4.4.3. Evaluation of the Effects of the Tested Compounds on the Antibiotic Susceptibility Profile

Standardized microbial suspensions of *E. faecium* E5 and *S. aureus* ATCC 6538 were put in contact with subinhibitory concentrations (0.25 mg/mL) of tested compounds **5** and **6** prepared in broth. After incubation at 37 ◦C for 24 h, the bacterial cultures were used to evaluate their antibiotic susceptibility profile. The disk diffusion method was performed to assess the susceptibility to the following antibiotics: ampicillin, linezolid, penicillin, vancomycin for Gram-positive *E. faecium* E5 strain and azithromycin, cefoxitin, clindamycin, linezolid, penicillin, rifampicin, trimethoprim-sulfamethoxazole, and vancomycin (bioMérieux, Paris, France) for Gram-positive *S. aureus* ATCC 6538 strain. The reading of the results was performed following the Clinical and Laboratory Standards Institute (CLSI, Berwyn, PA, USA) guidelines.
