Abstract
The study assessed the antibacterial and antibiofilm capability of
Vernonia amygdalina
and
Senna siamea
against both ESBL- and non-ESBL-producing bacteria. The result from the phytochemical screening revealed that secondary metabolites such as alkaloids, flavonoids, saponins, tannins, coumarins, triterpenoids, and phytosteroids were present in both plants, except glycosides, which were exclusively detected in
Vernonia amygdalina
. The antibacterial activity showed that
Senna siamea
had its highest zone of inhibition against
K. pneumoniae
, whereas
Vernonia amygdalina
recorded its highest effect on
E. coli
. The MIC values for
Senna siamea
ranged from 6.25 to 25.00 mg/mL, while the MICs of
Vernonia amygdalina
ranged from 12.50 ± 0.00 to 50.00 ± 0.00 mg/mL. Combination testing indicated synergy between the two extracts only for
E. coli
. Antibiofilm assays showed clear dose-dependent inhibition. At 100 mg/mL,
Vernonia amygdalina
showed 99.01% inhibition against ESBL
K. pneumoniae
, while
Senna siamea
at the same concentration reached 99.72% against
S. aureus
. These data demonstrate the relevant antibacterial and antibiofilm activities for each extract and support continuing efforts that could include them in new strategies against resistant pathogens, including ESBL-producers.