Abstract: A method for treating bacterial infections in a patient is provided. The method includes the step of administering a therapeutically effective amount of a single naturally-occurring or engineered bacteriocin, or combinations thereof, designed to have high specific activity against the bacterial infection to the patient so that a rate of resistance to the bacteriocin in the patient is decreased. The colicins and other bacteriocins or combinations of colicins and other bacteriocins target and kill specific bacterial pathogens in a manner that results in a high specific killing activity and decreased incidence of pathogen resistance. To this end, the characteristics of existing colicins and other bacteriocins are modified in order to enhance and amplify their therapeutic value.