COMPARISON OF GENETIC GROUPS DETERMINED BY MOLECULAR AND IMMUNOLOGICAL ANALYSES OF GIARDIA ISOLATED FROM ANIMALS AND HUMANS IN SWITZERLAND AND AUSTRALIA

Nine axenic isolates of Giardia originating from four different host s pecies in Switzerland were subjected to genetic analysis using the pol ymerase chain reaction (PCR) to amplify segments of,genes encoding dif ferent trophozoite variant surface proteins (VSPs). Three genotypes we re identified on the basis of product yield, size, and restriction-fra gment-length polymorphisms (RFLPs). Five G. duodenalis isolates (O1, B 1, B2, B3-1 A1 and C1 - from a sheep, three calves and a dog, respecti vely) were classified as belonging to genetic group I of Andrews et al . (1989). DNA amplified from the VSP genes tsp11, tsa417 and vsp1267 o f these isolates was indistinguishable in size and restriction charact eristics from that amplified from group-I Giardia isolated from humans in Australia. One human-derived Swiss isolate (H2-17A1), typed as bel onging to genetic group II, yielded a vsp1267-specific PCR product tha t was indistinguishable by size or restriction sites from the equivale nt 1.6-kb product amplified from human-derived Australian group-II org anisms. This isolate also yielded 1.8-kb tsp11 and 0.52-kb tsa417/tsp1 1-like PCR products possessing RFLPs typical of group-II organisms. Th ree isolates (O2-4A1, O3 and H3-15K2 - originating from two sheep and a human, respectively) represent a novel genotype that is closely rela ted to genetic groups I and II. These three isolates exhibited identic al RFLPs in their tsp11 PCR products and failed to yield a vsp1267 PCR product, An antiserum specific for the 90-kDa VSP of the sheep-derive d clone O2-4A1 reacted strongly by immunofluorescence and on Western b lots with surface proteins from the O2, O3 and H3 isolates only - cons istent with the genetic classification determined above. The data prov ide no evidence for the occurrence of host-specific genotypes.