IN-VITRO GENOTYPIC VARIATION OF CAMPYLOBACTER-COLI DOCUMENTED BY PULSED-FIELD GEL-ELECTROPHORETIC DNA PROFILING, IMPLICATIONS FOR EPIDEMIOLOGIC STUDIES

Six isolates of Campylobacter coli from different pig herds were subcu ltured up to 50 times over a 6-month period and DNA samples suitable f or pulsed-field gel electrophoretic (PFGE) profiling prepared at regul ar (1, 20, 40 and 50 passages) intervals. In 5/6 strains, changes in t he banding patterns of Sma1, Sal1 and/or BamH1 digests were observed. In one such strain the differences were considered artifactual. Howeve r, significant alterations in PFGE profiles between subcultures of fou r strains were seen, irrespective of the restriction enzyme used. Spon taneous intramolecular genomic rearrangements were considered the most likely mechanism for the changes observed. A numerical analysis based upon the combined distribution of Sma1- and Sal1-derived fragments cl ustered most strain subcultures together, with the exception of those from one isolate which were divided into two clusters. The effect of s pontaneous genetic change on PFGE profiles must be considered when eva luating strain relationships. Numerical techniques may aid data interp retation but results must be evaluated cautiously. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.