Antibiotics: End Of An Era?
By Stephanie Smith
MRSA is rarely out of the news, but it's place a our most feared bacterium is under threat from two more super-resistant superbugs, VRSA and C. difficile. What's going to happen when the bugs combine to breach our final defences asks Stephanie Smith.When Alexander Fleming discovered the first antibiotic in 1928, it was heralded as a medical miracle. However, as early as the 1940s, only a few years after the first mass production of penicillin, the bacteria it was supposed to be fighting had already started to evolve resistance to the wonder drug, beating us at our own game.
It can take as much as ten years from the point of discovery for an antibiotic to become available on the market. It can take just a few days or weeks for a superbug to evolve it’s defence. With more and more bacteria evolving resistance to even our most potent drugs like Vancomycin, are we seeing an end to the era of the antibiotic?
Like MRSA, the superbugs Clostridium difficile (C. difficile) and Vancomycin resistant Staphylococcus aureus (VRSA), have proliferated as a result of the overuse and misuse of antibiotics. Increased usage of Vancomycin, the last resort drug against prescribed to MRSA patients, VRSA. Unlike MRSA, these strains can be controlled by other drugs but its increased prevalence means that its only a matter of time before resistant strains swap information resulting in Staphylococcus immune to all known antibiotics, including the last resorts.
Professor Tom Evans, from the University of Glasgow’s Biomedical Research Centre recently pointed out that it’s only “natural that such a strain will evolve with the increased use of Vancomycin. We can’t stop bacteria evolving.” He added, “But it is our actions that are speeding up their evolution”.
The other big worry bug, C. difficile, kills nearly three times more people than MRSA. The bacterium is found in small numbers amidst the normal bacteria found in our guts. But in patients treated with arrays of antibiotics, normal intestinal bacteria levels drop and C. difficile advantageously multiplies producing toxins that damage the cells lining the intestine. The result is severe diarrhoea and in some cases ulceration and bleeding. From 2003 to 2006 some UK health boards reported an increase of 49% in the cases of C. difficile.
Another worrying finding has been that some superbugs have evolved the ability to produce the toxin Panton-Valentine Leukocidin (PVL). The PVL toxin destroys leukocytes – white blood cells that are core to our immune system. The effects can range from skin infections to pneumonia. Once in your lungs you could die in less than 24 hours. Many researchers are already thinking outside the box in an attempt to prevent the nation’s health reverting back to a pre-antibiotic era.
In 2006 Professor Marcin Filutowicz of the University of Wisconsin-Madison announced his team would be focusing their efforts on finding compounds that rendered bacteria harmless rather than killing them. The drugs will specifically attack plasmid DNA, the circular chromosomes that code for non essential bacterial genes, such as those involved in antibiotic resistance. If bacteria lacked plasmids then they wouldn’t carry genes for antibiotic resistance, “You could actually drink a cup [of the bacteria] and you’d be fine” says Filutowicz.
Perhaps by simply rendering bacteria harmless, rather than killing them completely, their evolutionary counter response may not be as strong. By avoiding ‘carpet bombing’ bacteria with antibiotics we may also dodge destroying our good bacteria as well as the bad.
Another hope came last year when researchers found away to harness the natural antibiotics made by the soil bacterium Streptomyces. A group, led by Professor Tony Maxwell of the John Innes Centre in Norwich and Professor Lutz Heide of the Pharmazeutisches Institute in Tubingen Germany, found away to modify the bacteria to manufacture new varieties of these antibiotics safe enough to be administered to humans.
Two of the natural antibiotics produced by Streptomyces are called novobiocin and clorobiocin. They work by interfering with the packaging of bacterial DNA without affecting human DNA. By looking at what parts of the molecules are essential for their antibacterial activity the hope is to design new effective antibiotics with fewer side effects.But like the discovery of all wonder drugs before them it will take time before your local GP will prescribe them so what do we do until then?
Professor Evans, like many, believes that it could be as simple as cleaner hospitals and better screening and isolation of cases, “measures like strict cleaning of door knobs, bed rails and staff uniforms would help minimise the spread of these bugs in hospitals”.
Get more musings from Stephanie at her homepage. Or more weird science from the multitude:
- Scary - The revenge of the goose
- Maybe another time - The rules of distraction
- Poor little buggers - Scientists: old before their time
Your Say
"Are you referring to VRSA, or VRE (vanc resistant enterococcus?). I have yet to see a vanc resistant staph, or even see more than the really odd sporadic case report about this bacteria. VRE is increasingly prevalent however."
Brown McCallum MD
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