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Bacteriocin production was tested in two sets of Escherichia coli strains: one isolated in 1978 from healthy children of rubber tree tappers and Indians in Amazonia, Brazil ( n = 35), and the second one isolated in 2004 from healthy adult volunteers in the Moravia region, Czech Republic ( n = 53). Although the occurrence of bacteriocin production was rather similar in both groups (54.3% and 43.4% respectively), the spectra of bacteriocin-encoding determinants in both groups were different. Altogether, 12 different bacteriocin-encoding determinants were found among the tested strains. The occurrence of colicin E1- and Y-genes was higher ( P = 0.02 and P = 0.009 respectively) while the occurrence of microcin V gene was lower ( P = 0.02) among Amazonian strains compared with Moravian strains. The colicin-encoding determinants of colicins Ia, M, Y and E1 were amplified from Amazonian and Moravian producer strains and sequenced, as were chromosomal 16S rRNA, gyrB and tonB genes. While sequence alignments of chromosomal loci revealed no clusters with respect to geographical origin of strains, the colicin-encoding genes were very similar among the strains of each origin but different between the two geographic groups. [ABSTRACT FROM AUTHOR]