Care must be taken when identifying biochemical isolates of Shigella because of serological cross reactions with which organism?

The identification of biochemical isolates of Shigella can be complicated due to serological cross-reactions with E. coli. Shigella is closely related to certain strains of E. coli, especially the pathotypes that are part of the Enterobacteriaceae family. This close relationship can lead to similarities in the biochemical and serological properties of the two genera, making it challenging to distinguish between them based solely on these tests.

For instance, both Shigella and certain E. coli strains may ferment glucose but not lactose, which can lead to misidentification if serological testing is not performed or is misinterpreted. It's also important to note that some E. coli strains possess pathogenic characteristics that may resemble those of Shigella, further complicating identification. Thus, care must be taken to ensure accurate identification, as treating a patient for the wrong infection could lead to inappropriate management of their illness.