Objective: To determine the virulence factors-biofilm, nuclease and phosphatase production in Staphylococcus aureus isolates. To determine the effect of silver nano particles and antibiotics on MRSA by MIC determination and kirby baeur method respectively and finally to compare antibacterial activity of silver nano particles and antibiotics.Methods: In the present study, we explore the antibacterial activity of silver nanoparticles (Ag-NPs) dispersion (10 nm) against reference strain and clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). We evaluated the antibacterial activity of Ag-NPs against MRSA isolated from patients in Saveetha Medical College and Hospital, a tertiary care centre in Chennai, Tamil Nadu. The bactericidal activity of different concentrations of Ag-NPs (200, 100, 50, 25, 12.5, 6.25, 3.125, and 1.5625 μg/ml) was tested by determining MIC using microbroth dilution and MBC by agar dilution methods.. In addition, the virulence factors phosphatase, nuclease, and biofilm production were tested.Result: The values of minimal inhibitory concentration and minimal bactericidal concentration of Ag-NPs against all clinical isolates of MRSA and a single of S. aureus were found in the range of 12.5–50 μg/ml and 12.5–25 μg/ml, respectively, indicating very good bactericidal activity. Ag-NPs with the highest concentration showed almost no growth for up to 16 h representing a bactericidal effect at this concentration. Effect was proportional to dose since 50.0 μg/ml was the most effective dose since the bacterial population did not recover and 12.5 μg/ml was the least effective. All the MRSA isolates were positive for the virulence factors.Conclusion: The study result suggests that Ag-NPs could be used as an effective alternative antibacterial agent.
Comparative study of virulence factors among methicillin resistant Staphylococcus aureus clinical isolates
