Genetic diversity in the microsporidian Encephalitozoon hellem demonstrated by pulsed-field gel electrophoresis

Encephalitozoon hellem is a microsporidian species responsible for opportun istic infections in AIDS patients. Use of a novel chitinase-based method al lowed unsheared chromosomal DNA to be recovered from eleven E. hellem isola tes derived from three geographic regions. All isolates: were typed by 18S rDNA sequencing, which showed that they belonged to internal transcribed sp acer type I. After ethidium bromide staining, pulsed-field get electrophore sis (PFGE) analysis discriminated two new karyotypes comprising 7 and 8 chr omosomal bands respectively, ranging in size from 205- to 272-kb pairs. Gen omic size was estimated to be 2.39 Mb. Our data indicate PFGE is useful for typing E. hellem and confirms genetic diversity among E. hellem genotypes.