Relationship between multiple drug-resistance & enterotoxin production by Shigella species.

Culture filtrates prepared with strains of Shigella dysenteriae 1 and those of Sh. flexneri and Sh. sonnei, collected from different geographical locations in India caused accumulation of fluid in rabbit gut loops, indicating their capability to produce Shiga and Shiga-like toxins respectively. Sh. boydii strains were noted for the first time to produce Shiga-like toxins. The failure of production of fluid accumulation in rabbit gut by Shigella strains that lacked the R-markers of the antibiotics tested and the gradual enhancement in the secretory response by strains containing R-markers in the increasing order indicate a possible correlation between acquisition of higher number of R-markers and enterotoxic activity. The non-transferable and non-curable nature of most of the drug resistance markers, coupled with the failure of the two transconjugants to elicit a secretory response and the capacity of the single cured variant to retain this property suggest the involvement of certain chromosomal locii in mediating drug resistance and enterotoxicity in Shigella.