The electrophoretic polymorphism of
esterases was compared with that of other
enzymes in Escherichia coli populations by investigating
allozyme distribution of four
esterases (A, B, C and I) within both the subspecific groups I, II and III and the new groups A, B1, B2, C, D and E, which have been distinguished by electrophoretic analysis of 11 and 35
enzymes respectively in the 72 reference strains of the ECOR collection. Electrophoretic distribution of
esterases was distinct for each of the three subspecific groups as indicated by distributions of
allozymes and electrophoretic types (distinctive combination of
allozyme for the four
esterases).
Esterase polymorphisms of the three subspecific groups appeared to have similar features to those of three previously studied natural populations of strains obtained from human and animal gastro-intestinal tracts and extra-intestinal
infections in humans. Multiple correspondence analyses using data obtained from the four
esterases and the 11 other
enzymes also distinguished the groups A, B1, B2, C, D and E. All strains of group B2 showed the B2 electrophoretic pattern of
esterase B, which appeared to be a marker of a distinct cluster of strains frequently implicated in extra-intestinal
infections.