Identification and characterization of Salmonella isolates by automated ribotyping

Abstract

A study was conducted with the RiboPrinter, an automated ribotyping system, to evaluate its ability to identify and characterize isolates of Salmonella from broiler operations. Isolates of Salmonella obtained from a local broiler company were serotyped by a reference laboratory and ribotyped using the RiboPrinter. The RiboPrinter generated ribotype patterns by probing EcoRI digests of Salmonella DNA with an E. coli DNA probe to the ribosomal RNA operon. The RiboPrinter identified isolates by band matching of their ribotype patterns to ribotype patterns in its database. In addition, the RiboPrinter characterized isolates by sorting them into ribotypes on the basis of the similarity of their ribotype patterns. Of 117 isolates, the RiboPrinter identified 34 (29%) at the serotype level, 11 (9%) at the strain level, 46 (39%) at the genus level, and 26 (22%) were not identified. Thus, only 38% of the isolates were identified at or below the serotype level, indicating that the RiboPrinter was limited in its ability to identify Salmonella isolates by band matching. In contrast, the RiboPrinter was very effective at characterizing Salmonella isolates. Out of 108 isolates, the RiboPrinter detected 31 ribotypes, compared to serotyping which only detected 22 types of Salmonella. Thus, automated ribotyping was more discriminatory than serotyping. However, when results of both typing methods were combined, 40 types of Salmonella were detected, indicating that the best discrimination was obtained when automated ribotyping and serotyping were used together.