Colicine typing of Escherichia coli in pigs.

Abstract

Summary The effect of cultural conditions on the size of the zone of inhibition surrounding growth of colicine-producing organisms was examined. The size of the zone was not altered by the addition of 5 per cent. bovine blood to tryptic soy agar, but was slightly increased by raising the temperature of incubation from 37° to 40°C and substantially increased by extending incubation of producer organisms from 24 to 48 hr. A colicine typing system based on colicine production by field strains of E. coli was evolved and compared with serological typing in epidemiological investigations of E. coli on pigs. Colicine-producing isolates belonging to particular serological types generally belonged to the same colicine type. However, isolates belonging to a number of serological types frequently belonged to the same colicine type. A colicine typing system based on the sensitivity of field strains of E. coli to nine standard colicinogenic strains was too unreliable to serve as the basis for a colicine typing system.