Strains displayed a unique genotype, only F13 and F14 are closely related. The ganglioside epitopes in the LOS and the anti-ganglioside responses in the GBS/MFS patients were determined using monoclonal antibodies and defined serum samples5–8. DNA was isolated using the Wizard Genomic kit (Promega, Madison, Wisconsin). PCR for the cstII gene used a primer set based on the cstII DNA sequence of C. jejuni OH4384 (ref. 11)(5′-ATGAAAAAAGTTATTATTGCTGGAAATG-3′ and 5′-TTATTTTCCTTTGAAATAAT-GCTTTATTC-3′). Variability in cstII was assessed with AluI and DraI RFLP analysis. Associations were verified with Instat (Graphpad Software, San Diego, California) using 2× 2 contingency tables. Fisher’s exact tests determined two sided P-values (P< 0.05 considered significant). GB: Guillain–Barré associated isolate; MF: Miller Fisher associated isolate, F: isolate from GB family member. The collection of control strains consists of Penner type strains and isolates from enteritis patients from the same geographical locale and isolation period as the GBS and MFS strains. Note that all MFS-derived strains are GQ1b-positive.