Confirmation of human Campylobacter concisus isolates misidentified as Campylobacter mucosalis and suggestions for improved differentiation between the two species.

A strain from human diarrhea originally identified as Campylobacter mucosalis (NCTC 12408) was examined by using 64 phenotypic characters. The similarity of this strain to 297 isolates of Campylobacter, Helicobacter, Arcobacter, and related taxa was then determined with a computer-supported data analysis program, MVSP. NCTC 12408 showed closest similarity to 20 type, reference, and field isolates of Campylobacter concisus. These strains were clearly separated from those of C. mucosalis in the numerical analysis of phenotypic tests; a table was constructed from the data used to aid in differentiating these two species in the clinical laboratory. The identity of NCTC 12408 was confirmed as C. concisus by visual comparison of its sodium dodecyl sulfate-polyacrylamide gel whole-cell protein electrophoregram with those of type strains of C. concisus and C. mucosalis. These data suggest that genuine human infection with C. mucosalis has not yet been reported.