DNA base compositions and base sequence relatedness of atypical<i>Campylobacter jejuni</i>strains from clinical material

Abstract

The relationships of nitrate-negative campylobacters (NNC) resembling Campylobacter jejuni were investigated by DNA base composition estimation (Tm method) and DNA-DNA hybridization (S1 endonuclease assay). The 8 NNC strains which were from clinical material formed a homogeneous DNA group with a high level of relatedness (approx. 70%) to typical (nitrate-positive) C. jejuni, but were less similar (approx. 35%) to Campylobacter coli, and only slightly related (≥ 10%) to Campylobacter fetus, Campylobacter laridis and Campylobacter sputorum. The NNC strains showed small but consistent genome differences from typical C. jejuni. As these differences can be correlated with several bacteriological test differences, we conclude that the NNC strains constitute a distinct subspecies within C. jejuni.