Final answer:
Bacteria gain resistance through mutations that affect antibiotic function or bacterial vulnerability, leading to resistant 'super bugs' such as MRSA. As these resistant bacteria become prevalent, it's imperative to develop novel medicines to maintain the effectiveness of treatments.
Step-by-step explanation:
Bacteria become resistant to medicines through mutations and other mechanisms. These mutations can alter the target site of the antibiotic, produce enzymes that degrade the medicine, prevent the antibiotic from entering the bacterial cell, or pump the drug out of the cell via efflux pumps.
This phenomenon is a direct consequence of the overuse and misuse of antibiotics, leading to 'super bugs' such as MRSA (methicillin-resistant Staphylococcus aureus), which are difficult to treat due to their resistance to multiple antibiotics. Mutations increase a bacterium's chances for survival by conferring an advantage in the presence of antibiotics. Only those bacteria with resistance traits will survive and reproduce, leading to a higher frequency of resistant bacteria in the population.