Clinical Microbiology and Antimicrobial Chemotherapy. 2025; 27(2):258-264
To compare antibacterial activity of macrocidins A and Z against staphylococci and their effect on staphylococcal biofilms.
The antibacterial activity of macrocidins A and Z produced by Didymella baileyae VIZR 1.53 was studied by serial dilution method against 120 staphylococcal cultures isolated from orthopedic patients. The effect of macrocidins on biofilm formation of 60 S. aureus clinical cultures was assessed by O’Toole method by co-incubation of active substances with bacteria and subsequent MBIC50/90. The impact on the formed biofilms was assessed after treating the formed staphylococcal biofilms with different concentrations of macrocidins using MBEC50/90 calculation. Statistical analysis was performed in GraphPad Prism 9.0.
The MIC50/90 macrocidin A against S. aureus – 256 mg/L, MIC50/90 of macrocidin Z – 256⁄256 mg/L. Macrocidin Z was found to be more active against S. epidermidis than against S. aureus (MIC50/90 128⁄128 mg/L). Comparison of the susceptibility of methicillin-sensitive and methicillin-resistant S. aureus and S. epidermidis did not reveal any differences in the MIC50/90 of macrocidins, indicating sensitivity to the compounds regardless of their antibiotic susceptibility. A pronounced inhibitory effect of macrocidins on biofilm formation by S. aureus was established, more pronounced for macrocidin Z, as well as differences in the effect of macrocidins on biofilms depending on the antibiotic susceptibility of the strains. It was shown that macrocidins in the tested concentrations (8–256 mg/l) did not have a destructive effect, regardless of their antibiotic sensitivity profile.
Macrocidins A and Z significantly inhibited the growth of S. aureus and S. epidermidis. The ability to suppress biofilm formation at low concentrations is also of interest, especially for the possible use of macrocidins as antibacterial and antiadhesive compounds.