Reducing tetracycline resistance in living cells

A pharmaceutical composition for converting tetracycline resistant bacteria into tetracycline sensitive bacteria comprising a 13,5 derivative of tetracycline and a tetracycline-type antibiotic which is not a 13,5 derivative of tetracycline, and a pharmaceutically acceptable carrier.

C5 esters having the formula ##STR22## wherein R.sub.1 and R.sub.2 are selected from the group consisting of a methylene group, hydroxyl, hydrogen or a group consisting of organic entities comprising from 1-12 carbon atoms, with or without other heteroatoms including sulfur, oxygen, halogen, nitrogen, and the like, and takes form as linear, branched, or cyclic alkyl, aryl, or alkylaryl structures;

• and A is selected from the group consisting of a methylene groups, and any linear, branched, or ling structure comprising from 1-6 carbon atoms and optionally including heteroatoms of oxygen and nitrogen.

A compound of the following formula ##STR23## where R is an organic entity comprising 1-12 carbon atoms and optionally including one or more heteroatoms or halogen atoms;

• R.sup.1 is an organic entity comprising 1-12 carbon atoms and optionally including one or more heteroatoms or halogen atoms;
• and A is a hydrogen atom, a methylene group and any linear, branched or ring structure comprising from 1-6 carbon atoms and optionally including one or more heteroatoms.

A method for converting tetracycline resistant bacteria into tetracycline sensitive bacteria, comprising contacting the resistant bacteria with a predetermined quantity of at least a first composition selected from C5 esters of tetracycline or a 13,5 derivative of tetracycline, and concomitantly administering to the cell a predetermined quantity of at least a second composition selected from a tetracycline, a tetracycline analogue or a tetracycline derivative which is not a C5 ester of tetracycline nor a 13,5 derivative of tetracycline.