microbelog

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Mixing your drugs kills superbugs!

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Pseudomonas aeruginosa

We hear a lot in the news about multidrug-resistant (MDR) bacteria but not very much about the efforts made to tackle these so-called ‘superbugs’.

At the recent ‘Antibiotics 2011’ meeting hosted by the Royal Society of Chemistry, I heard some interesting talks from senior scientists working for the pharmaceutical giants GlaxoSmithKline and Bayer.

A favoured (but not very interesting) approach by big pharma companies is to buy up smaller biotech companies with promising drugs because it’s much cheaper than trying to develop them on their own. A more interesting approach is to invest in the better delivery of antibiotics that are already licensed for clinical use.

One example of this is to aerosolise antibiotics used to treat lung infections so they can be inhaled: different droplet sizes will reach different parts of the infected airway or lungs. This concentrates the drug in the infected area and, hopefully, obliterates the infection. Even MDR strains are only resistant up to certain concentrations of antibiotics (known as the minimum inhibitory concentration, or MIC). Go higher than the MIC and the drugs work.

The big idea is that it’s a lot cheaper and easier to find new and more effective ways of using antibiotics that are already licensed than it is to develop new antibiotics from scratch. Now, academics are getting in on the act.

A recent study from Gerry Wright’s lab screened for synergistic (i.e. favourable) effects between the antibiotic minocycline and a library of non-antibiotic drugs that are used to treat other non-infectious diseases. They tested all drug combinations against MDR Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus (MRSA).

The exciting, and surprising, results showed that some non-antibiotic drugs enhanced the activity of minocycline. For example, all the MDR strains of P. aeruginosa — a major cause of death for people with cystic fibrosis — were susceptible to minocycline combined with loperamide, which is better known as Imodium and is used to treat diarrhoea, or benserazide, which is used to treat Parkinson’s disease. MRSA strains were susceptible to minocycline and disulfiram, which is sold as Antabuse and used to treat alcoholism.

Interestingly, different combinations were effective against different bacterial strains, suggesting drug combinations could be tailored to treat different infections. It is also worth noting that this was all carried out in vitro (i.e. in a lab), so the effects in animals and humans may be very different.

Nevertheless, this is an exciting study that deserves to be publicised and investigated further by scientists and clinicians. It seems there may still be a lot of life left in the antibiotics already in clinical use: perhaps the superbugs aren’t really so super after all.

Ejim L., Farha MA., Falconer SB., Wildehain J., Coombes BK., Tyers M., Brown ED. and Wright GD. (2011). Combinations of antibiotics and nonantibiotic drugs enhance antimicrobial efficacy. Nature Chem Biol. 7:348-50.

Posted by Matt Hutchings

Image credit: AJC1 on Flickr

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Written by microbelog

11/08/2011 at 10:35 am

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