Synergistic potential between camphene, myrcene, and ceftazidime against medically important bacteria

Bacterial multidrug resistance represents a major global public health challenge, highlighting the need for alternative or complementary therapeutic strategies. This study evaluated the antibacterial effects of myrcene (MYR), camphene (CAM), their combination, and their association with ceftazidime (CAZ).

Antibacterial activity was assessed using the broth microdilution method to determine the minimum inhibitory concentrations (MICs) against 14 strains. The individual and combined effects of MYR and CAM were evaluated, followed by the release of cytoplasmic material absorbing at 260 nm, checkerboard assay, and in vitro hemolysis assay.

MYR inhibited the growth of Pseudomonas aeruginosa and Acinetobacter baumannii by more than 50%, while CAM showed inhibitory activity against Staphylococcus aureus. The combined use of MYR and CAM enhanced antibacterial effects, with increases ranging from 1.8% to 44.2% and 2.0% to 39.8% compared to their individual activities, respectively. Terpenes combined with CAZ lowered MIC in six strains, notably reducing A. baumannii resistance by eightfold. Cytoplasmic release indicated membrane involvement, and terpenes showed no hemolytic activity.

The results indicate that terpenes, particularly in combination with CAZ, may enhance antibacterial activity against specific resistant strains, suggesting a promising adjunctive therapeutic strategy.