EFFECTS OF BIOCIDES ON ACANTHAMOEBA-CASTELLANII AS MEASURED BY FLOW-CYTOMETRY AND PLAQUE-ASSAY

The lethal effects of various biocides, in particular two agents (chlo rhexidine diacetate and polyhexamethylene biguanide) on cysts and trop hozoites of Acanthamoeba casteilanii have been measured by both plaque assay and flow cytometry (FCM). Minimum amoebicidal concentrations ag ainst trophozoites were generally the same by the two methods whereas minimum cysticidal concentrations were occasionally higher by FCM. Con centrations of biguanides required to produce an equal reduction in vi ability were also higher by FCM than by plaque assay.