Antibiotic resistant bacteria emerge from improper and over usage of antibiotics. However, antibiotic resistant bacteria have some disadvantages of their own.  When not exposed to antibiotics, non-resistant bacteria are often selected for due to the fact that there is an energetic cost associated with being immune to antibiotics. Because of this, it is now desired to reduce antibiotic use in proper situations with the hope of decreasing resistance among bacteria. This is often successful. However, due to the vast complexity of these studies, the results are not easily interpreted. Patients are often taking a cocktail of antibiotics to fight disease and it is possible for there to be contact between hospitals and the community, resulting in the exchange of resistant bacteria. This makes the process increasingly difficult. Additionally, depending on which antibiotics are reduced in usage, the results can vary. For instance, in the case of Staphylococcus aureus, otherwise known as MRSA, a reduction in the use of penicillins does not result in decreased resistance because many strains of S. aureus are already resistant to penicillin.  On the other hand, a reduction in the use of clindamycin and methicillin lead to lessened antibiotic resistance.

Using mathematical models of MRSA circulation, the impact of an overall antibiotic use reduction was observed in both hospital and community environments. The researchers then created a number of simulations of reductions in antibiotic use to further understand the level of antibiotic resistance. The results showed that there is much room for improvement in our previous attempts to decrease resistance. Referring to a hospital only, antibiotic reduction campaign in France in 2002, it was shown that the reduction in resistance was cut short by antibiotic use outside of the hospital. These results highlight that simply reducing overall antibiotic use is not the best method of reducing resistance. Instead, this study has helped us further understand that highly systematic, class-specific designed campaigns are preferential and should be employed in the future.