Resistogram Typing—A New Epidemiological Tool: Application To Escherichia Coli

Many chemical compounds exert selective toxicity within a species of microorganism. This fact can be used to define a profile of a strain based on its resistance to selected compounds: the profile of the strain is referred to as its “resistogram”. The compounds are so chosen that the organisms do not meet them under natural circumstances. Therefore, unlike the antibiotics, the compounds do not lend selective advantage to resistant elements within the population and for epidemiological purposes the resistogram type would be expected to remain stable.

The potential value of the new approach is illustrated by its application to the species Escherichia coli. A simple and rapid method of resistogram typing based on eight substances was evolved. This was applied to the study of 50 strains from urinary infections. In these strains somatic serotype and source were known, giving an indication of the extent of their diversity. Good agreement was found between serotyping and resistogram typing. In a few instances different strains fell into a single resistogram type, but in other cases strains of the same serotype from different patients could be distinguished by means of the resistogram.