Antibiofilm properties of chemically synthesized silver nanoparticles found against Pseudomonas aeruginosa

Abstract

Nanomedicine is now being introduced as a recent trend in the field of medicine. It has been documented that metal nanoparticles have antimicrobial effects for bacteria, fungi and viruses. Recent advances in technology has revived the use of silver nanoparticles in the medical field; treatment, diagnosis, monitoring and control of disease. It has been used since ancient times for treating wide range of illnesses. Bacterial cells adheres to surfaces and develop structures known as biofilms. These structures are natural survival strategy of the bacteria to invade the host. They are more tolerant to commonly used antimicrobial agents, thus being more difficult to be controlled. This leads to increase in severity of infection. In this study, we have investigated the effect of silver nanoparticles in the formation of biofilm in multidrug resistant strains of Pseudomonas aeruginosa. Observation showed that biofilm formation occurred at bacterial concentration of 10(6) cfu/ml for the sensitive strain of P. aeruginosa while in the resistant strain, the biofilm was evident at bacterial concentration of about 10(3) cfu/ml. The biofilm were then tested against various concentrations of silver nanoparticles to determine the inhibitory effect of the silver nanoparticles. In the sensitive strain, 20 μg/ml of silver nanoparticles inhibited the growth optimally at bacterial concentration of 10(4) cfu/ml with an inhibition rate of 67%. Similarly, silver nanoparticles inhibited the formation of biofilm in the resistant strain at an optimal bacterial concentration of 10(5) cfu/ml with an inhibition rate of 56%. Thus, silver nanoparticles could be used as a potential alternative therapy to reduce severity of disease due to P. aeruginosa infections.

Figure 1

Development of biofilm [[15]].

Figure 2

Biofilm formation in P. aeruginosa strains. Formation of biofilm in three strains of Pseudomonas aeruginosa; strain 6 (representative susceptible strain), strain 19 (representative of a multidrug resistant strain) and the ATCC 27853 (American Type Culture collection) strain which was used for comparison. It is observed that the biofilm is formed at bacterial cells of concentration of 10³ cfu/ml in both the susceptible and multidrug resistant strain, which is indicated by an elevated value of OD.

Figure 3

Activity of silver nanoparticles in P. aeruginosa sensitive strain. (a) Biofilm inhibition assay of sample 6 (representative of susceptible strain). (b) Biofilm inhibition assay of sample 19 (representative of multidrug resistant strain).

Figure 4

X-ray diffraction pattern for silver (Ag).