Antibacterial effect of silver nanoparticles in Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa has great intrinsic antimicrobial resistance limiting the number of effective antibiotics. Thus, other antimicrobial agents such as silver nanoparticles (AgNPs) are considered potential agents to help manage and prevent infections. AgNPs can be used in several applications against bacteria resistant to common antibiotics or even multi-resistant bacteria such as P. aeruginosa. This study assessed the antimicrobial activity of commercial 10 nm AgNPs on two hospital strains of P. aeruginosa resistant to a large number of antibiotics and a reference strain from a culture collection. All strains were susceptible to 5 µg/mL nanoparticles solution. Reference strains INCQS 0230 and P.a.1 were sensitive to AgNPs at concentrations of 1.25 and 0.156 µg/mL, respectively; however, this was not observed for hospital strain P.a.2, which was more resistant to all antibiotics and AgNPs tested. Cytotoxicity evaluation indicated that AgNPs, up to a concentration of 2.5 µg/mL, are very safe for all cell lines tested. At 5.0 µg/mL, AgNPs had a discrete cytotoxic effect on tumor cells HeLa and HepG2. Results showed the potential of using AgNPs as an alternative to conventional antimicrobial agents that are currently used, and a perspective for application of nanosilver with antibiotics to enhance antimicrobial activity.

Keywords: AgNPs; Pseudomonas aeruginosa; antimicrobial activity; bacterial resistance; silver nanoparticles.

Figure 1

Test of susceptibility to antimicrobials. Antibiotics tested: chloramphenicol (Clo), ampicillin + sulbactam (Asb), vancomycin (Van), ceftazidime (Caz), amikacin (Ami), penicillin (Pen), erythromycin (Eri), cefoxitin (Cfo), levofloxacin (Lvx), meropenem (Mer), and oxacillin (Oxa).

Figure 2

Behavior of the Pseudomonas aeruginosa INCQS 0230 strain tested at different concentrations of silver nanoparticles: 0.156, 1.25, and 5.0 µg/mL.

Figure 3

Behavior of the Pseudomonas aeruginosa P.a.1 strain tested at different concentrations of silver nanoparticles: 0.156, 1.25, and 5.0 µg/mL.

Figure 4

Behavior of the Pseudomonas aeruginosa P.a.2 strain tested at different concentrations of silver nanoparticles: 0.156, 1.25, and 5.0 µg/mL.

Figure 5

Viability of NCTC 929, HeLa, and HepG2 cells after exposure to silver nanoparticles (AgNPs). Notes: NCTC 929 (mouse fibroblasts), HeLa (human cervix adenocarcinoma), and HepG2 (human hepatocarcinoma) cells were pre-cultured for 24 hours, and then incubated at concentrations of 10, 5.0, 2.5, 1.25, 0.625, 0.312, and 0.156 µg/mL AgNPs (10 nm) for 24 hours. Cell viability was estimated by absorbance after uptake of neutral red.