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Ryan Young, Harry Flynn, Jorge Maestre-Mesa, Eduardo C. Alfonso, Darlene Miller; Molecular Surveillance of Contact Lenses, Cases, and Solutions for the Presence of Free-Living Amoeba Among Patients with Infectious Keratitis. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6171.
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To determine the prevalence of free-living amoeba among patients’ contact lenses, cases, and solutions and to compare multiplex PCR with standard culture techniques in the detection of free-living amoeba among patients with infectious keratitis.
We evaluated the efficacy of a multiplex PCR assay for the detection of free-living amoeba (Acanthamoeba, Vahlkampfia, Naegleria, and Hartmanella) and compared PCR results with cultures of 187 contact lenses and lens cases and 47 contact lens solutions collected within the last 5 years.
Free-living amoeba were isolated in 27 of 187 contact lenses and cases by combined PCR and culture techniques, for an overall prevalence of 14.4%. 10 cases of amoeba (9 verified Acanthamoeba and one unidentified free-living amoeba) were identified by culture techniques alone (5.3%), while 17 cases of amoeba (8 Acanthamoeba and 9 Hartmanella) were identified by multiplex PCR (9.1%) (Χ2 = 12.213, p = 0.0005). The sensitivity and specificity of culture, using PCR as the gold standard, were 23.5% and 96.5%, respectively. Acanthamoeba was isolated in one of 47 contact lens solutions by PCR, for a prevalence of 2.1%. All cultures of contact lens solutions were negative for free-living amoeba. Among the 187 patients with contact lenses and cases cultured, 42 had corneal cultures done, of which 5 were positive for Acanthamoeba for a prevalence of 11.9%. Three of the 5 cases were confirmed by cultures of contact lenses and cases. No cases of Vahlkampfia or Naegleria were identified in this study.
Acanthamoeba and Hartmanella were more frequently isolated by PCR than by traditional culture techniques. Multiplex PCR assay is a useful adjunct to standard culture techniques for the detection of free-living amoeba in contact lenses, cases, and solutions in patients with recalcitrant infectious keratitis. Hartmanella may be a more frequent cause of amoebic keratitis than previously recognized in South Florida.
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