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AGGLUTINATION TEST FOR THE INVESTIGATION OF THE GENUS NAEGLERIA

Summary Using a formalinized suspension of a human pathogen (N. fowleri), an antiserum has been produced which agglutinated four pathogenic strains to a titre of 1 : 256. Seven wild isolates (N. gruberi) were agglutinated to a titre of only 1 : 16, suggesting the presence of a common group antigen. Cross‐agglutinating antibody has been removed by absorption with a suspension of a wild isolate, leaving a serum which continued to agglutinate pathogenic strains without significant loss of titre. Out of seventy‐one cultures of Naegleria species isolated from the environment and maintained in serial subculture over a twelvemonth period, nineteen gave a positive reaction with the antiserum. One sero‐positive strain recovered from tap‐water in the house of a recent case of primary amoebic meningoencephalitis, produced fatal infection in mice following intranasal inoculation. It is suggested that N. fowleri, like N. gruberi, may be free‐living in fresh water; but that it causes human disease only when environmental conditions allow it to increase in numbers and susceptible individuals are suitably exposed to it.