Final answer:
Non-resistant bacterial cells die after mupirocin exposure as it inhibits a key enzyme for protein synthesis, leading to cell death. Resistant strains such as MRSA have mechanisms to evade the effects of antibiotics, making treatment difficult.
Step-by-step explanation:
Bacterial cells that are not resistant to mupirocin die after exposure because mupirocin specifically inhibits the enzyme isoleucyl-tRNA synthetase in bacteria, an essential enzyme for the synthesis of isoleucine-containing proteins. Without the ability to synthesize proteins properly, the non-resistant bacterial cells cannot sustain necessary life processes, leading to their death. Resistant bacteria, however, have developed mechanisms such as the modification of the target enzyme, preventing the antibiotic from entering the cell, or actively pumping the antibiotic out of the cell through efflux pumps. Such resistance mechanisms can be spread between bacteria via horizontal gene transfer, complicating the treatment of infections. Moreover, indiscriminate use of antibiotics and the lack of new antibiotic development have contributed to the rise in antibiotic-resistant bacterial strains like MRSA (methicillin-resistant Staphylococcus aureus), posing significant challenges in healthcare.