Biofilm formation and eradication of Staphylococcus aureus: a study of culture conditions and endolysin ZAM-CS effect

Staphylococcus aureus significantly contributes to healthcare-associated infections, with biofilm formation causing chronic, antibiotic-resistant cases. Because biofilms show high resistance to conventional antibiotics, endolysins have emerged as a promising alternative for treating antibiotic-resistant, biofilm-associated infections. This study evaluated the effects of four culture media and different incubation times on biofilm formation in methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) S. aureus strains and assessed the anti-biofilm efficacy of a novel chimeric endolysin called ZAM-CS (catalytic domain of SAL-1 endolysin and binding domain of lysostaphin). Biofilms were grown for 24, 48, and 72 hours in Mueller-Hinton broth (MHB), Luria broth (LB), terrific broth (TB), and tryptic soy broth (TSB). The crystal violet assay was used to assess the biomass of the biofilm. The optimal biofilm conditions were then used to test ZAM-CS's activity at different concentrations. MSSA formed the strongest biofilms in TB. MRSA formed stable, high-biomass biofilms in TSB, TB, and LB, while MHB was the least supportive medium for both strains. ZAM-CS significantly reduced biofilm biomass in both MSSA and MRSA (up to 77%). ZAM-CS's rapid and potent anti-biofilm activity at low concentrations highlights its potential as a promising treatment against antibiotic-resistant S. aureus biofilm infections.