Types of Dysentery Bacilli isolated at No. 3 Australian General Hospital, Cairo, March—August, 1916, with Observations on the Variability of the Mannite Fermenting Group

Abstract

1. Of 123 dysentery bacilli isolated, forty-seven were B. dysenteriae Shiga, seventy-six were mannite fermenters.2. The biochemical activities of forty-nine strains of the latter were investigated immediately after isolation and again six months later. They showed variability as regards the fermentation of maltose, saccharose, dextrin, raffinose, arabinose, isodulcite, sorbite and glycerin and in the formation of indol. The same strain varied at different times, some gaining, others losing one or other of the above properties.Similar observations by other observers and the authors are discussed and the conclusion is arrived at that the separation of the mannite fermenting dysentery bacilli into groups on the ground of their action upon the above carbohydrates is unsound and that the only carbo-hydrates of service for their identification are glucose, mannite, lactose and dulcite.3. An experiment conducted during two and a half months upon a particular strain of dysentery bacillus shows that the fermentation of saccharose was in this strain a “recessive character” and only maintained by artificial selection.4. One-sixth of the mannite fermenting dysentery organisms isolated were not agglutinated by a univalent Y (rabbit's) serum at the time of isolation but half of these acquired this property by cultivation. Others were well agglutinated by the patient's serum. An experiment is described in which agglutinability to Y serum was lost under prolonged cultivation on saccharose peptone media. In this experiment successive cultures were made every few days and the material for subcultivation was taken from daughter colonies (buds), which arose in the saccharose plates. Agglutinability was rapidly regained by propagation in broth. From the author's experience and from a survey of the literature, the conclusion is arrived at that no one univalent serum will agglutinate all dysentery bacilli of the mannite fermenting type and that a bacillus with the morphological, cultural, and biochemical characters of dysentery bacilli of this type is not discredited as an etiological factor because it is not agglutinated by any particular univalent serum.In conclusion we express our indebtedness to Miss Rhodes of the Lister Institute for retesting many of the cultures in London, in January, 1917, and convey to her our grateful appreciation of her kindness in so doing.