Induced Increase in Resistance of Entamoeba histolytica to Fumagillin

Abstract

ALTHOUGH there has been much work on in vitro effects of various amœbicidal agents on Entamoeba histolytica, I have not found any published data dealing with the induced increase in resistance of this protozoan to amœbicidal agents. The antiamœbic activity of fumagillin was first studied by McCowen et al. ¹ and was confirmed by Hrenoff and Nakamura². Many workers have since studied the clinical efficacy of fumagillin in amœbiasis^3–7. The present work was undertaken to determine the activity of fumagillin against a number of newly isolated strains of E. histolytica from a variety of clinical infections. Also, an attempt was made to increase resistance of these strains to this highly active amœbacidal antibiotic. The main reason for using fumagillin in these experiments is that it is not antibacterial in activity and therefore this agent can be studied in cultures of amœbæ growing in association with a mixed bacterial flora. The associated bacteria are required because E. histolytica cannot be cultivated axenically consistently. Furthermore, use of fumagillin minimizes the indirect activity of the drug on amœbæ since the bacterial flora apparently are unaffected, and the inhibition of the amœbæ can be considered as directly due to the antibiotic.