Evaluation of the Antimicrobial Activity ZnO/Ampicillin Nanocomposite Against Sensitive and Resistant Strains: Role of γ-Irradiation on Its Biological Activity

ABSTRACT

In this study the ampicillin trihydrate was modified to ZnO/ampicillin nanocomposite to improve its effectiveness as a bactericidal agent against sensitive and resistant bacterial strains. The antimicrobial activity of the standard ampicillin trihydrate and ZnO/ampicillin nanocomposite on three pathogenic bacterial strains, Gram-negative short rods, Salmonellae typhimurium, and Gram-positive cocci Staphylococcus aureus were investigated. These strains were recommended in the British Pharmacopeias to be used as the most sensitive strains for the antibiotic sensitivity test of ampicillin. Another strain of Staphylococcus aureus referred as ampicillin resistant clinical isolate was also used. Stock cultures were maintained on nutrient agar slants at 40°C until required. Gamma-irradiation unit of Co⁶⁰was used for irradiation of the standards ampicillin trihydrate and ZnO ampicillin nanocomposite at the sterilizing dose 25 kGy. The antibacterial activity of the standard ampicillin was significantly enhanced by its ZnO nanoparticles. Also, the new compound showed antibacterial activity against the clinically resistant isolate Staphylococcus aureus. The results of the sterilization of ZnO ampicillin nanocomposite at 25 kGy indicated that the antimicrobial activity did not influenced at this dose with Salmonellae typhimurium and the sensitive strains S. aureus, while an increase of its minimum inhibitory concentration (MIC) value from 64–128 μg/m⁻¹was recorded with the resistant clinical isolate S. aureaus. This may be used as an indication for some physical and or chemical changes induced after irradiation of the newly prepared compound.

KEYWORDS:

• ampicillin
• ZnO/nanoparticles
• ZnO/ampicillin nanocomposite
• antibacterial activity
• gamma-irradiation

Acknowledgments

The authors are grateful for the grant obtained from the members in National Center for Radiation Research and Technology Atomic Energy Authority, Egyptian Petroleum Research Institute (EPRI), and Labelled Compounds Department, Hot Laboratories Center, Atomic Energy Authority.