Resistotyping of campylobacters: fulfilling a need

A 9-month trial of a simple typing scheme for ¿thermophilic' enteric campylobacter isolates at a large Public Health Laboratory is described. Resistotyping was performed with six agents in a method modified by Bolton and colleagues from an earlier scheme, and biotyping was performed by a modified Lior scheme involving three tests. Reproducibility was excellent in both schemes, with test variation < 2%. Five household clusters and one larger presumptive milk-borne outbreak were identified in this scheme, and confirmed in pyrolysis mass spectrometry. The 328 isolates from new patients, excluding duplication from these clusters, were divided into 35 resistotypes with the largest group comprising 22% of isolates. In combined bio- and resistotyping, 86 types were found, with the largest group comprising 9.5% of isolates. The results are contrasted with salmonella sero- and phage-typing, where, on the same basis, the 176 isolates in the same period were divided into 40 groups, with the largest comprising 45% of isolates. Resistotyping, with or without additional biotyping, proved to be a convenient, simple, rapid, highly discriminatory, reproducible and inexpensive method well suited to use in local laboratories. It is a strong candidate for first-line national and local surveillance of campylobacter infections, fulfilling a need for monitoring of this important cause of enteric disease.