Shigella flexneri 6 biotypes: a review.

Except in gas production, S. flexneri 6 is generally similar to other S. flexneri. S. flexneri 6 contains both aerogenic and anaerogenic strains which are identical serologically. It is not surprising that S. flexneri 6 is not separable from other S. flexneri types on the basis of DNA relatedness (overall genetic makeup) (4). The Manchester biotype is seen in the United States, and is easily separable from other Enterobacteriaceae by biochemical tests. One can no longer assume à priori that any given biochemical reaction rules an organism out of Shigella. This is particularly true for the production of gas from glucose, but also applies to the fermentation of lactose and the production of H2S. Clinical laboratory personnel should be alert to these possibilities.