Influence of plasmids on bacterial susceptibility to the bactericidal activity of sera. I. Characteristic of R plasmids of enteropathogenic strains of Escherichia coli isolated from clinical cases.

The 47 enteropathogenic Escherichia coli strains isolated from the cases of infant diarrhoea were characterized from the point of view of antigenic structures and drug resistance. Six R plasmids were obtained from these strains and were tested for protective activity of E. coli K12 W 1485 against lethal action of sera. Out of three sera tested, the investigated plasmids showed the most evident protective activity upon lethal action of neonatal serum. One of the plasmids appeared even more efficient than R100.1.