SPECIFICITY AND SENSITIVITY OF A MICROCOLONY TECHNIQUE FOR FLUORESCENT ANTIBODY IDENTIFICATION OF PATHOGENIC ESCHERICHIA COLI SEROTYPES

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Abstract
The specificity and sensitivity of a fluorescent antibody technique applied to growing microcolonies has been investigated using serotypes of Escherichia coli responsible for infective enteritis as a model. Microcolonies of 10 E. coli serotypes showed bright fluorescence when treated with homologous conjugated antiserum but no fluorescence when treated with heterologous conjugated antisera. Microcolonies of Enterobacteriaceae strains of other genera or of E. coli strains not associated with infective enteritis showed no fluorescence when treated with conjugated antisera prepared against the enteritis serotypes.Experiments with artificially infected faecal suspensions showed that the sensitivity of the microcolony technique was approximately one hundred times greater than that of the direct smear method. A number of other advantages and possible disadvantages of the microcolony technique are discussed and its usefulness in epidemiological work is suggested.