Antibacterial Activity of Phosphangold(I) Thiolate and Enhancing Activity in Combination with Available Antibiotics Against Staphylococcus aureus

Abstract

With the widespread increase of bacterial resistance to available antibiotics and the lack of resources for the discovery of new classes of antibiotics, the multidrug-resistant S. aureus has become a global concern. The methicillin-resistant Staphylococcus aureus (MRSA) has been reported as a serious threat in health settings. There is now a strong demand for new antibacterial agents as only a few antibiotics can combat MRSA infections. This article aims to in vitro investigate the antibacterial properties of new (phosphanegold(I) thiolate) compounds against S. aureus strains. The disc diffusion method was applied as a preliminary screening method of the gold compounds against different Gram-positive and Gram-negative bacteria. In contrast, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-killing assay methods were carried out to investigate the antibacterial activity of selected compounds against different Methicillin-resistant Staphylococcus aureus (MRSA) species. Moreover, combinations of available antibiotics and selected (phosphanegold(I) thiolate) compound were investigated using the checkerboard method. Two out of five compounds belong to phosphangold(I) thiolate named 3F2 and 3F3 were showing antibacterial activity against Gram-positive bacteria, predominantly Staphylococcus aureus strains with MIC values within the range from 4 µg/mL- 8 µg/mL and 30 µg/mL – 60 µg/mL, respectively. Only 3F2 was exhibited good and promising antibacterial activity against different S.aureus strains including MRSA strains. Additionally, the 3F2 was exhibited synergistic activity and positive drug interaction when combine with ciprofloxacin at sub-inhibitory concentration. These findings suggested that the new investigated phosphanegold(I) thiolate, mainly 3F2 compound, may have great potential to act as an antibacterial agent with action against Gram-positive bacteria that mainly prevent or control MRSA infection's growth. Thus, further investigations are needed to fully understand the mechanism of action of tested (phosphanegold(I) thiolate against S.aureus.