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Differentiation of Catalase-Positive Campylobacters With Special Reference to Morphology

Department of Bacteriology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada

ABSTRACT

Examination of three groups of catalase-positive campylobacters by phase-contrast microscopy showed significant differences in cell size between the groups. These differences were most striking when the spiral forms of the organisms were observed. Campylobacter jejuni consistently produced small, tightly coiled spirals with a mean wavelength and amplitude of 1.12 and 0.48 µm, respectively. Campylobacter fetus subsp. fetus produced intermediate-sized spirals (mean wavelength and amplitude of 1.80 and 0.55 µn, respectively); C. fetus subsp. venerealis produced the largest spirals (mean wavelength and amplitude of 2.43 and 0.73 µm, respectively). Organisms belonging to the different groups could be distinguished by a trained observer on the basis of size alone, without actual measurement. Two additional features which distinguish C. jejuni from C. fetus subsp. fetus and C. fetus subsp. venerealis are the tendencies of C. jejuni to swarm on moist agar plates and to undergo rapid coccal transformation in normal atmospheric air. These findings should help in clarifying the subdivision of catalase-positive campylobacters and in making a rapid presumptive species or subspecies identification.