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2013 Agenda and Abstracts | < Previous | Next >

2013 OMIG Abstract 7

The Comparison of Culture Isolation to Validated PCR for the Detection of
Acanthamoeba from Ocular Samples

Regis P. Kowalski, MS, [M]ASCP1, Melissa A. Melan, PhD2, Lisa M. Karenchak, BS1, Leela V. Raju, MD1. 1Ophthalmic Microbiology, 2Molecular Diagnostics, UPMC, and the University of Pittsburgh, Pittsburgh, PA

Purpose: The diagnosis of acanthamoeba keratitis is commonly ascertained with a combination of clinical presentation; isolation in culture; observation on stained material; and, confocal microscopy. Our institution has validated PCR to detect acanthamoeba DNA from ocular samples to complement testing.

Methods: The laboratory records of patients with a differential of acanthamoeba keratitis were reviewed (May 2012 to June 2013), without recording patient identifiers, for: 1) acanthamoeba culture isolation and 2) acanthamoeba DNA detection by PCR. For acanthamoeba isolation, corneal samples were planted on non-nutrient agar (Noble Agar) overlaid with Enterobacter aerogenes and monitored for growth over 7 days. Validated PCR for acanthamoeba DNA was processed at the Division of Molecular Diagnostics, UPMC, Pittsburgh, PA.

Results: Culture isolation and PCR were processed on 77 patients. Of these, 65 (84%) were (culture-neg, PCR-neg); 7 (9%) were (culture-pos, PCR-pos); 2 (3%) were (culture-neg, PCR-pos); and, 3 (4%) were (culture-pos, PCR-neg). Culture and PCR were statistically equivalent for detecting acanthamoeba from corneal samples (p=1.0, McNemar’s). Eleven (14%) of the (culture-neg, PCR-neg) corneal samples were positive for other pathogens (4 Pseudomonas aeruginosa, and one each of MRSA, Klebsiella pneumoniae, Moraxella lacunata, Fusarium, Aspergillus, Candida albicans, and HSV).

Conclusions: The present study indicates no real advantage of PCR over culture isolation for acanthamoeba detection. Our laboratory data suggests that although acanthamoeba can be the primary suspect in specific cases of severe persistent keratitis, other pathogens such as bacteria, fungus, and virus must still be considered as part of the differential diagnosis. Our plan is to continue to use PCR as part of a complementary test for the support of acanthamoeba keratitis.

Disclosure: NONE

2013 Agenda and Abstracts | < Previous | Next >