucleation. Pathologic evaluation of the enucleated globe revealed acute suppurative panophthalmitis with Gram, PAS and GMS positive, modified AFB negative, branching filamentous bacteria, suggestive of Actinomyces. Standard microbiologic identification techniques utilizing biochemical tests on vitreous samples obtained at the time of enucleation did not identify Actinomyces despite the histologic appearance. Subsequent PCR analysis on the vitreous fluid also failed to demonstrate bacterial ribosomal genetic material. Because of the histologic appearance of bacteria, the presence of a PCR inhibitor was suspected, and its effect eliminated biochemically. Repeat PCR and DNA sequencing then confirmed the diagnosis of Actinomyces israelii endophthalmitis. Conclusions:Actinomyces, an oral saprophyte, may be a cause of endogenous endophthalmitis, especially in immunocompromised patients with a recent dental history. Microbiology laboratories should be alerted if the presence of this organism is suspected, since special isolation and identification techniques may be required. Furthermore, clinicians should be aware that PCR, often considered the "gold standard" for identifying minute quantities of organisms through the presence of genetic material, can actually produce false negative results. Intraocular fluid may contain a naturally occurring inhibitor that interferes with PCR. Laboratory personnel should be aware of the existence of these inhibitors and the techniques available for inactivating them; if strong clinical suspicion questions a negative PCR result, attempts at neutralizing an inhibitor should be undertaken.
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