Interaction of Nanoparticles with Multidrug-Resistant Bacteria

Infections due to drug-resistant bacteria have emerged
as a global
health risk and are expected to grow at an alarming rate in the coming
decades. The number of new antibacterial compounds under preclinical
and clinical development is dismayingly low; thus, efforts are underway
to either increase the activity of existing compounds or identify
other alternatives. Nanoparticles (NPs) have been shown to possess
antimicrobial properties along with the ability to improve the activity
of existing antimicrobial drugs, including against bacteria. The present
study evaluated the effects of carbon nanotubes, graphene, and silver
NPs against drug-resistant Escherichia coli and Staphylococcus aureus. NPs increased
nucleic acid and protein leakage, along with increased crystal violet
dye uptake, suggesting damage to the cell envelope. Scanning electron
microscopy revealed morphological changes in both bacteria, which
are reminiscent of stress and cell envelope damage. An increase in
the leakage of intracellular components and a decrease in the minimum
inhibitory concentration (MIC) were observed in the drug–NP
combinations. Coarse-grained molecular dynamics studies revealed interactions
between NPs and bacterial membranes as well as peptidoglycan. These
findings suggest that NPs enhance the activity of drugs, particularly
those inhibiting cell wall biosynthesis, and that drug–NP combinations
could aid in combating drug-resistant bacteria.