Background: The emergence of antibiotic resistance, particularly resistance to methicillin in Staphylococcus aureus has made the treatment process more difficult. Therefore, producing of an effective vaccine seems to be necessary to prevent infections with methicillin-resistant Staphylococcus aureus (MRSA). In this study, a mixture of naloxone and alum has been used to improve the efficacy of a vaccine against MRSA.

Materials and Methods: MRSA 834 strain was grown on TSB medium and the grown cells were harvested and killed by sonication and were used as a vaccine model. Balb/c mice were divided into six groups and the vaccines were either injected alone, with naloxone, alum, or a mixture of naloxone - alum and control group received naloxone and PBS buffer. Total IgG antibody level was measured by ELISA method and finally, the challenge test of this bacterium was performed and the mice were examined regarding the degree of bacteria growth in their kidneys.

Results: The serum level of Total IgG antibody in the mixture of naloxone – alum with MRSA group was shown to be significantly increased (p<0.05). Furthermore, the lowest bacterial load was observed in this group.

Conclusion: It seems that a mixture of naloxone and alum as an adjuvant with the killed methicillin-resistant Staphylococcus aureus enhances the humoral immunity leading to a high level of protection against MRSA infections. Therefore, this seems to be a good option for improving the performance of this vaccine.