D-Maltose coated silver nanoparticles and their synergistic effect in combination with ampicillin

Abstract

Resistance of pathogenic bacteria to conventional antibiotics has made them a much more challenging threat to public health. It is urgent to develop strategies to combat drug resistant bacteria. In the current study, d-maltose coated silver nanoparticles (AgNPs) were examined for their antibacterial and their synergistic effect in combination with ampicillin against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). AgNPs were synthesized using a modified Tollen’s method, providing highly stable AgNPs. Antibacterial activities of AgNPs were evaluated by determining their minimum inhibition concentration and minimum bactericidal concentration. It was found that S. aureus and E. coli were inhibited by AgNPs. Formation of AgNPs and ampicillin complexes were optimized after mixing them for at least 10 min. These complexes were stable for 1–3 days with no loss of activity. Interestingly, the synergism of the MIC AgNP1, the largest nanoparticle examined, and 2.5 µg cm−3 of ampicillin revealed a 27 and 77% fold increase compared with the ampicillin control against S. aureus and E. coli, respectively. Synergism was found even with low levels of ampicillin. Therefore, these AgNPs could be used as an adjunct treatment in conjunction with an antibiotic to solve the problem of drug-resistant bacteria.