The future is bright for gold-based antibiotics

Spanish researchers have identified several gold-based compounds with the potential to treat multidrug-resistant bacteria, or "superbugs". The compounds were found to be effective against at least one hard-to-treat bacterium, with some proving effective against several.

Drug-resistant infections kill an estimated 700,000 people worldwide each year, and with the figure projected to rise to 10 million by 2050 if no action is taken, the World Health Organisation (WHO) has classified antibiotic resistance as one of the greatest public health threats facing humanity.

The development of new antibiotics has stalled in recent years, with few new treatments being developed, and the compounds identified by the Spanish researchers are seen as a promising new approach. Gold is known to have antibacterial properties, making gold metalloantibiotics – compounds with a gold ion at their core – a potentially exciting new approach to tackling antibiotic resistance.

The researchers studied the activity of 19 gold complexes against a range of multidrug-resistant bacteria isolated from patients. The complexes all belong to the same family but have slightly different structures. The six bacteria studied were Methicillin-Resistant Staphylococcus Aureus (MRSA), Staphylococcus Epidermidis, Pseudomonas Aeruginosa, Stenotrophomonas Maltophilia, Acinetobacter Baumannii, and Escherichia Coli, all of which are multidrug-resistant. Four (S. aureus, P. aeruginosa, A. baumannii, and E. coli) are on the World Health Organisation's list of antibiotic-resistant 'priority pathogens'.

In tests, 16 of the 19 gold complexes were highly effective against MRSA and S. epidermis. Another 16 of the complexes were effective against the other bacteria, all of which are gram-negative. Gram-negative bacteria have greater inbuilt resistance to antibiotics, and the need for new treatments is particularly pressing.

Gold complexes use a variety of techniques to kill bacteria, including stopping enzymes from working, disrupting the function of the bacterial membrane, and damaging DNA. Crucially, this multimodal mechanism should prevent antimicrobial resistance from developing.

The type of gold complexes studied, known as gold (III) complexes, are relatively straightforward and inexpensive to make. They can also be easily modified, providing a vast amount of scope for drug development. The researchers say that the gold-based drugs hold great potential as new antibiotics.

The findings of the study were presented at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Copenhagen. Dr Sara M. Soto González, of the Barcelona Institute for Global Health, Barcelona, Spain, and colleagues conducted the study.

Dr Soto González concludes: "All of the gold compounds were effective against at least one of the bacterial species studied and some displayed potent activity against several multidrug-resistant bacteria. It is particularly exciting to see that some of the gold complexes were effective against MRSA and multidrug-resistant A. baumannii, as they are the two biggest causes of hospital-acquired infections."  The researchers say that with research on other types of gold metalloantibiotics also providing promising results, the future is bright for gold-based antibiotics.