California Department of Health Services, Viral and Rickettsial Disease Laboratory, 850 Marina Bay Parkway, Richmond, California 94804,1 Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, Ohio 43210,2 Centers for Disease Control and Prevention, Division of Parasitic Diseases, Atlanta, Georgia 303413
Received 22 November 2004/ Returned for modification 24 January 2005/ Accepted 31 March 2005
Balamuthia mandrillaris is a free-living ameba that causes granulomatous amebic encephalitis in both immunocompromised and immunocompetent individuals. Because of a lack of pathognomonic symptoms and the difficulty in recognizing amebas in biopsied tissues, most cases are not diagnosed or effectively treated, leading to a >95% mortality. We report here on five cases of balamuthiasis that were diagnosed by indirect immunofluorescence (IIF) staining of serum for anti-Balamuthia antibodies (titer
1:128) and confirmed by IIF of unstained brain tissue sections and/or detection of amebas in hematoxylin-eosin-stained slides. Additionally, we have used the PCR for the detection of mitochondrial 16S rRNA gene DNA from the ameba in clinical specimens such as brain tissue and cerebrospinal fluid (CSF) from individuals with Balamuthia encephalitis. Balamuthia DNA was successfully detected by the PCR in clinical samples from all five individuals. It was detected in brain tissue from three cases, in CSF from three cases, and in one of two samples of lung tissue from two individuals, but not in two samples of kidney tissue tested. One sample of unfixed brain tissue was culture positive for Balamuthia. In order to test the sensitivity of the PCR for detection of Balamuthia DNA, CSF specimens from two individuals negative for amebic infection were spiked with Balamuthia amebas. We found that it was possible to detect Balamuthia DNA in the PCR mixtures containing mitochondrial DNA from 1 to as little as 0.2 ameba per reaction mixture. A single Balamuthia ameba contains multiple mitochondrial targets; thus, 0.2 ameba represents multiple targets for amplification and is not equivalent to 0.2 of an ameba as a target.
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