Antibacterial and Oxacillin Resistance Reversing Effect of Harmaline in Different Strains of Staphylococcus Aureus

Background: Harmaline is a naturally occurring indole alkaloid with many medicinal effects. Its antimicrobial effect against different pathogens has been reported previously. Objective: To explore the ability of harmaline to revers oxacillin resistance in the methicillin-resistant strain of Staphylococcus aureus (MRSA). Materials and methods: Briefly, 124 isolates of MRSA were procured from different wards of the Medical Complex City, Baghdad, Iraq. The type of the bacteria and the strain had been checked using conventional methods to identify MRSA. Oxacillin resistance was checked using the conventional antibiotic sensitivity test. Moreover, the bacteriostatic and cidal effects of each harmaline and oxacillin were screened to determine their IC50 and IC90 for each effect. Eventually, the interaction between the two drugs for the bactericidal effect was screened using the well-known isobologram technique. Results: The results showed that harmaline got a mild to moderate bactericidal effect against MRSA and produced a moderate synergistic effect when both drugs were combined at a ratio of 3:7 and 5:5 (harmaline/oxacillin). Besides, an additive effect or mild synergy was noticed in the other combinations. Conclusion: Overall, harmaline can be suggested as a chemo-sensitizer or a pharmacophore to develop better synergistic drugs for oxacillin against MRSA but further safety and pharmacokinetic studies are indicated to optimize this effect.