Quinine sulfate inhibits invasion of Salmonella typhimurium and Shigella flexneri:

Background: The incidence of typhoid fever and shigellosis parallels that of malaria, so many individuals who are on antimalarial drugs can be found in areas where these diseases are widespread. We investigated the effect of quinine sulfate on the growth and invasion of Salmonella typhimurium and Shigella flexneri M90T to determine whether people on antimalarials can have secondary gain from some protection against typhoid fever and shigellosis. Methods: The effect of 50 and 100 µM quinine sulfate on the invasive ability of Salmonella typhimurium and Shigella flexneri M90T into human colon adenocarcinoma-2 (Caco-2) cells was studied during the infection period. The invasive efficiency was expressed as the number of viable internalized bacteria by counting the colonyforming units. Results. The invasive ability of Salmonella typhimurium and Shigella flexneri M90T was significantly inhibited by 50 and 100 µM quinine sulfate in a dose-dependent manner (for Salmonella typhimurium) when the drug was added to Caco-2 cell monolayers during the infection period. Conclusions: Since so many people who are on antimalarial drugs visit and inhabit areas that are endemic to typhoid fever and Shigella infection, a study on the influence of these drugs on the disease is long overdue. Our data indicate that quinine sulfate interferes with the invasion and internalization of Salmonella typhimurium and Shigella flexneri M90T into host cells. Further studies on additional strains/serotypes with other newer antimalarials at various concentrations are needed to verify this effect of quinine sulfate and to draw conclusions on its significance in vivo.