2.4. Antibacterial activity
The pathogenic strains of Escherichia coli and Staphylococcus
aureus were used to determine the antibacterial activity of the silver
nanoparticles. The bacterial cultures were maintained on Nutrient
Agar (NA) slants that contained peptone, 5.0; meat extract, 1.0;
yeast extract, 2.0; sodium chloride, 5.0; agar, 15.0 g per liter of
distilled water. The test bacterial suspensions (100 L) containing
104 cells mL−1 were spread on NA plates. Freshly prepared silver
nanoparticle (synthesized with 10.0 mL of aqueous ALE, 1.0 mM
silver nitrate incubated at room temperature for 20 min) samples
(50 l) were added onto the filter paper (O = 5.5 mm) which
would be put in the seeded plates. Control samples lacking the silver
nitrate were used to assess the antimicrobial activity of the
ALE. The samples were initially incubated for 15 min at 4 ◦C (to
allow diffusion) and then at 37 ◦C for 24 h for the bacterial cultures.
Positive test results were scored when a zone of inhibition was
observed around the filter paper after the incubation period. The
cultures that were inhibited by the bio-inspired silver nanoparticles
were also subjected to the antimicrobial activity experiments
with gentamycin (400 units/mL) [12–13].