Individuals colonized with or exposed to certain bacteria may develop antimicrobial resistance. This will  require a change in therapy so that the particular bacteria is eradicated. Where eradication is not possible, there may still be better suppression with an alternative agent and the resistant strain may die out allowing the original agent to be effective again. Antibiotic prophylaxis is only advocated when all the benefits outweigh all the risks and resistance is one of those.