Synergism effect of silver nanoparticles and cefotaxime to treat biofilm formation of Staphylococcus aureus clinical isolates

Background. Staphylococcus aureus, is a major pathogen causing infections in both hospital and community settings. Multi-drug-resistant strains, particularly Methicillin-resistant Staphylococcus aureus (MRSA), complicate treatment, as these strains can evade antibiotics. Biofilm formation by S. aureus protects bacterial cells from immune responses and antibiotics, making infections difficult to treat. This study evalua­tes the synergistic effect of silver nanoparticles (AgNPs) and cefotaxime in inhibiting biofilm formation by clinical S. aureus isolates, especially multi-drug-resistant strains. Materials and Methods. Thirty clinical S. aureus isolates were obtained from patients with skin infections. Identification was confirmed using biochemical tests and the VITEK2 system. Antimicrobial susceptibility testing was performed using the disk diffusion method on antibiotics including ciprofloxacin, imipenem, amoxicillin-clavulanic acid, cefotaxime, and chloramphenicol. Minimum inhibitory concentrations (MICs) were also determined. Biofilm formation was quantified using crystal violet staining. Silver nanoparticles (AgNPs) were synthesized using sodium borohydride and characterized by atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM). Results. All isolates were susceptible to ciprofloxacin and imipenem. Ninety percent were susceptible to amoxicillin-clavulanic acid, while 70% were susceptible to cefotaxime. All isolates were resistant to chloramphenicol. Biofilm formation assays showed variability in biofilm production. AgNPs alone demonstrated superior efficacy in inhibiting biofilm formation. The combination of AgNPs and cefotaxime exhibited the strongest inhibition, suggesting a synergistic effect. Conclusion. This study suggests that AgNPs alone are more effective than cefotaxime in inhibiting biofilm formation. The combination of AgNPs and cefotaxime showed the most potent effect, providing a promising strategy for treating multi-drug-resistant S. aureus infections. AgNPs may serve as an adjunct to antibiotics in overcoming biofilm-associated infections.