Abstract
Purpose: :
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.
Methods: :
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.
Results: :
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.
Conclusions: :
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.
Keywords: Acanthamoeba • keratitis • contact lens