We tested if some ultra-highly diluted (by a factor of 1060) homeopathic remedies could induce demonstrable enhanced resistance to the bacteria, Escherichia coli, against infectivity potentials of the host-specific DNA bacteriophage- ΦX174. Evaluation of anti-viral efficacy, if any, of certain homeopathic remedies with claimed anti-viral effect was made with the aid of the ‘bacteriophage assay system’ by ‘top layer agar plating’ method of plaque counting. The number of plaques was recorded in agar-plated petri dishes, containing different drug-treated (1% v/v; Belladonna 30C, Rhus Tox 30C, Arnica 30C, and subsequently Aconite 30C) or placebo treated (succussed 1% “alcoholic vehicle” of the drug, Alc-30C, considered placebo or +tive control) bacteria plus the untreated phage mixture. The plaques actually represented the colony of bacteria lysed (or infected) by the phage ΦX174. Conversely, we exposed ΦX174 to the homeopathic drugs and placebo before allowing them to interact with the untreated bacteria to ascertain if the drug itself had any direct effect on infective potential of the phage DNA entering into the bacterial cell. The “blinded” observers noted that each of homeopathic remedy showed significant decrease in plaque numbers in petri dishes with pre-treated (1h prior to infection) bacteria as compared to untreated and placebo-treated controls; however, only insignificant change in plaque number was noted when ΦX174 were pre-treated with the drugs. Thus, the plaque formation directly related to the constitutive expression of E gene (lysis gene) of the phage when inside E. coli, was apparently “blocked” partially by the homeopathic remedies, presumably by inactivation of the E gene by a product of the host genome known to be regulated by a cluster of genes, providing evidence for the ultra-highly diluted homeopathic remedies to have anti-viral effects and ability to modulate expression of certain relevant gene(s) even in bacteria with a simple genetic system.