Figure 2: Y. enterocolitica biotypes. Y. enterocolitica biotypes are classified into three distinct group: a historically defined nonpathogenic group (biogroup 1A); a weakly pathogenic group that are unable to kill mice (biogroups 2 to 5); a highly pathogenic, mouse-lethal group (biogroup 1B). Biotype 1A strains are clustered into two clonal groups (A and B) when typed by repetitive extragenic palindrome (REP)—and enterobacterial repetitive intergenic consensus (ERIC)—PCR ngerprinting [11], and two groups when typed by fluorescent amplified fragment length polymorphism (FAFLP) [12].