Cross-resistance is the tolerance to a usually toxic substance as a result of exposure to a similarly acting substance. It is a phenomenon affecting e.g. pesticide

Pesticide

Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s and antibiotic

Antibiotic

An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s. As an example rifabutin

Rifabutin

Rifabutin is a bactericidal antibiotic drug primarily used in the treatment of tuberculosis. The drug is a semi-synthetic derivative of rifamycin S. Its effect is based on blocking the DNA-dependent RNA-polymerase of the bacteria. It is effective against Gram-positive and some Gram-negative...

 and rifampin cross react in the treatment of tuberculosis. This sort of resistance is also see against drugs involved with the treatment of HIV. Drugs ending with "- ine" and "-inavir" are the most common.