The Effect of Silver Nanoparticles on Listeria monocytogenes PCM2191 Peptidoglycan Metabolism and Cell Permeability

Listeria monocytogenes is Gram-positive bacterial pathogen, a causative agent of food poisoning and systemic disease – listeriosis. This species is still susceptible to several conventionally used antibiotics but an increase in its resistance has been reported. For this reason the search for new, alternative therapies is an urgent task. Silver nanoparticles seem to be the promising antibacterial agent. Minimal inhibitory concentration of silver nanoparticles was determined. Sublethal concentrations were used in study of nanosilver effect on cells lysis by estimation of the number of cells surviving the treatment with 0.25 or 0.5 of minimal inhibitory concentrations of silver nanoparticles. Autolysis of isolated peptidoglycan was studied by measuring the absorbance of preparation subjected to nanosilver treatment. Silver nanoparticles effect on L. monocytogenes envelopes permeability was determined by measuring the efflux of cF, DNA and proteins. It was demonstrated that nanosilver enhanced the lysis of L. monocytogenes cells and, to the lesser extent, autolysis of isolated peptidoglycan. The increase in the efflux of carboxyfluoresceine, DNA and proteins was also noted. The obtained results allow to postulate that L. monocytogenes peptidoglycan, constituting the main component of cell wall, is the target of silver nanoparticles activity against this pathogen.