Study on the activity of blackberry (Rubus caesius L.) extracts against MRSA

In one of its reports, the WHO published a list of the pathogenic bacteria that pose the greatest threat to human health due to their rapidly growing resistance to currently used antibiotics. This group is called "ESKAPE" and includes, among others, Gram-positive, resistant strains of Staphylococcus aureus. This bacterium can cause a range of infections, from folliculitis and abscesses to severe cases like sepsis, and causes approximately 15% of invasive infections in hospitals worldwide. Methicillin-resistant S. aureus (MRSA), in addition to resistance to β-lactam antibiotics, is resistant to aminoglycosides, fluoroquinolones, macrolides, chloramphenicol, and tetracycline. Some strains can produce a biofilm. The growing resistance of bacteria to available antibiotics forces us to search for alternative antibacterial drugs. Plants of the genus Rubus are a source of natural compounds used in many infectious diseases. Rubus caesius (dewberry) contains, among others, anthocyanins, tannins, flavonoids, and phenolic acids known for their antioxidant and antibacterial properties [1]. However, there are no reports on the antibacterial activity of blackberry leaves (L_H2O, L_EtOH) against S. aureus. The activity of the extracts was tested in vitro on reference strains of S. aureus and clinical strains of MRSA (MIC 0.16 - 3.125 mg/ml, MBC 0.78 - 6.25 mg/ml). We studied the interactions of amikacin and cefoxitin with the tested R. caesius extracts and their effect on the inhibition of biofilms produced by clinical strains of MRSA. We show that the extracts tested have a bactericidal effect on clinical strains and inhibit biofilm formation. We suggest that our results will influence a reduction in antibiotic doses and increase their therapeutic effect, which may potentially lead to a faster elimination of microorganisms from the human body.

Reference:

Hering, A.; et al. Polyphenolic Characterization, Antioxidant, Antihyaluronidase and Antimicrobial Activity of Young Leaves and Stem Extracts from Rubus caesius L. Molecules 2022, 27, 6181. https://doi.org/10.3390/ molecules27196181