Electrophoretic protein typing of Campylobacter jejuni subspecies "doylei" (nitrate-negative campylobacter-like organisms) from human faeces and gastric mucosa.

Twenty-seven strains comprising 23 clinical isolates of nitrate negative campylobacters (NNC) from Australia, South Africa, the United Kingdom and the Federal Republic of Germany, a representative of the CNW (catalase negative/weak) group and reference strains of three other Campylobacter species, were characterized by one-dimensional SDS-polyacrylamide gel electrophoresis of cellular proteins. The protein patterns were highly reproducible, and were used as the basis for a numerical analysis which showed that the reference strain (NCTC 11951) of Campylobacter jejuni subspecies "doylei", and 20 NNC isolates formed a distinct group at the 74% similarity level. The protein patterns showed unexpectedly low similarity between subspecies "doylei" and the type strain of Campylobacter jejuni and revealed that some NNC strains were quite distinct from subspecies "doylei". Four electrophoretic (EP) types (I-IV) were identified from phenons formed at the 81% similarity level. Three of these (I, III, IV) corresponded to geographical location of strain isolation but the type II strains were from diverse locations. The correlation observed between EP-type, catalase production and sensitivity to 2, 3, 5, triphenyltetrazolium chloride indicated these latter two tests might be useful for biotyping within the subspecies.