Plasmids and serogroups in Campylobacter jejuni

For epidemiological purposes identification of Campylobacter strains is usually based on surface antigen characteristics. Two different systems, one for heat-stable (HS) and one for heat-labile (HL) antigen have dominated. In earlier studies we found a great variability in the two antigen systems. The aim of the present investigation was to analyse the frequency of plasmids in Campylobacter strains in the light of their possible use as an epidemiological tool as well as the relation between the presence of plasmids and surface antigens (HS and HL). Two hundred and forty-two strains from the same number of patients with diarrhea were analysed. In 70 (28.9%) plasmid(s) were found, in general one or two. Most of the plasmids were found in the molecular weight interval between 21-40 Md. There was no relation between the presence or size of plasmids and serogroup. We conclude that plasmid determination can be used as a complement to serotyping in epidemiological studies.