A late mannitol-fermenting strain and rapidly fermenting variant of Shigella Flexneri type Z.

Shigella organisms are divided biochemically into two main groups distinguished by their ability to ferment mannitol. Non-mannitol-fermenting strains of Sh. flexneri type 88 (biochemical type newcastle) and of Sh. flexneri type 103 (Mumford and Mohr, 1944) are, however, well recognized, and it is probable that similar variants occur among other mannitol-fermenting dysentery bacilli. The organism described in this paper is of interest not only as a late-mannitolfermenting variant of Sh. flexneri type Z, but also because the strain itself gave rise to variants which fermented mannitol within 24 hours. The strain was originally isolated by Dr. Rickards at the Royal Lancaster Infirmary from a patient with a typical bacillary exudate. Dr. Rickards found that the organism was agglutinated by Flexner Z serum, though it failed to ferment mannitol. The culture was sent to the Dysentery Reference Laboratory, where its identification was confirmed serologically as Sh. flexneri type Z.