Antimicrobial activity of Bacillus subtilis silver nanoparticles

We tested the hypothesis that silver nanoparticles (BsAgNPs) made by Bacillus subtilis subsp. inaquosorum exhibit antibacterial and antifungal activities. The bacteria formed nanoparticles in UV-visible spectra with the peak around 430 nanometer detected by surface plasmon resonance and Lambdamax. The FTIR spectra, SEM and XRD revealed the involvement of interaction of biological moieties in the formation of crystalline cuboidal nanoparticles that were had an average size of 10-20 nm. The particles exerted dose dependent antibacterial and antifungal activities and high dose equivalent to standard antibiotics. Minimum inhibitory concentration, minimum bactericidal and fungicidal concentrations were in the range from 3.1-25 microgram/ml and 6.3-50 microgram/ml, respectively. BsAgNPs significantly inhibited the growth of multiple strains including multidrug resistant (MDR) bacteria. Moreover, the combination of BsAgNPs and antibiotics showed synergistic inhibition of MDR strains. These data show that BsAgNPs have a great potential in the treatment of MDR bacteria without or with standard antibiotics.