ELISA for virulence marker antigen (VMA) is done to detect virulence in -

EIEC :clinically EIEC resembles shigellosis ranging from mild diarrhoea to frank dysentry and occur in childrenas well as in adults. For lab diagnosis of EIEC ,the Sereny test used to be employed. Mice may be used instead of guinea pig. Cell penetration of HeLa or HEP-2 cells in culture is a more human diagnostic test. This ability to penetrate cells is determined by large plasmid, detection of which can also be a diagnostic test. The plasmid code for outer membrane antigens called the virulence marker antigen (VMA) which can be detected by ELISA (VMA ELISA) test REF:Ananthanarayan & Panicker's Textbook of Microbiology 8th Edition pg no : 277