An Unusual Strain of Escherichia coli in Septicæmia as an example of the Transformative Effect of Symbiosis

Abstract

A 54-YEAR-OLD male patient was admitted to hospital with signs of septicæmia and obstructive jaundice after having suffered from gall-bladder troubles for the past five years. By blood culture in brain-heart infusion broth a rich growth of a highly polymorphous Gram-negative organism was obtained (Fig. 1, top) which gave the typical biochemical reactions of an Escherichia coli and a positive hæmagglutination test. The macroscopic appearance of the colonies also did not differ from a slightly mucoid E. coli culture. No dwarf colonies were found. The polymorphism (filaments with broad swellings, globular and club-shaped forms) was most marked on a culture 24–48 hr. old on 5 per cent rabbit blood agar. After three days the majority of the filaments had broken up into chains of rods and the bizarre forms had disappeared. This aberrant morphology persisted for ten months if the strain was subcultured only on blood agar. After this time it grew in more or less uniform short filaments. If subcultured exclusively on plain agar, it reverted after five months to the typical size and shape of E. coli. No morphological change could now be brought about by transferring it from plain to blood agar.