Synergistic Antibacterial Effect of Casein-AgNPs Combined with Tigecycline against Acinetobacter baumannii.

Yu-Hsuan Chen,Sheng-Hui Lin,Wei-Hsun Wang,Sung-Pin Tseng,Chi-Sheng Chien,Chi-Jen Shih,Yuan-Ting Yang-Wang

doi:10.3390/polym13091529

Abstract

Acinetobacter baumannii (A. baumannii) is a common and challenging pathogen of nosocomial infections, due to its ability to survive on inanimate objects, desiccation tolerance, and resistance to disinfectants. In this study, we investigated an antibacterial strategy to combat A. baumannii via the combination of antibiotics and silver protein. This strategy used a functional platform consisting of silver nanoparticles (AgNPs) resurrected from silver-based calcium thiophosphate (SSCP) through casein and arginine. Then, the silver protein was combined with tigecycline, the first drug in glycylcycline antibiotic, to synergistically inhibit the viability of A. baumannii. The synergistic antibacterial activity was confirmed by the 96-well checkerboard method to determine their minimum inhibitory concentrations (MIC) and calculated for the combination index (CI). The MIC of the combination of silver protein and tigecycline (0.31 mg/mL, 0.16 µg/mL) was significantly lower than that of the individual MIC, and the CI was 0.59, which indicates a synergistic effect. Consequently, we integrated the detailed synergistic antibacterial properties when silver protein was combined with tigecycline. The result could make for a promising approach for the treatment of A. baumannii.

Highlights

Infections from common pathogens, such as Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii, have resulted in difficulties [1,2]
T Arginine has the highest affinity towards silver ions among all amino acids, which may bind at various electron rich sites, e.g., nitrogen atoms of α-amino groups as well as guanidino side chains, in addition to carboxyl moieties at the C-terminus [33,34]
We proposed the combination of a functional platform consisting of silver nanoparticles (AgNPs) and tigecycline providing two different antibacterial mechanisms to increase its efficiency

Summary

Introduction

Infections from common pathogens, such as Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii, have resulted in difficulties [1,2]. Infectious patients may extend their inpatient days, require more medical resources, and increase the economic burden [3]. Among such pathogens, A. baumannii is mostly acquired within health-care facilities. The dosage of tigecycline has been increasing because of the higher incidence of infection that does not respond to first-line antibiotics. To combat A. baumannii infection, a practical therapy has been used combining tigecycline and other antibiotics, such as colistin, amikacin, levofloxacin, rifampicin, and so on [6]

Methods

Results

Conclusion