The parasitic protozoan Entamoeba histolytica infests the host (typically human) through ingestion of contaminated food or water. Its two life stages include the trophozoite and pre-cystic minuta forms. Active infection occurs only via the trophozoite stage. This stage is marked by repeated binary fission in the wall of the host's intestine.
Which of the following describes the only action that would be ineffective against the trophozoite stage?