COMPARATIVE RECOVERIES OF NAEGLERIA-FOWLERI AMEBAS FROM SEEDED RIVER WATER BY FILTRATION AND CENTRIFUGATION

Detection of pathogenic Naegleria fowleri in environmental water sampl es, which is necessary for the prevention of primary amoebic meningoen cephalitis, generally requires concentrating the samples, Two concentr ation techniques, filtration and centrifugation, were used to study th e recovery of N. fowleri, in vegetative or cystic form, that had been mixed with the two other thermotolerant Naegleria species, N. lovanien sis and N. australiensis. Counting of amoebae was performed by the mos t probable number method on 10 water replicates of 100 ml and 10 ml ea ch. With both concentration methods, recovery was better for cysts tha n for trophozoites (53% +/- 21% versus 5% +/- 5% by filtration and 57% +/- 25% versus 22% a 5% by centrifugation), The recovery of Naegleria trophozoites by filtration was very low, and centrifugation was signi ficantly better than filtration in recovery of Naegleria trophozoites (22% +/- 5% versus 5% +/- 5%; P < 0.001), For cysts, however, filtrati on appeared as efficient as centrifugation, with equivalent values for recovery (53% +/- 21% versus 57% +/- 25%; P > 0.7), Although the reco very of cysts of N. fowleri obtained by filtration (51% +/- 24%) appea red higher than that by centrifugation (36% +/- 23%), the difference w as not significant (P > 0.1), Both concentration methods have highly v ariable recovery rates, making accurate quantification of low concentr ations (< 100/liter) of N. fowleri in the environment difficult.