Combating multidrug-resistant Staphylococcus aureus isolated from camel milk with extracts of Eucalyptus globulus and Calotropis procera, and their potential role in modulation of resistance to beta-lactam drugs

This study aimed to evaluate the efficacy of Eucalyptus globulus and Calotropis procera against MDRSA and their potential role in modulating resistance to beta-lactam drugs. The study used a total of n = 263 camel milk samples as well as aqueous and ethanolic extracts of both plants from the Cholistan Desert and the Suleman Mountain Range in Pakistan. Different concentrations of the two plants (25, 12.6, 6.25, and 3.125 mg/mL), either alone or in combination with each other, were tested against MDRSA by well diffusion and broth dilution methods. Further, the efficacy of both plant extracts in combination with cefotaxime (30 μg) and ampicillin (1 μg) was also tested. The results indicate that the zone of inhibition (ZOI) of E. globulus alone and in combination with C. procera was nearly 3 times as large as that of C. procera. Ethanolic extracts of the two plants plants, alone or in combination with either of the two antibiotics, had a significantly (P <0.05) larger ZOI than their aqueous extracts did. Further, the modulation factor for the drugs in combination with ethanolic extracts of both plants exhibited strong synergy (P <0.05), and the minimum inhibitory concentration (MIC) of ethanolic extracts was also significantly lower than that of the aqueous extract of either plant (P <0.05). In conclusion, the ethanolic extracts of E. globulus and C. procera alone and in combination are effective against MDRSA and can play a role in modulating resistance to beta-lactam antibiotics.