Wound infections became a great challenge, especially after the emergence of bacterial resistance to commonly used antibiotics. Medicinal plants can be the source of alternative antibacterial agents effective against multi drug resistant (MDR) bacteria. This research aimed to evaluate the effectiveness of different Silybum marianum seed extracts in fighting MDR bacteria that infect wounds. First, thirty purified bacterial cultures obtained from superficial, infected wounds were subjected to antibiotic sensitivity tests. The selected MDR isolates were then used to test the antimicrobial effects of different S. marianum seed extracts. The most potent extract was evaluated for its impact on the ultrastructure of the cells of sensitive bacterial isolates using transmission electron microscopy (TEM). The bioactive ingredients of this extract were analyzed by means of gas chromatography–mass spectroscopy (GC–MS). Then, in-silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties were predicted for the main components. The results indicated that four out of 30 bacterial isolates were considered MDR bacteria. Primary morphological features of colonies, secondary (automatic) identification using the Biomerieux Vitek 2 System, and 16S rRNA sequencing of the four isolates confirmed that they represent Staphylococcus aureus, Stenotrophomonas maltophilia, Klebsiella pneumoniae, and Escherichia coli. Among different extracts of S. marianum seeds, ethanol extract showed the strongest inhibitory effect on both Gram-positive and Gram-negative bacteria, with minimum inhibitory concentration (MIC) values between 9.375 and 1.172 mg/mL. However, at concentrations four times higher, this extract was unable to kill bacterial cells, indicating that it had a bacteriostatic effect on the tested MDR strains. TEM revealed denaturation and distorted cell ultrastructure in S. aureus and S. maltophilia after exposure to ethanol extract. In addition, GC–MS analysis of the ethanol extract identified nine compounds known to have important biological activities, and ADMET analysis showed good drug-likeness for two of these compounds. Consequently, S. marianum seeds could be a good source of alternative bacteriostatic agents effective against MDR bacterial strains that cause wound infections.

The development of bacterial resistance to conventional treatments (chiefly antibiotics) has led to the complication of wound infections, thus rendering the search for novel alternative infection-fighting techniques even more urgent. Historically, medicinal plants have been widely used to obtain natural health products, thus, they constitute sources for very promising alternative antibacterial agents against multidrug-resistant (MDR) bacteria. Thus, this study aimed to evaluate the in vitro antibacterial activity of different seed extracts of Silybum marianum against antibiotic-resistant wound infection–causing bacteria (Staphylococcus aureus strain NBRC 100910, Stenotrophomonas maltophilia strain IAM 12423, Klebsiella pneumoniae strain DSM 30104, and Escherichia coli strain NBRC 102203). The most effective extract was selected to investigate its antioxidant potency, assess its effects on the bacterial cell ultrastructure using transmission electron microscopy (TEM), and screen its bioactive components using gas chromatography–mass spectroscopy (GC–MS) analysis. The results indicated that most antibiotics were ineffective against the bacterial isolates; hence, the bacterial isolates were considered to be MDR bacteria. Ethanol extract exhibited the highest inhibition activity against gram-positive and -negative bacteria alongside high antioxidant and antibacterial activities, as revealed by the denaturation and deformation of the ultrastructure of methicillin-resistant S. aureus and S. maltophilia observed via TEM. The GC–MS analysis of ethanol extract revealed the presence of diverse active components with numerous biological activities. Therefore, S. marianum seeds might be promising antioxidant and antibacterial agents against MDR wound infection–causing bacterial strains.