A new antibiotic tested on mice sees the fight against super bugs move a small but important step forward, says an article published in Nature today.
The new family of antibiotics were able to kill most methicillin-resistant staphylococcus aureus (MRSA) bacteria cells in mice.

The retinoid compounds are similar in structure to Vitamin A, have low levels of toxicity and work by disrupting the outer bacterial membrane (something that is hard for bacteria to fix). They can work synergistically with the common antibiotic gentamicin, and the study’s authors think it is unlikely the bacteria will develop resistance to them.

Currently, more than 4000 natural and synthetic retinoids have been described, so it is possible that more antimicrobial candidates will be found amongst them.

With antimicrobial resistance an increasingly serious threat to global public health, it is hoped the study will aid the development of new, effective, clinically useful antibiotic drugs.
New Zealand has one of the highest rates of MRSA in the developed world so the discovery has been welcomed by local experts in the field.

Dr Heather Hendrickson, Senior Lecturer in Molecular Bioscience, Massey University said the new paper from Kim and colleagues took some “nice steps” towards measuring the effectiveness of an often overlooked class of potential antimicrobials against MRSA.

“They started with a massive screen of small synthetic molecules (over 82,000 of them) and came up with 185 candidates that allowed tiny worms called Caenorhabditis elegans to survive when they were in the presence of infectious MRSA bacteria. In the initial test, if the worms lived, the well was dark. But if the worms had died, the well they had been put in would light up with a fluorescent stain.”

”MRSA did not easily evolve worrying levels of resistance to the retinoids and that is an important feature in the hunt for new antimicrobials.”

Associate Professor Siouxsie Wiles, a microbiologist at the University of Auckland said the paper’s findings were exciting news given the catastrophic future we faced due to antibiotic resistant ‘superbugs’. She said a close read of the research shows the antibiotics reduced the number of MRSA in mice from about 1 billion to 50 million which was still “plenty of bacteria”.

“Now it’s fingers crossed those compounds can be improved upon so they can beat the odds and make it through animal and human trials and into the clinic.”

Kurt Krause, Professor of Biochemistry at the University of Otago and an Infectious Diseases Specialist, said new antibiotics are urgently needed as there have been more cases of Vancomycin-resistant Staph. Aureus (VRSA) and MRSA.

“MRSA is a pathogenic bacterium of major clinical importance, and is a worldwide cause of large numbers of serious infections each year. Vancomycin remains the mainstay antibiotic in use for these infections. But with the continual risk of the development of more Vancomycin Insensitive Staphylococcus aureus coupled with an increased global spread of antimicrobial resistance, new drugs against staph and other Gram-positive pathogens are badly needed.”

He adds that while the study shows a compound which has strong anti-MRSA properties, more work on drug optimisation needs to be done.

“Animal and other pre-clinical and clinical studies would be needed before these compounds would have the potential to see clinical use.”

New Zealand has had its antimicrobial plan up and running since last year. The plan can be found here.

It explains that antimicrobial resistance is a major concern because resistant infections can spread to others, imposing huge costs to individuals and society. And it says that New Zealand’s rate of antimicrobial resistance is comparatively low, particularly when compared to countries in neighbouring regions, New Zealand should not become complacent, as there has been a rise in antimicrobial resistance to some types of infections and the country has increasing antimicrobial use.

The many pronged plan includes a major push to get health professionals to not prescribe, or to discourage the use of, antibiotics for viral colds, flus and flu-like illnesses like respiratory tract infections.

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