Acanthamoeba can be differentiated by the polymerase chain reaction and simple plating assays

Acanthamoeba are opportunistic pathogens with invasive and noninvasive spec ies. For clinical purposes it is important to differentiate potentially pat hogenic from nonpathogenic isolates. For the rapid and sensitive identifica tion of Acanthamoeba at the genus level, we used a polymerase chain reactio n (PCR)-based method which detected as few as five cells. Further, we teste d nine isolates of Acanthamoeba for their ability to produce cytopathic eff ects (CPE) on corneal epithelial cells. On the basis of the results, Acanth amoeba were divided into pathogenic or nonpathogenic groups. However, becau se CPE assays are not available to every diagnostic laboratory, we develope d a simple plating assay based on osmotolerance which correlated well with the CPE assays. Pathogenic Acanthamoeba showed growth on higher osmolarity (agar plates containing one molar mannitol), while growth of nonpathogens w as inhibited on these plates. In conclusion, we have developed methods for the rapid identification and differentiation of Acanthamoeba.