2 DISTINCT VARIETIES OF GIARDIA IN A MIXED INFECTION FROM A SINGLE HUMAN PATIENT

Twenty-five in vitro cultures of Giardia duodenalis derived from a Bri sbane patient were established to assess the genetic heterogeneity of a population. Each of the established lines carried a predominance of one of two distinct varieties of Giardia. The two varieties were heter ogeneous by four unambiguous criteria that were representative of the whole genome. These included restriction enzyme polymorphisms, hybridi zation with the cloned rDNA repeat and with a gene encoding a cysteine -rich surface protein, electrophoretic karyotyping and DNA fingerprint ing. Differences between parasites derived from this patient were grea ter than have been seen between all other established G. duodenalis in vitro cultures from both humans and animals. The cultures were heavil y selected such that a single Giardia line carried a predominance of o ne genotype and was not representative of the entire original populati on.